diff --git a/crates/wasi-common/src/ctx.rs b/crates/wasi-common/src/ctx.rs
index 981007c515..899e272c0f 100644
--- a/crates/wasi-common/src/ctx.rs
+++ b/crates/wasi-common/src/ctx.rs
@@ -1,16 +1,44 @@
 use crate::fdentry::{Descriptor, FdEntry};
 use crate::sys::fdentry_impl::OsHandle;
 use crate::virtfs::{VirtualDir, VirtualDirEntry};
-use crate::{wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
 use std::borrow::Borrow;
 use std::collections::HashMap;
-use std::env;
-use std::ffi::{CString, OsString};
+use std::ffi::{self, CString, OsString};
 use std::fs::File;
 use std::path::{Path, PathBuf};
+use std::{env, io, string};
+
+/// Possible errors when `WasiCtxBuilder` fails building
+/// `WasiCtx`.
+#[derive(Debug, thiserror::Error)]
+pub enum WasiCtxBuilderError {
+    /// General I/O error was encountered.
+    #[error("general I/O error encountered: {0}")]
+    Io(#[from] io::Error),
+    /// Provided sequence of bytes was not a valid UTF-8.
+    #[error("provided sequence is not valid UTF-8: {0}")]
+    InvalidUtf8(#[from] string::FromUtf8Error),
+    /// Provided sequence of bytes was not a valid UTF-16.
+    ///
+    /// This error is expected to only occur on Windows hosts.
+    #[error("provided sequence is not valid UTF-16: {0}")]
+    InvalidUtf16(#[from] string::FromUtf16Error),
+    /// Provided sequence of bytes contained an unexpected NUL byte.
+    #[error("provided sequence contained an unexpected NUL byte")]
+    UnexpectedNul(#[from] ffi::NulError),
+    /// Provided `File` is not a directory.
+    #[error("preopened directory path {} is not a directory", .0.display())]
+    NotADirectory(PathBuf),
+    /// `WasiCtx` has too many opened files.
+    #[error("context object has too many opened files")]
+    TooManyFilesOpen,
+}
+
+type WasiCtxBuilderResult<T> = std::result::Result<T, WasiCtxBuilderError>;
 
 enum PendingFdEntry {
-    Thunk(fn() -> Result<FdEntry>),
+    Thunk(fn() -> io::Result<FdEntry>),
     File(File),
 }
 
@@ -20,7 +48,7 @@ impl std::fmt::Debug for PendingFdEntry {
             Self::Thunk(f) => write!(
                 fmt,
                 "PendingFdEntry::Thunk({:p})",
-                f as *const fn() -> Result<FdEntry>
+                f as *const fn() -> io::Result<FdEntry>
             ),
             Self::File(f) => write!(fmt, "PendingFdEntry::File({:?})", f),
         }
@@ -46,17 +74,29 @@ impl From<OsString> for PendingCString {
 }
 
 impl PendingCString {
-    fn into_string(self) -> Result<String> {
-        match self {
-            Self::Bytes(v) => String::from_utf8(v).map_err(|_| Error::EILSEQ),
-            Self::OsString(s) => s.into_string().map_err(|_| Error::EILSEQ),
-        }
+    fn into_string(self) -> WasiCtxBuilderResult<String> {
+        let res = match self {
+            Self::Bytes(v) => String::from_utf8(v)?,
+            #[cfg(unix)]
+            Self::OsString(s) => {
+                use std::os::unix::ffi::OsStringExt;
+                String::from_utf8(s.into_vec())?
+            }
+            #[cfg(windows)]
+            Self::OsString(s) => {
+                use std::os::windows::ffi::OsStrExt;
+                let bytes: Vec<u16> = s.encode_wide().collect();
+                String::from_utf16(&bytes)?
+            }
+        };
+        Ok(res)
     }
 
-    /// Create a `CString` containing valid UTF-8, or fail with `Error::EILSEQ`.
-    fn into_utf8_cstring(self) -> Result<CString> {
-        self.into_string()
-            .and_then(|s| CString::new(s).map_err(|_| Error::EILSEQ))
+    /// Create a `CString` containing valid UTF-8.
+    fn into_utf8_cstring(self) -> WasiCtxBuilderResult<CString> {
+        let s = self.into_string()?;
+        let s = CString::new(s)?;
+        Ok(s)
     }
 }
 
@@ -87,8 +127,7 @@ impl WasiCtxBuilder {
 
     /// Add arguments to the command-line arguments list.
     ///
-    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail
-    /// with `Error::EILSEQ`.
+    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail.
     pub fn args<S: AsRef<[u8]>>(&mut self, args: impl IntoIterator<Item = S>) -> &mut Self {
         self.args
             .as_mut()
@@ -99,8 +138,7 @@ impl WasiCtxBuilder {
 
     /// Add an argument to the command-line arguments list.
     ///
-    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail
-    /// with `Error::EILSEQ`.
+    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail.
     pub fn arg<S: AsRef<[u8]>>(&mut self, arg: S) -> &mut Self {
         self.args
             .as_mut()
@@ -112,7 +150,7 @@ impl WasiCtxBuilder {
     /// Inherit the command-line arguments from the host process.
     ///
     /// If any arguments from the host process contain invalid UTF-8, `WasiCtxBuilder::build()` will
-    /// fail with `Error::EILSEQ`.
+    /// fail.
     pub fn inherit_args(&mut self) -> &mut Self {
         let args = self.args.as_mut().unwrap();
         args.clear();
@@ -159,8 +197,7 @@ impl WasiCtxBuilder {
     /// Inherit the environment variables from the host process.
     ///
     /// If any environment variables from the host process contain invalid Unicode (UTF-16 for
-    /// Windows, UTF-8 for other platforms), `WasiCtxBuilder::build()` will fail with
-    /// `Error::EILSEQ`.
+    /// Windows, UTF-8 for other platforms), `WasiCtxBuilder::build()` will fail.
     pub fn inherit_env(&mut self) -> &mut Self {
         let env = self.env.as_mut().unwrap();
         env.clear();
@@ -171,7 +208,7 @@ impl WasiCtxBuilder {
     /// Add an entry to the environment.
     ///
     /// Environment variable keys and values must be valid UTF-8 with no NUL bytes, or else
-    /// `WasiCtxBuilder::build()` will fail with `Error::EILSEQ`.
+    /// `WasiCtxBuilder::build()` will fail.
     pub fn env<S: AsRef<[u8]>>(&mut self, k: S, v: S) -> &mut Self {
         self.env
             .as_mut()
@@ -183,7 +220,7 @@ impl WasiCtxBuilder {
     /// Add entries to the environment.
     ///
     /// Environment variable keys and values must be valid UTF-8 with no NUL bytes, or else
-    /// `WasiCtxBuilder::build()` will fail with `Error::EILSEQ`.
+    /// `WasiCtxBuilder::build()` will fail.
     pub fn envs<S: AsRef<[u8]>, T: Borrow<(S, S)>>(
         &mut self,
         envs: impl IntoIterator<Item = T>,
@@ -270,22 +307,22 @@ impl WasiCtxBuilder {
     /// Build a `WasiCtx`, consuming this `WasiCtxBuilder`.
     ///
     /// If any of the arguments or environment variables in this builder cannot be converted into
-    /// `CString`s, either due to NUL bytes or Unicode conversions, this returns `Error::EILSEQ`.
-    pub fn build(&mut self) -> Result<WasiCtx> {
+    /// `CString`s, either due to NUL bytes or Unicode conversions, this will fail.
+    pub fn build(&mut self) -> WasiCtxBuilderResult<WasiCtx> {
         // Process arguments and environment variables into `CString`s, failing quickly if they
         // contain any NUL bytes, or if conversion from `OsString` fails.
         let args = self
             .args
             .take()
-            .ok_or(Error::EINVAL)?
+            .unwrap()
             .into_iter()
             .map(|arg| arg.into_utf8_cstring())
-            .collect::<Result<Vec<CString>>>()?;
+            .collect::<WasiCtxBuilderResult<Vec<CString>>>()?;
 
         let env = self
             .env
             .take()
-            .ok_or(Error::EINVAL)?
+            .unwrap()
             .into_iter()
             .map(|(k, v)| {
                 k.into_string().and_then(|mut pair| {
@@ -294,15 +331,16 @@ impl WasiCtxBuilder {
                         pair.push_str(v.as_str());
                         // We have valid UTF-8, but the keys and values have not yet been checked
                         // for NULs, so we do a final check here.
-                        CString::new(pair).map_err(|_| Error::EILSEQ)
+                        let s = CString::new(pair)?;
+                        Ok(s)
                     })
                 })
             })
-            .collect::<Result<Vec<CString>>>()?;
+            .collect::<WasiCtxBuilderResult<Vec<CString>>>()?;
 
         let mut fds: HashMap<wasi::__wasi_fd_t, FdEntry> = HashMap::new();
         // Populate the non-preopen fds.
-        for (fd, pending) in self.fds.take().ok_or(Error::EINVAL)? {
+        for (fd, pending) in self.fds.take().unwrap() {
             log::debug!("WasiCtx inserting ({:?}, {:?})", fd, pending);
             match pending {
                 PendingFdEntry::Thunk(f) => {
@@ -317,20 +355,22 @@ impl WasiCtxBuilder {
         // so we start from there. This variable is initially 2, though, because the loop
         // immediately does the increment and check for overflow.
         let mut preopen_fd: wasi::__wasi_fd_t = 2;
-        for (guest_path, dir) in self.preopens.take().ok_or(Error::EINVAL)? {
+        for (guest_path, dir) in self.preopens.take().unwrap() {
             // We do the increment at the beginning of the loop body, so that we don't overflow
             // unnecessarily if we have exactly the maximum number of file descriptors.
-            preopen_fd = preopen_fd.checked_add(1).ok_or(Error::ENFILE)?;
+            preopen_fd = preopen_fd
+                .checked_add(1)
+                .ok_or(WasiCtxBuilderError::TooManyFilesOpen)?;
 
             match &dir {
                 Descriptor::OsHandle(handle) => {
                     if !handle.metadata()?.is_dir() {
-                        return Err(Error::EBADF);
+                        return Err(WasiCtxBuilderError::NotADirectory(guest_path));
                     }
                 }
                 Descriptor::VirtualFile(virt) => {
                     if virt.get_file_type() != wasi::__WASI_FILETYPE_DIRECTORY {
-                        return Err(Error::EBADF);
+                        return Err(WasiCtxBuilderError::NotADirectory(guest_path));
                     }
                 }
                 Descriptor::Stdin | Descriptor::Stdout | Descriptor::Stderr => {
@@ -341,7 +381,9 @@ impl WasiCtxBuilder {
             // We don't currently allow setting file descriptors other than 0-2, but this will avoid
             // collisions if we restore that functionality in the future.
             while fds.contains_key(&preopen_fd) {
-                preopen_fd = preopen_fd.checked_add(1).ok_or(Error::ENFILE)?;
+                preopen_fd = preopen_fd
+                    .checked_add(1)
+                    .ok_or(WasiCtxBuilderError::TooManyFilesOpen)?;
             }
             let mut fe = FdEntry::from(dir)?;
             fe.preopen_path = Some(guest_path);
@@ -369,7 +411,7 @@ impl WasiCtx {
     /// - Environment variables are inherited from the host process.
     ///
     /// To override these behaviors, use `WasiCtxBuilder`.
-    pub fn new<S: AsRef<[u8]>>(args: impl IntoIterator<Item = S>) -> Result<Self> {
+    pub fn new<S: AsRef<[u8]>>(args: impl IntoIterator<Item = S>) -> WasiCtxBuilderResult<Self> {
         WasiCtxBuilder::new()
             .args(args)
             .inherit_stdio()
@@ -383,30 +425,30 @@ impl WasiCtx {
     }
 
     /// Get an immutable `FdEntry` corresponding to the specified raw WASI `fd`.
-    pub(crate) unsafe fn get_fd_entry(&self, fd: wasi::__wasi_fd_t) -> Result<&FdEntry> {
-        self.fds.get(&fd).ok_or(Error::EBADF)
+    pub(crate) unsafe fn get_fd_entry(&self, fd: wasi::__wasi_fd_t) -> WasiResult<&FdEntry> {
+        self.fds.get(&fd).ok_or(WasiError::EBADF)
     }
 
     /// Get a mutable `FdEntry` corresponding to the specified raw WASI `fd`.
     pub(crate) unsafe fn get_fd_entry_mut(
         &mut self,
         fd: wasi::__wasi_fd_t,
-    ) -> Result<&mut FdEntry> {
-        self.fds.get_mut(&fd).ok_or(Error::EBADF)
+    ) -> WasiResult<&mut FdEntry> {
+        self.fds.get_mut(&fd).ok_or(WasiError::EBADF)
     }
 
     /// Insert the specified `FdEntry` into the `WasiCtx` object.
     ///
     /// The `FdEntry` will automatically get another free raw WASI `fd` assigned. Note that
     /// the two subsequent free raw WASI `fd`s do not have to be stored contiguously.
-    pub(crate) fn insert_fd_entry(&mut self, fe: FdEntry) -> Result<wasi::__wasi_fd_t> {
+    pub(crate) fn insert_fd_entry(&mut self, fe: FdEntry) -> WasiResult<wasi::__wasi_fd_t> {
         // Never insert where stdio handles are expected to be.
         let mut fd = 3;
         while self.fds.contains_key(&fd) {
             if let Some(next_fd) = fd.checked_add(1) {
                 fd = next_fd;
             } else {
-                return Err(Error::EMFILE);
+                return Err(WasiError::EMFILE);
             }
         }
         self.fds.insert(fd, fe);
@@ -424,7 +466,7 @@ impl WasiCtx {
     }
 
     /// Remove `FdEntry` corresponding to the specified raw WASI `fd` from the `WasiCtx` object.
-    pub(crate) fn remove_fd_entry(&mut self, fd: wasi::__wasi_fd_t) -> Result<FdEntry> {
-        self.fds.remove(&fd).ok_or(Error::EBADF)
+    pub(crate) fn remove_fd_entry(&mut self, fd: wasi::__wasi_fd_t) -> WasiResult<FdEntry> {
+        self.fds.remove(&fd).ok_or(WasiError::EBADF)
     }
 }
diff --git a/crates/wasi-common/src/error.rs b/crates/wasi-common/src/error.rs
deleted file mode 100644
index 3da299f91b..0000000000
--- a/crates/wasi-common/src/error.rs
+++ /dev/null
@@ -1,249 +0,0 @@
-// Due to https://github.com/rust-lang/rust/issues/64247
-#![allow(clippy::use_self)]
-use crate::wasi;
-use std::convert::Infallible;
-use std::num::TryFromIntError;
-use std::{ffi, str};
-use thiserror::Error;
-
-#[derive(Clone, Copy, Debug, Error, Eq, PartialEq)]
-#[repr(u16)]
-#[error("{:?} ({})", self, wasi::strerror(*self as wasi::__wasi_errno_t))]
-pub enum WasiError {
-    ESUCCESS = wasi::__WASI_ERRNO_SUCCESS,
-    E2BIG = wasi::__WASI_ERRNO_2BIG,
-    EACCES = wasi::__WASI_ERRNO_ACCES,
-    EADDRINUSE = wasi::__WASI_ERRNO_ADDRINUSE,
-    EADDRNOTAVAIL = wasi::__WASI_ERRNO_ADDRNOTAVAIL,
-    EAFNOSUPPORT = wasi::__WASI_ERRNO_AFNOSUPPORT,
-    EAGAIN = wasi::__WASI_ERRNO_AGAIN,
-    EALREADY = wasi::__WASI_ERRNO_ALREADY,
-    EBADF = wasi::__WASI_ERRNO_BADF,
-    EBADMSG = wasi::__WASI_ERRNO_BADMSG,
-    EBUSY = wasi::__WASI_ERRNO_BUSY,
-    ECANCELED = wasi::__WASI_ERRNO_CANCELED,
-    ECHILD = wasi::__WASI_ERRNO_CHILD,
-    ECONNABORTED = wasi::__WASI_ERRNO_CONNABORTED,
-    ECONNREFUSED = wasi::__WASI_ERRNO_CONNREFUSED,
-    ECONNRESET = wasi::__WASI_ERRNO_CONNRESET,
-    EDEADLK = wasi::__WASI_ERRNO_DEADLK,
-    EDESTADDRREQ = wasi::__WASI_ERRNO_DESTADDRREQ,
-    EDOM = wasi::__WASI_ERRNO_DOM,
-    EDQUOT = wasi::__WASI_ERRNO_DQUOT,
-    EEXIST = wasi::__WASI_ERRNO_EXIST,
-    EFAULT = wasi::__WASI_ERRNO_FAULT,
-    EFBIG = wasi::__WASI_ERRNO_FBIG,
-    EHOSTUNREACH = wasi::__WASI_ERRNO_HOSTUNREACH,
-    EIDRM = wasi::__WASI_ERRNO_IDRM,
-    EILSEQ = wasi::__WASI_ERRNO_ILSEQ,
-    EINPROGRESS = wasi::__WASI_ERRNO_INPROGRESS,
-    EINTR = wasi::__WASI_ERRNO_INTR,
-    EINVAL = wasi::__WASI_ERRNO_INVAL,
-    EIO = wasi::__WASI_ERRNO_IO,
-    EISCONN = wasi::__WASI_ERRNO_ISCONN,
-    EISDIR = wasi::__WASI_ERRNO_ISDIR,
-    ELOOP = wasi::__WASI_ERRNO_LOOP,
-    EMFILE = wasi::__WASI_ERRNO_MFILE,
-    EMLINK = wasi::__WASI_ERRNO_MLINK,
-    EMSGSIZE = wasi::__WASI_ERRNO_MSGSIZE,
-    EMULTIHOP = wasi::__WASI_ERRNO_MULTIHOP,
-    ENAMETOOLONG = wasi::__WASI_ERRNO_NAMETOOLONG,
-    ENETDOWN = wasi::__WASI_ERRNO_NETDOWN,
-    ENETRESET = wasi::__WASI_ERRNO_NETRESET,
-    ENETUNREACH = wasi::__WASI_ERRNO_NETUNREACH,
-    ENFILE = wasi::__WASI_ERRNO_NFILE,
-    ENOBUFS = wasi::__WASI_ERRNO_NOBUFS,
-    ENODEV = wasi::__WASI_ERRNO_NODEV,
-    ENOENT = wasi::__WASI_ERRNO_NOENT,
-    ENOEXEC = wasi::__WASI_ERRNO_NOEXEC,
-    ENOLCK = wasi::__WASI_ERRNO_NOLCK,
-    ENOLINK = wasi::__WASI_ERRNO_NOLINK,
-    ENOMEM = wasi::__WASI_ERRNO_NOMEM,
-    ENOMSG = wasi::__WASI_ERRNO_NOMSG,
-    ENOPROTOOPT = wasi::__WASI_ERRNO_NOPROTOOPT,
-    ENOSPC = wasi::__WASI_ERRNO_NOSPC,
-    ENOSYS = wasi::__WASI_ERRNO_NOSYS,
-    ENOTCONN = wasi::__WASI_ERRNO_NOTCONN,
-    ENOTDIR = wasi::__WASI_ERRNO_NOTDIR,
-    ENOTEMPTY = wasi::__WASI_ERRNO_NOTEMPTY,
-    ENOTRECOVERABLE = wasi::__WASI_ERRNO_NOTRECOVERABLE,
-    ENOTSOCK = wasi::__WASI_ERRNO_NOTSOCK,
-    ENOTSUP = wasi::__WASI_ERRNO_NOTSUP,
-    ENOTTY = wasi::__WASI_ERRNO_NOTTY,
-    ENXIO = wasi::__WASI_ERRNO_NXIO,
-    EOVERFLOW = wasi::__WASI_ERRNO_OVERFLOW,
-    EOWNERDEAD = wasi::__WASI_ERRNO_OWNERDEAD,
-    EPERM = wasi::__WASI_ERRNO_PERM,
-    EPIPE = wasi::__WASI_ERRNO_PIPE,
-    EPROTO = wasi::__WASI_ERRNO_PROTO,
-    EPROTONOSUPPORT = wasi::__WASI_ERRNO_PROTONOSUPPORT,
-    EPROTOTYPE = wasi::__WASI_ERRNO_PROTOTYPE,
-    ERANGE = wasi::__WASI_ERRNO_RANGE,
-    EROFS = wasi::__WASI_ERRNO_ROFS,
-    ESPIPE = wasi::__WASI_ERRNO_SPIPE,
-    ESRCH = wasi::__WASI_ERRNO_SRCH,
-    ESTALE = wasi::__WASI_ERRNO_STALE,
-    ETIMEDOUT = wasi::__WASI_ERRNO_TIMEDOUT,
-    ETXTBSY = wasi::__WASI_ERRNO_TXTBSY,
-    EXDEV = wasi::__WASI_ERRNO_XDEV,
-    ENOTCAPABLE = wasi::__WASI_ERRNO_NOTCAPABLE,
-}
-
-impl WasiError {
-    pub fn as_raw_errno(self) -> wasi::__wasi_errno_t {
-        self as wasi::__wasi_errno_t
-    }
-}
-
-#[derive(Debug, Error)]
-pub enum Error {
-    #[error("WASI error code: {0}")]
-    Wasi(#[from] WasiError),
-    #[error("IO error: {0}")]
-    Io(#[from] std::io::Error),
-}
-
-impl From<TryFromIntError> for Error {
-    fn from(_: TryFromIntError) -> Self {
-        Self::EOVERFLOW
-    }
-}
-
-impl From<Infallible> for Error {
-    fn from(_: Infallible) -> Self {
-        unreachable!()
-    }
-}
-
-impl From<str::Utf8Error> for Error {
-    fn from(_: str::Utf8Error) -> Self {
-        Self::EILSEQ
-    }
-}
-
-impl From<ffi::NulError> for Error {
-    fn from(_: ffi::NulError) -> Self {
-        Self::EILSEQ
-    }
-}
-
-impl From<&ffi::NulError> for Error {
-    fn from(_: &ffi::NulError) -> Self {
-        Self::EILSEQ
-    }
-}
-
-impl Error {
-    pub(crate) fn as_wasi_error(&self) -> WasiError {
-        match self {
-            Self::Wasi(err) => *err,
-            Self::Io(err) => {
-                let err = match err.raw_os_error() {
-                    Some(code) => Self::from_raw_os_error(code),
-                    None => {
-                        log::debug!("Inconvertible OS error: {}", err);
-                        Self::EIO
-                    }
-                };
-                err.as_wasi_error()
-            }
-        }
-    }
-
-    pub const ESUCCESS: Self = Error::Wasi(WasiError::ESUCCESS);
-    pub const E2BIG: Self = Error::Wasi(WasiError::E2BIG);
-    pub const EACCES: Self = Error::Wasi(WasiError::EACCES);
-    pub const EADDRINUSE: Self = Error::Wasi(WasiError::EADDRINUSE);
-    pub const EADDRNOTAVAIL: Self = Error::Wasi(WasiError::EADDRNOTAVAIL);
-    pub const EAFNOSUPPORT: Self = Error::Wasi(WasiError::EAFNOSUPPORT);
-    pub const EAGAIN: Self = Error::Wasi(WasiError::EAGAIN);
-    pub const EALREADY: Self = Error::Wasi(WasiError::EALREADY);
-    pub const EBADF: Self = Error::Wasi(WasiError::EBADF);
-    pub const EBADMSG: Self = Error::Wasi(WasiError::EBADMSG);
-    pub const EBUSY: Self = Error::Wasi(WasiError::EBUSY);
-    pub const ECANCELED: Self = Error::Wasi(WasiError::ECANCELED);
-    pub const ECHILD: Self = Error::Wasi(WasiError::ECHILD);
-    pub const ECONNABORTED: Self = Error::Wasi(WasiError::ECONNABORTED);
-    pub const ECONNREFUSED: Self = Error::Wasi(WasiError::ECONNREFUSED);
-    pub const ECONNRESET: Self = Error::Wasi(WasiError::ECONNRESET);
-    pub const EDEADLK: Self = Error::Wasi(WasiError::EDEADLK);
-    pub const EDESTADDRREQ: Self = Error::Wasi(WasiError::EDESTADDRREQ);
-    pub const EDOM: Self = Error::Wasi(WasiError::EDOM);
-    pub const EDQUOT: Self = Error::Wasi(WasiError::EDQUOT);
-    pub const EEXIST: Self = Error::Wasi(WasiError::EEXIST);
-    pub const EFAULT: Self = Error::Wasi(WasiError::EFAULT);
-    pub const EFBIG: Self = Error::Wasi(WasiError::EFBIG);
-    pub const EHOSTUNREACH: Self = Error::Wasi(WasiError::EHOSTUNREACH);
-    pub const EIDRM: Self = Error::Wasi(WasiError::EIDRM);
-    pub const EILSEQ: Self = Error::Wasi(WasiError::EILSEQ);
-    pub const EINPROGRESS: Self = Error::Wasi(WasiError::EINPROGRESS);
-    pub const EINTR: Self = Error::Wasi(WasiError::EINTR);
-    pub const EINVAL: Self = Error::Wasi(WasiError::EINVAL);
-    pub const EIO: Self = Error::Wasi(WasiError::EIO);
-    pub const EISCONN: Self = Error::Wasi(WasiError::EISCONN);
-    pub const EISDIR: Self = Error::Wasi(WasiError::EISDIR);
-    pub const ELOOP: Self = Error::Wasi(WasiError::ELOOP);
-    pub const EMFILE: Self = Error::Wasi(WasiError::EMFILE);
-    pub const EMLINK: Self = Error::Wasi(WasiError::EMLINK);
-    pub const EMSGSIZE: Self = Error::Wasi(WasiError::EMSGSIZE);
-    pub const EMULTIHOP: Self = Error::Wasi(WasiError::EMULTIHOP);
-    pub const ENAMETOOLONG: Self = Error::Wasi(WasiError::ENAMETOOLONG);
-    pub const ENETDOWN: Self = Error::Wasi(WasiError::ENETDOWN);
-    pub const ENETRESET: Self = Error::Wasi(WasiError::ENETRESET);
-    pub const ENETUNREACH: Self = Error::Wasi(WasiError::ENETUNREACH);
-    pub const ENFILE: Self = Error::Wasi(WasiError::ENFILE);
-    pub const ENOBUFS: Self = Error::Wasi(WasiError::ENOBUFS);
-    pub const ENODEV: Self = Error::Wasi(WasiError::ENODEV);
-    pub const ENOENT: Self = Error::Wasi(WasiError::ENOENT);
-    pub const ENOEXEC: Self = Error::Wasi(WasiError::ENOEXEC);
-    pub const ENOLCK: Self = Error::Wasi(WasiError::ENOLCK);
-    pub const ENOLINK: Self = Error::Wasi(WasiError::ENOLINK);
-    pub const ENOMEM: Self = Error::Wasi(WasiError::ENOMEM);
-    pub const ENOMSG: Self = Error::Wasi(WasiError::ENOMSG);
-    pub const ENOPROTOOPT: Self = Error::Wasi(WasiError::ENOPROTOOPT);
-    pub const ENOSPC: Self = Error::Wasi(WasiError::ENOSPC);
-    pub const ENOSYS: Self = Error::Wasi(WasiError::ENOSYS);
-    pub const ENOTCONN: Self = Error::Wasi(WasiError::ENOTCONN);
-    pub const ENOTDIR: Self = Error::Wasi(WasiError::ENOTDIR);
-    pub const ENOTEMPTY: Self = Error::Wasi(WasiError::ENOTEMPTY);
-    pub const ENOTRECOVERABLE: Self = Error::Wasi(WasiError::ENOTRECOVERABLE);
-    pub const ENOTSOCK: Self = Error::Wasi(WasiError::ENOTSOCK);
-    pub const ENOTSUP: Self = Error::Wasi(WasiError::ENOTSUP);
-    pub const ENOTTY: Self = Error::Wasi(WasiError::ENOTTY);
-    pub const ENXIO: Self = Error::Wasi(WasiError::ENXIO);
-    pub const EOVERFLOW: Self = Error::Wasi(WasiError::EOVERFLOW);
-    pub const EOWNERDEAD: Self = Error::Wasi(WasiError::EOWNERDEAD);
-    pub const EPERM: Self = Error::Wasi(WasiError::EPERM);
-    pub const EPIPE: Self = Error::Wasi(WasiError::EPIPE);
-    pub const EPROTO: Self = Error::Wasi(WasiError::EPROTO);
-    pub const EPROTONOSUPPORT: Self = Error::Wasi(WasiError::EPROTONOSUPPORT);
-    pub const EPROTOTYPE: Self = Error::Wasi(WasiError::EPROTOTYPE);
-    pub const ERANGE: Self = Error::Wasi(WasiError::ERANGE);
-    pub const EROFS: Self = Error::Wasi(WasiError::EROFS);
-    pub const ESPIPE: Self = Error::Wasi(WasiError::ESPIPE);
-    pub const ESRCH: Self = Error::Wasi(WasiError::ESRCH);
-    pub const ESTALE: Self = Error::Wasi(WasiError::ESTALE);
-    pub const ETIMEDOUT: Self = Error::Wasi(WasiError::ETIMEDOUT);
-    pub const ETXTBSY: Self = Error::Wasi(WasiError::ETXTBSY);
-    pub const EXDEV: Self = Error::Wasi(WasiError::EXDEV);
-    pub const ENOTCAPABLE: Self = Error::Wasi(WasiError::ENOTCAPABLE);
-}
-
-pub(crate) trait FromRawOsError {
-    fn from_raw_os_error(code: i32) -> Self;
-}
-
-pub(crate) type Result<T> = std::result::Result<T, Error>;
-
-pub(crate) trait AsWasiError {
-    fn as_wasi_error(&self) -> WasiError;
-}
-
-impl<T> AsWasiError for Result<T> {
-    fn as_wasi_error(&self) -> WasiError {
-        self.as_ref()
-            .err()
-            .unwrap_or(&Error::ESUCCESS)
-            .as_wasi_error()
-    }
-}
diff --git a/crates/wasi-common/src/fdentry.rs b/crates/wasi-common/src/fdentry.rs
index c2c9a719da..56ab57e5e7 100644
--- a/crates/wasi-common/src/fdentry.rs
+++ b/crates/wasi-common/src/fdentry.rs
@@ -3,7 +3,7 @@ use crate::sys::fdentry_impl::{
     descriptor_as_oshandle, determine_type_and_access_rights, OsHandle,
 };
 use crate::virtfs::VirtualFile;
-use crate::{wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
 use std::marker::PhantomData;
 use std::mem::ManuallyDrop;
 use std::ops::{Deref, DerefMut};
@@ -56,22 +56,22 @@ impl Descriptor {
     /// Return a reference to the `OsHandle` or `VirtualFile` treating it as an
     /// actual file/dir, and allowing operations which require an actual file and
     /// not just a stream or socket file descriptor.
-    pub(crate) fn as_file<'descriptor>(&'descriptor self) -> Result<&'descriptor Descriptor> {
+    pub(crate) fn as_file<'descriptor>(&'descriptor self) -> WasiResult<&'descriptor Descriptor> {
         match self {
             Self::OsHandle(_) => Ok(self),
             Self::VirtualFile(_) => Ok(self),
-            _ => Err(Error::EBADF),
+            _ => Err(WasiError::EBADF),
         }
     }
 
     /// Like `as_file`, but return a mutable reference.
     pub(crate) fn as_file_mut<'descriptor>(
         &'descriptor mut self,
-    ) -> Result<&'descriptor mut Descriptor> {
+    ) -> WasiResult<&'descriptor mut Descriptor> {
         match self {
             Self::OsHandle(_) => Ok(self),
             Self::VirtualFile(_) => Ok(self),
-            _ => Err(Error::EBADF),
+            _ => Err(WasiError::EBADF),
         }
     }
 
@@ -100,7 +100,7 @@ pub(crate) struct FdEntry {
 }
 
 impl FdEntry {
-    pub(crate) fn from(file: Descriptor) -> Result<Self> {
+    pub(crate) fn from(file: Descriptor) -> io::Result<Self> {
         match file {
             Descriptor::OsHandle(handle) => unsafe { determine_type_and_access_rights(&handle) }
                 .map(|(file_type, rights_base, rights_inheriting)| Self {
@@ -129,7 +129,7 @@ impl FdEntry {
         }
     }
 
-    pub(crate) fn duplicate_stdin() -> Result<Self> {
+    pub(crate) fn duplicate_stdin() -> io::Result<Self> {
         unsafe { determine_type_and_access_rights(&io::stdin()) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 file_type,
@@ -141,7 +141,7 @@ impl FdEntry {
         )
     }
 
-    pub(crate) fn duplicate_stdout() -> Result<Self> {
+    pub(crate) fn duplicate_stdout() -> io::Result<Self> {
         unsafe { determine_type_and_access_rights(&io::stdout()) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 file_type,
@@ -153,7 +153,7 @@ impl FdEntry {
         )
     }
 
-    pub(crate) fn duplicate_stderr() -> Result<Self> {
+    pub(crate) fn duplicate_stderr() -> io::Result<Self> {
         unsafe { determine_type_and_access_rights(&io::stderr()) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 file_type,
@@ -165,7 +165,7 @@ impl FdEntry {
         )
     }
 
-    pub(crate) fn null() -> Result<Self> {
+    pub(crate) fn null() -> io::Result<Self> {
         Self::from(OsHandle::from(dev_null()?).into())
     }
 
@@ -175,12 +175,12 @@ impl FdEntry {
     /// The `FdEntry` can only be converted into a valid `Descriptor` object if
     /// the specified set of base rights `rights_base`, and inheriting rights `rights_inheriting`
     /// is a subset of rights attached to this `FdEntry`. The check is performed using
-    /// `FdEntry::validate_rights` method. If the check fails, `Error::ENOTCAPABLE` is returned.
+    /// `FdEntry::validate_rights` method. If the check fails, `WasiError::ENOTCAPABLE` is returned.
     pub(crate) fn as_descriptor(
         &self,
         rights_base: wasi::__wasi_rights_t,
         rights_inheriting: wasi::__wasi_rights_t,
-    ) -> Result<&Descriptor> {
+    ) -> WasiResult<&Descriptor> {
         self.validate_rights(rights_base, rights_inheriting)?;
         Ok(&self.descriptor)
     }
@@ -191,12 +191,12 @@ impl FdEntry {
     /// The `FdEntry` can only be converted into a valid `Descriptor` object if
     /// the specified set of base rights `rights_base`, and inheriting rights `rights_inheriting`
     /// is a subset of rights attached to this `FdEntry`. The check is performed using
-    /// `FdEntry::validate_rights` method. If the check fails, `Error::ENOTCAPABLE` is returned.
+    /// `FdEntry::validate_rights` method. If the check fails, `WasiError::ENOTCAPABLE` is returned.
     pub(crate) fn as_descriptor_mut(
         &mut self,
         rights_base: wasi::__wasi_rights_t,
         rights_inheriting: wasi::__wasi_rights_t,
-    ) -> Result<&mut Descriptor> {
+    ) -> WasiResult<&mut Descriptor> {
         self.validate_rights(rights_base, rights_inheriting)?;
         Ok(&mut self.descriptor)
     }
@@ -205,12 +205,12 @@ impl FdEntry {
     /// inheriting rights `rights_inheriting`; i.e., if rights attached to this `FdEntry` object
     /// are a superset.
     ///
-    /// Upon unsuccessful check, `Error::ENOTCAPABLE` is returned.
+    /// Upon unsuccessful check, `WasiError::ENOTCAPABLE` is returned.
     fn validate_rights(
         &self,
         rights_base: wasi::__wasi_rights_t,
         rights_inheriting: wasi::__wasi_rights_t,
-    ) -> Result<()> {
+    ) -> WasiResult<()> {
         let missing_base = !self.rights_base & rights_base;
         let missing_inheriting = !self.rights_inheriting & rights_inheriting;
         if missing_base != 0 || missing_inheriting != 0 {
@@ -226,7 +226,7 @@ impl FdEntry {
                 missing_base,
                 missing_inheriting
             );
-            Err(Error::ENOTCAPABLE)
+            Err(WasiError::ENOTCAPABLE)
         } else {
             Ok(())
         }
diff --git a/crates/wasi-common/src/fs/file.rs b/crates/wasi-common/src/fs/file.rs
index f87c6acfb9..d8b0dbf717 100644
--- a/crates/wasi-common/src/fs/file.rs
+++ b/crates/wasi-common/src/fs/file.rs
@@ -1,5 +1,6 @@
 use crate::fs::Metadata;
-use crate::{host, hostcalls, hostcalls_impl, wasi, Result, WasiCtx};
+use crate::wasi::{self, WasiResult};
+use crate::{host, hostcalls, hostcalls_impl, WasiCtx};
 use std::io;
 
 /// A reference to an open file on the filesystem.
@@ -34,7 +35,7 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::sync_all`].
     ///
     /// [`std::fs::File::sync_all`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.sync_all
-    pub fn sync_all(&self) -> Result<()> {
+    pub fn sync_all(&self) -> WasiResult<()> {
         unsafe {
             hostcalls_impl::fd_sync(self.ctx, &mut [], self.fd)?;
         }
@@ -47,7 +48,7 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::sync_data`].
     ///
     /// [`std::fs::File::sync_data`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.sync_data
-    pub fn sync_data(&self) -> Result<()> {
+    pub fn sync_data(&self) -> WasiResult<()> {
         unsafe {
             hostcalls_impl::fd_datasync(self.ctx, &mut [], self.fd)?;
         }
@@ -60,7 +61,7 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::set_len`].
     ///
     /// [`std::fs::File::set_len`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.set_len
-    pub fn set_len(&self, size: u64) -> Result<()> {
+    pub fn set_len(&self, size: u64) -> WasiResult<()> {
         unsafe {
             hostcalls_impl::fd_filestat_set_size(self.ctx, &mut [], self.fd, size)?;
         }
@@ -72,7 +73,7 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::metadata`].
     ///
     /// [`std::fs::File::metadata`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.metadata
-    pub fn metadata(&self) -> Result<Metadata> {
+    pub fn metadata(&self) -> WasiResult<Metadata> {
         Ok(Metadata {})
     }
 }
diff --git a/crates/wasi-common/src/helpers.rs b/crates/wasi-common/src/helpers.rs
index f176b8d1fe..4fb365882b 100644
--- a/crates/wasi-common/src/helpers.rs
+++ b/crates/wasi-common/src/helpers.rs
@@ -1,10 +1,11 @@
-use crate::{Error, Result};
+use crate::wasi::WasiResult;
 use std::str;
 
 /// Creates not-owned WASI path from byte slice.
 ///
 /// NB WASI spec requires bytes to be valid UTF-8. Otherwise,
 /// `__WASI_ERRNO_ILSEQ` error is returned.
-pub(crate) fn path_from_slice<'a>(s: &'a [u8]) -> Result<&'a str> {
-    str::from_utf8(s).map_err(|_| Error::EILSEQ)
+pub(crate) fn path_from_slice<'a>(s: &'a [u8]) -> WasiResult<&'a str> {
+    let s = str::from_utf8(s)?;
+    Ok(s)
 }
diff --git a/crates/wasi-common/src/host.rs b/crates/wasi-common/src/host.rs
index 47221e2763..56598b17a2 100644
--- a/crates/wasi-common/src/host.rs
+++ b/crates/wasi-common/src/host.rs
@@ -5,7 +5,6 @@
 #![allow(non_snake_case)]
 
 use crate::wasi::*;
-use crate::{Error, Result};
 use std::{convert::TryInto, io, mem, slice};
 use wig::witx_host_types;
 
@@ -67,11 +66,13 @@ pub struct Dirent {
 impl Dirent {
     /// Serialize the directory entry to the format define by `__wasi_fd_readdir`,
     /// so that the serialized entries can be concatenated by the implementation.
-    pub fn to_wasi_raw(&self) -> Result<Vec<u8>> {
+    pub fn to_wasi_raw(&self) -> WasiResult<Vec<u8>> {
         let name = self.name.as_bytes();
         let namlen = name.len();
         let dirent_size = mem::size_of::<__wasi_dirent_t>();
-        let offset = dirent_size.checked_add(namlen).ok_or(Error::EOVERFLOW)?;
+        let offset = dirent_size
+            .checked_add(namlen)
+            .ok_or(WasiError::EOVERFLOW)?;
 
         let mut raw = Vec::<u8>::with_capacity(offset);
         raw.resize(offset, 0);
diff --git a/crates/wasi-common/src/hostcalls_impl/fs.rs b/crates/wasi-common/src/hostcalls_impl/fs.rs
index e10009242e..a9706d741b 100644
--- a/crates/wasi-common/src/hostcalls_impl/fs.rs
+++ b/crates/wasi-common/src/hostcalls_impl/fs.rs
@@ -8,7 +8,8 @@ use crate::memory::*;
 use crate::sandboxed_tty_writer::SandboxedTTYWriter;
 use crate::sys::hostcalls_impl::fs_helpers::path_open_rights;
 use crate::sys::{host_impl, hostcalls_impl};
-use crate::{helpers, host, wasi, wasi32, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
+use crate::{helpers, host, wasi32};
 use filetime::{set_file_handle_times, FileTime};
 use log::trace;
 use std::convert::TryInto;
@@ -20,13 +21,13 @@ pub(crate) unsafe fn fd_close(
     wasi_ctx: &mut WasiCtx,
     _memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_close(fd={:?})", fd);
 
     if let Ok(fe) = wasi_ctx.get_fd_entry(fd) {
         // can't close preopened files
         if fe.preopen_path.is_some() {
-            return Err(Error::ENOTSUP);
+            return Err(WasiError::ENOTSUP);
         }
     }
 
@@ -38,7 +39,7 @@ pub(crate) unsafe fn fd_datasync(
     wasi_ctx: &WasiCtx,
     _memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_datasync(fd={:?})", fd);
 
     let file = wasi_ctx
@@ -60,7 +61,7 @@ pub(crate) unsafe fn fd_pread(
     iovs_len: wasi32::size_t,
     offset: wasi::__wasi_filesize_t,
     nread: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_pread(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, offset={}, nread={:#x?})",
         fd,
@@ -78,7 +79,7 @@ pub(crate) unsafe fn fd_pread(
     let iovs = dec_iovec_slice(memory, iovs_ptr, iovs_len)?;
 
     if offset > i64::max_value() as u64 {
-        return Err(Error::EIO);
+        return Err(WasiError::EIO);
     }
     let buf_size = iovs
         .iter()
@@ -90,7 +91,7 @@ pub(crate) unsafe fn fd_pread(
             cast_iovlen
         })
         .fold(Some(0u32), |len, iov| len.and_then(|x| x.checked_add(iov)))
-        .ok_or(Error::EINVAL)?;
+        .ok_or(WasiError::EINVAL)?;
     let mut buf = vec![0; buf_size as usize];
     let host_nread = match file {
         Descriptor::OsHandle(fd) => hostcalls_impl::fd_pread(&fd, &mut buf, offset)?,
@@ -128,7 +129,7 @@ pub(crate) unsafe fn fd_pwrite(
     iovs_len: wasi32::size_t,
     offset: wasi::__wasi_filesize_t,
     nwritten: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_pwrite(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, offset={}, nwritten={:#x?})",
         fd,
@@ -148,7 +149,7 @@ pub(crate) unsafe fn fd_pwrite(
     let iovs = dec_ciovec_slice(memory, iovs_ptr, iovs_len)?;
 
     if offset > i64::max_value() as u64 {
-        return Err(Error::EIO);
+        return Err(WasiError::EIO);
     }
     let buf_size = iovs
         .iter()
@@ -160,7 +161,7 @@ pub(crate) unsafe fn fd_pwrite(
             cast_iovlen
         })
         .fold(Some(0u32), |len, iov| len.and_then(|x| x.checked_add(iov)))
-        .ok_or(Error::EINVAL)?;
+        .ok_or(WasiError::EINVAL)?;
     let mut buf = Vec::with_capacity(buf_size as usize);
     for iov in &iovs {
         buf.extend_from_slice(std::slice::from_raw_parts(
@@ -190,7 +191,7 @@ pub(crate) unsafe fn fd_read(
     iovs_ptr: wasi32::uintptr_t,
     iovs_len: wasi32::size_t,
     nread: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_read(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, nread={:#x?})",
         fd,
@@ -212,7 +213,7 @@ pub(crate) unsafe fn fd_read(
         Descriptor::OsHandle(file) => file.read_vectored(&mut iovs).map_err(Into::into),
         Descriptor::VirtualFile(virt) => virt.read_vectored(&mut iovs),
         Descriptor::Stdin => io::stdin().read_vectored(&mut iovs).map_err(Into::into),
-        _ => return Err(Error::EBADF),
+        _ => return Err(WasiError::EBADF),
     };
 
     let host_nread = maybe_host_nread?;
@@ -227,11 +228,11 @@ pub(crate) unsafe fn fd_renumber(
     _memory: &mut [u8],
     from: wasi::__wasi_fd_t,
     to: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_renumber(from={:?}, to={:?})", from, to);
 
     if !wasi_ctx.contains_fd_entry(from) {
-        return Err(Error::EBADF);
+        return Err(WasiError::EBADF);
     }
 
     // Don't allow renumbering over a pre-opened resource.
@@ -239,11 +240,11 @@ pub(crate) unsafe fn fd_renumber(
     // userspace is capable of removing entries from its tables as well.
     let from_fe = wasi_ctx.get_fd_entry(from)?;
     if from_fe.preopen_path.is_some() {
-        return Err(Error::ENOTSUP);
+        return Err(WasiError::ENOTSUP);
     }
     if let Ok(to_fe) = wasi_ctx.get_fd_entry(to) {
         if to_fe.preopen_path.is_some() {
-            return Err(Error::ENOTSUP);
+            return Err(WasiError::ENOTSUP);
         }
     }
 
@@ -260,7 +261,7 @@ pub(crate) unsafe fn fd_seek(
     offset: wasi::__wasi_filedelta_t,
     whence: wasi::__wasi_whence_t,
     newoffset: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_seek(fd={:?}, offset={:?}, whence={}, newoffset={:#x?})",
         fd,
@@ -283,7 +284,7 @@ pub(crate) unsafe fn fd_seek(
         wasi::__WASI_WHENCE_CUR => SeekFrom::Current(offset),
         wasi::__WASI_WHENCE_END => SeekFrom::End(offset),
         wasi::__WASI_WHENCE_SET => SeekFrom::Start(offset as u64),
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     };
     let host_newoffset = match file {
         Descriptor::OsHandle(fd) => fd.seek(pos)?,
@@ -305,7 +306,7 @@ pub(crate) unsafe fn fd_tell(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     newoffset: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_tell(fd={:?}, newoffset={:#x?})", fd, newoffset);
 
     let file = wasi_ctx
@@ -333,7 +334,7 @@ pub(crate) unsafe fn fd_fdstat_get(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     fdstat_ptr: wasi32::uintptr_t, // *mut wasi::__wasi_fdstat_t
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_fdstat_get(fd={:?}, fdstat_ptr={:#x?})", fd, fdstat_ptr);
 
     let mut fdstat = dec_fdstat_byref(memory, fdstat_ptr)?;
@@ -361,7 +362,7 @@ pub(crate) unsafe fn fd_fdstat_set_flags(
     _memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     fdflags: wasi::__wasi_fdflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_fdstat_set_flags(fd={:?}, fdflags={:#x?})", fd, fdflags);
 
     let descriptor = wasi_ctx
@@ -400,7 +401,7 @@ pub(crate) unsafe fn fd_fdstat_set_rights(
     fd: wasi::__wasi_fd_t,
     fs_rights_base: wasi::__wasi_rights_t,
     fs_rights_inheriting: wasi::__wasi_rights_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_fdstat_set_rights(fd={:?}, fs_rights_base={:#x?}, fs_rights_inheriting={:#x?})",
         fd,
@@ -412,7 +413,7 @@ pub(crate) unsafe fn fd_fdstat_set_rights(
     if fe.rights_base & fs_rights_base != fs_rights_base
         || fe.rights_inheriting & fs_rights_inheriting != fs_rights_inheriting
     {
-        return Err(Error::ENOTCAPABLE);
+        return Err(WasiError::ENOTCAPABLE);
     }
     fe.rights_base = fs_rights_base;
     fe.rights_inheriting = fs_rights_inheriting;
@@ -424,7 +425,7 @@ pub(crate) unsafe fn fd_sync(
     wasi_ctx: &WasiCtx,
     _memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_sync(fd={:?})", fd);
 
     let file = wasi_ctx
@@ -449,7 +450,7 @@ pub(crate) unsafe fn fd_write(
     iovs_ptr: wasi32::uintptr_t,
     iovs_len: wasi32::size_t,
     nwritten: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_write(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, nwritten={:#x?})",
         fd,
@@ -480,7 +481,7 @@ pub(crate) unsafe fn fd_write(
                 virt.write_vectored(&iovs)?
             }
         }
-        Descriptor::Stdin => return Err(Error::EBADF),
+        Descriptor::Stdin => return Err(WasiError::EBADF),
         Descriptor::Stdout => {
             // lock for the duration of the scope
             let stdout = io::stdout();
@@ -512,7 +513,7 @@ pub(crate) unsafe fn fd_advise(
     offset: wasi::__wasi_filesize_t,
     len: wasi::__wasi_filesize_t,
     advice: wasi::__wasi_advice_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_advise(fd={:?}, offset={}, len={}, advice={:?})",
         fd,
@@ -543,7 +544,7 @@ pub(crate) unsafe fn fd_allocate(
     fd: wasi::__wasi_fd_t,
     offset: wasi::__wasi_filesize_t,
     len: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_allocate(fd={:?}, offset={}, len={})", fd, offset, len);
 
     let file = wasi_ctx
@@ -556,10 +557,10 @@ pub(crate) unsafe fn fd_allocate(
             let metadata = fd.metadata()?;
 
             let current_size = metadata.len();
-            let wanted_size = offset.checked_add(len).ok_or(Error::E2BIG)?;
+            let wanted_size = offset.checked_add(len).ok_or(WasiError::E2BIG)?;
             // This check will be unnecessary when rust-lang/rust#63326 is fixed
             if wanted_size > i64::max_value() as u64 {
-                return Err(Error::E2BIG);
+                return Err(WasiError::E2BIG);
             }
 
             if wanted_size > current_size {
@@ -583,7 +584,7 @@ pub(crate) unsafe fn path_create_directory(
     dirfd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_create_directory(dirfd={:?}, path_ptr={:#x?}, path_len={})",
         dirfd,
@@ -612,7 +613,7 @@ pub(crate) unsafe fn path_link(
     new_dirfd: wasi::__wasi_fd_t,
     new_path_ptr: wasi32::uintptr_t,
     new_path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_link(old_dirfd={:?}, old_flags={:?}, old_path_ptr={:#x?}, old_path_len={}, new_dirfd={:?}, new_path_ptr={:#x?}, new_path_len={})",
         old_dirfd,
@@ -664,7 +665,7 @@ pub(crate) unsafe fn path_open(
     fs_rights_inheriting: wasi::__wasi_rights_t,
     fs_flags: wasi::__wasi_fdflags_t,
     fd_out_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_open(dirfd={:?}, dirflags={:?}, path_ptr={:#x?}, path_len={:?}, oflags={:#x?}, fs_rights_base={:#x?}, fs_rights_inheriting={:#x?}, fs_flags={:#x?}, fd_out_ptr={:#x?})",
         dirfd,
@@ -739,7 +740,7 @@ pub(crate) unsafe fn path_readlink(
     buf_ptr: wasi32::uintptr_t,
     buf_len: wasi32::size_t,
     buf_used: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_readlink(dirfd={:?}, path_ptr={:#x?}, path_len={:?}, buf_ptr={:#x?}, buf_len={}, buf_used={:#x?})",
         dirfd,
@@ -783,7 +784,7 @@ pub(crate) unsafe fn path_rename(
     new_dirfd: wasi::__wasi_fd_t,
     new_path_ptr: wasi32::uintptr_t,
     new_path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_rename(old_dirfd={:?}, old_path_ptr={:#x?}, old_path_len={:?}, new_dirfd={:?}, new_path_ptr={:#x?}, new_path_len={:?})",
         old_dirfd,
@@ -838,7 +839,7 @@ pub(crate) unsafe fn fd_filestat_get(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     filestat_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_filestat_get(fd={:?}, filestat_ptr={:#x?})",
         fd,
@@ -871,7 +872,7 @@ pub(crate) unsafe fn fd_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_filestat_set_times(fd={:?}, st_atim={}, st_mtim={}, fst_flags={:#x?})",
         fd,
@@ -893,14 +894,14 @@ pub(crate) fn fd_filestat_set_times_impl(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let set_atim = fst_flags & wasi::__WASI_FSTFLAGS_ATIM != 0;
     let set_atim_now = fst_flags & wasi::__WASI_FSTFLAGS_ATIM_NOW != 0;
     let set_mtim = fst_flags & wasi::__WASI_FSTFLAGS_MTIM != 0;
     let set_mtim_now = fst_flags & wasi::__WASI_FSTFLAGS_MTIM_NOW != 0;
 
     if (set_atim && set_atim_now) || (set_mtim && set_mtim_now) {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
     let atim = if set_atim {
         let time = UNIX_EPOCH + Duration::from_nanos(st_atim);
@@ -937,7 +938,7 @@ pub(crate) unsafe fn fd_filestat_set_size(
     _memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     st_size: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_filestat_set_size(fd={:?}, st_size={})", fd, st_size);
 
     let file = wasi_ctx
@@ -947,7 +948,7 @@ pub(crate) unsafe fn fd_filestat_set_size(
 
     // This check will be unnecessary when rust-lang/rust#63326 is fixed
     if st_size > i64::max_value() as u64 {
-        return Err(Error::E2BIG);
+        return Err(WasiError::E2BIG);
     }
     match file {
         Descriptor::OsHandle(fd) => fd.set_len(st_size).map_err(Into::into),
@@ -968,7 +969,7 @@ pub(crate) unsafe fn path_filestat_get(
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
     filestat_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_filestat_get(dirfd={:?}, dirflags={:?}, path_ptr={:#x?}, path_len={}, filestat_ptr={:#x?})",
         dirfd,
@@ -1013,7 +1014,7 @@ pub(crate) unsafe fn path_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_filestat_set_times(dirfd={:?}, dirflags={:?}, path_ptr={:#x?}, path_len={}, st_atim={}, st_mtim={}, fst_flags={:#x?})",
         dirfd,
@@ -1056,7 +1057,7 @@ pub(crate) unsafe fn path_symlink(
     dirfd: wasi::__wasi_fd_t,
     new_path_ptr: wasi32::uintptr_t,
     new_path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_symlink(old_path_ptr={:#x?}, old_path_len={}, dirfd={:?}, new_path_ptr={:#x?}, new_path_len={})",
         old_path_ptr,
@@ -1089,7 +1090,7 @@ pub(crate) unsafe fn path_unlink_file(
     dirfd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_unlink_file(dirfd={:?}, path_ptr={:#x?}, path_len={})",
         dirfd,
@@ -1116,7 +1117,7 @@ pub(crate) unsafe fn path_remove_directory(
     dirfd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_remove_directory(dirfd={:?}, path_ptr={:#x?}, path_len={})",
         dirfd,
@@ -1151,7 +1152,7 @@ pub(crate) unsafe fn fd_prestat_get(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     prestat_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_prestat_get(fd={:?}, prestat_ptr={:#x?})",
         fd,
@@ -1160,9 +1161,9 @@ pub(crate) unsafe fn fd_prestat_get(
 
     // TODO: should we validate any rights here?
     let fe = wasi_ctx.get_fd_entry(fd)?;
-    let po_path = fe.preopen_path.as_ref().ok_or(Error::ENOTSUP)?;
+    let po_path = fe.preopen_path.as_ref().ok_or(WasiError::ENOTSUP)?;
     if fe.file_type != wasi::__WASI_FILETYPE_DIRECTORY {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     let path = host_impl::path_from_host(po_path.as_os_str())?;
@@ -1187,7 +1188,7 @@ pub(crate) unsafe fn fd_prestat_dir_name(
     fd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_prestat_dir_name(fd={:?}, path_ptr={:#x?}, path_len={})",
         fd,
@@ -1197,15 +1198,15 @@ pub(crate) unsafe fn fd_prestat_dir_name(
 
     // TODO: should we validate any rights here?
     let fe = wasi_ctx.get_fd_entry(fd)?;
-    let po_path = fe.preopen_path.as_ref().ok_or(Error::ENOTSUP)?;
+    let po_path = fe.preopen_path.as_ref().ok_or(WasiError::ENOTSUP)?;
     if fe.file_type != wasi::__WASI_FILETYPE_DIRECTORY {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     let path = host_impl::path_from_host(po_path.as_os_str())?;
 
     if path.len() > dec_usize(path_len) {
-        return Err(Error::ENAMETOOLONG);
+        return Err(WasiError::ENAMETOOLONG);
     }
 
     trace!("     | (path_ptr,path_len)='{}'", path);
@@ -1221,7 +1222,7 @@ pub(crate) unsafe fn fd_readdir(
     buf_len: wasi32::size_t,
     cookie: wasi::__wasi_dircookie_t,
     buf_used: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_readdir(fd={:?}, buf={:#x?}, buf_len={}, cookie={:#x?}, buf_used={:#x?})",
         fd,
@@ -1241,10 +1242,10 @@ pub(crate) unsafe fn fd_readdir(
 
     trace!("     | (buf,buf_len)={:?}", host_buf);
 
-    fn copy_entities<T: Iterator<Item = Result<Dirent>>>(
+    fn copy_entities<T: Iterator<Item = WasiResult<Dirent>>>(
         iter: T,
         mut host_buf: &mut [u8],
-    ) -> Result<usize> {
+    ) -> WasiResult<usize> {
         let mut host_bufused = 0;
         for dirent in iter {
             let dirent_raw = dirent?.to_wasi_raw()?;
diff --git a/crates/wasi-common/src/hostcalls_impl/fs_helpers.rs b/crates/wasi-common/src/hostcalls_impl/fs_helpers.rs
index 0a72552e27..b1a8e555a2 100644
--- a/crates/wasi-common/src/hostcalls_impl/fs_helpers.rs
+++ b/crates/wasi-common/src/hostcalls_impl/fs_helpers.rs
@@ -2,7 +2,8 @@
 use crate::sys::fdentry_impl::OsHandle;
 use crate::sys::host_impl;
 use crate::sys::hostcalls_impl::fs_helpers::*;
-use crate::{error::WasiError, fdentry::Descriptor, fdentry::FdEntry, wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
+use crate::{fdentry::Descriptor, fdentry::FdEntry};
 use std::path::{Component, Path};
 
 #[derive(Debug)]
@@ -20,7 +21,7 @@ impl PathGet {
         &self.path
     }
 
-    pub(crate) fn path_create_directory(self) -> Result<()> {
+    pub(crate) fn path_create_directory(self) -> WasiResult<()> {
         match &self.dirfd {
             Descriptor::OsHandle(file) => {
                 crate::sys::hostcalls_impl::path_create_directory(&file, &self.path)
@@ -38,7 +39,7 @@ impl PathGet {
         write: bool,
         oflags: u16,
         fs_flags: u16,
-    ) -> Result<Descriptor> {
+    ) -> WasiResult<Descriptor> {
         match &self.dirfd {
             Descriptor::OsHandle(_) => {
                 crate::sys::hostcalls_impl::path_open(self, read, write, oflags, fs_flags)
@@ -64,7 +65,7 @@ impl<'a, 'b> PathRef<'a, 'b> {
         PathRef { dirfd, path }
     }
 
-    fn open(&self) -> Result<Descriptor> {
+    fn open(&self) -> WasiResult<Descriptor> {
         match self.dirfd {
             Descriptor::OsHandle(file) => Ok(Descriptor::OsHandle(OsHandle::from(openat(
                 &file, &self.path,
@@ -84,7 +85,7 @@ impl<'a, 'b> PathRef<'a, 'b> {
         }
     }
 
-    fn readlink(&self) -> Result<String> {
+    fn readlink(&self) -> WasiResult<String> {
         match self.dirfd {
             Descriptor::OsHandle(file) => readlinkat(file, self.path),
             Descriptor::VirtualFile(virt) => {
@@ -107,17 +108,17 @@ pub(crate) fn path_get(
     dirflags: wasi::__wasi_lookupflags_t,
     path: &str,
     needs_final_component: bool,
-) -> Result<PathGet> {
+) -> WasiResult<PathGet> {
     const MAX_SYMLINK_EXPANSIONS: usize = 128;
 
     if path.contains('\0') {
         // if contains NUL, return EILSEQ
-        return Err(Error::EILSEQ);
+        return Err(WasiError::EILSEQ);
     }
 
     if fe.file_type != wasi::__WASI_FILETYPE_DIRECTORY {
         // if `dirfd` doesn't refer to a directory, return `ENOTDIR`.
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     let dirfd = fe
@@ -148,7 +149,7 @@ pub(crate) fn path_get(
                 let ends_with_slash = cur_path.ends_with('/');
                 let mut components = Path::new(&cur_path).components();
                 let head = match components.next() {
-                    None => return Err(Error::ENOENT),
+                    None => return Err(WasiError::ENOENT),
                     Some(p) => p,
                 };
                 let tail = components.as_path();
@@ -166,18 +167,18 @@ pub(crate) fn path_get(
                 match head {
                     Component::Prefix(_) | Component::RootDir => {
                         // path is absolute!
-                        return Err(Error::ENOTCAPABLE);
+                        return Err(WasiError::ENOTCAPABLE);
                     }
                     Component::CurDir => {
                         // "." so skip
                     }
                     Component::ParentDir => {
                         // ".." so pop a dir
-                        let _ = dir_stack.pop().ok_or(Error::ENOTCAPABLE)?;
+                        let _ = dir_stack.pop().ok_or(WasiError::ENOTCAPABLE)?;
 
                         // we're not allowed to pop past the original directory
                         if dir_stack.is_empty() {
-                            return Err(Error::ENOTCAPABLE);
+                            return Err(WasiError::ENOTCAPABLE);
                         }
                     }
                     Component::Normal(head) => {
@@ -188,14 +189,17 @@ pub(crate) fn path_get(
                         }
 
                         if !path_stack.is_empty() || (ends_with_slash && !needs_final_component) {
-                            match PathRef::new(dir_stack.last().ok_or(Error::ENOTCAPABLE)?, &head)
-                                .open()
+                            match PathRef::new(
+                                dir_stack.last().ok_or(WasiError::ENOTCAPABLE)?,
+                                &head,
+                            )
+                            .open()
                             {
                                 Ok(new_dir) => {
                                     dir_stack.push(new_dir);
                                 }
                                 Err(e) => {
-                                    match e.as_wasi_error() {
+                                    match e {
                                         WasiError::ELOOP
                                         | WasiError::EMLINK
                                         | WasiError::ENOTDIR =>
@@ -204,14 +208,14 @@ pub(crate) fn path_get(
                                         {
                                             // attempt symlink expansion
                                             let mut link_path = PathRef::new(
-                                                dir_stack.last().ok_or(Error::ENOTCAPABLE)?,
+                                                dir_stack.last().ok_or(WasiError::ENOTCAPABLE)?,
                                                 &head,
                                             )
                                             .readlink()?;
 
                                             symlink_expansions += 1;
                                             if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
-                                                return Err(Error::ELOOP);
+                                                return Err(WasiError::ELOOP);
                                             }
 
                                             if head.ends_with('/') {
@@ -238,13 +242,16 @@ pub(crate) fn path_get(
                         {
                             // if there's a trailing slash, or if `LOOKUP_SYMLINK_FOLLOW` is set, attempt
                             // symlink expansion
-                            match PathRef::new(dir_stack.last().ok_or(Error::ENOTCAPABLE)?, &head)
-                                .readlink()
+                            match PathRef::new(
+                                dir_stack.last().ok_or(WasiError::ENOTCAPABLE)?,
+                                &head,
+                            )
+                            .readlink()
                             {
                                 Ok(mut link_path) => {
                                     symlink_expansions += 1;
                                     if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
-                                        return Err(Error::ELOOP);
+                                        return Err(WasiError::ELOOP);
                                     }
 
                                     if head.ends_with('/') {
@@ -260,12 +267,12 @@ pub(crate) fn path_get(
                                     continue;
                                 }
                                 Err(e) => {
-                                    if e.as_wasi_error() != WasiError::EINVAL
-                                        && e.as_wasi_error() != WasiError::ENOENT
+                                    if e != WasiError::EINVAL
+                                        && e != WasiError::ENOENT
                                         // this handles the cases when trying to link to
                                         // a destination that already exists, and the target
                                         // path contains a slash
-                                        && e.as_wasi_error() != WasiError::ENOTDIR
+                                        && e != WasiError::ENOTDIR
                                     {
                                         return Err(e);
                                     }
@@ -275,7 +282,7 @@ pub(crate) fn path_get(
 
                         // not a symlink, so we're done;
                         return Ok(PathGet {
-                            dirfd: dir_stack.pop().ok_or(Error::ENOTCAPABLE)?,
+                            dirfd: dir_stack.pop().ok_or(WasiError::ENOTCAPABLE)?,
                             path: head,
                         });
                     }
@@ -285,7 +292,7 @@ pub(crate) fn path_get(
                 // no further components to process. means we've hit a case like "." or "a/..", or if the
                 // input path has trailing slashes and `needs_final_component` is not set
                 return Ok(PathGet {
-                    dirfd: dir_stack.pop().ok_or(Error::ENOTCAPABLE)?,
+                    dirfd: dir_stack.pop().ok_or(WasiError::ENOTCAPABLE)?,
                     path: String::from("."),
                 });
             }
diff --git a/crates/wasi-common/src/hostcalls_impl/misc.rs b/crates/wasi-common/src/hostcalls_impl/misc.rs
index ca3225e0a7..456beca24c 100644
--- a/crates/wasi-common/src/hostcalls_impl/misc.rs
+++ b/crates/wasi-common/src/hostcalls_impl/misc.rs
@@ -3,7 +3,8 @@ use crate::ctx::WasiCtx;
 use crate::fdentry::Descriptor;
 use crate::memory::*;
 use crate::sys::hostcalls_impl;
-use crate::{wasi, wasi32, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
+use crate::wasi32;
 use log::{error, trace};
 use std::convert::TryFrom;
 
@@ -12,7 +13,7 @@ pub(crate) fn args_get(
     memory: &mut [u8],
     argv_ptr: wasi32::uintptr_t,
     argv_buf: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "args_get(argv_ptr={:#x?}, argv_buf={:#x?})",
         argv_ptr,
@@ -31,7 +32,9 @@ pub(crate) fn args_get(
         argv.push(arg_ptr);
 
         let len = wasi32::uintptr_t::try_from(arg_bytes.len())?;
-        argv_buf_offset = argv_buf_offset.checked_add(len).ok_or(Error::EOVERFLOW)?;
+        argv_buf_offset = argv_buf_offset
+            .checked_add(len)
+            .ok_or(WasiError::EOVERFLOW)?;
     }
 
     enc_slice_of_wasi32_uintptr(memory, argv.as_slice(), argv_ptr)
@@ -42,7 +45,7 @@ pub(crate) fn args_sizes_get(
     memory: &mut [u8],
     argc_ptr: wasi32::uintptr_t,
     argv_buf_size_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "args_sizes_get(argc_ptr={:#x?}, argv_buf_size_ptr={:#x?})",
         argc_ptr,
@@ -70,7 +73,7 @@ pub(crate) fn environ_get(
     memory: &mut [u8],
     environ_ptr: wasi32::uintptr_t,
     environ_buf: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "environ_get(environ_ptr={:#x?}, environ_buf={:#x?})",
         environ_ptr,
@@ -91,7 +94,7 @@ pub(crate) fn environ_get(
         let len = wasi32::uintptr_t::try_from(env_bytes.len())?;
         environ_buf_offset = environ_buf_offset
             .checked_add(len)
-            .ok_or(Error::EOVERFLOW)?;
+            .ok_or(WasiError::EOVERFLOW)?;
     }
 
     enc_slice_of_wasi32_uintptr(memory, environ.as_slice(), environ_ptr)
@@ -102,7 +105,7 @@ pub(crate) fn environ_sizes_get(
     memory: &mut [u8],
     environ_count_ptr: wasi32::uintptr_t,
     environ_size_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "environ_sizes_get(environ_count_ptr={:#x?}, environ_size_ptr={:#x?})",
         environ_count_ptr,
@@ -116,7 +119,7 @@ pub(crate) fn environ_sizes_get(
         .try_fold(0, |acc: u32, pair| {
             acc.checked_add(pair.as_bytes_with_nul().len() as u32)
         })
-        .ok_or(Error::EOVERFLOW)?;
+        .ok_or(WasiError::EOVERFLOW)?;
 
     trace!("     | *environ_count_ptr={:?}", environ_count);
 
@@ -132,14 +135,14 @@ pub(crate) fn random_get(
     memory: &mut [u8],
     buf_ptr: wasi32::uintptr_t,
     buf_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("random_get(buf_ptr={:#x?}, buf_len={:?})", buf_ptr, buf_len);
 
     let buf = dec_slice_of_mut_u8(memory, buf_ptr, buf_len)?;
 
     getrandom::getrandom(buf).map_err(|err| {
         error!("getrandom failure: {:?}", err);
-        Error::EIO
+        WasiError::EIO
     })
 }
 
@@ -148,7 +151,7 @@ pub(crate) fn clock_res_get(
     memory: &mut [u8],
     clock_id: wasi::__wasi_clockid_t,
     resolution_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "clock_res_get(clock_id={:?}, resolution_ptr={:#x?})",
         clock_id,
@@ -168,7 +171,7 @@ pub(crate) fn clock_time_get(
     clock_id: wasi::__wasi_clockid_t,
     precision: wasi::__wasi_timestamp_t,
     time_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "clock_time_get(clock_id={:?}, precision={:?}, time_ptr={:#x?})",
         clock_id,
@@ -183,7 +186,7 @@ pub(crate) fn clock_time_get(
     enc_timestamp_byref(memory, time_ptr, time)
 }
 
-pub(crate) fn sched_yield(_wasi_ctx: &WasiCtx, _memory: &mut [u8]) -> Result<()> {
+pub(crate) fn sched_yield(_wasi_ctx: &WasiCtx, _memory: &mut [u8]) -> WasiResult<()> {
     trace!("sched_yield()");
 
     std::thread::yield_now();
@@ -198,7 +201,7 @@ pub(crate) fn poll_oneoff(
     output: wasi32::uintptr_t,
     nsubscriptions: wasi32::size_t,
     nevents: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "poll_oneoff(input={:#x?}, output={:#x?}, nsubscriptions={}, nevents={:#x?})",
         input,
@@ -208,7 +211,7 @@ pub(crate) fn poll_oneoff(
     );
 
     if u64::from(nsubscriptions) > wasi::__wasi_filesize_t::max_value() {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     enc_int_byref(memory, nevents, 0)?;
@@ -222,7 +225,7 @@ pub(crate) fn poll_oneoff(
     // As mandated by the WASI spec:
     // > If `nsubscriptions` is 0, returns `errno::inval`.
     if subscriptions.is_empty() {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
     for subscription in subscriptions {
         match subscription.u.tag {
@@ -258,7 +261,7 @@ pub(crate) fn poll_oneoff(
                     Err(err) => {
                         let event = wasi::__wasi_event_t {
                             userdata: subscription.userdata,
-                            error: err.as_wasi_error().as_raw_errno(),
+                            error: err.as_raw_errno(),
                             r#type: wasi::__WASI_EVENTTYPE_FD_READ,
                             fd_readwrite: wasi::__wasi_event_fd_readwrite_t {
                                 nbytes: 0,
@@ -286,7 +289,7 @@ pub(crate) fn poll_oneoff(
                     Err(err) => {
                         let event = wasi::__wasi_event_t {
                             userdata: subscription.userdata,
-                            error: err.as_wasi_error().as_raw_errno(),
+                            error: err.as_raw_errno(),
                             r#type: wasi::__WASI_EVENTTYPE_FD_WRITE,
                             fd_readwrite: wasi::__wasi_event_fd_readwrite_t {
                                 nbytes: 0,
@@ -310,7 +313,7 @@ pub(crate) fn poll_oneoff(
     // events have been filtered out as errors in the code above.
     hostcalls_impl::poll_oneoff(timeout, fd_events, &mut events)?;
 
-    let events_count = u32::try_from(events.len()).map_err(|_| Error::EOVERFLOW)?;
+    let events_count = u32::try_from(events.len()).map_err(|_| WasiError::EOVERFLOW)?;
 
     enc_events(memory, output, nsubscriptions, events)?;
 
@@ -319,7 +322,9 @@ pub(crate) fn poll_oneoff(
     enc_int_byref(memory, nevents, events_count)
 }
 
-fn wasi_clock_to_relative_ns_delay(wasi_clock: wasi::__wasi_subscription_clock_t) -> Result<u128> {
+fn wasi_clock_to_relative_ns_delay(
+    wasi_clock: wasi::__wasi_subscription_clock_t,
+) -> WasiResult<u128> {
     use std::time::SystemTime;
 
     if wasi_clock.flags != wasi::__WASI_SUBCLOCKFLAGS_SUBSCRIPTION_CLOCK_ABSTIME {
@@ -327,7 +332,7 @@ fn wasi_clock_to_relative_ns_delay(wasi_clock: wasi::__wasi_subscription_clock_t
     }
     let now: u128 = SystemTime::now()
         .duration_since(SystemTime::UNIX_EPOCH)
-        .map_err(|_| Error::ENOTCAPABLE)?
+        .map_err(|_| WasiError::ENOTCAPABLE)?
         .as_nanos();
     let deadline = u128::from(wasi_clock.timeout);
     Ok(deadline.saturating_sub(now))
@@ -357,6 +362,6 @@ pub(crate) fn proc_raise(
     _wasi_ctx: &WasiCtx,
     _memory: &mut [u8],
     _sig: wasi::__wasi_signal_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("proc_raise")
 }
diff --git a/crates/wasi-common/src/hostcalls_impl/sock.rs b/crates/wasi-common/src/hostcalls_impl/sock.rs
index 9089e421f9..6e133bb235 100644
--- a/crates/wasi-common/src/hostcalls_impl/sock.rs
+++ b/crates/wasi-common/src/hostcalls_impl/sock.rs
@@ -1,5 +1,6 @@
 use crate::ctx::WasiCtx;
-use crate::{wasi, wasi32, Result};
+use crate::wasi::{self, WasiResult};
+use crate::wasi32;
 
 pub fn sock_recv(
     _wasi_ctx: &WasiCtx,
@@ -10,7 +11,7 @@ pub fn sock_recv(
     _ri_flags: wasi::__wasi_riflags_t,
     _ro_datalen: wasi32::uintptr_t,
     _ro_flags: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("sock_recv")
 }
 
@@ -22,7 +23,7 @@ pub fn sock_send(
     _si_data_len: wasi32::size_t,
     _si_flags: wasi::__wasi_siflags_t,
     _so_datalen: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("sock_send")
 }
 
@@ -31,6 +32,6 @@ pub fn sock_shutdown(
     _memory: &mut [u8],
     _sock: wasi::__wasi_fd_t,
     _how: wasi::__wasi_sdflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("sock_shutdown")
 }
diff --git a/crates/wasi-common/src/lib.rs b/crates/wasi-common/src/lib.rs
index 7e074eba3b..b20066b1cd 100644
--- a/crates/wasi-common/src/lib.rs
+++ b/crates/wasi-common/src/lib.rs
@@ -22,7 +22,6 @@
 )]
 
 mod ctx;
-mod error;
 mod fdentry;
 pub mod fs;
 mod helpers;
@@ -43,6 +42,3 @@ pub mod hostcalls {
 
 pub use ctx::{WasiCtx, WasiCtxBuilder};
 pub use sys::preopen_dir;
-
-pub use error::Error;
-pub(crate) use error::Result;
diff --git a/crates/wasi-common/src/memory.rs b/crates/wasi-common/src/memory.rs
index 4c9cb10844..a45dc537ae 100644
--- a/crates/wasi-common/src/memory.rs
+++ b/crates/wasi-common/src/memory.rs
@@ -8,38 +8,39 @@
 //! are not held for long durations.
 
 #![allow(unused)]
-use crate::{host, wasi, wasi32, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
+use crate::{host, wasi32};
 use num::PrimInt;
 use std::convert::TryFrom;
 use std::mem::{align_of, size_of};
 use std::{ptr, slice};
 
-fn dec_ptr(memory: &[u8], ptr: wasi32::uintptr_t, len: usize) -> Result<*const u8> {
+fn dec_ptr(memory: &[u8], ptr: wasi32::uintptr_t, len: usize) -> WasiResult<*const u8> {
     // check for overflow
-    let checked_len = (ptr as usize).checked_add(len).ok_or(Error::EFAULT)?;
+    let checked_len = (ptr as usize).checked_add(len).ok_or(WasiError::EFAULT)?;
 
     // translate the pointer
     memory
         .get(ptr as usize..checked_len)
-        .ok_or(Error::EFAULT)
+        .ok_or(WasiError::EFAULT)
         .map(|mem| mem.as_ptr())
 }
 
-fn dec_ptr_mut(memory: &mut [u8], ptr: wasi32::uintptr_t, len: usize) -> Result<*mut u8> {
+fn dec_ptr_mut(memory: &mut [u8], ptr: wasi32::uintptr_t, len: usize) -> WasiResult<*mut u8> {
     // check for overflow
-    let checked_len = (ptr as usize).checked_add(len).ok_or(Error::EFAULT)?;
+    let checked_len = (ptr as usize).checked_add(len).ok_or(WasiError::EFAULT)?;
 
     // translate the pointer
     memory
         .get_mut(ptr as usize..checked_len)
-        .ok_or(Error::EFAULT)
+        .ok_or(WasiError::EFAULT)
         .map(|mem| mem.as_mut_ptr())
 }
 
-fn dec_ptr_to<'memory, T>(memory: &'memory [u8], ptr: wasi32::uintptr_t) -> Result<&'memory T> {
+fn dec_ptr_to<'memory, T>(memory: &'memory [u8], ptr: wasi32::uintptr_t) -> WasiResult<&'memory T> {
     // check that the ptr is aligned
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     dec_ptr(memory, ptr, size_of::<T>()).map(|p| unsafe { &*(p as *const T) })
@@ -48,49 +49,49 @@ fn dec_ptr_to<'memory, T>(memory: &'memory [u8], ptr: wasi32::uintptr_t) -> Resu
 fn dec_ptr_to_mut<'memory, T>(
     memory: &'memory mut [u8],
     ptr: wasi32::uintptr_t,
-) -> Result<&'memory mut T> {
+) -> WasiResult<&'memory mut T> {
     // check that the ptr is aligned
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     dec_ptr_mut(memory, ptr, size_of::<T>()).map(|p| unsafe { &mut *(p as *mut T) })
 }
 
 /// This function does not perform endianness conversions!
-fn dec_raw_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> Result<T> {
+fn dec_raw_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> WasiResult<T> {
     dec_ptr_to::<T>(memory, ptr).map(|p| unsafe { ptr::read(p) })
 }
 
 /// This function does not perform endianness conversions!
-fn enc_raw_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> Result<()> {
+fn enc_raw_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> WasiResult<()> {
     dec_ptr_to_mut::<T>(memory, ptr).map(|p| unsafe { ptr::write(p, t) })
 }
 
-pub(crate) fn dec_int_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> Result<T>
+pub(crate) fn dec_int_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> WasiResult<T>
 where
     T: PrimInt,
 {
     dec_raw_byref::<T>(memory, ptr).map(|i| PrimInt::from_le(i))
 }
 
-pub(crate) fn enc_int_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> Result<()>
+pub(crate) fn enc_int_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> WasiResult<()>
 where
     T: PrimInt,
 {
     enc_raw_byref::<T>(memory, ptr, PrimInt::to_le(t))
 }
 
-fn check_slice_of<T>(ptr: wasi32::uintptr_t, len: wasi32::size_t) -> Result<(usize, usize)> {
+fn check_slice_of<T>(ptr: wasi32::uintptr_t, len: wasi32::size_t) -> WasiResult<(usize, usize)> {
     // check alignment, and that length doesn't overflow
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
     let len = dec_usize(len);
     let len_bytes = if let Some(len) = size_of::<T>().checked_mul(len) {
         len
     } else {
-        return Err(Error::EOVERFLOW);
+        return Err(WasiError::EOVERFLOW);
     };
 
     Ok((len, len_bytes))
@@ -100,7 +101,7 @@ fn dec_raw_slice_of<'memory, T>(
     memory: &'memory [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory [T]> {
+) -> WasiResult<&'memory [T]> {
     let (len, len_bytes) = check_slice_of::<T>(ptr, len)?;
     let ptr = dec_ptr(memory, ptr, len_bytes)? as *const T;
     Ok(unsafe { slice::from_raw_parts(ptr, len) })
@@ -110,7 +111,7 @@ fn dec_raw_slice_of_mut<'memory, T>(
     memory: &'memory mut [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory mut [T]> {
+) -> WasiResult<&'memory mut [T]> {
     let (len, len_bytes) = check_slice_of::<T>(ptr, len)?;
     let ptr = dec_ptr_mut(memory, ptr, len_bytes)? as *mut T;
     Ok(unsafe { slice::from_raw_parts_mut(ptr, len) })
@@ -120,16 +121,16 @@ fn raw_slice_for_enc<'memory, T>(
     memory: &'memory mut [u8],
     slice: &[T],
     ptr: wasi32::uintptr_t,
-) -> Result<&'memory mut [T]> {
+) -> WasiResult<&'memory mut [T]> {
     // check alignment
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
     // check that length doesn't overflow
     let len_bytes = if let Some(len) = size_of::<T>().checked_mul(slice.len()) {
         len
     } else {
-        return Err(Error::EOVERFLOW);
+        return Err(WasiError::EOVERFLOW);
     };
 
     // get the pointer into guest memory
@@ -142,7 +143,7 @@ pub(crate) fn dec_slice_of_u8<'memory>(
     memory: &'memory [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory [u8]> {
+) -> WasiResult<&'memory [u8]> {
     dec_raw_slice_of::<u8>(memory, ptr, len)
 }
 
@@ -150,7 +151,7 @@ pub(crate) fn dec_slice_of_mut_u8<'memory>(
     memory: &'memory mut [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory mut [u8]> {
+) -> WasiResult<&'memory mut [u8]> {
     dec_raw_slice_of_mut::<u8>(memory, ptr, len)
 }
 
@@ -158,7 +159,7 @@ pub(crate) fn enc_slice_of_u8(
     memory: &mut [u8],
     slice: &[u8],
     ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let output = raw_slice_for_enc::<u8>(memory, slice, ptr)?;
 
     output.copy_from_slice(slice);
@@ -170,7 +171,7 @@ pub(crate) fn enc_slice_of_wasi32_uintptr(
     memory: &mut [u8],
     slice: &[wasi32::uintptr_t],
     ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let mut output_iter = raw_slice_for_enc::<wasi32::uintptr_t>(memory, slice, ptr)?.into_iter();
 
     for p in slice {
@@ -182,7 +183,10 @@ pub(crate) fn enc_slice_of_wasi32_uintptr(
 
 macro_rules! dec_enc_scalar {
     ($ty:ident, $dec_byref:ident, $enc_byref:ident) => {
-        pub(crate) fn $dec_byref(memory: &mut [u8], ptr: wasi32::uintptr_t) -> Result<wasi::$ty> {
+        pub(crate) fn $dec_byref(
+            memory: &mut [u8],
+            ptr: wasi32::uintptr_t,
+        ) -> WasiResult<wasi::$ty> {
             dec_int_byref::<wasi::$ty>(memory, ptr)
         }
 
@@ -190,7 +194,7 @@ macro_rules! dec_enc_scalar {
             memory: &mut [u8],
             ptr: wasi32::uintptr_t,
             x: wasi::$ty,
-        ) -> Result<()> {
+        ) -> WasiResult<()> {
             enc_int_byref::<wasi::$ty>(memory, ptr, x)
         }
     };
@@ -200,7 +204,7 @@ pub(crate) fn dec_ciovec_slice(
     memory: &[u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<Vec<host::__wasi_ciovec_t>> {
+) -> WasiResult<Vec<host::__wasi_ciovec_t>> {
     let raw_slice = dec_raw_slice_of::<wasi32::__wasi_ciovec_t>(memory, ptr, len)?;
 
     raw_slice
@@ -220,7 +224,7 @@ pub(crate) fn dec_iovec_slice(
     memory: &[u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<Vec<host::__wasi_iovec_t>> {
+) -> WasiResult<Vec<host::__wasi_iovec_t>> {
     let raw_slice = dec_raw_slice_of::<wasi32::__wasi_iovec_t>(memory, ptr, len)?;
 
     raw_slice
@@ -248,7 +252,7 @@ dec_enc_scalar!(__wasi_linkcount_t, dev_linkcount_byref, enc_linkcount_byref);
 pub(crate) fn dec_filestat_byref(
     memory: &mut [u8],
     filestat_ptr: wasi32::uintptr_t,
-) -> Result<wasi::__wasi_filestat_t> {
+) -> WasiResult<wasi::__wasi_filestat_t> {
     let raw = dec_raw_byref::<wasi::__wasi_filestat_t>(memory, filestat_ptr)?;
 
     Ok(wasi::__wasi_filestat_t {
@@ -267,7 +271,7 @@ pub(crate) fn enc_filestat_byref(
     memory: &mut [u8],
     filestat_ptr: wasi32::uintptr_t,
     filestat: wasi::__wasi_filestat_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let raw = wasi::__wasi_filestat_t {
         dev: PrimInt::to_le(filestat.dev),
         ino: PrimInt::to_le(filestat.ino),
@@ -285,7 +289,7 @@ pub(crate) fn enc_filestat_byref(
 pub(crate) fn dec_fdstat_byref(
     memory: &mut [u8],
     fdstat_ptr: wasi32::uintptr_t,
-) -> Result<wasi::__wasi_fdstat_t> {
+) -> WasiResult<wasi::__wasi_fdstat_t> {
     let raw = dec_raw_byref::<wasi::__wasi_fdstat_t>(memory, fdstat_ptr)?;
 
     Ok(wasi::__wasi_fdstat_t {
@@ -300,7 +304,7 @@ pub(crate) fn enc_fdstat_byref(
     memory: &mut [u8],
     fdstat_ptr: wasi32::uintptr_t,
     fdstat: wasi::__wasi_fdstat_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let raw = wasi::__wasi_fdstat_t {
         fs_filetype: PrimInt::to_le(fdstat.fs_filetype),
         fs_flags: PrimInt::to_le(fdstat.fs_flags),
@@ -326,7 +330,7 @@ dec_enc_scalar!(__wasi_oflags_t, dec_oflags_byref, enc_oflags_byref);
 pub(crate) fn dec_prestat_byref(
     memory: &mut [u8],
     prestat_ptr: wasi32::uintptr_t,
-) -> Result<host::__wasi_prestat_t> {
+) -> WasiResult<host::__wasi_prestat_t> {
     let raw = dec_raw_byref::<wasi32::__wasi_prestat_t>(memory, prestat_ptr)?;
 
     match PrimInt::from_le(raw.tag) {
@@ -338,7 +342,7 @@ pub(crate) fn dec_prestat_byref(
                 },
             },
         }),
-        _ => Err(Error::EINVAL),
+        _ => Err(WasiError::EINVAL),
     }
 }
 
@@ -346,7 +350,7 @@ pub(crate) fn enc_prestat_byref(
     memory: &mut [u8],
     prestat_ptr: wasi32::uintptr_t,
     prestat: host::__wasi_prestat_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let raw = match prestat.tag {
         wasi::__WASI_PREOPENTYPE_DIR => Ok(wasi32::__wasi_prestat_t {
             tag: PrimInt::to_le(wasi::__WASI_PREOPENTYPE_DIR),
@@ -356,7 +360,7 @@ pub(crate) fn enc_prestat_byref(
                 },
             },
         }),
-        _ => Err(Error::EINVAL),
+        _ => Err(WasiError::EINVAL),
     }?;
 
     enc_raw_byref::<wasi32::__wasi_prestat_t>(memory, prestat_ptr, raw)
@@ -377,7 +381,7 @@ pub(crate) fn enc_usize_byref(
     memory: &mut [u8],
     usize_ptr: wasi32::uintptr_t,
     host_usize: usize,
-) -> Result<()> {
+) -> WasiResult<()> {
     enc_int_byref::<wasi32::size_t>(memory, usize_ptr, enc_usize(host_usize))
 }
 
@@ -402,7 +406,7 @@ pub(crate) fn dec_subscriptions(
     memory: &mut [u8],
     input: wasi32::uintptr_t,
     nsubscriptions: wasi32::size_t,
-) -> Result<Vec<wasi::__wasi_subscription_t>> {
+) -> WasiResult<Vec<wasi::__wasi_subscription_t>> {
     let raw_input_slice =
         dec_raw_slice_of::<wasi::__wasi_subscription_t>(memory, input, nsubscriptions)?;
 
@@ -435,14 +439,14 @@ pub(crate) fn dec_subscriptions(
                         }),
                     },
                 },
-                _ => return Err(Error::EINVAL),
+                _ => return Err(WasiError::EINVAL),
             };
             Ok(wasi::__wasi_subscription_t {
                 userdata,
                 u: wasi::__wasi_subscription_u_t { tag, u },
             })
         })
-        .collect::<Result<Vec<_>>>()
+        .collect::<WasiResult<Vec<_>>>()
 }
 
 pub(crate) fn enc_events(
@@ -450,7 +454,7 @@ pub(crate) fn enc_events(
     output: wasi32::uintptr_t,
     nsubscriptions: wasi32::size_t,
     events: Vec<wasi::__wasi_event_t>,
-) -> Result<()> {
+) -> WasiResult<()> {
     let mut raw_output_iter =
         dec_raw_slice_of_mut::<wasi::__wasi_event_t>(memory, output, nsubscriptions)?.into_iter();
 
diff --git a/crates/wasi-common/src/old/snapshot_0/ctx.rs b/crates/wasi-common/src/old/snapshot_0/ctx.rs
index d6da885165..e9979bb46e 100644
--- a/crates/wasi-common/src/old/snapshot_0/ctx.rs
+++ b/crates/wasi-common/src/old/snapshot_0/ctx.rs
@@ -1,14 +1,42 @@
 use crate::old::snapshot_0::fdentry::FdEntry;
-use crate::old::snapshot_0::{wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use std::borrow::Borrow;
 use std::collections::HashMap;
-use std::env;
-use std::ffi::{CString, OsString};
+use std::ffi::{self, CString, OsString};
 use std::fs::File;
 use std::path::{Path, PathBuf};
+use std::{env, io, string};
+
+/// Possible errors when `WasiCtxBuilder` fails building
+/// `WasiCtx`.
+#[derive(Debug, thiserror::Error)]
+pub enum WasiCtxBuilderError {
+    /// General I/O error was encountered.
+    #[error("general I/O error encountered: {0}")]
+    Io(#[from] io::Error),
+    /// Provided sequence of bytes was not a valid UTF-8.
+    #[error("provided sequence is not valid UTF-8: {0}")]
+    InvalidUtf8(#[from] string::FromUtf8Error),
+    /// Provided sequence of bytes was not a valid UTF-16.
+    ///
+    /// This error is expected to only occur on Windows hosts.
+    #[error("provided sequence is not valid UTF-16: {0}")]
+    InvalidUtf16(#[from] string::FromUtf16Error),
+    /// Provided sequence of bytes contained an unexpected NUL byte.
+    #[error("provided sequence contained an unexpected NUL byte")]
+    UnexpectedNul(#[from] ffi::NulError),
+    /// Provided `File` is not a directory.
+    #[error("preopened directory path {} is not a directory", .0.display())]
+    NotADirectory(PathBuf),
+    /// `WasiCtx` has too many opened files.
+    #[error("context object has too many opened files")]
+    TooManyFilesOpen,
+}
+
+type WasiCtxBuilderResult<T> = std::result::Result<T, WasiCtxBuilderError>;
 
 enum PendingFdEntry {
-    Thunk(fn() -> Result<FdEntry>),
+    Thunk(fn() -> io::Result<FdEntry>),
     File(File),
 }
 
@@ -18,7 +46,7 @@ impl std::fmt::Debug for PendingFdEntry {
             Self::Thunk(f) => write!(
                 fmt,
                 "PendingFdEntry::Thunk({:p})",
-                f as *const fn() -> Result<FdEntry>
+                f as *const fn() -> io::Result<FdEntry>
             ),
             Self::File(f) => write!(fmt, "PendingFdEntry::File({:?})", f),
         }
@@ -44,17 +72,29 @@ impl From<OsString> for PendingCString {
 }
 
 impl PendingCString {
-    fn into_string(self) -> Result<String> {
-        match self {
-            Self::Bytes(v) => String::from_utf8(v).map_err(|_| Error::EILSEQ),
-            Self::OsString(s) => s.into_string().map_err(|_| Error::EILSEQ),
-        }
+    fn into_string(self) -> WasiCtxBuilderResult<String> {
+        let res = match self {
+            Self::Bytes(v) => String::from_utf8(v)?,
+            #[cfg(unix)]
+            Self::OsString(s) => {
+                use std::os::unix::ffi::OsStringExt;
+                String::from_utf8(s.into_vec())?
+            }
+            #[cfg(windows)]
+            Self::OsString(s) => {
+                use std::os::windows::ffi::OsStrExt;
+                let bytes: Vec<u16> = s.encode_wide().collect();
+                String::from_utf16(&bytes)?
+            }
+        };
+        Ok(res)
     }
 
-    /// Create a `CString` containing valid UTF-8, or fail with `Error::EILSEQ`.
-    fn into_utf8_cstring(self) -> Result<CString> {
-        self.into_string()
-            .and_then(|s| CString::new(s).map_err(|_| Error::EILSEQ))
+    /// Create a `CString` containing valid UTF-8, or fail.
+    fn into_utf8_cstring(self) -> WasiCtxBuilderResult<CString> {
+        let s = self.into_string()?;
+        let s = CString::new(s)?;
+        Ok(s)
     }
 }
 
@@ -85,8 +125,7 @@ impl WasiCtxBuilder {
 
     /// Add arguments to the command-line arguments list.
     ///
-    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail
-    /// with `Error::EILSEQ`.
+    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail.
     pub fn args<S: AsRef<[u8]>>(mut self, args: impl IntoIterator<Item = S>) -> Self {
         self.args = args
             .into_iter()
@@ -97,8 +136,7 @@ impl WasiCtxBuilder {
 
     /// Add an argument to the command-line arguments list.
     ///
-    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail
-    /// with `Error::EILSEQ`.
+    /// Arguments must be valid UTF-8 with no NUL bytes, or else `WasiCtxBuilder::build()` will fail.
     pub fn arg<S: AsRef<[u8]>>(mut self, arg: S) -> Self {
         self.args.push(arg.as_ref().to_vec().into());
         self
@@ -107,7 +145,7 @@ impl WasiCtxBuilder {
     /// Inherit the command-line arguments from the host process.
     ///
     /// If any arguments from the host process contain invalid UTF-8, `WasiCtxBuilder::build()` will
-    /// fail with `Error::EILSEQ`.
+    /// fail.
     pub fn inherit_args(mut self) -> Self {
         self.args = env::args_os().map(PendingCString::OsString).collect();
         self
@@ -127,8 +165,7 @@ impl WasiCtxBuilder {
     /// Inherit the environment variables from the host process.
     ///
     /// If any environment variables from the host process contain invalid Unicode (UTF-16 for
-    /// Windows, UTF-8 for other platforms), `WasiCtxBuilder::build()` will fail with
-    /// `Error::EILSEQ`.
+    /// Windows, UTF-8 for other platforms), `WasiCtxBuilder::build()` will fail.
     pub fn inherit_env(mut self) -> Self {
         self.env = std::env::vars_os()
             .map(|(k, v)| (k.into(), v.into()))
@@ -139,7 +176,7 @@ impl WasiCtxBuilder {
     /// Add an entry to the environment.
     ///
     /// Environment variable keys and values must be valid UTF-8 with no NUL bytes, or else
-    /// `WasiCtxBuilder::build()` will fail with `Error::EILSEQ`.
+    /// `WasiCtxBuilder::build()` will fail.
     pub fn env<S: AsRef<[u8]>>(mut self, k: S, v: S) -> Self {
         self.env
             .insert(k.as_ref().to_vec().into(), v.as_ref().to_vec().into());
@@ -149,7 +186,7 @@ impl WasiCtxBuilder {
     /// Add entries to the environment.
     ///
     /// Environment variable keys and values must be valid UTF-8 with no NUL bytes, or else
-    /// `WasiCtxBuilder::build()` will fail with `Error::EILSEQ`.
+    /// `WasiCtxBuilder::build()` will fail.
     pub fn envs<S: AsRef<[u8]>, T: Borrow<(S, S)>>(
         mut self,
         envs: impl IntoIterator<Item = T>,
@@ -191,15 +228,15 @@ impl WasiCtxBuilder {
     /// Build a `WasiCtx`, consuming this `WasiCtxBuilder`.
     ///
     /// If any of the arguments or environment variables in this builder cannot be converted into
-    /// `CString`s, either due to NUL bytes or Unicode conversions, this returns `Error::EILSEQ`.
-    pub fn build(self) -> Result<WasiCtx> {
+    /// `CString`s, either due to NUL bytes or Unicode conversions, this returns an error.
+    pub fn build(self) -> WasiCtxBuilderResult<WasiCtx> {
         // Process arguments and environment variables into `CString`s, failing quickly if they
         // contain any NUL bytes, or if conversion from `OsString` fails.
         let args = self
             .args
             .into_iter()
             .map(|arg| arg.into_utf8_cstring())
-            .collect::<Result<Vec<CString>>>()?;
+            .collect::<WasiCtxBuilderResult<Vec<CString>>>()?;
 
         let env = self
             .env
@@ -211,11 +248,12 @@ impl WasiCtxBuilder {
                         pair.push_str(v.as_str());
                         // We have valid UTF-8, but the keys and values have not yet been checked
                         // for NULs, so we do a final check here.
-                        CString::new(pair).map_err(|_| Error::EILSEQ)
+                        let s = CString::new(pair)?;
+                        Ok(s)
                     })
                 })
             })
-            .collect::<Result<Vec<CString>>>()?;
+            .collect::<WasiCtxBuilderResult<Vec<CString>>>()?;
 
         let mut fds: HashMap<wasi::__wasi_fd_t, FdEntry> = HashMap::new();
         // Populate the non-preopen fds.
@@ -237,16 +275,20 @@ impl WasiCtxBuilder {
         for (guest_path, dir) in self.preopens {
             // We do the increment at the beginning of the loop body, so that we don't overflow
             // unnecessarily if we have exactly the maximum number of file descriptors.
-            preopen_fd = preopen_fd.checked_add(1).ok_or(Error::ENFILE)?;
+            preopen_fd = preopen_fd
+                .checked_add(1)
+                .ok_or(WasiCtxBuilderError::TooManyFilesOpen)?;
 
             if !dir.metadata()?.is_dir() {
-                return Err(Error::EBADF);
+                return Err(WasiCtxBuilderError::NotADirectory(guest_path));
             }
 
             // We don't currently allow setting file descriptors other than 0-2, but this will avoid
             // collisions if we restore that functionality in the future.
             while fds.contains_key(&preopen_fd) {
-                preopen_fd = preopen_fd.checked_add(1).ok_or(Error::ENFILE)?;
+                preopen_fd = preopen_fd
+                    .checked_add(1)
+                    .ok_or(WasiCtxBuilderError::TooManyFilesOpen)?;
             }
             let mut fe = FdEntry::from(dir)?;
             fe.preopen_path = Some(guest_path);
@@ -274,7 +316,7 @@ impl WasiCtx {
     /// - Environment variables are inherited from the host process.
     ///
     /// To override these behaviors, use `WasiCtxBuilder`.
-    pub fn new<S: AsRef<[u8]>>(args: impl IntoIterator<Item = S>) -> Result<Self> {
+    pub fn new<S: AsRef<[u8]>>(args: impl IntoIterator<Item = S>) -> WasiCtxBuilderResult<Self> {
         WasiCtxBuilder::new()
             .args(args)
             .inherit_stdio()
@@ -288,30 +330,30 @@ impl WasiCtx {
     }
 
     /// Get an immutable `FdEntry` corresponding to the specified raw WASI `fd`.
-    pub(crate) unsafe fn get_fd_entry(&self, fd: wasi::__wasi_fd_t) -> Result<&FdEntry> {
-        self.fds.get(&fd).ok_or(Error::EBADF)
+    pub(crate) unsafe fn get_fd_entry(&self, fd: wasi::__wasi_fd_t) -> WasiResult<&FdEntry> {
+        self.fds.get(&fd).ok_or(WasiError::EBADF)
     }
 
     /// Get a mutable `FdEntry` corresponding to the specified raw WASI `fd`.
     pub(crate) unsafe fn get_fd_entry_mut(
         &mut self,
         fd: wasi::__wasi_fd_t,
-    ) -> Result<&mut FdEntry> {
-        self.fds.get_mut(&fd).ok_or(Error::EBADF)
+    ) -> WasiResult<&mut FdEntry> {
+        self.fds.get_mut(&fd).ok_or(WasiError::EBADF)
     }
 
     /// Insert the specified `FdEntry` into the `WasiCtx` object.
     ///
     /// The `FdEntry` will automatically get another free raw WASI `fd` assigned. Note that
     /// the two subsequent free raw WASI `fd`s do not have to be stored contiguously.
-    pub(crate) fn insert_fd_entry(&mut self, fe: FdEntry) -> Result<wasi::__wasi_fd_t> {
+    pub(crate) fn insert_fd_entry(&mut self, fe: FdEntry) -> WasiResult<wasi::__wasi_fd_t> {
         // Never insert where stdio handles are expected to be.
         let mut fd = 3;
         while self.fds.contains_key(&fd) {
             if let Some(next_fd) = fd.checked_add(1) {
                 fd = next_fd;
             } else {
-                return Err(Error::EMFILE);
+                return Err(WasiError::EMFILE);
             }
         }
         self.fds.insert(fd, fe);
@@ -329,7 +371,7 @@ impl WasiCtx {
     }
 
     /// Remove `FdEntry` corresponding to the specified raw WASI `fd` from the `WasiCtx` object.
-    pub(crate) fn remove_fd_entry(&mut self, fd: wasi::__wasi_fd_t) -> Result<FdEntry> {
-        self.fds.remove(&fd).ok_or(Error::EBADF)
+    pub(crate) fn remove_fd_entry(&mut self, fd: wasi::__wasi_fd_t) -> WasiResult<FdEntry> {
+        self.fds.remove(&fd).ok_or(WasiError::EBADF)
     }
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/error.rs b/crates/wasi-common/src/old/snapshot_0/error.rs
deleted file mode 100644
index 83f137e03c..0000000000
--- a/crates/wasi-common/src/old/snapshot_0/error.rs
+++ /dev/null
@@ -1,234 +0,0 @@
-// Due to https://github.com/rust-lang/rust/issues/64247
-#![allow(clippy::use_self)]
-use crate::old::snapshot_0::wasi;
-use std::convert::Infallible;
-use std::num::TryFromIntError;
-use std::{ffi, str};
-use thiserror::Error;
-
-#[derive(Clone, Copy, Debug, Error, Eq, PartialEq)]
-#[repr(u16)]
-#[error("{:?} ({})", self, wasi::strerror(*self as wasi::__wasi_errno_t))]
-pub enum WasiError {
-    ESUCCESS = wasi::__WASI_ERRNO_SUCCESS,
-    E2BIG = wasi::__WASI_ERRNO_2BIG,
-    EACCES = wasi::__WASI_ERRNO_ACCES,
-    EADDRINUSE = wasi::__WASI_ERRNO_ADDRINUSE,
-    EADDRNOTAVAIL = wasi::__WASI_ERRNO_ADDRNOTAVAIL,
-    EAFNOSUPPORT = wasi::__WASI_ERRNO_AFNOSUPPORT,
-    EAGAIN = wasi::__WASI_ERRNO_AGAIN,
-    EALREADY = wasi::__WASI_ERRNO_ALREADY,
-    EBADF = wasi::__WASI_ERRNO_BADF,
-    EBADMSG = wasi::__WASI_ERRNO_BADMSG,
-    EBUSY = wasi::__WASI_ERRNO_BUSY,
-    ECANCELED = wasi::__WASI_ERRNO_CANCELED,
-    ECHILD = wasi::__WASI_ERRNO_CHILD,
-    ECONNABORTED = wasi::__WASI_ERRNO_CONNABORTED,
-    ECONNREFUSED = wasi::__WASI_ERRNO_CONNREFUSED,
-    ECONNRESET = wasi::__WASI_ERRNO_CONNRESET,
-    EDEADLK = wasi::__WASI_ERRNO_DEADLK,
-    EDESTADDRREQ = wasi::__WASI_ERRNO_DESTADDRREQ,
-    EDOM = wasi::__WASI_ERRNO_DOM,
-    EDQUOT = wasi::__WASI_ERRNO_DQUOT,
-    EEXIST = wasi::__WASI_ERRNO_EXIST,
-    EFAULT = wasi::__WASI_ERRNO_FAULT,
-    EFBIG = wasi::__WASI_ERRNO_FBIG,
-    EHOSTUNREACH = wasi::__WASI_ERRNO_HOSTUNREACH,
-    EIDRM = wasi::__WASI_ERRNO_IDRM,
-    EILSEQ = wasi::__WASI_ERRNO_ILSEQ,
-    EINPROGRESS = wasi::__WASI_ERRNO_INPROGRESS,
-    EINTR = wasi::__WASI_ERRNO_INTR,
-    EINVAL = wasi::__WASI_ERRNO_INVAL,
-    EIO = wasi::__WASI_ERRNO_IO,
-    EISCONN = wasi::__WASI_ERRNO_ISCONN,
-    EISDIR = wasi::__WASI_ERRNO_ISDIR,
-    ELOOP = wasi::__WASI_ERRNO_LOOP,
-    EMFILE = wasi::__WASI_ERRNO_MFILE,
-    EMLINK = wasi::__WASI_ERRNO_MLINK,
-    EMSGSIZE = wasi::__WASI_ERRNO_MSGSIZE,
-    EMULTIHOP = wasi::__WASI_ERRNO_MULTIHOP,
-    ENAMETOOLONG = wasi::__WASI_ERRNO_NAMETOOLONG,
-    ENETDOWN = wasi::__WASI_ERRNO_NETDOWN,
-    ENETRESET = wasi::__WASI_ERRNO_NETRESET,
-    ENETUNREACH = wasi::__WASI_ERRNO_NETUNREACH,
-    ENFILE = wasi::__WASI_ERRNO_NFILE,
-    ENOBUFS = wasi::__WASI_ERRNO_NOBUFS,
-    ENODEV = wasi::__WASI_ERRNO_NODEV,
-    ENOENT = wasi::__WASI_ERRNO_NOENT,
-    ENOEXEC = wasi::__WASI_ERRNO_NOEXEC,
-    ENOLCK = wasi::__WASI_ERRNO_NOLCK,
-    ENOLINK = wasi::__WASI_ERRNO_NOLINK,
-    ENOMEM = wasi::__WASI_ERRNO_NOMEM,
-    ENOMSG = wasi::__WASI_ERRNO_NOMSG,
-    ENOPROTOOPT = wasi::__WASI_ERRNO_NOPROTOOPT,
-    ENOSPC = wasi::__WASI_ERRNO_NOSPC,
-    ENOSYS = wasi::__WASI_ERRNO_NOSYS,
-    ENOTCONN = wasi::__WASI_ERRNO_NOTCONN,
-    ENOTDIR = wasi::__WASI_ERRNO_NOTDIR,
-    ENOTEMPTY = wasi::__WASI_ERRNO_NOTEMPTY,
-    ENOTRECOVERABLE = wasi::__WASI_ERRNO_NOTRECOVERABLE,
-    ENOTSOCK = wasi::__WASI_ERRNO_NOTSOCK,
-    ENOTSUP = wasi::__WASI_ERRNO_NOTSUP,
-    ENOTTY = wasi::__WASI_ERRNO_NOTTY,
-    ENXIO = wasi::__WASI_ERRNO_NXIO,
-    EOVERFLOW = wasi::__WASI_ERRNO_OVERFLOW,
-    EOWNERDEAD = wasi::__WASI_ERRNO_OWNERDEAD,
-    EPERM = wasi::__WASI_ERRNO_PERM,
-    EPIPE = wasi::__WASI_ERRNO_PIPE,
-    EPROTO = wasi::__WASI_ERRNO_PROTO,
-    EPROTONOSUPPORT = wasi::__WASI_ERRNO_PROTONOSUPPORT,
-    EPROTOTYPE = wasi::__WASI_ERRNO_PROTOTYPE,
-    ERANGE = wasi::__WASI_ERRNO_RANGE,
-    EROFS = wasi::__WASI_ERRNO_ROFS,
-    ESPIPE = wasi::__WASI_ERRNO_SPIPE,
-    ESRCH = wasi::__WASI_ERRNO_SRCH,
-    ESTALE = wasi::__WASI_ERRNO_STALE,
-    ETIMEDOUT = wasi::__WASI_ERRNO_TIMEDOUT,
-    ETXTBSY = wasi::__WASI_ERRNO_TXTBSY,
-    EXDEV = wasi::__WASI_ERRNO_XDEV,
-    ENOTCAPABLE = wasi::__WASI_ERRNO_NOTCAPABLE,
-}
-
-impl WasiError {
-    pub fn as_raw_errno(self) -> wasi::__wasi_errno_t {
-        self as wasi::__wasi_errno_t
-    }
-}
-
-#[derive(Debug, Error)]
-pub enum Error {
-    #[error("WASI error code: {0}")]
-    Wasi(#[from] WasiError),
-    #[error("IO error: {0}")]
-    Io(#[from] std::io::Error),
-}
-
-impl From<TryFromIntError> for Error {
-    fn from(_: TryFromIntError) -> Self {
-        Self::EOVERFLOW
-    }
-}
-
-impl From<Infallible> for Error {
-    fn from(_: Infallible) -> Self {
-        unreachable!()
-    }
-}
-
-impl From<str::Utf8Error> for Error {
-    fn from(_: str::Utf8Error) -> Self {
-        Self::EILSEQ
-    }
-}
-
-impl From<ffi::NulError> for Error {
-    fn from(_: ffi::NulError) -> Self {
-        Self::EILSEQ
-    }
-}
-
-impl From<&ffi::NulError> for Error {
-    fn from(_: &ffi::NulError) -> Self {
-        Self::EILSEQ
-    }
-}
-
-impl Error {
-    pub(crate) fn as_wasi_error(&self) -> WasiError {
-        match self {
-            Self::Wasi(err) => *err,
-            Self::Io(err) => {
-                let err = match err.raw_os_error() {
-                    Some(code) => Self::from_raw_os_error(code),
-                    None => {
-                        log::debug!("Inconvertible OS error: {}", err);
-                        Self::EIO
-                    }
-                };
-                err.as_wasi_error()
-            }
-        }
-    }
-
-    pub const ESUCCESS: Self = Error::Wasi(WasiError::ESUCCESS);
-    pub const E2BIG: Self = Error::Wasi(WasiError::E2BIG);
-    pub const EACCES: Self = Error::Wasi(WasiError::EACCES);
-    pub const EADDRINUSE: Self = Error::Wasi(WasiError::EADDRINUSE);
-    pub const EADDRNOTAVAIL: Self = Error::Wasi(WasiError::EADDRNOTAVAIL);
-    pub const EAFNOSUPPORT: Self = Error::Wasi(WasiError::EAFNOSUPPORT);
-    pub const EAGAIN: Self = Error::Wasi(WasiError::EAGAIN);
-    pub const EALREADY: Self = Error::Wasi(WasiError::EALREADY);
-    pub const EBADF: Self = Error::Wasi(WasiError::EBADF);
-    pub const EBADMSG: Self = Error::Wasi(WasiError::EBADMSG);
-    pub const EBUSY: Self = Error::Wasi(WasiError::EBUSY);
-    pub const ECANCELED: Self = Error::Wasi(WasiError::ECANCELED);
-    pub const ECHILD: Self = Error::Wasi(WasiError::ECHILD);
-    pub const ECONNABORTED: Self = Error::Wasi(WasiError::ECONNABORTED);
-    pub const ECONNREFUSED: Self = Error::Wasi(WasiError::ECONNREFUSED);
-    pub const ECONNRESET: Self = Error::Wasi(WasiError::ECONNRESET);
-    pub const EDEADLK: Self = Error::Wasi(WasiError::EDEADLK);
-    pub const EDESTADDRREQ: Self = Error::Wasi(WasiError::EDESTADDRREQ);
-    pub const EDOM: Self = Error::Wasi(WasiError::EDOM);
-    pub const EDQUOT: Self = Error::Wasi(WasiError::EDQUOT);
-    pub const EEXIST: Self = Error::Wasi(WasiError::EEXIST);
-    pub const EFAULT: Self = Error::Wasi(WasiError::EFAULT);
-    pub const EFBIG: Self = Error::Wasi(WasiError::EFBIG);
-    pub const EHOSTUNREACH: Self = Error::Wasi(WasiError::EHOSTUNREACH);
-    pub const EIDRM: Self = Error::Wasi(WasiError::EIDRM);
-    pub const EILSEQ: Self = Error::Wasi(WasiError::EILSEQ);
-    pub const EINPROGRESS: Self = Error::Wasi(WasiError::EINPROGRESS);
-    pub const EINTR: Self = Error::Wasi(WasiError::EINTR);
-    pub const EINVAL: Self = Error::Wasi(WasiError::EINVAL);
-    pub const EIO: Self = Error::Wasi(WasiError::EIO);
-    pub const EISCONN: Self = Error::Wasi(WasiError::EISCONN);
-    pub const EISDIR: Self = Error::Wasi(WasiError::EISDIR);
-    pub const ELOOP: Self = Error::Wasi(WasiError::ELOOP);
-    pub const EMFILE: Self = Error::Wasi(WasiError::EMFILE);
-    pub const EMLINK: Self = Error::Wasi(WasiError::EMLINK);
-    pub const EMSGSIZE: Self = Error::Wasi(WasiError::EMSGSIZE);
-    pub const EMULTIHOP: Self = Error::Wasi(WasiError::EMULTIHOP);
-    pub const ENAMETOOLONG: Self = Error::Wasi(WasiError::ENAMETOOLONG);
-    pub const ENETDOWN: Self = Error::Wasi(WasiError::ENETDOWN);
-    pub const ENETRESET: Self = Error::Wasi(WasiError::ENETRESET);
-    pub const ENETUNREACH: Self = Error::Wasi(WasiError::ENETUNREACH);
-    pub const ENFILE: Self = Error::Wasi(WasiError::ENFILE);
-    pub const ENOBUFS: Self = Error::Wasi(WasiError::ENOBUFS);
-    pub const ENODEV: Self = Error::Wasi(WasiError::ENODEV);
-    pub const ENOENT: Self = Error::Wasi(WasiError::ENOENT);
-    pub const ENOEXEC: Self = Error::Wasi(WasiError::ENOEXEC);
-    pub const ENOLCK: Self = Error::Wasi(WasiError::ENOLCK);
-    pub const ENOLINK: Self = Error::Wasi(WasiError::ENOLINK);
-    pub const ENOMEM: Self = Error::Wasi(WasiError::ENOMEM);
-    pub const ENOMSG: Self = Error::Wasi(WasiError::ENOMSG);
-    pub const ENOPROTOOPT: Self = Error::Wasi(WasiError::ENOPROTOOPT);
-    pub const ENOSPC: Self = Error::Wasi(WasiError::ENOSPC);
-    pub const ENOSYS: Self = Error::Wasi(WasiError::ENOSYS);
-    pub const ENOTCONN: Self = Error::Wasi(WasiError::ENOTCONN);
-    pub const ENOTDIR: Self = Error::Wasi(WasiError::ENOTDIR);
-    pub const ENOTEMPTY: Self = Error::Wasi(WasiError::ENOTEMPTY);
-    pub const ENOTRECOVERABLE: Self = Error::Wasi(WasiError::ENOTRECOVERABLE);
-    pub const ENOTSOCK: Self = Error::Wasi(WasiError::ENOTSOCK);
-    pub const ENOTSUP: Self = Error::Wasi(WasiError::ENOTSUP);
-    pub const ENOTTY: Self = Error::Wasi(WasiError::ENOTTY);
-    pub const ENXIO: Self = Error::Wasi(WasiError::ENXIO);
-    pub const EOVERFLOW: Self = Error::Wasi(WasiError::EOVERFLOW);
-    pub const EOWNERDEAD: Self = Error::Wasi(WasiError::EOWNERDEAD);
-    pub const EPERM: Self = Error::Wasi(WasiError::EPERM);
-    pub const EPIPE: Self = Error::Wasi(WasiError::EPIPE);
-    pub const EPROTO: Self = Error::Wasi(WasiError::EPROTO);
-    pub const EPROTONOSUPPORT: Self = Error::Wasi(WasiError::EPROTONOSUPPORT);
-    pub const EPROTOTYPE: Self = Error::Wasi(WasiError::EPROTOTYPE);
-    pub const ERANGE: Self = Error::Wasi(WasiError::ERANGE);
-    pub const EROFS: Self = Error::Wasi(WasiError::EROFS);
-    pub const ESPIPE: Self = Error::Wasi(WasiError::ESPIPE);
-    pub const ESRCH: Self = Error::Wasi(WasiError::ESRCH);
-    pub const ESTALE: Self = Error::Wasi(WasiError::ESTALE);
-    pub const ETIMEDOUT: Self = Error::Wasi(WasiError::ETIMEDOUT);
-    pub const ETXTBSY: Self = Error::Wasi(WasiError::ETXTBSY);
-    pub const EXDEV: Self = Error::Wasi(WasiError::EXDEV);
-    pub const ENOTCAPABLE: Self = Error::Wasi(WasiError::ENOTCAPABLE);
-}
-
-pub(crate) trait FromRawOsError {
-    fn from_raw_os_error(code: i32) -> Self;
-}
diff --git a/crates/wasi-common/src/old/snapshot_0/fdentry.rs b/crates/wasi-common/src/old/snapshot_0/fdentry.rs
index aab0178b93..cf248277f1 100644
--- a/crates/wasi-common/src/old/snapshot_0/fdentry.rs
+++ b/crates/wasi-common/src/old/snapshot_0/fdentry.rs
@@ -2,7 +2,7 @@ use crate::old::snapshot_0::sys::dev_null;
 use crate::old::snapshot_0::sys::fdentry_impl::{
     descriptor_as_oshandle, determine_type_and_access_rights, OsHandle,
 };
-use crate::old::snapshot_0::{wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use std::marker::PhantomData;
 use std::mem::ManuallyDrop;
 use std::ops::{Deref, DerefMut};
@@ -21,18 +21,18 @@ impl Descriptor {
     /// Return a reference to the `OsHandle` treating it as an actual file/dir, and
     /// allowing operations which require an actual file and not just a stream or
     /// socket file descriptor.
-    pub(crate) fn as_file(&self) -> Result<&OsHandle> {
+    pub(crate) fn as_file(&self) -> WasiResult<&OsHandle> {
         match self {
             Self::OsHandle(file) => Ok(file),
-            _ => Err(Error::EBADF),
+            _ => Err(WasiError::EBADF),
         }
     }
 
     /// Like `as_file`, but return a mutable reference.
-    pub(crate) fn as_file_mut(&mut self) -> Result<&mut OsHandle> {
+    pub(crate) fn as_file_mut(&mut self) -> WasiResult<&mut OsHandle> {
         match self {
             Self::OsHandle(file) => Ok(file),
-            _ => Err(Error::EBADF),
+            _ => Err(WasiError::EBADF),
         }
     }
 
@@ -64,7 +64,7 @@ impl FdEntry {
     /// Create an FdEntry with *maximal* possible rights from a given `File`.
     /// If this is not desired, the rights of the resulting `FdEntry` should
     /// be manually restricted.
-    pub(crate) fn from(file: fs::File) -> Result<Self> {
+    pub(crate) fn from(file: fs::File) -> io::Result<Self> {
         unsafe { determine_type_and_access_rights(&file) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 file_type,
@@ -76,7 +76,7 @@ impl FdEntry {
         )
     }
 
-    pub(crate) fn duplicate_stdin() -> Result<Self> {
+    pub(crate) fn duplicate_stdin() -> io::Result<Self> {
         unsafe { determine_type_and_access_rights(&io::stdin()) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 file_type,
@@ -88,7 +88,7 @@ impl FdEntry {
         )
     }
 
-    pub(crate) fn duplicate_stdout() -> Result<Self> {
+    pub(crate) fn duplicate_stdout() -> io::Result<Self> {
         unsafe { determine_type_and_access_rights(&io::stdout()) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 file_type,
@@ -100,7 +100,7 @@ impl FdEntry {
         )
     }
 
-    pub(crate) fn duplicate_stderr() -> Result<Self> {
+    pub(crate) fn duplicate_stderr() -> io::Result<Self> {
         unsafe { determine_type_and_access_rights(&io::stderr()) }.map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 file_type,
@@ -112,7 +112,7 @@ impl FdEntry {
         )
     }
 
-    pub(crate) fn null() -> Result<Self> {
+    pub(crate) fn null() -> io::Result<Self> {
         Self::from(dev_null()?)
     }
 
@@ -127,7 +127,7 @@ impl FdEntry {
         &self,
         rights_base: wasi::__wasi_rights_t,
         rights_inheriting: wasi::__wasi_rights_t,
-    ) -> Result<&Descriptor> {
+    ) -> WasiResult<&Descriptor> {
         self.validate_rights(rights_base, rights_inheriting)?;
         Ok(&self.descriptor)
     }
@@ -143,7 +143,7 @@ impl FdEntry {
         &mut self,
         rights_base: wasi::__wasi_rights_t,
         rights_inheriting: wasi::__wasi_rights_t,
-    ) -> Result<&mut Descriptor> {
+    ) -> WasiResult<&mut Descriptor> {
         self.validate_rights(rights_base, rights_inheriting)?;
         Ok(&mut self.descriptor)
     }
@@ -157,10 +157,10 @@ impl FdEntry {
         &self,
         rights_base: wasi::__wasi_rights_t,
         rights_inheriting: wasi::__wasi_rights_t,
-    ) -> Result<()> {
+    ) -> WasiResult<()> {
         if !self.rights_base & rights_base != 0 || !self.rights_inheriting & rights_inheriting != 0
         {
-            Err(Error::ENOTCAPABLE)
+            Err(WasiError::ENOTCAPABLE)
         } else {
             Ok(())
         }
diff --git a/crates/wasi-common/src/old/snapshot_0/helpers.rs b/crates/wasi-common/src/old/snapshot_0/helpers.rs
index f540eb8f12..e4426ffc2e 100644
--- a/crates/wasi-common/src/old/snapshot_0/helpers.rs
+++ b/crates/wasi-common/src/old/snapshot_0/helpers.rs
@@ -1,10 +1,11 @@
-use crate::old::snapshot_0::{Error, Result};
+use crate::old::snapshot_0::wasi::WasiResult;
 use std::str;
 
 /// Creates not-owned WASI path from byte slice.
 ///
 /// NB WASI spec requires bytes to be valid UTF-8. Otherwise,
 /// `__WASI_ERRNO_ILSEQ` error is returned.
-pub(crate) fn path_from_slice<'a>(s: &'a [u8]) -> Result<&'a str> {
-    str::from_utf8(s).map_err(|_| Error::EILSEQ)
+pub(crate) fn path_from_slice<'a>(s: &'a [u8]) -> WasiResult<&'a str> {
+    let s = str::from_utf8(s)?;
+    Ok(s)
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/host.rs b/crates/wasi-common/src/old/snapshot_0/host.rs
index b029fcf10e..e9cef3b750 100644
--- a/crates/wasi-common/src/old/snapshot_0/host.rs
+++ b/crates/wasi-common/src/old/snapshot_0/host.rs
@@ -5,7 +5,6 @@
 #![allow(non_snake_case)]
 
 use crate::old::snapshot_0::wasi::*;
-use crate::old::snapshot_0::{Error, Result};
 use std::{convert::TryInto, io, mem, slice};
 use wig::witx_host_types;
 
@@ -52,11 +51,13 @@ pub(crate) struct Dirent {
 impl Dirent {
     /// Serialize the directory entry to the format define by `__wasi_fd_readdir`,
     /// so that the serialized entries can be concatenated by the implementation.
-    pub fn to_wasi_raw(&self) -> Result<Vec<u8>> {
+    pub fn to_wasi_raw(&self) -> WasiResult<Vec<u8>> {
         let name = self.name.as_bytes();
         let namlen = name.len();
         let dirent_size = mem::size_of::<__wasi_dirent_t>();
-        let offset = dirent_size.checked_add(namlen).ok_or(Error::EOVERFLOW)?;
+        let offset = dirent_size
+            .checked_add(namlen)
+            .ok_or(WasiError::EOVERFLOW)?;
 
         let mut raw = Vec::<u8>::with_capacity(offset);
         raw.resize(offset, 0);
diff --git a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs.rs b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs.rs
index ff23ae0a5e..a038ad4bf8 100644
--- a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs.rs
+++ b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs.rs
@@ -7,7 +7,8 @@ use crate::old::snapshot_0::memory::*;
 use crate::old::snapshot_0::sys::fdentry_impl::determine_type_rights;
 use crate::old::snapshot_0::sys::hostcalls_impl::fs_helpers::path_open_rights;
 use crate::old::snapshot_0::sys::{host_impl, hostcalls_impl};
-use crate::old::snapshot_0::{helpers, host, wasi, wasi32, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
+use crate::old::snapshot_0::{helpers, host, wasi32};
 use crate::sandboxed_tty_writer::SandboxedTTYWriter;
 use filetime::{set_file_handle_times, FileTime};
 use log::trace;
@@ -20,13 +21,13 @@ pub(crate) unsafe fn fd_close(
     wasi_ctx: &mut WasiCtx,
     _mem: &mut [u8],
     fd: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_close(fd={:?})", fd);
 
     if let Ok(fe) = wasi_ctx.get_fd_entry(fd) {
         // can't close preopened files
         if fe.preopen_path.is_some() {
-            return Err(Error::ENOTSUP);
+            return Err(WasiError::ENOTSUP);
         }
     }
 
@@ -38,7 +39,7 @@ pub(crate) unsafe fn fd_datasync(
     wasi_ctx: &WasiCtx,
     _mem: &mut [u8],
     fd: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_datasync(fd={:?})", fd);
 
     let fd = wasi_ctx
@@ -57,7 +58,7 @@ pub(crate) unsafe fn fd_pread(
     iovs_len: wasi32::size_t,
     offset: wasi::__wasi_filesize_t,
     nread: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_pread(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, offset={}, nread={:#x?})",
         fd,
@@ -75,7 +76,7 @@ pub(crate) unsafe fn fd_pread(
     let iovs = dec_iovec_slice(memory, iovs_ptr, iovs_len)?;
 
     if offset > i64::max_value() as u64 {
-        return Err(Error::EIO);
+        return Err(WasiError::EIO);
     }
     let buf_size = iovs.iter().map(|v| v.buf_len).sum();
     let mut buf = vec![0; buf_size];
@@ -106,7 +107,7 @@ pub(crate) unsafe fn fd_pwrite(
     iovs_len: wasi32::size_t,
     offset: wasi::__wasi_filesize_t,
     nwritten: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_pwrite(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, offset={}, nwritten={:#x?})",
         fd,
@@ -126,7 +127,7 @@ pub(crate) unsafe fn fd_pwrite(
     let iovs = dec_ciovec_slice(memory, iovs_ptr, iovs_len)?;
 
     if offset > i64::max_value() as u64 {
-        return Err(Error::EIO);
+        return Err(WasiError::EIO);
     }
     let buf_size = iovs.iter().map(|v| v.buf_len).sum();
     let mut buf = Vec::with_capacity(buf_size);
@@ -150,7 +151,7 @@ pub(crate) unsafe fn fd_read(
     iovs_ptr: wasi32::uintptr_t,
     iovs_len: wasi32::size_t,
     nread: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_read(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, nread={:#x?})",
         fd,
@@ -171,7 +172,7 @@ pub(crate) unsafe fn fd_read(
     {
         Descriptor::OsHandle(file) => file.read_vectored(&mut iovs),
         Descriptor::Stdin => io::stdin().read_vectored(&mut iovs),
-        _ => return Err(Error::EBADF),
+        _ => return Err(WasiError::EBADF),
     };
 
     let host_nread = maybe_host_nread?;
@@ -186,11 +187,11 @@ pub(crate) unsafe fn fd_renumber(
     _mem: &mut [u8],
     from: wasi::__wasi_fd_t,
     to: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_renumber(from={:?}, to={:?})", from, to);
 
     if !wasi_ctx.contains_fd_entry(from) {
-        return Err(Error::EBADF);
+        return Err(WasiError::EBADF);
     }
 
     // Don't allow renumbering over a pre-opened resource.
@@ -198,11 +199,11 @@ pub(crate) unsafe fn fd_renumber(
     // userspace is capable of removing entries from its tables as well.
     let from_fe = wasi_ctx.get_fd_entry(from)?;
     if from_fe.preopen_path.is_some() {
-        return Err(Error::ENOTSUP);
+        return Err(WasiError::ENOTSUP);
     }
     if let Ok(to_fe) = wasi_ctx.get_fd_entry(to) {
         if to_fe.preopen_path.is_some() {
-            return Err(Error::ENOTSUP);
+            return Err(WasiError::ENOTSUP);
         }
     }
 
@@ -219,7 +220,7 @@ pub(crate) unsafe fn fd_seek(
     offset: wasi::__wasi_filedelta_t,
     whence: wasi::__wasi_whence_t,
     newoffset: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_seek(fd={:?}, offset={:?}, whence={}, newoffset={:#x?})",
         fd,
@@ -242,7 +243,7 @@ pub(crate) unsafe fn fd_seek(
         wasi::__WASI_WHENCE_CUR => SeekFrom::Current(offset),
         wasi::__WASI_WHENCE_END => SeekFrom::End(offset),
         wasi::__WASI_WHENCE_SET => SeekFrom::Start(offset as u64),
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     };
     let host_newoffset = fd.seek(pos)?;
 
@@ -256,7 +257,7 @@ pub(crate) unsafe fn fd_tell(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     newoffset: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_tell(fd={:?}, newoffset={:#x?})", fd, newoffset);
 
     let fd = wasi_ctx
@@ -276,7 +277,7 @@ pub(crate) unsafe fn fd_fdstat_get(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     fdstat_ptr: wasi32::uintptr_t, // *mut wasi::__wasi_fdstat_t
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_fdstat_get(fd={:?}, fdstat_ptr={:#x?})", fd, fdstat_ptr);
 
     let mut fdstat = dec_fdstat_byref(memory, fdstat_ptr)?;
@@ -303,7 +304,7 @@ pub(crate) unsafe fn fd_fdstat_set_flags(
     _mem: &mut [u8],
     fd: wasi::__wasi_fd_t,
     fdflags: wasi::__wasi_fdflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_fdstat_set_flags(fd={:?}, fdflags={:#x?})", fd, fdflags);
 
     let fd = wasi_ctx
@@ -320,7 +321,7 @@ pub(crate) unsafe fn fd_fdstat_set_rights(
     fd: wasi::__wasi_fd_t,
     fs_rights_base: wasi::__wasi_rights_t,
     fs_rights_inheriting: wasi::__wasi_rights_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_fdstat_set_rights(fd={:?}, fs_rights_base={:#x?}, fs_rights_inheriting={:#x?})",
         fd,
@@ -332,7 +333,7 @@ pub(crate) unsafe fn fd_fdstat_set_rights(
     if fe.rights_base & fs_rights_base != fs_rights_base
         || fe.rights_inheriting & fs_rights_inheriting != fs_rights_inheriting
     {
-        return Err(Error::ENOTCAPABLE);
+        return Err(WasiError::ENOTCAPABLE);
     }
     fe.rights_base = fs_rights_base;
     fe.rights_inheriting = fs_rights_inheriting;
@@ -344,7 +345,7 @@ pub(crate) unsafe fn fd_sync(
     wasi_ctx: &WasiCtx,
     _mem: &mut [u8],
     fd: wasi::__wasi_fd_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_sync(fd={:?})", fd);
 
     let fd = wasi_ctx
@@ -361,7 +362,7 @@ pub(crate) unsafe fn fd_write(
     iovs_ptr: wasi32::uintptr_t,
     iovs_len: wasi32::size_t,
     nwritten: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_write(fd={:?}, iovs_ptr={:#x?}, iovs_len={:?}, nwritten={:#x?})",
         fd,
@@ -385,7 +386,7 @@ pub(crate) unsafe fn fd_write(
                 file.write_vectored(&iovs)?
             }
         }
-        Descriptor::Stdin => return Err(Error::EBADF),
+        Descriptor::Stdin => return Err(WasiError::EBADF),
         Descriptor::Stdout => {
             // lock for the duration of the scope
             let stdout = io::stdout();
@@ -417,7 +418,7 @@ pub(crate) unsafe fn fd_advise(
     offset: wasi::__wasi_filesize_t,
     len: wasi::__wasi_filesize_t,
     advice: wasi::__wasi_advice_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_advise(fd={:?}, offset={}, len={}, advice={:?})",
         fd,
@@ -440,7 +441,7 @@ pub(crate) unsafe fn fd_allocate(
     fd: wasi::__wasi_fd_t,
     offset: wasi::__wasi_filesize_t,
     len: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_allocate(fd={:?}, offset={}, len={})", fd, offset, len);
 
     let fd = wasi_ctx
@@ -451,10 +452,10 @@ pub(crate) unsafe fn fd_allocate(
     let metadata = fd.metadata()?;
 
     let current_size = metadata.len();
-    let wanted_size = offset.checked_add(len).ok_or(Error::E2BIG)?;
+    let wanted_size = offset.checked_add(len).ok_or(WasiError::E2BIG)?;
     // This check will be unnecessary when rust-lang/rust#63326 is fixed
     if wanted_size > i64::max_value() as u64 {
-        return Err(Error::E2BIG);
+        return Err(WasiError::E2BIG);
     }
 
     if wanted_size > current_size {
@@ -470,7 +471,7 @@ pub(crate) unsafe fn path_create_directory(
     dirfd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_create_directory(dirfd={:?}, path_ptr={:#x?}, path_len={})",
         dirfd,
@@ -499,7 +500,7 @@ pub(crate) unsafe fn path_link(
     new_dirfd: wasi::__wasi_fd_t,
     new_path_ptr: wasi32::uintptr_t,
     new_path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_link(old_dirfd={:?}, old_flags={:?}, old_path_ptr={:#x?}, old_path_len={}, new_dirfd={:?}, new_path_ptr={:#x?}, new_path_len={})",
         old_dirfd,
@@ -551,7 +552,7 @@ pub(crate) unsafe fn path_open(
     fs_rights_inheriting: wasi::__wasi_rights_t,
     fs_flags: wasi::__wasi_fdflags_t,
     fd_out_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_open(dirfd={:?}, dirflags={:?}, path_ptr={:#x?}, path_len={:?}, oflags={:#x?}, fs_rights_base={:#x?}, fs_rights_inheriting={:#x?}, fs_flags={:#x?}, fd_out_ptr={:#x?})",
         dirfd,
@@ -616,7 +617,7 @@ pub(crate) unsafe fn path_readlink(
     buf_ptr: wasi32::uintptr_t,
     buf_len: wasi32::size_t,
     buf_used: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_readlink(dirfd={:?}, path_ptr={:#x?}, path_len={:?}, buf_ptr={:#x?}, buf_len={}, buf_used={:#x?})",
         dirfd,
@@ -655,7 +656,7 @@ pub(crate) unsafe fn path_rename(
     new_dirfd: wasi::__wasi_fd_t,
     new_path_ptr: wasi32::uintptr_t,
     new_path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_rename(old_dirfd={:?}, old_path_ptr={:#x?}, old_path_len={:?}, new_dirfd={:?}, new_path_ptr={:#x?}, new_path_len={:?})",
         old_dirfd,
@@ -702,7 +703,7 @@ pub(crate) unsafe fn fd_filestat_get(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     filestat_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_filestat_get(fd={:?}, filestat_ptr={:#x?})",
         fd,
@@ -724,7 +725,7 @@ pub(crate) unsafe fn fd_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_filestat_set_times(fd={:?}, st_atim={}, st_mtim={}, fst_flags={:#x?})",
         fd,
@@ -746,14 +747,14 @@ pub(crate) fn fd_filestat_set_times_impl(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let set_atim = fst_flags & wasi::__WASI_FSTFLAGS_ATIM != 0;
     let set_atim_now = fst_flags & wasi::__WASI_FSTFLAGS_ATIM_NOW != 0;
     let set_mtim = fst_flags & wasi::__WASI_FSTFLAGS_MTIM != 0;
     let set_mtim_now = fst_flags & wasi::__WASI_FSTFLAGS_MTIM_NOW != 0;
 
     if (set_atim && set_atim_now) || (set_mtim && set_mtim_now) {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
     let atim = if set_atim {
         let time = UNIX_EPOCH + Duration::from_nanos(st_atim);
@@ -782,7 +783,7 @@ pub(crate) unsafe fn fd_filestat_set_size(
     _mem: &mut [u8],
     fd: wasi::__wasi_fd_t,
     st_size: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("fd_filestat_set_size(fd={:?}, st_size={})", fd, st_size);
 
     let fd = wasi_ctx
@@ -792,7 +793,7 @@ pub(crate) unsafe fn fd_filestat_set_size(
 
     // This check will be unnecessary when rust-lang/rust#63326 is fixed
     if st_size > i64::max_value() as u64 {
-        return Err(Error::E2BIG);
+        return Err(WasiError::E2BIG);
     }
     fd.set_len(st_size).map_err(Into::into)
 }
@@ -805,7 +806,7 @@ pub(crate) unsafe fn path_filestat_get(
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
     filestat_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_filestat_get(dirfd={:?}, dirflags={:?}, path_ptr={:#x?}, path_len={}, filestat_ptr={:#x?})",
         dirfd,
@@ -845,7 +846,7 @@ pub(crate) unsafe fn path_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_filestat_set_times(dirfd={:?}, dirflags={:?}, path_ptr={:#x?}, path_len={}, st_atim={}, st_mtim={}, fst_flags={:#x?})",
         dirfd,
@@ -881,7 +882,7 @@ pub(crate) unsafe fn path_symlink(
     dirfd: wasi::__wasi_fd_t,
     new_path_ptr: wasi32::uintptr_t,
     new_path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_symlink(old_path_ptr={:#x?}, old_path_len={}, dirfd={:?}, new_path_ptr={:#x?}, new_path_len={})",
         old_path_ptr,
@@ -909,7 +910,7 @@ pub(crate) unsafe fn path_unlink_file(
     dirfd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_unlink_file(dirfd={:?}, path_ptr={:#x?}, path_len={})",
         dirfd,
@@ -933,7 +934,7 @@ pub(crate) unsafe fn path_remove_directory(
     dirfd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "path_remove_directory(dirfd={:?}, path_ptr={:#x?}, path_len={})",
         dirfd,
@@ -965,7 +966,7 @@ pub(crate) unsafe fn fd_prestat_get(
     memory: &mut [u8],
     fd: wasi::__wasi_fd_t,
     prestat_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_prestat_get(fd={:?}, prestat_ptr={:#x?})",
         fd,
@@ -974,9 +975,9 @@ pub(crate) unsafe fn fd_prestat_get(
 
     // TODO: should we validate any rights here?
     let fe = wasi_ctx.get_fd_entry(fd)?;
-    let po_path = fe.preopen_path.as_ref().ok_or(Error::ENOTSUP)?;
+    let po_path = fe.preopen_path.as_ref().ok_or(WasiError::ENOTSUP)?;
     if fe.file_type != wasi::__WASI_FILETYPE_DIRECTORY {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     let path = host_impl::path_from_host(po_path.as_os_str())?;
@@ -1001,7 +1002,7 @@ pub(crate) unsafe fn fd_prestat_dir_name(
     fd: wasi::__wasi_fd_t,
     path_ptr: wasi32::uintptr_t,
     path_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_prestat_dir_name(fd={:?}, path_ptr={:#x?}, path_len={})",
         fd,
@@ -1011,15 +1012,15 @@ pub(crate) unsafe fn fd_prestat_dir_name(
 
     // TODO: should we validate any rights here?
     let fe = wasi_ctx.get_fd_entry(fd)?;
-    let po_path = fe.preopen_path.as_ref().ok_or(Error::ENOTSUP)?;
+    let po_path = fe.preopen_path.as_ref().ok_or(WasiError::ENOTSUP)?;
     if fe.file_type != wasi::__WASI_FILETYPE_DIRECTORY {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     let path = host_impl::path_from_host(po_path.as_os_str())?;
 
     if path.len() > dec_usize(path_len) {
-        return Err(Error::ENAMETOOLONG);
+        return Err(WasiError::ENAMETOOLONG);
     }
 
     trace!("     | (path_ptr,path_len)='{}'", path);
@@ -1035,7 +1036,7 @@ pub(crate) unsafe fn fd_readdir(
     buf_len: wasi32::size_t,
     cookie: wasi::__wasi_dircookie_t,
     buf_used: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "fd_readdir(fd={:?}, buf={:#x?}, buf_len={}, cookie={:#x?}, buf_used={:#x?})",
         fd,
diff --git a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs_helpers.rs b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs_helpers.rs
index ff41bbc3a9..c646cc895e 100644
--- a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs_helpers.rs
+++ b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/fs_helpers.rs
@@ -1,7 +1,8 @@
 #![allow(non_camel_case_types)]
+use crate::old::snapshot_0::fdentry::FdEntry;
 use crate::old::snapshot_0::sys::host_impl;
 use crate::old::snapshot_0::sys::hostcalls_impl::fs_helpers::*;
-use crate::old::snapshot_0::{error::WasiError, fdentry::FdEntry, wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use std::fs::File;
 use std::path::{Component, Path};
 
@@ -31,17 +32,17 @@ pub(crate) fn path_get(
     dirflags: wasi::__wasi_lookupflags_t,
     path: &str,
     needs_final_component: bool,
-) -> Result<PathGet> {
+) -> WasiResult<PathGet> {
     const MAX_SYMLINK_EXPANSIONS: usize = 128;
 
     if path.contains('\0') {
         // if contains NUL, return EILSEQ
-        return Err(Error::EILSEQ);
+        return Err(WasiError::EILSEQ);
     }
 
     if fe.file_type != wasi::__WASI_FILETYPE_DIRECTORY {
         // if `dirfd` doesn't refer to a directory, return `ENOTDIR`.
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     let dirfd = fe
@@ -72,7 +73,7 @@ pub(crate) fn path_get(
                 let ends_with_slash = cur_path.ends_with('/');
                 let mut components = Path::new(&cur_path).components();
                 let head = match components.next() {
-                    None => return Err(Error::ENOENT),
+                    None => return Err(WasiError::ENOENT),
                     Some(p) => p,
                 };
                 let tail = components.as_path();
@@ -90,18 +91,18 @@ pub(crate) fn path_get(
                 match head {
                     Component::Prefix(_) | Component::RootDir => {
                         // path is absolute!
-                        return Err(Error::ENOTCAPABLE);
+                        return Err(WasiError::ENOTCAPABLE);
                     }
                     Component::CurDir => {
                         // "." so skip
                     }
                     Component::ParentDir => {
                         // ".." so pop a dir
-                        let _ = dir_stack.pop().ok_or(Error::ENOTCAPABLE)?;
+                        let _ = dir_stack.pop().ok_or(WasiError::ENOTCAPABLE)?;
 
                         // we're not allowed to pop past the original directory
                         if dir_stack.is_empty() {
-                            return Err(Error::ENOTCAPABLE);
+                            return Err(WasiError::ENOTCAPABLE);
                         }
                     }
                     Component::Normal(head) => {
@@ -112,12 +113,12 @@ pub(crate) fn path_get(
                         }
 
                         if !path_stack.is_empty() || (ends_with_slash && !needs_final_component) {
-                            match openat(dir_stack.last().ok_or(Error::ENOTCAPABLE)?, &head) {
+                            match openat(dir_stack.last().ok_or(WasiError::ENOTCAPABLE)?, &head) {
                                 Ok(new_dir) => {
                                     dir_stack.push(new_dir);
                                 }
                                 Err(e) => {
-                                    match e.as_wasi_error() {
+                                    match e {
                                         WasiError::ELOOP
                                         | WasiError::EMLINK
                                         | WasiError::ENOTDIR =>
@@ -126,13 +127,13 @@ pub(crate) fn path_get(
                                         {
                                             // attempt symlink expansion
                                             let mut link_path = readlinkat(
-                                                dir_stack.last().ok_or(Error::ENOTCAPABLE)?,
+                                                dir_stack.last().ok_or(WasiError::ENOTCAPABLE)?,
                                                 &head,
                                             )?;
 
                                             symlink_expansions += 1;
                                             if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
-                                                return Err(Error::ELOOP);
+                                                return Err(WasiError::ELOOP);
                                             }
 
                                             if head.ends_with('/') {
@@ -159,11 +160,12 @@ pub(crate) fn path_get(
                         {
                             // if there's a trailing slash, or if `LOOKUP_SYMLINK_FOLLOW` is set, attempt
                             // symlink expansion
-                            match readlinkat(dir_stack.last().ok_or(Error::ENOTCAPABLE)?, &head) {
+                            match readlinkat(dir_stack.last().ok_or(WasiError::ENOTCAPABLE)?, &head)
+                            {
                                 Ok(mut link_path) => {
                                     symlink_expansions += 1;
                                     if symlink_expansions > MAX_SYMLINK_EXPANSIONS {
-                                        return Err(Error::ELOOP);
+                                        return Err(WasiError::ELOOP);
                                     }
 
                                     if head.ends_with('/') {
@@ -179,12 +181,12 @@ pub(crate) fn path_get(
                                     continue;
                                 }
                                 Err(e) => {
-                                    if e.as_wasi_error() != WasiError::EINVAL
-                                        && e.as_wasi_error() != WasiError::ENOENT
+                                    if e != WasiError::EINVAL
+                                        && e != WasiError::ENOENT
                                         // this handles the cases when trying to link to
                                         // a destination that already exists, and the target
                                         // path contains a slash
-                                        && e.as_wasi_error() != WasiError::ENOTDIR
+                                        && e != WasiError::ENOTDIR
                                     {
                                         return Err(e);
                                     }
@@ -194,7 +196,7 @@ pub(crate) fn path_get(
 
                         // not a symlink, so we're done;
                         return Ok(PathGet {
-                            dirfd: dir_stack.pop().ok_or(Error::ENOTCAPABLE)?,
+                            dirfd: dir_stack.pop().ok_or(WasiError::ENOTCAPABLE)?,
                             path: head,
                         });
                     }
@@ -204,7 +206,7 @@ pub(crate) fn path_get(
                 // no further components to process. means we've hit a case like "." or "a/..", or if the
                 // input path has trailing slashes and `needs_final_component` is not set
                 return Ok(PathGet {
-                    dirfd: dir_stack.pop().ok_or(Error::ENOTCAPABLE)?,
+                    dirfd: dir_stack.pop().ok_or(WasiError::ENOTCAPABLE)?,
                     path: String::from("."),
                 });
             }
diff --git a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/misc.rs b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/misc.rs
index 14820a3e66..d577533bce 100644
--- a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/misc.rs
+++ b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/misc.rs
@@ -3,7 +3,8 @@ use crate::old::snapshot_0::ctx::WasiCtx;
 use crate::old::snapshot_0::fdentry::Descriptor;
 use crate::old::snapshot_0::memory::*;
 use crate::old::snapshot_0::sys::hostcalls_impl;
-use crate::old::snapshot_0::{wasi, wasi32, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
+use crate::old::snapshot_0::wasi32;
 use log::{error, trace};
 use std::convert::TryFrom;
 
@@ -12,7 +13,7 @@ pub(crate) fn args_get(
     memory: &mut [u8],
     argv_ptr: wasi32::uintptr_t,
     argv_buf: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "args_get(argv_ptr={:#x?}, argv_buf={:#x?})",
         argv_ptr,
@@ -31,7 +32,9 @@ pub(crate) fn args_get(
         argv.push(arg_ptr);
 
         let len = wasi32::uintptr_t::try_from(arg_bytes.len())?;
-        argv_buf_offset = argv_buf_offset.checked_add(len).ok_or(Error::EOVERFLOW)?;
+        argv_buf_offset = argv_buf_offset
+            .checked_add(len)
+            .ok_or(WasiError::EOVERFLOW)?;
     }
 
     enc_slice_of_wasi32_uintptr(memory, argv.as_slice(), argv_ptr)
@@ -42,7 +45,7 @@ pub(crate) fn args_sizes_get(
     memory: &mut [u8],
     argc_ptr: wasi32::uintptr_t,
     argv_buf_size_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "args_sizes_get(argc_ptr={:#x?}, argv_buf_size_ptr={:#x?})",
         argc_ptr,
@@ -70,7 +73,7 @@ pub(crate) fn environ_get(
     memory: &mut [u8],
     environ_ptr: wasi32::uintptr_t,
     environ_buf: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "environ_get(environ_ptr={:#x?}, environ_buf={:#x?})",
         environ_ptr,
@@ -91,7 +94,7 @@ pub(crate) fn environ_get(
         let len = wasi32::uintptr_t::try_from(env_bytes.len())?;
         environ_buf_offset = environ_buf_offset
             .checked_add(len)
-            .ok_or(Error::EOVERFLOW)?;
+            .ok_or(WasiError::EOVERFLOW)?;
     }
 
     enc_slice_of_wasi32_uintptr(memory, environ.as_slice(), environ_ptr)
@@ -102,7 +105,7 @@ pub(crate) fn environ_sizes_get(
     memory: &mut [u8],
     environ_count_ptr: wasi32::uintptr_t,
     environ_size_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "environ_sizes_get(environ_count_ptr={:#x?}, environ_size_ptr={:#x?})",
         environ_count_ptr,
@@ -116,7 +119,7 @@ pub(crate) fn environ_sizes_get(
         .try_fold(0, |acc: u32, pair| {
             acc.checked_add(pair.as_bytes_with_nul().len() as u32)
         })
-        .ok_or(Error::EOVERFLOW)?;
+        .ok_or(WasiError::EOVERFLOW)?;
 
     trace!("     | *environ_count_ptr={:?}", environ_count);
 
@@ -132,14 +135,14 @@ pub(crate) fn random_get(
     memory: &mut [u8],
     buf_ptr: wasi32::uintptr_t,
     buf_len: wasi32::size_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!("random_get(buf_ptr={:#x?}, buf_len={:?})", buf_ptr, buf_len);
 
     let buf = dec_slice_of_mut_u8(memory, buf_ptr, buf_len)?;
 
     getrandom::getrandom(buf).map_err(|err| {
         error!("getrandom failure: {:?}", err);
-        Error::EIO
+        WasiError::EIO
     })
 }
 
@@ -148,7 +151,7 @@ pub(crate) fn clock_res_get(
     memory: &mut [u8],
     clock_id: wasi::__wasi_clockid_t,
     resolution_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "clock_res_get(clock_id={:?}, resolution_ptr={:#x?})",
         clock_id,
@@ -168,7 +171,7 @@ pub(crate) fn clock_time_get(
     clock_id: wasi::__wasi_clockid_t,
     precision: wasi::__wasi_timestamp_t,
     time_ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "clock_time_get(clock_id={:?}, precision={:?}, time_ptr={:#x?})",
         clock_id,
@@ -183,7 +186,7 @@ pub(crate) fn clock_time_get(
     enc_timestamp_byref(memory, time_ptr, time)
 }
 
-pub(crate) fn sched_yield(_wasi_ctx: &WasiCtx, _memory: &mut [u8]) -> Result<()> {
+pub(crate) fn sched_yield(_wasi_ctx: &WasiCtx, _memory: &mut [u8]) -> WasiResult<()> {
     trace!("sched_yield()");
 
     std::thread::yield_now();
@@ -198,7 +201,7 @@ pub(crate) fn poll_oneoff(
     output: wasi32::uintptr_t,
     nsubscriptions: wasi32::size_t,
     nevents: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     trace!(
         "poll_oneoff(input={:#x?}, output={:#x?}, nsubscriptions={}, nevents={:#x?})",
         input,
@@ -208,7 +211,7 @@ pub(crate) fn poll_oneoff(
     );
 
     if u64::from(nsubscriptions) > wasi::__wasi_filesize_t::max_value() {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     enc_int_byref(memory, nevents, 0)?;
@@ -253,7 +256,7 @@ pub(crate) fn poll_oneoff(
                     Err(err) => {
                         let event = wasi::__wasi_event_t {
                             userdata: subscription.userdata,
-                            error: err.as_wasi_error().as_raw_errno(),
+                            error: err.as_raw_errno(),
                             r#type: wasi::__WASI_EVENTTYPE_FD_READ,
                             fd_readwrite: wasi::__wasi_event_fd_readwrite_t {
                                 nbytes: 0,
@@ -281,7 +284,7 @@ pub(crate) fn poll_oneoff(
                     Err(err) => {
                         let event = wasi::__wasi_event_t {
                             userdata: subscription.userdata,
-                            error: err.as_wasi_error().as_raw_errno(),
+                            error: err.as_raw_errno(),
                             r#type: wasi::__WASI_EVENTTYPE_FD_WRITE,
                             fd_readwrite: wasi::__wasi_event_fd_readwrite_t {
                                 nbytes: 0,
@@ -301,7 +304,7 @@ pub(crate) fn poll_oneoff(
 
     hostcalls_impl::poll_oneoff(timeout, fd_events, &mut events)?;
 
-    let events_count = u32::try_from(events.len()).map_err(|_| Error::EOVERFLOW)?;
+    let events_count = u32::try_from(events.len()).map_err(|_| WasiError::EOVERFLOW)?;
 
     enc_events(memory, output, nsubscriptions, events)?;
 
@@ -310,7 +313,9 @@ pub(crate) fn poll_oneoff(
     enc_int_byref(memory, nevents, events_count)
 }
 
-fn wasi_clock_to_relative_ns_delay(wasi_clock: wasi::__wasi_subscription_clock_t) -> Result<u128> {
+fn wasi_clock_to_relative_ns_delay(
+    wasi_clock: wasi::__wasi_subscription_clock_t,
+) -> WasiResult<u128> {
     use std::time::SystemTime;
 
     if wasi_clock.flags != wasi::__WASI_SUBCLOCKFLAGS_SUBSCRIPTION_CLOCK_ABSTIME {
@@ -318,7 +323,7 @@ fn wasi_clock_to_relative_ns_delay(wasi_clock: wasi::__wasi_subscription_clock_t
     }
     let now: u128 = SystemTime::now()
         .duration_since(SystemTime::UNIX_EPOCH)
-        .map_err(|_| Error::ENOTCAPABLE)?
+        .map_err(|_| WasiError::ENOTCAPABLE)?
         .as_nanos();
     let deadline = u128::from(wasi_clock.timeout);
     Ok(deadline.saturating_sub(now))
@@ -348,6 +353,6 @@ pub(crate) fn proc_raise(
     _wasi_ctx: &WasiCtx,
     _memory: &mut [u8],
     _sig: wasi::__wasi_signal_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("proc_raise")
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/sock.rs b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/sock.rs
index ac485413ad..0e92ce4e21 100644
--- a/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/sock.rs
+++ b/crates/wasi-common/src/old/snapshot_0/hostcalls_impl/sock.rs
@@ -1,4 +1,5 @@
-use crate::old::snapshot_0::{wasi, wasi32, Result, WasiCtx};
+use crate::old::snapshot_0::wasi::{self, WasiResult};
+use crate::old::snapshot_0::{wasi32, WasiCtx};
 
 pub fn sock_recv(
     _wasi_ctx: &WasiCtx,
@@ -9,7 +10,7 @@ pub fn sock_recv(
     _ri_flags: wasi::__wasi_riflags_t,
     _ro_datalen: wasi32::uintptr_t,
     _ro_flags: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("sock_recv")
 }
 
@@ -21,7 +22,7 @@ pub fn sock_send(
     _si_data_len: wasi32::size_t,
     _si_flags: wasi::__wasi_siflags_t,
     _so_datalen: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("sock_send")
 }
 
@@ -30,6 +31,6 @@ pub fn sock_shutdown(
     _memory: &mut [u8],
     _sock: wasi::__wasi_fd_t,
     _how: wasi::__wasi_sdflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     unimplemented!("sock_shutdown")
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/memory.rs b/crates/wasi-common/src/old/snapshot_0/memory.rs
index c4f1d007ec..7f46db6c1e 100644
--- a/crates/wasi-common/src/old/snapshot_0/memory.rs
+++ b/crates/wasi-common/src/old/snapshot_0/memory.rs
@@ -8,38 +8,39 @@
 //! are not held for long durations.
 
 #![allow(unused)]
-use crate::old::snapshot_0::{host, wasi, wasi32, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
+use crate::old::snapshot_0::{host, wasi32};
 use num::PrimInt;
 use std::convert::TryFrom;
 use std::mem::{align_of, size_of};
 use std::{ptr, slice};
 
-fn dec_ptr(memory: &[u8], ptr: wasi32::uintptr_t, len: usize) -> Result<*const u8> {
+fn dec_ptr(memory: &[u8], ptr: wasi32::uintptr_t, len: usize) -> WasiResult<*const u8> {
     // check for overflow
-    let checked_len = (ptr as usize).checked_add(len).ok_or(Error::EFAULT)?;
+    let checked_len = (ptr as usize).checked_add(len).ok_or(WasiError::EFAULT)?;
 
     // translate the pointer
     memory
         .get(ptr as usize..checked_len)
-        .ok_or(Error::EFAULT)
+        .ok_or(WasiError::EFAULT)
         .map(|mem| mem.as_ptr())
 }
 
-fn dec_ptr_mut(memory: &mut [u8], ptr: wasi32::uintptr_t, len: usize) -> Result<*mut u8> {
+fn dec_ptr_mut(memory: &mut [u8], ptr: wasi32::uintptr_t, len: usize) -> WasiResult<*mut u8> {
     // check for overflow
-    let checked_len = (ptr as usize).checked_add(len).ok_or(Error::EFAULT)?;
+    let checked_len = (ptr as usize).checked_add(len).ok_or(WasiError::EFAULT)?;
 
     // translate the pointer
     memory
         .get_mut(ptr as usize..checked_len)
-        .ok_or(Error::EFAULT)
+        .ok_or(WasiError::EFAULT)
         .map(|mem| mem.as_mut_ptr())
 }
 
-fn dec_ptr_to<'memory, T>(memory: &'memory [u8], ptr: wasi32::uintptr_t) -> Result<&'memory T> {
+fn dec_ptr_to<'memory, T>(memory: &'memory [u8], ptr: wasi32::uintptr_t) -> WasiResult<&'memory T> {
     // check that the ptr is aligned
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     dec_ptr(memory, ptr, size_of::<T>()).map(|p| unsafe { &*(p as *const T) })
@@ -48,49 +49,49 @@ fn dec_ptr_to<'memory, T>(memory: &'memory [u8], ptr: wasi32::uintptr_t) -> Resu
 fn dec_ptr_to_mut<'memory, T>(
     memory: &'memory mut [u8],
     ptr: wasi32::uintptr_t,
-) -> Result<&'memory mut T> {
+) -> WasiResult<&'memory mut T> {
     // check that the ptr is aligned
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     dec_ptr_mut(memory, ptr, size_of::<T>()).map(|p| unsafe { &mut *(p as *mut T) })
 }
 
 /// This function does not perform endianness conversions!
-fn dec_raw_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> Result<T> {
+fn dec_raw_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> WasiResult<T> {
     dec_ptr_to::<T>(memory, ptr).map(|p| unsafe { ptr::read(p) })
 }
 
 /// This function does not perform endianness conversions!
-fn enc_raw_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> Result<()> {
+fn enc_raw_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> WasiResult<()> {
     dec_ptr_to_mut::<T>(memory, ptr).map(|p| unsafe { ptr::write(p, t) })
 }
 
-pub(crate) fn dec_int_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> Result<T>
+pub(crate) fn dec_int_byref<T>(memory: &[u8], ptr: wasi32::uintptr_t) -> WasiResult<T>
 where
     T: PrimInt,
 {
     dec_raw_byref::<T>(memory, ptr).map(|i| PrimInt::from_le(i))
 }
 
-pub(crate) fn enc_int_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> Result<()>
+pub(crate) fn enc_int_byref<T>(memory: &mut [u8], ptr: wasi32::uintptr_t, t: T) -> WasiResult<()>
 where
     T: PrimInt,
 {
     enc_raw_byref::<T>(memory, ptr, PrimInt::to_le(t))
 }
 
-fn check_slice_of<T>(ptr: wasi32::uintptr_t, len: wasi32::size_t) -> Result<(usize, usize)> {
+fn check_slice_of<T>(ptr: wasi32::uintptr_t, len: wasi32::size_t) -> WasiResult<(usize, usize)> {
     // check alignment, and that length doesn't overflow
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
     let len = dec_usize(len);
     let len_bytes = if let Some(len) = size_of::<T>().checked_mul(len) {
         len
     } else {
-        return Err(Error::EOVERFLOW);
+        return Err(WasiError::EOVERFLOW);
     };
 
     Ok((len, len_bytes))
@@ -100,7 +101,7 @@ fn dec_raw_slice_of<'memory, T>(
     memory: &'memory [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory [T]> {
+) -> WasiResult<&'memory [T]> {
     let (len, len_bytes) = check_slice_of::<T>(ptr, len)?;
     let ptr = dec_ptr(memory, ptr, len_bytes)? as *const T;
     Ok(unsafe { slice::from_raw_parts(ptr, len) })
@@ -110,7 +111,7 @@ fn dec_raw_slice_of_mut<'memory, T>(
     memory: &'memory mut [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory mut [T]> {
+) -> WasiResult<&'memory mut [T]> {
     let (len, len_bytes) = check_slice_of::<T>(ptr, len)?;
     let ptr = dec_ptr_mut(memory, ptr, len_bytes)? as *mut T;
     Ok(unsafe { slice::from_raw_parts_mut(ptr, len) })
@@ -120,16 +121,16 @@ fn raw_slice_for_enc<'memory, T>(
     memory: &'memory mut [u8],
     slice: &[T],
     ptr: wasi32::uintptr_t,
-) -> Result<&'memory mut [T]> {
+) -> WasiResult<&'memory mut [T]> {
     // check alignment
     if ptr as usize % align_of::<T>() != 0 {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
     // check that length doesn't overflow
     let len_bytes = if let Some(len) = size_of::<T>().checked_mul(slice.len()) {
         len
     } else {
-        return Err(Error::EOVERFLOW);
+        return Err(WasiError::EOVERFLOW);
     };
 
     // get the pointer into guest memory
@@ -142,7 +143,7 @@ pub(crate) fn dec_slice_of_u8<'memory>(
     memory: &'memory [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory [u8]> {
+) -> WasiResult<&'memory [u8]> {
     dec_raw_slice_of::<u8>(memory, ptr, len)
 }
 
@@ -150,7 +151,7 @@ pub(crate) fn dec_slice_of_mut_u8<'memory>(
     memory: &'memory mut [u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<&'memory mut [u8]> {
+) -> WasiResult<&'memory mut [u8]> {
     dec_raw_slice_of_mut::<u8>(memory, ptr, len)
 }
 
@@ -158,7 +159,7 @@ pub(crate) fn enc_slice_of_u8(
     memory: &mut [u8],
     slice: &[u8],
     ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let output = raw_slice_for_enc::<u8>(memory, slice, ptr)?;
 
     output.copy_from_slice(slice);
@@ -170,7 +171,7 @@ pub(crate) fn enc_slice_of_wasi32_uintptr(
     memory: &mut [u8],
     slice: &[wasi32::uintptr_t],
     ptr: wasi32::uintptr_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let mut output_iter = raw_slice_for_enc::<wasi32::uintptr_t>(memory, slice, ptr)?.into_iter();
 
     for p in slice {
@@ -182,7 +183,10 @@ pub(crate) fn enc_slice_of_wasi32_uintptr(
 
 macro_rules! dec_enc_scalar {
     ($ty:ident, $dec_byref:ident, $enc_byref:ident) => {
-        pub(crate) fn $dec_byref(memory: &mut [u8], ptr: wasi32::uintptr_t) -> Result<wasi::$ty> {
+        pub(crate) fn $dec_byref(
+            memory: &mut [u8],
+            ptr: wasi32::uintptr_t,
+        ) -> WasiResult<wasi::$ty> {
             dec_int_byref::<wasi::$ty>(memory, ptr)
         }
 
@@ -190,7 +194,7 @@ macro_rules! dec_enc_scalar {
             memory: &mut [u8],
             ptr: wasi32::uintptr_t,
             x: wasi::$ty,
-        ) -> Result<()> {
+        ) -> WasiResult<()> {
             enc_int_byref::<wasi::$ty>(memory, ptr, x)
         }
     };
@@ -200,7 +204,7 @@ pub(crate) fn dec_ciovec_slice(
     memory: &[u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<Vec<host::__wasi_ciovec_t>> {
+) -> WasiResult<Vec<host::__wasi_ciovec_t>> {
     let raw_slice = dec_raw_slice_of::<wasi32::__wasi_ciovec_t>(memory, ptr, len)?;
 
     raw_slice
@@ -220,7 +224,7 @@ pub(crate) fn dec_iovec_slice(
     memory: &[u8],
     ptr: wasi32::uintptr_t,
     len: wasi32::size_t,
-) -> Result<Vec<host::__wasi_iovec_t>> {
+) -> WasiResult<Vec<host::__wasi_iovec_t>> {
     let raw_slice = dec_raw_slice_of::<wasi32::__wasi_iovec_t>(memory, ptr, len)?;
 
     raw_slice
@@ -248,7 +252,7 @@ dec_enc_scalar!(__wasi_linkcount_t, dev_linkcount_byref, enc_linkcount_byref);
 pub(crate) fn dec_filestat_byref(
     memory: &mut [u8],
     filestat_ptr: wasi32::uintptr_t,
-) -> Result<wasi::__wasi_filestat_t> {
+) -> WasiResult<wasi::__wasi_filestat_t> {
     let raw = dec_raw_byref::<wasi::__wasi_filestat_t>(memory, filestat_ptr)?;
 
     Ok(wasi::__wasi_filestat_t {
@@ -267,7 +271,7 @@ pub(crate) fn enc_filestat_byref(
     memory: &mut [u8],
     filestat_ptr: wasi32::uintptr_t,
     filestat: wasi::__wasi_filestat_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let raw = wasi::__wasi_filestat_t {
         dev: PrimInt::to_le(filestat.dev),
         ino: PrimInt::to_le(filestat.ino),
@@ -285,7 +289,7 @@ pub(crate) fn enc_filestat_byref(
 pub(crate) fn dec_fdstat_byref(
     memory: &mut [u8],
     fdstat_ptr: wasi32::uintptr_t,
-) -> Result<wasi::__wasi_fdstat_t> {
+) -> WasiResult<wasi::__wasi_fdstat_t> {
     let raw = dec_raw_byref::<wasi::__wasi_fdstat_t>(memory, fdstat_ptr)?;
 
     Ok(wasi::__wasi_fdstat_t {
@@ -300,7 +304,7 @@ pub(crate) fn enc_fdstat_byref(
     memory: &mut [u8],
     fdstat_ptr: wasi32::uintptr_t,
     fdstat: wasi::__wasi_fdstat_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let raw = wasi::__wasi_fdstat_t {
         fs_filetype: PrimInt::to_le(fdstat.fs_filetype),
         fs_flags: PrimInt::to_le(fdstat.fs_flags),
@@ -326,7 +330,7 @@ dec_enc_scalar!(__wasi_oflags_t, dec_oflags_byref, enc_oflags_byref);
 pub(crate) fn dec_prestat_byref(
     memory: &mut [u8],
     prestat_ptr: wasi32::uintptr_t,
-) -> Result<host::__wasi_prestat_t> {
+) -> WasiResult<host::__wasi_prestat_t> {
     let raw = dec_raw_byref::<wasi32::__wasi_prestat_t>(memory, prestat_ptr)?;
 
     match PrimInt::from_le(raw.tag) {
@@ -338,7 +342,7 @@ pub(crate) fn dec_prestat_byref(
                 },
             },
         }),
-        _ => Err(Error::EINVAL),
+        _ => Err(WasiError::EINVAL),
     }
 }
 
@@ -346,7 +350,7 @@ pub(crate) fn enc_prestat_byref(
     memory: &mut [u8],
     prestat_ptr: wasi32::uintptr_t,
     prestat: host::__wasi_prestat_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     let raw = match prestat.tag {
         wasi::__WASI_PREOPENTYPE_DIR => Ok(wasi32::__wasi_prestat_t {
             tag: PrimInt::to_le(wasi::__WASI_PREOPENTYPE_DIR),
@@ -356,7 +360,7 @@ pub(crate) fn enc_prestat_byref(
                 },
             },
         }),
-        _ => Err(Error::EINVAL),
+        _ => Err(WasiError::EINVAL),
     }?;
 
     enc_raw_byref::<wasi32::__wasi_prestat_t>(memory, prestat_ptr, raw)
@@ -377,7 +381,7 @@ pub(crate) fn enc_usize_byref(
     memory: &mut [u8],
     usize_ptr: wasi32::uintptr_t,
     host_usize: usize,
-) -> Result<()> {
+) -> WasiResult<()> {
     enc_int_byref::<wasi32::size_t>(memory, usize_ptr, enc_usize(host_usize))
 }
 
@@ -402,7 +406,7 @@ pub(crate) fn dec_subscriptions(
     memory: &mut [u8],
     input: wasi32::uintptr_t,
     nsubscriptions: wasi32::size_t,
-) -> Result<Vec<wasi::__wasi_subscription_t>> {
+) -> WasiResult<Vec<wasi::__wasi_subscription_t>> {
     let raw_input_slice =
         dec_raw_slice_of::<wasi::__wasi_subscription_t>(memory, input, nsubscriptions)?;
 
@@ -436,14 +440,14 @@ pub(crate) fn dec_subscriptions(
                         }),
                     },
                 },
-                _ => return Err(Error::EINVAL),
+                _ => return Err(WasiError::EINVAL),
             };
             Ok(wasi::__wasi_subscription_t {
                 userdata,
                 u: wasi::__wasi_subscription_u_t { tag, u },
             })
         })
-        .collect::<Result<Vec<_>>>()
+        .collect::<WasiResult<Vec<_>>>()
 }
 
 pub(crate) fn enc_events(
@@ -451,7 +455,7 @@ pub(crate) fn enc_events(
     output: wasi32::uintptr_t,
     nsubscriptions: wasi32::size_t,
     events: Vec<wasi::__wasi_event_t>,
-) -> Result<()> {
+) -> WasiResult<()> {
     let mut raw_output_iter =
         dec_raw_slice_of_mut::<wasi::__wasi_event_t>(memory, output, nsubscriptions)?.into_iter();
 
diff --git a/crates/wasi-common/src/old/snapshot_0/mod.rs b/crates/wasi-common/src/old/snapshot_0/mod.rs
index 8226d731b0..d17e3035ce 100644
--- a/crates/wasi-common/src/old/snapshot_0/mod.rs
+++ b/crates/wasi-common/src/old/snapshot_0/mod.rs
@@ -1,5 +1,4 @@
 mod ctx;
-mod error;
 mod fdentry;
 mod helpers;
 mod host;
@@ -14,6 +13,3 @@ pub mod hostcalls {
 }
 
 pub use ctx::{WasiCtx, WasiCtxBuilder};
-
-pub type Error = error::Error;
-pub type Result<T> = std::result::Result<T, Error>;
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/host_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/host_impl.rs
index b151e703e1..ea14861f10 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/host_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/host_impl.rs
@@ -1,16 +1,16 @@
-use crate::old::snapshot_0::{wasi, Result};
+use crate::old::snapshot_0::wasi::{self, WasiResult};
 use std::convert::TryFrom;
 
 pub(crate) const O_RSYNC: yanix::file::OFlag = yanix::file::OFlag::SYNC;
 
-pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> Result<wasi::__wasi_device_t> {
+pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> WasiResult<wasi::__wasi_device_t> {
     wasi::__wasi_device_t::try_from(dev).map_err(Into::into)
 }
 
-pub(crate) fn stino_from_nix(ino: libc::ino_t) -> Result<wasi::__wasi_inode_t> {
+pub(crate) fn stino_from_nix(ino: libc::ino_t) -> WasiResult<wasi::__wasi_inode_t> {
     wasi::__wasi_device_t::try_from(ino).map_err(Into::into)
 }
 
-pub(crate) fn stnlink_from_nix(nlink: libc::nlink_t) -> Result<wasi::__wasi_linkcount_t> {
+pub(crate) fn stnlink_from_nix(nlink: libc::nlink_t) -> WasiResult<wasi::__wasi_linkcount_t> {
     Ok(nlink.into())
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/hostcalls_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/hostcalls_impl.rs
index bffb9c6b10..8923114c8f 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/hostcalls_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/bsd/hostcalls_impl.rs
@@ -1,8 +1,8 @@
 use crate::old::snapshot_0::hostcalls_impl::PathGet;
-use crate::old::snapshot_0::{Error, Result};
+use crate::old::snapshot_0::wasi::{WasiError, WasiResult};
 use std::os::unix::prelude::AsRawFd;
 
-pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_unlink_file(resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{unlinkat, AtFlag};
     match unsafe {
         unlinkat(
@@ -32,7 +32,7 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
                 } {
                     Ok(stat) => {
                         if FileType::from_stat_st_mode(stat.st_mode) == FileType::Directory {
-                            return Err(Error::EISDIR);
+                            return Err(WasiError::EISDIR);
                         }
                     }
                     Err(err) => {
@@ -47,7 +47,7 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
     }
 }
 
-pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{fstatat, symlinkat, AtFlag};
 
     log::debug!("path_symlink old_path = {:?}", old_path);
@@ -69,7 +69,7 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
                         AtFlag::SYMLINK_NOFOLLOW,
                     )
                 } {
-                    Ok(_) => return Err(Error::EEXIST),
+                    Ok(_) => return Err(WasiError::EEXIST),
                     Err(err) => {
                         log::debug!("path_symlink fstatat error: {:?}", err);
                     }
@@ -81,7 +81,7 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
     }
 }
 
-pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use yanix::file::{fstatat, renameat, AtFlag};
     match unsafe {
         renameat(
@@ -113,9 +113,9 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
                     Ok(_) => {
                         // check if destination contains a trailing slash
                         if resolved_new.path().contains('/') {
-                            return Err(Error::ENOTDIR);
+                            return Err(WasiError::ENOTDIR);
                         } else {
-                            return Err(Error::ENOENT);
+                            return Err(WasiError::ENOENT);
                         }
                     }
                     Err(err) => {
@@ -132,13 +132,13 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
 
 pub(crate) mod fd_readdir_impl {
     use crate::old::snapshot_0::sys::fdentry_impl::OsHandle;
-    use crate::old::snapshot_0::Result;
+    use crate::old::snapshot_0::wasi::WasiResult;
     use std::sync::{Mutex, MutexGuard};
     use yanix::dir::Dir;
 
     pub(crate) fn get_dir_from_os_handle<'a>(
         os_handle: &'a mut OsHandle,
-    ) -> Result<MutexGuard<'a, Dir>> {
+    ) -> WasiResult<MutexGuard<'a, Dir>> {
         let dir = match os_handle.dir {
             Some(ref mut dir) => dir,
             None => {
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/fdentry_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/fdentry_impl.rs
index a46177c3c5..a9bee8eeb9 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/fdentry_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/fdentry_impl.rs
@@ -1,5 +1,5 @@
 use crate::old::snapshot_0::fdentry::{Descriptor, OsHandleRef};
-use crate::old::snapshot_0::{sys::unix::sys_impl, wasi, Error, Result};
+use crate::old::snapshot_0::{sys::unix::sys_impl, wasi};
 use std::fs::File;
 use std::io;
 use std::mem::ManuallyDrop;
@@ -29,7 +29,7 @@ pub(crate) fn descriptor_as_oshandle<'lifetime>(
 /// This function is unsafe because it operates on a raw file descriptor.
 pub(crate) unsafe fn determine_type_and_access_rights<Fd: AsRawFd>(
     fd: &Fd,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -51,7 +51,7 @@ pub(crate) unsafe fn determine_type_and_access_rights<Fd: AsRawFd>(
 /// This function is unsafe because it operates on a raw file descriptor.
 pub(crate) unsafe fn determine_type_rights<Fd: AsRawFd>(
     fd: &Fd,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -111,7 +111,7 @@ pub(crate) unsafe fn determine_type_rights<Fd: AsRawFd>(
                     wasi::RIGHTS_SOCKET_BASE,
                     wasi::RIGHTS_SOCKET_INHERITING,
                 ),
-                _ => return Err(Error::EINVAL),
+                _ => return Err(io::Error::from_raw_os_error(libc::EINVAL)),
             }
         } else if ft.is_fifo() {
             log::debug!("Host fd {:?} is a fifo", fd.as_raw_fd());
@@ -122,7 +122,7 @@ pub(crate) unsafe fn determine_type_rights<Fd: AsRawFd>(
             )
         } else {
             log::debug!("Host fd {:?} is unknown", fd.as_raw_fd());
-            return Err(Error::EINVAL);
+            return Err(io::Error::from_raw_os_error(libc::EINVAL));
         }
     };
 
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/host_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/host_impl.rs
index 688fcc63e2..f96473da90 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/host_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/host_impl.rs
@@ -3,94 +3,101 @@
 #![allow(non_snake_case)]
 #![allow(dead_code)]
 use crate::old::snapshot_0::host::FileType;
-use crate::old::snapshot_0::{
-    error::FromRawOsError, helpers, sys::unix::sys_impl, wasi, Error, Result,
-};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
+use crate::old::snapshot_0::{helpers, sys::unix::sys_impl};
 use std::ffi::OsStr;
+use std::io;
 use std::os::unix::prelude::OsStrExt;
 use yanix::file::OFlag;
 
 pub(crate) use sys_impl::host_impl::*;
 
-impl FromRawOsError for Error {
-    fn from_raw_os_error(code: i32) -> Self {
-        match code {
-            libc::EPERM => Self::EPERM,
-            libc::ENOENT => Self::ENOENT,
-            libc::ESRCH => Self::ESRCH,
-            libc::EINTR => Self::EINTR,
-            libc::EIO => Self::EIO,
-            libc::ENXIO => Self::ENXIO,
-            libc::E2BIG => Self::E2BIG,
-            libc::ENOEXEC => Self::ENOEXEC,
-            libc::EBADF => Self::EBADF,
-            libc::ECHILD => Self::ECHILD,
-            libc::EAGAIN => Self::EAGAIN,
-            libc::ENOMEM => Self::ENOMEM,
-            libc::EACCES => Self::EACCES,
-            libc::EFAULT => Self::EFAULT,
-            libc::EBUSY => Self::EBUSY,
-            libc::EEXIST => Self::EEXIST,
-            libc::EXDEV => Self::EXDEV,
-            libc::ENODEV => Self::ENODEV,
-            libc::ENOTDIR => Self::ENOTDIR,
-            libc::EISDIR => Self::EISDIR,
-            libc::EINVAL => Self::EINVAL,
-            libc::ENFILE => Self::ENFILE,
-            libc::EMFILE => Self::EMFILE,
-            libc::ENOTTY => Self::ENOTTY,
-            libc::ETXTBSY => Self::ETXTBSY,
-            libc::EFBIG => Self::EFBIG,
-            libc::ENOSPC => Self::ENOSPC,
-            libc::ESPIPE => Self::ESPIPE,
-            libc::EROFS => Self::EROFS,
-            libc::EMLINK => Self::EMLINK,
-            libc::EPIPE => Self::EPIPE,
-            libc::EDOM => Self::EDOM,
-            libc::ERANGE => Self::ERANGE,
-            libc::EDEADLK => Self::EDEADLK,
-            libc::ENAMETOOLONG => Self::ENAMETOOLONG,
-            libc::ENOLCK => Self::ENOLCK,
-            libc::ENOSYS => Self::ENOSYS,
-            libc::ENOTEMPTY => Self::ENOTEMPTY,
-            libc::ELOOP => Self::ELOOP,
-            libc::ENOMSG => Self::ENOMSG,
-            libc::EIDRM => Self::EIDRM,
-            libc::ENOLINK => Self::ENOLINK,
-            libc::EPROTO => Self::EPROTO,
-            libc::EMULTIHOP => Self::EMULTIHOP,
-            libc::EBADMSG => Self::EBADMSG,
-            libc::EOVERFLOW => Self::EOVERFLOW,
-            libc::EILSEQ => Self::EILSEQ,
-            libc::ENOTSOCK => Self::ENOTSOCK,
-            libc::EDESTADDRREQ => Self::EDESTADDRREQ,
-            libc::EMSGSIZE => Self::EMSGSIZE,
-            libc::EPROTOTYPE => Self::EPROTOTYPE,
-            libc::ENOPROTOOPT => Self::ENOPROTOOPT,
-            libc::EPROTONOSUPPORT => Self::EPROTONOSUPPORT,
-            libc::EAFNOSUPPORT => Self::EAFNOSUPPORT,
-            libc::EADDRINUSE => Self::EADDRINUSE,
-            libc::EADDRNOTAVAIL => Self::EADDRNOTAVAIL,
-            libc::ENETDOWN => Self::ENETDOWN,
-            libc::ENETUNREACH => Self::ENETUNREACH,
-            libc::ENETRESET => Self::ENETRESET,
-            libc::ECONNABORTED => Self::ECONNABORTED,
-            libc::ECONNRESET => Self::ECONNRESET,
-            libc::ENOBUFS => Self::ENOBUFS,
-            libc::EISCONN => Self::EISCONN,
-            libc::ENOTCONN => Self::ENOTCONN,
-            libc::ETIMEDOUT => Self::ETIMEDOUT,
-            libc::ECONNREFUSED => Self::ECONNREFUSED,
-            libc::EHOSTUNREACH => Self::EHOSTUNREACH,
-            libc::EALREADY => Self::EALREADY,
-            libc::EINPROGRESS => Self::EINPROGRESS,
-            libc::ESTALE => Self::ESTALE,
-            libc::EDQUOT => Self::EDQUOT,
-            libc::ECANCELED => Self::ECANCELED,
-            libc::EOWNERDEAD => Self::EOWNERDEAD,
-            libc::ENOTRECOVERABLE => Self::ENOTRECOVERABLE,
-            x => {
-                log::debug!("Unknown errno value: {}", x);
+impl From<io::Error> for WasiError {
+    fn from(err: io::Error) -> Self {
+        match err.raw_os_error() {
+            Some(code) => match code {
+                libc::EPERM => Self::EPERM,
+                libc::ENOENT => Self::ENOENT,
+                libc::ESRCH => Self::ESRCH,
+                libc::EINTR => Self::EINTR,
+                libc::EIO => Self::EIO,
+                libc::ENXIO => Self::ENXIO,
+                libc::E2BIG => Self::E2BIG,
+                libc::ENOEXEC => Self::ENOEXEC,
+                libc::EBADF => Self::EBADF,
+                libc::ECHILD => Self::ECHILD,
+                libc::EAGAIN => Self::EAGAIN,
+                libc::ENOMEM => Self::ENOMEM,
+                libc::EACCES => Self::EACCES,
+                libc::EFAULT => Self::EFAULT,
+                libc::EBUSY => Self::EBUSY,
+                libc::EEXIST => Self::EEXIST,
+                libc::EXDEV => Self::EXDEV,
+                libc::ENODEV => Self::ENODEV,
+                libc::ENOTDIR => Self::ENOTDIR,
+                libc::EISDIR => Self::EISDIR,
+                libc::EINVAL => Self::EINVAL,
+                libc::ENFILE => Self::ENFILE,
+                libc::EMFILE => Self::EMFILE,
+                libc::ENOTTY => Self::ENOTTY,
+                libc::ETXTBSY => Self::ETXTBSY,
+                libc::EFBIG => Self::EFBIG,
+                libc::ENOSPC => Self::ENOSPC,
+                libc::ESPIPE => Self::ESPIPE,
+                libc::EROFS => Self::EROFS,
+                libc::EMLINK => Self::EMLINK,
+                libc::EPIPE => Self::EPIPE,
+                libc::EDOM => Self::EDOM,
+                libc::ERANGE => Self::ERANGE,
+                libc::EDEADLK => Self::EDEADLK,
+                libc::ENAMETOOLONG => Self::ENAMETOOLONG,
+                libc::ENOLCK => Self::ENOLCK,
+                libc::ENOSYS => Self::ENOSYS,
+                libc::ENOTEMPTY => Self::ENOTEMPTY,
+                libc::ELOOP => Self::ELOOP,
+                libc::ENOMSG => Self::ENOMSG,
+                libc::EIDRM => Self::EIDRM,
+                libc::ENOLINK => Self::ENOLINK,
+                libc::EPROTO => Self::EPROTO,
+                libc::EMULTIHOP => Self::EMULTIHOP,
+                libc::EBADMSG => Self::EBADMSG,
+                libc::EOVERFLOW => Self::EOVERFLOW,
+                libc::EILSEQ => Self::EILSEQ,
+                libc::ENOTSOCK => Self::ENOTSOCK,
+                libc::EDESTADDRREQ => Self::EDESTADDRREQ,
+                libc::EMSGSIZE => Self::EMSGSIZE,
+                libc::EPROTOTYPE => Self::EPROTOTYPE,
+                libc::ENOPROTOOPT => Self::ENOPROTOOPT,
+                libc::EPROTONOSUPPORT => Self::EPROTONOSUPPORT,
+                libc::EAFNOSUPPORT => Self::EAFNOSUPPORT,
+                libc::EADDRINUSE => Self::EADDRINUSE,
+                libc::EADDRNOTAVAIL => Self::EADDRNOTAVAIL,
+                libc::ENETDOWN => Self::ENETDOWN,
+                libc::ENETUNREACH => Self::ENETUNREACH,
+                libc::ENETRESET => Self::ENETRESET,
+                libc::ECONNABORTED => Self::ECONNABORTED,
+                libc::ECONNRESET => Self::ECONNRESET,
+                libc::ENOBUFS => Self::ENOBUFS,
+                libc::EISCONN => Self::EISCONN,
+                libc::ENOTCONN => Self::ENOTCONN,
+                libc::ETIMEDOUT => Self::ETIMEDOUT,
+                libc::ECONNREFUSED => Self::ECONNREFUSED,
+                libc::EHOSTUNREACH => Self::EHOSTUNREACH,
+                libc::EALREADY => Self::EALREADY,
+                libc::EINPROGRESS => Self::EINPROGRESS,
+                libc::ESTALE => Self::ESTALE,
+                libc::EDQUOT => Self::EDQUOT,
+                libc::ECANCELED => Self::ECANCELED,
+                libc::EOWNERDEAD => Self::EOWNERDEAD,
+                libc::ENOTRECOVERABLE => Self::ENOTRECOVERABLE,
+                libc::ENOTSUP => Self::ENOTSUP,
+                x => {
+                    log::debug!("Unknown errno value: {}", x);
+                    Self::EIO
+                }
+            },
+            None => {
+                log::debug!("Other I/O error: {}", err);
                 Self::EIO
             }
         }
@@ -154,13 +161,13 @@ pub(crate) fn nix_from_oflags(oflags: wasi::__wasi_oflags_t) -> OFlag {
     nix_flags
 }
 
-pub(crate) fn filestat_from_nix(filestat: libc::stat) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn filestat_from_nix(filestat: libc::stat) -> WasiResult<wasi::__wasi_filestat_t> {
     use std::convert::TryInto;
 
-    fn filestat_to_timestamp(secs: u64, nsecs: u64) -> Result<wasi::__wasi_timestamp_t> {
+    fn filestat_to_timestamp(secs: u64, nsecs: u64) -> WasiResult<wasi::__wasi_timestamp_t> {
         secs.checked_mul(1_000_000_000)
             .and_then(|sec_nsec| sec_nsec.checked_add(nsecs))
-            .ok_or(Error::EOVERFLOW)
+            .ok_or(WasiError::EOVERFLOW)
     }
 
     let filetype = yanix::file::FileType::from_stat_st_mode(filestat.st_mode);
@@ -195,7 +202,7 @@ pub(crate) fn filestat_from_nix(filestat: libc::stat) -> Result<wasi::__wasi_fil
 ///
 /// NB WASI spec requires OS string to be valid UTF-8. Otherwise,
 /// `__WASI_ERRNO_ILSEQ` error is returned.
-pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String> {
+pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> WasiResult<String> {
     helpers::path_from_slice(s.as_ref().as_bytes()).map(String::from)
 }
 
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs.rs
index d22d711c6b..2766838fa1 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs.rs
@@ -3,7 +3,7 @@
 use crate::old::snapshot_0::host::Dirent;
 use crate::old::snapshot_0::hostcalls_impl::PathGet;
 use crate::old::snapshot_0::sys::{fdentry_impl::OsHandle, host_impl, unix::sys_impl};
-use crate::old::snapshot_0::{wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use std::convert::TryInto;
 use std::fs::File;
 use std::os::unix::fs::FileExt;
@@ -15,21 +15,25 @@ pub(crate) fn fd_pread(
     file: &File,
     buf: &mut [u8],
     offset: wasi::__wasi_filesize_t,
-) -> Result<usize> {
+) -> WasiResult<usize> {
     file.read_at(buf, offset).map_err(Into::into)
 }
 
-pub(crate) fn fd_pwrite(file: &File, buf: &[u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+pub(crate) fn fd_pwrite(
+    file: &File,
+    buf: &[u8],
+    offset: wasi::__wasi_filesize_t,
+) -> WasiResult<usize> {
     file.write_at(buf, offset).map_err(Into::into)
 }
 
-pub(crate) fn fd_fdstat_get(fd: &File) -> Result<wasi::__wasi_fdflags_t> {
+pub(crate) fn fd_fdstat_get(fd: &File) -> WasiResult<wasi::__wasi_fdflags_t> {
     unsafe { yanix::fcntl::get_status_flags(fd.as_raw_fd()) }
         .map(host_impl::fdflags_from_nix)
         .map_err(Into::into)
 }
 
-pub(crate) fn fd_fdstat_set_flags(fd: &File, fdflags: wasi::__wasi_fdflags_t) -> Result<()> {
+pub(crate) fn fd_fdstat_set_flags(fd: &File, fdflags: wasi::__wasi_fdflags_t) -> WasiResult<()> {
     let nix_flags = host_impl::nix_from_fdflags(fdflags);
     unsafe { yanix::fcntl::set_status_flags(fd.as_raw_fd(), nix_flags) }.map_err(Into::into)
 }
@@ -39,7 +43,7 @@ pub(crate) fn fd_advise(
     advice: wasi::__wasi_advice_t,
     offset: wasi::__wasi_filesize_t,
     len: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     use yanix::fadvise::{posix_fadvise, PosixFadviseAdvice};
     let offset = offset.try_into()?;
     let len = len.try_into()?;
@@ -50,12 +54,12 @@ pub(crate) fn fd_advise(
         wasi::__WASI_ADVICE_NOREUSE => PosixFadviseAdvice::NoReuse,
         wasi::__WASI_ADVICE_RANDOM => PosixFadviseAdvice::Random,
         wasi::__WASI_ADVICE_NORMAL => PosixFadviseAdvice::Normal,
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     };
     unsafe { posix_fadvise(file.as_raw_fd(), offset, len, host_advice) }.map_err(Into::into)
 }
 
-pub(crate) fn path_create_directory(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_create_directory(resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{mkdirat, Mode};
     unsafe {
         mkdirat(
@@ -67,7 +71,7 @@ pub(crate) fn path_create_directory(resolved: PathGet) -> Result<()> {
     .map_err(Into::into)
 }
 
-pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use yanix::file::{linkat, AtFlag};
     unsafe {
         linkat(
@@ -87,7 +91,7 @@ pub(crate) fn path_open(
     write: bool,
     oflags: wasi::__wasi_oflags_t,
     fs_flags: wasi::__wasi_fdflags_t,
-) -> Result<File> {
+) -> WasiResult<File> {
     use yanix::file::{fstatat, openat, AtFlag, FileType, Mode, OFlag};
 
     let mut nix_all_oflags = if read && write {
@@ -136,7 +140,7 @@ pub(crate) fn path_open(
                     } {
                         Ok(stat) => {
                             if FileType::from_stat_st_mode(stat.st_mode) == FileType::Socket {
-                                return Err(Error::ENOTSUP);
+                                return Err(WasiError::ENOTSUP);
                             }
                         }
                         Err(err) => {
@@ -158,7 +162,7 @@ pub(crate) fn path_open(
                     } {
                         Ok(stat) => {
                             if FileType::from_stat_st_mode(stat.st_mode) == FileType::Symlink {
-                                return Err(Error::ELOOP);
+                                return Err(WasiError::ELOOP);
                             }
                         }
                         Err(err) => {
@@ -169,7 +173,7 @@ pub(crate) fn path_open(
                 // FreeBSD returns EMLINK instead of ELOOP when using O_NOFOLLOW on
                 // a symlink.
                 libc::EMLINK if !(nix_all_oflags & OFlag::NOFOLLOW).is_empty() => {
-                    return Err(Error::ELOOP);
+                    return Err(WasiError::ELOOP);
                 }
                 _ => {}
             }
@@ -184,7 +188,7 @@ pub(crate) fn path_open(
     Ok(unsafe { File::from_raw_fd(new_fd) })
 }
 
-pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize> {
+pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> WasiResult<usize> {
     use std::cmp::min;
     use yanix::file::readlinkat;
     let read_link = unsafe { readlinkat(resolved.dirfd().as_raw_fd(), resolved.path()) }
@@ -197,7 +201,7 @@ pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize>
     Ok(copy_len)
 }
 
-pub(crate) fn fd_filestat_get(file: &std::fs::File) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn fd_filestat_get(file: &std::fs::File) -> WasiResult<wasi::__wasi_filestat_t> {
     use yanix::file::fstat;
     unsafe { fstat(file.as_raw_fd()) }
         .map_err(Into::into)
@@ -207,7 +211,7 @@ pub(crate) fn fd_filestat_get(file: &std::fs::File) -> Result<wasi::__wasi_files
 pub(crate) fn path_filestat_get(
     resolved: PathGet,
     dirflags: wasi::__wasi_lookupflags_t,
-) -> Result<wasi::__wasi_filestat_t> {
+) -> WasiResult<wasi::__wasi_filestat_t> {
     use yanix::file::{fstatat, AtFlag};
     let atflags = match dirflags {
         0 => AtFlag::empty(),
@@ -224,7 +228,7 @@ pub(crate) fn path_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     use std::time::{Duration, UNIX_EPOCH};
     use yanix::filetime::*;
 
@@ -234,7 +238,7 @@ pub(crate) fn path_filestat_set_times(
     let set_mtim_now = fst_flags & wasi::__WASI_FSTFLAGS_MTIM_NOW != 0;
 
     if (set_atim && set_atim_now) || (set_mtim && set_mtim_now) {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     let symlink_nofollow = wasi::__WASI_LOOKUPFLAGS_SYMLINK_FOLLOW != dirflags;
@@ -265,7 +269,7 @@ pub(crate) fn path_filestat_set_times(
     .map_err(Into::into)
 }
 
-pub(crate) fn path_remove_directory(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_remove_directory(resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{unlinkat, AtFlag};
     unsafe {
         unlinkat(
@@ -280,7 +284,7 @@ pub(crate) fn path_remove_directory(resolved: PathGet) -> Result<()> {
 pub(crate) fn fd_readdir<'a>(
     os_handle: &'a mut OsHandle,
     cookie: wasi::__wasi_dircookie_t,
-) -> Result<impl Iterator<Item = Result<Dirent>> + 'a> {
+) -> WasiResult<impl Iterator<Item = WasiResult<Dirent>> + 'a> {
     use yanix::dir::{DirIter, Entry, EntryExt, SeekLoc};
 
     // Get an instance of `Dir`; this is host-specific due to intricasies
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs_helpers.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs_helpers.rs
index 609e42dc5c..0be360f3d5 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs_helpers.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/fs_helpers.rs
@@ -1,7 +1,7 @@
 #![allow(non_camel_case_types)]
 #![allow(unused_unsafe)]
 use crate::old::snapshot_0::sys::host_impl;
-use crate::old::snapshot_0::{wasi, Result};
+use crate::old::snapshot_0::wasi::{self, WasiResult};
 use std::fs::File;
 use yanix::file::OFlag;
 
@@ -36,7 +36,7 @@ pub(crate) fn path_open_rights(
     (needed_base, needed_inheriting)
 }
 
-pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
+pub(crate) fn openat(dirfd: &File, path: &str) -> WasiResult<File> {
     use std::os::unix::prelude::{AsRawFd, FromRawFd};
     use yanix::file::{openat, Mode};
 
@@ -54,7 +54,7 @@ pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
     .map_err(Into::into)
 }
 
-pub(crate) fn readlinkat(dirfd: &File, path: &str) -> Result<String> {
+pub(crate) fn readlinkat(dirfd: &File, path: &str) -> WasiResult<String> {
     use std::os::unix::prelude::AsRawFd;
     use yanix::file::readlinkat;
 
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/misc.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/misc.rs
index e6e270159f..914a25d94a 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/misc.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/hostcalls_impl/misc.rs
@@ -1,22 +1,24 @@
 #![allow(non_camel_case_types)]
 #![allow(unused_unsafe)]
 use crate::old::snapshot_0::hostcalls_impl::{ClockEventData, FdEventData};
-use crate::old::snapshot_0::{wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use std::io;
 use yanix::clock::{clock_getres, clock_gettime, ClockId};
 
-fn wasi_clock_id_to_unix(clock_id: wasi::__wasi_clockid_t) -> Result<ClockId> {
+fn wasi_clock_id_to_unix(clock_id: wasi::__wasi_clockid_t) -> WasiResult<ClockId> {
     // convert the supported clocks to libc types, or return EINVAL
     match clock_id {
         wasi::__WASI_CLOCKID_REALTIME => Ok(ClockId::Realtime),
         wasi::__WASI_CLOCKID_MONOTONIC => Ok(ClockId::Monotonic),
         wasi::__WASI_CLOCKID_PROCESS_CPUTIME_ID => Ok(ClockId::ProcessCPUTime),
         wasi::__WASI_CLOCKID_THREAD_CPUTIME_ID => Ok(ClockId::ThreadCPUTime),
-        _ => Err(Error::EINVAL),
+        _ => Err(WasiError::EINVAL),
     }
 }
 
-pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_res_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     let clock_id = wasi_clock_id_to_unix(clock_id)?;
     let timespec = clock_getres(clock_id)?;
 
@@ -26,18 +28,20 @@ pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__
     (timespec.tv_sec as wasi::__wasi_timestamp_t)
         .checked_mul(1_000_000_000)
         .and_then(|sec_ns| sec_ns.checked_add(timespec.tv_nsec as wasi::__wasi_timestamp_t))
-        .map_or(Err(Error::EOVERFLOW), |resolution| {
+        .map_or(Err(WasiError::EOVERFLOW), |resolution| {
             // a supported clock can never return zero; this case will probably never get hit, but
             // make sure we follow the spec
             if resolution == 0 {
-                Err(Error::EINVAL)
+                Err(WasiError::EINVAL)
             } else {
                 Ok(resolution)
             }
         })
 }
 
-pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_time_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     let clock_id = wasi_clock_id_to_unix(clock_id)?;
     let timespec = clock_gettime(clock_id)?;
 
@@ -46,14 +50,14 @@ pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::_
     (timespec.tv_sec as wasi::__wasi_timestamp_t)
         .checked_mul(1_000_000_000)
         .and_then(|sec_ns| sec_ns.checked_add(timespec.tv_nsec as wasi::__wasi_timestamp_t))
-        .map_or(Err(Error::EOVERFLOW), Ok)
+        .map_or(Err(WasiError::EOVERFLOW), Ok)
 }
 
 pub(crate) fn poll_oneoff(
     timeout: Option<ClockEventData>,
     fd_events: Vec<FdEventData>,
     events: &mut Vec<wasi::__wasi_event_t>,
-) -> Result<()> {
+) -> WasiResult<()> {
     use std::{convert::TryInto, os::unix::prelude::AsRawFd};
     use yanix::poll::{poll, PollFd, PollFlags};
 
@@ -122,7 +126,7 @@ fn poll_oneoff_handle_timeout_event(
 fn poll_oneoff_handle_fd_event<'a>(
     ready_events: impl Iterator<Item = (FdEventData<'a>, yanix::poll::PollFd)>,
     events: &mut Vec<wasi::__wasi_event_t>,
-) -> Result<()> {
+) -> WasiResult<()> {
     use std::{convert::TryInto, os::unix::prelude::AsRawFd};
     use yanix::{file::fionread, poll::PollFlags};
 
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/host_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/host_impl.rs
index d867e51b6f..90ae925e43 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/host_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/host_impl.rs
@@ -1,16 +1,16 @@
-use crate::old::snapshot_0::{wasi, Result};
+use crate::old::snapshot_0::wasi::{self, WasiResult};
 use std::convert::TryInto;
 
 pub(crate) const O_RSYNC: yanix::file::OFlag = yanix::file::OFlag::RSYNC;
 
-pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> Result<wasi::__wasi_device_t> {
+pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> WasiResult<wasi::__wasi_device_t> {
     Ok(wasi::__wasi_device_t::from(dev))
 }
 
-pub(crate) fn stino_from_nix(ino: libc::ino_t) -> Result<wasi::__wasi_inode_t> {
+pub(crate) fn stino_from_nix(ino: libc::ino_t) -> WasiResult<wasi::__wasi_inode_t> {
     Ok(wasi::__wasi_device_t::from(ino))
 }
 
-pub(crate) fn stnlink_from_nix(nlink: libc::nlink_t) -> Result<wasi::__wasi_linkcount_t> {
+pub(crate) fn stnlink_from_nix(nlink: libc::nlink_t) -> WasiResult<wasi::__wasi_linkcount_t> {
     nlink.try_into().map_err(Into::into)
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/hostcalls_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/hostcalls_impl.rs
index 86b1ec443e..efcff139a9 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/hostcalls_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/linux/hostcalls_impl.rs
@@ -1,8 +1,8 @@
 use crate::old::snapshot_0::hostcalls_impl::PathGet;
-use crate::old::snapshot_0::Result;
+use crate::old::snapshot_0::wasi::WasiResult;
 use std::os::unix::prelude::AsRawFd;
 
-pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_unlink_file(resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{unlinkat, AtFlag};
     unsafe {
         unlinkat(
@@ -14,7 +14,7 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
     .map_err(Into::into)
 }
 
-pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> WasiResult<()> {
     use yanix::file::symlinkat;
 
     log::debug!("path_symlink old_path = {:?}", old_path);
@@ -24,7 +24,7 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
         .map_err(Into::into)
 }
 
-pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use yanix::file::renameat;
     unsafe {
         renameat(
@@ -39,10 +39,10 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
 
 pub(crate) mod fd_readdir_impl {
     use crate::old::snapshot_0::sys::fdentry_impl::OsHandle;
-    use crate::old::snapshot_0::Result;
+    use crate::old::snapshot_0::wasi::WasiResult;
     use yanix::dir::Dir;
 
-    pub(crate) fn get_dir_from_os_handle(os_handle: &mut OsHandle) -> Result<Box<Dir>> {
+    pub(crate) fn get_dir_from_os_handle(os_handle: &mut OsHandle) -> WasiResult<Box<Dir>> {
         // We need to duplicate the fd, because `opendir(3)`:
         //     After a successful call to fdopendir(), fd is used internally by the implementation,
         //     and should not otherwise be used by the application.
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/unix/mod.rs b/crates/wasi-common/src/old/snapshot_0/sys/unix/mod.rs
index d7e8288323..c5382556ab 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/unix/mod.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/unix/mod.rs
@@ -20,13 +20,9 @@ cfg_if::cfg_if! {
     }
 }
 
-use crate::old::snapshot_0::Result;
 use std::fs::{File, OpenOptions};
+use std::io::Result;
 
 pub(crate) fn dev_null() -> Result<File> {
-    OpenOptions::new()
-        .read(true)
-        .write(true)
-        .open("/dev/null")
-        .map_err(Into::into)
+    OpenOptions::new().read(true).write(true).open("/dev/null")
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/windows/fdentry_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/windows/fdentry_impl.rs
index 4b1c6ba39e..b5a35833d6 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/windows/fdentry_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/windows/fdentry_impl.rs
@@ -1,5 +1,5 @@
 use crate::old::snapshot_0::fdentry::{Descriptor, OsHandleRef};
-use crate::old::snapshot_0::{wasi, Error, Result};
+use crate::old::snapshot_0::wasi;
 use std::fs::File;
 use std::io;
 use std::mem::ManuallyDrop;
@@ -57,7 +57,7 @@ pub(crate) fn descriptor_as_oshandle<'lifetime>(
 /// This function is unsafe because it operates on a raw file handle.
 pub(crate) unsafe fn determine_type_and_access_rights<Handle: AsRawHandle>(
     handle: &Handle,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -88,7 +88,7 @@ pub(crate) unsafe fn determine_type_and_access_rights<Handle: AsRawHandle>(
 /// This function is unsafe because it operates on a raw file handle.
 pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
     handle: &Handle,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -106,7 +106,7 @@ pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
         } else if file_type.is_disk() {
             // disk file: file, dir or disk device
             let file = std::mem::ManuallyDrop::new(File::from_raw_handle(handle.as_raw_handle()));
-            let meta = file.metadata().map_err(|_| Error::EINVAL)?;
+            let meta = file.metadata()?;
             if meta.is_dir() {
                 (
                     wasi::__WASI_FILETYPE_DIRECTORY,
@@ -120,7 +120,7 @@ pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
                     wasi::RIGHTS_REGULAR_FILE_INHERITING,
                 )
             } else {
-                return Err(Error::EINVAL);
+                return Err(io::Error::from_raw_os_error(libc::EINVAL));
             }
         } else if file_type.is_pipe() {
             // pipe object: socket, named pipe or anonymous pipe
@@ -131,7 +131,7 @@ pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
                 wasi::RIGHTS_SOCKET_INHERITING,
             )
         } else {
-            return Err(Error::EINVAL);
+            return Err(io::Error::from_raw_os_error(libc::EINVAL));
         }
     };
     Ok((file_type, rights_base, rights_inheriting))
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/windows/host_impl.rs b/crates/wasi-common/src/old/snapshot_0/sys/windows/host_impl.rs
index 036c5010e4..53d8073724 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/windows/host_impl.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/windows/host_impl.rs
@@ -3,7 +3,7 @@
 #![allow(non_snake_case)]
 #![allow(unused)]
 use crate::old::snapshot_0::host::FileType;
-use crate::old::snapshot_0::{error::FromRawOsError, wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use std::convert::TryInto;
 use std::ffi::OsStr;
 use std::fs::OpenOptions;
@@ -15,34 +15,42 @@ use std::time::{SystemTime, UNIX_EPOCH};
 use winapi::shared::winerror;
 use winx::file::{AccessMode, Attributes, CreationDisposition, Flags};
 
-impl FromRawOsError for Error {
-    fn from_raw_os_error(code: i32) -> Self {
-        // TODO: implement error mapping between Windows and WASI
-        match code as u32 {
-            winerror::ERROR_SUCCESS => Self::ESUCCESS,
-            winerror::ERROR_BAD_ENVIRONMENT => Self::E2BIG,
-            winerror::ERROR_FILE_NOT_FOUND => Self::ENOENT,
-            winerror::ERROR_PATH_NOT_FOUND => Self::ENOENT,
-            winerror::ERROR_TOO_MANY_OPEN_FILES => Self::ENFILE,
-            winerror::ERROR_ACCESS_DENIED => Self::EACCES,
-            winerror::ERROR_SHARING_VIOLATION => Self::EACCES,
-            winerror::ERROR_PRIVILEGE_NOT_HELD => Self::ENOTCAPABLE, // TODO is this the correct mapping?
-            winerror::ERROR_INVALID_HANDLE => Self::EBADF,
-            winerror::ERROR_INVALID_NAME => Self::ENOENT,
-            winerror::ERROR_NOT_ENOUGH_MEMORY => Self::ENOMEM,
-            winerror::ERROR_OUTOFMEMORY => Self::ENOMEM,
-            winerror::ERROR_DIR_NOT_EMPTY => Self::ENOTEMPTY,
-            winerror::ERROR_NOT_READY => Self::EBUSY,
-            winerror::ERROR_BUSY => Self::EBUSY,
-            winerror::ERROR_NOT_SUPPORTED => Self::ENOTSUP,
-            winerror::ERROR_FILE_EXISTS => Self::EEXIST,
-            winerror::ERROR_BROKEN_PIPE => Self::EPIPE,
-            winerror::ERROR_BUFFER_OVERFLOW => Self::ENAMETOOLONG,
-            winerror::ERROR_NOT_A_REPARSE_POINT => Self::EINVAL,
-            winerror::ERROR_NEGATIVE_SEEK => Self::EINVAL,
-            winerror::ERROR_DIRECTORY => Self::ENOTDIR,
-            winerror::ERROR_ALREADY_EXISTS => Self::EEXIST,
-            _ => Self::ENOTSUP,
+impl From<io::Error> for WasiError {
+    fn from(err: io::Error) -> Self {
+        match err.raw_os_error() {
+            Some(code) => match code as u32 {
+                winerror::ERROR_SUCCESS => Self::ESUCCESS,
+                winerror::ERROR_BAD_ENVIRONMENT => Self::E2BIG,
+                winerror::ERROR_FILE_NOT_FOUND => Self::ENOENT,
+                winerror::ERROR_PATH_NOT_FOUND => Self::ENOENT,
+                winerror::ERROR_TOO_MANY_OPEN_FILES => Self::ENFILE,
+                winerror::ERROR_ACCESS_DENIED => Self::EACCES,
+                winerror::ERROR_SHARING_VIOLATION => Self::EACCES,
+                winerror::ERROR_PRIVILEGE_NOT_HELD => Self::ENOTCAPABLE,
+                winerror::ERROR_INVALID_HANDLE => Self::EBADF,
+                winerror::ERROR_INVALID_NAME => Self::ENOENT,
+                winerror::ERROR_NOT_ENOUGH_MEMORY => Self::ENOMEM,
+                winerror::ERROR_OUTOFMEMORY => Self::ENOMEM,
+                winerror::ERROR_DIR_NOT_EMPTY => Self::ENOTEMPTY,
+                winerror::ERROR_NOT_READY => Self::EBUSY,
+                winerror::ERROR_BUSY => Self::EBUSY,
+                winerror::ERROR_NOT_SUPPORTED => Self::ENOTSUP,
+                winerror::ERROR_FILE_EXISTS => Self::EEXIST,
+                winerror::ERROR_BROKEN_PIPE => Self::EPIPE,
+                winerror::ERROR_BUFFER_OVERFLOW => Self::ENAMETOOLONG,
+                winerror::ERROR_NOT_A_REPARSE_POINT => Self::EINVAL,
+                winerror::ERROR_NEGATIVE_SEEK => Self::EINVAL,
+                winerror::ERROR_DIRECTORY => Self::ENOTDIR,
+                winerror::ERROR_ALREADY_EXISTS => Self::EEXIST,
+                x => {
+                    log::debug!("unknown error value: {}", x);
+                    Self::EIO
+                }
+            },
+            None => {
+                log::debug!("Other I/O error: {}", err);
+                Self::EIO
+            }
         }
     }
 }
@@ -137,15 +145,15 @@ fn change_time(file: &File) -> io::Result<i64> {
     winx::file::change_time(file)
 }
 
-fn systemtime_to_timestamp(st: SystemTime) -> Result<u64> {
+fn systemtime_to_timestamp(st: SystemTime) -> WasiResult<u64> {
     st.duration_since(UNIX_EPOCH)
-        .map_err(|_| Error::EINVAL)? // date earlier than UNIX_EPOCH
+        .map_err(|_| WasiError::EINVAL)? // date earlier than UNIX_EPOCH
         .as_nanos()
         .try_into()
         .map_err(Into::into) // u128 doesn't fit into u64
 }
 
-pub(crate) fn filestat_from_win(file: &File) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn filestat_from_win(file: &File) -> WasiResult<wasi::__wasi_filestat_t> {
     let metadata = file.metadata()?;
     Ok(wasi::__wasi_filestat_t {
         dev: device_id(file)?,
@@ -163,7 +171,7 @@ pub(crate) fn filestat_from_win(file: &File) -> Result<wasi::__wasi_filestat_t>
 ///
 /// NB WASI spec requires OS string to be valid UTF-8. Otherwise,
 /// `__WASI_ERRNO_ILSEQ` error is returned.
-pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String> {
+pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> WasiResult<String> {
     let vec: Vec<u16> = s.as_ref().encode_wide().collect();
-    String::from_utf16(&vec).map_err(|_| Error::EILSEQ)
+    String::from_utf16(&vec).map_err(|_| WasiError::EILSEQ)
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs.rs b/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs.rs
index cc157e7882..f0f7453c7e 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs.rs
@@ -8,7 +8,7 @@ use crate::old::snapshot_0::hostcalls_impl::{fd_filestat_set_times_impl, PathGet
 use crate::old::snapshot_0::sys::fdentry_impl::determine_type_rights;
 use crate::old::snapshot_0::sys::host_impl::{self, path_from_host};
 use crate::old::snapshot_0::sys::hostcalls_impl::fs_helpers::PathGetExt;
-use crate::old::snapshot_0::{wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use log::{debug, trace};
 use std::convert::TryInto;
 use std::fs::{File, Metadata, OpenOptions};
@@ -44,16 +44,20 @@ pub(crate) fn fd_pread(
     file: &File,
     buf: &mut [u8],
     offset: wasi::__wasi_filesize_t,
-) -> Result<usize> {
+) -> WasiResult<usize> {
     read_at(file, buf, offset).map_err(Into::into)
 }
 
 // TODO refactor common code with unix
-pub(crate) fn fd_pwrite(file: &File, buf: &[u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+pub(crate) fn fd_pwrite(
+    file: &File,
+    buf: &[u8],
+    offset: wasi::__wasi_filesize_t,
+) -> WasiResult<usize> {
     write_at(file, buf, offset).map_err(Into::into)
 }
 
-pub(crate) fn fd_fdstat_get(fd: &File) -> Result<wasi::__wasi_fdflags_t> {
+pub(crate) fn fd_fdstat_get(fd: &File) -> WasiResult<wasi::__wasi_fdflags_t> {
     let mut fdflags = 0;
 
     let handle = unsafe { fd.as_raw_handle() };
@@ -79,7 +83,7 @@ pub(crate) fn fd_fdstat_get(fd: &File) -> Result<wasi::__wasi_fdflags_t> {
     Ok(fdflags)
 }
 
-pub(crate) fn fd_fdstat_set_flags(fd: &File, fdflags: wasi::__wasi_fdflags_t) -> Result<()> {
+pub(crate) fn fd_fdstat_set_flags(fd: &File, fdflags: wasi::__wasi_fdflags_t) -> WasiResult<()> {
     unimplemented!("fd_fdstat_set_flags")
 }
 
@@ -88,7 +92,7 @@ pub(crate) fn fd_advise(
     advice: wasi::__wasi_advice_t,
     _offset: wasi::__wasi_filesize_t,
     _len: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     match advice {
         wasi::__WASI_ADVICE_DONTNEED
         | wasi::__WASI_ADVICE_SEQUENTIAL
@@ -96,18 +100,18 @@ pub(crate) fn fd_advise(
         | wasi::__WASI_ADVICE_NOREUSE
         | wasi::__WASI_ADVICE_RANDOM
         | wasi::__WASI_ADVICE_NORMAL => {}
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     }
 
     Ok(())
 }
 
-pub(crate) fn path_create_directory(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_create_directory(resolved: PathGet) -> WasiResult<()> {
     let path = resolved.concatenate()?;
     std::fs::create_dir(&path).map_err(Into::into)
 }
 
-pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     unimplemented!("path_link")
 }
 
@@ -117,7 +121,7 @@ pub(crate) fn path_open(
     write: bool,
     oflags: wasi::__wasi_oflags_t,
     fdflags: wasi::__wasi_fdflags_t,
-) -> Result<File> {
+) -> WasiResult<File> {
     use winx::file::{AccessMode, CreationDisposition, Flags};
 
     // convert open flags
@@ -143,11 +147,11 @@ pub(crate) fn path_open(
         Ok(file_type) => {
             // check if we are trying to open a symlink
             if file_type.is_symlink() {
-                return Err(Error::ELOOP);
+                return Err(WasiError::ELOOP);
             }
             // check if we are trying to open a file as a dir
             if file_type.is_file() && oflags & wasi::__WASI_OFLAGS_DIRECTORY != 0 {
-                return Err(Error::ENOTDIR);
+                return Err(WasiError::ENOTDIR);
             }
         }
         Err(err) => match err.raw_os_error() {
@@ -162,7 +166,7 @@ pub(crate) fn path_open(
             }
             None => {
                 log::debug!("Inconvertible OS error: {}", err);
-                return Err(Error::EIO);
+                return Err(WasiError::EIO);
             }
         },
     }
@@ -236,7 +240,7 @@ fn dirent_from_path<P: AsRef<Path>>(
     path: P,
     name: &str,
     cookie: wasi::__wasi_dircookie_t,
-) -> Result<Dirent> {
+) -> WasiResult<Dirent> {
     let path = path.as_ref();
     trace!("dirent_from_path: opening {}", path.to_string_lossy());
 
@@ -285,7 +289,7 @@ fn dirent_from_path<P: AsRef<Path>>(
 pub(crate) fn fd_readdir(
     fd: &File,
     cookie: wasi::__wasi_dircookie_t,
-) -> Result<impl Iterator<Item = Result<Dirent>>> {
+) -> WasiResult<impl Iterator<Item = WasiResult<Dirent>>> {
     use winx::file::get_file_path;
 
     let cookie = cookie.try_into()?;
@@ -321,7 +325,7 @@ pub(crate) fn fd_readdir(
     Ok(iter.skip(cookie))
 }
 
-pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize> {
+pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> WasiResult<usize> {
     use winx::file::get_file_path;
 
     let path = resolved.concatenate()?;
@@ -335,8 +339,8 @@ pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize>
     let dir_path = PathBuf::from(strip_extended_prefix(dir_path));
     let target_path = target_path
         .strip_prefix(dir_path)
-        .map_err(|_| Error::ENOTCAPABLE)
-        .and_then(|path| path.to_str().map(String::from).ok_or(Error::EILSEQ))?;
+        .map_err(|_| WasiError::ENOTCAPABLE)
+        .and_then(|path| path.to_str().map(String::from).ok_or(WasiError::EILSEQ))?;
 
     if buf.len() > 0 {
         let mut chars = target_path.chars();
@@ -358,7 +362,7 @@ pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize>
     }
 }
 
-fn strip_trailing_slashes_and_concatenate(resolved: &PathGet) -> Result<Option<PathBuf>> {
+fn strip_trailing_slashes_and_concatenate(resolved: &PathGet) -> WasiResult<Option<PathBuf>> {
     if resolved.path().ends_with('/') {
         let suffix = resolved.path().trim_end_matches('/');
         concatenate(resolved.dirfd(), Path::new(suffix)).map(Some)
@@ -367,7 +371,7 @@ fn strip_trailing_slashes_and_concatenate(resolved: &PathGet) -> Result<Option<P
     }
 }
 
-pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use std::fs;
 
     let old_path = resolved_old.concatenate()?;
@@ -378,12 +382,12 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
     //
     // [std::fs::rename]: https://doc.rust-lang.org/std/fs/fn.rename.html
     if old_path.is_dir() && new_path.is_file() {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
     // Second sanity check: check we're not trying to rename a file into a path
     // ending in a trailing slash.
     if old_path.is_file() && resolved_new.path().ends_with('/') {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     // TODO handle symlinks
@@ -399,7 +403,7 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
                     // So most likely dealing with new_path == dir.
                     // Eliminate case old_path == file first.
                     if old_path.is_file() {
-                        return Err(Error::EISDIR);
+                        return Err(WasiError::EISDIR);
                     } else {
                         // Ok, let's try removing an empty dir at new_path if it exists
                         // and is a nonempty dir.
@@ -413,7 +417,7 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
                     // a file instead of a dir, and if so, throw ENOTDIR.
                     if let Some(path) = strip_trailing_slashes_and_concatenate(&resolved_old)? {
                         if path.is_file() {
-                            return Err(Error::ENOTDIR);
+                            return Err(WasiError::ENOTDIR);
                         }
                     }
                 }
@@ -424,19 +428,19 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
         }
         None => {
             log::debug!("Inconvertible OS error: {}", err);
-            Err(Error::EIO)
+            Err(WasiError::EIO)
         }
     }
 }
 
-pub(crate) fn fd_filestat_get(file: &std::fs::File) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn fd_filestat_get(file: &std::fs::File) -> WasiResult<wasi::__wasi_filestat_t> {
     host_impl::filestat_from_win(file)
 }
 
 pub(crate) fn path_filestat_get(
     resolved: PathGet,
     dirflags: wasi::__wasi_lookupflags_t,
-) -> Result<wasi::__wasi_filestat_t> {
+) -> WasiResult<wasi::__wasi_filestat_t> {
     let path = resolved.concatenate()?;
     let file = File::open(path)?;
     host_impl::filestat_from_win(&file)
@@ -448,7 +452,7 @@ pub(crate) fn path_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     mut st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     use winx::file::AccessMode;
     let path = resolved.concatenate()?;
     let file = OpenOptions::new()
@@ -457,7 +461,7 @@ pub(crate) fn path_filestat_set_times(
     fd_filestat_set_times_impl(&file, st_atim, st_mtim, fst_flags)
 }
 
-pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> WasiResult<()> {
     use std::os::windows::fs::{symlink_dir, symlink_file};
 
     let old_path = concatenate(resolved.dirfd(), Path::new(old_path))?;
@@ -479,14 +483,14 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
                 winerror::ERROR_ACCESS_DENIED => {
                     // does the target exist?
                     if new_path.exists() {
-                        return Err(Error::EEXIST);
+                        return Err(WasiError::EEXIST);
                     }
                 }
                 winerror::ERROR_INVALID_NAME => {
                     // does the target without trailing slashes exist?
                     if let Some(path) = strip_trailing_slashes_and_concatenate(&resolved)? {
                         if path.exists() {
-                            return Err(Error::EEXIST);
+                            return Err(WasiError::EEXIST);
                         }
                     }
                 }
@@ -497,12 +501,12 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
         }
         None => {
             log::debug!("Inconvertible OS error: {}", err);
-            Err(Error::EIO)
+            Err(WasiError::EIO)
         }
     }
 }
 
-pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_unlink_file(resolved: PathGet) -> WasiResult<()> {
     use std::fs;
 
     let path = resolved.concatenate()?;
@@ -532,19 +536,19 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
             }
             None => {
                 log::debug!("Inconvertible OS error: {}", err);
-                Err(Error::EIO)
+                Err(WasiError::EIO)
             }
         }
     } else if file_type.is_dir() {
-        Err(Error::EISDIR)
+        Err(WasiError::EISDIR)
     } else if file_type.is_file() {
         fs::remove_file(path).map_err(Into::into)
     } else {
-        Err(Error::EINVAL)
+        Err(WasiError::EINVAL)
     }
 }
 
-pub(crate) fn path_remove_directory(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_remove_directory(resolved: PathGet) -> WasiResult<()> {
     let path = resolved.concatenate()?;
     std::fs::remove_dir(&path).map_err(Into::into)
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs_helpers.rs b/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs_helpers.rs
index a89a37f6e0..63efce5a4c 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs_helpers.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/fs_helpers.rs
@@ -1,6 +1,6 @@
 #![allow(non_camel_case_types)]
 use crate::old::snapshot_0::hostcalls_impl::PathGet;
-use crate::old::snapshot_0::{wasi, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
 use std::ffi::{OsStr, OsString};
 use std::fs::File;
 use std::os::windows::ffi::{OsStrExt, OsStringExt};
@@ -8,11 +8,11 @@ use std::path::{Path, PathBuf};
 use winapi::shared::winerror;
 
 pub(crate) trait PathGetExt {
-    fn concatenate(&self) -> Result<PathBuf>;
+    fn concatenate(&self) -> WasiResult<PathBuf>;
 }
 
 impl PathGetExt for PathGet {
-    fn concatenate(&self) -> Result<PathBuf> {
+    fn concatenate(&self) -> WasiResult<PathBuf> {
         concatenate(self.dirfd(), Path::new(self.path()))
     }
 }
@@ -46,7 +46,7 @@ pub(crate) fn path_open_rights(
     (needed_base, needed_inheriting)
 }
 
-pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
+pub(crate) fn openat(dirfd: &File, path: &str) -> WasiResult<File> {
     use std::fs::OpenOptions;
     use std::os::windows::fs::OpenOptionsExt;
     use winx::file::Flags;
@@ -63,13 +63,13 @@ pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
     if let Some(code) = err.raw_os_error() {
         log::debug!("openat error={:?}", code);
         if code as u32 == winerror::ERROR_INVALID_NAME {
-            return Err(Error::ENOTDIR);
+            return Err(WasiError::ENOTDIR);
         }
     }
     Err(err.into())
 }
 
-pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> Result<String> {
+pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> WasiResult<String> {
     use winx::file::get_file_path;
 
     let path = concatenate(dirfd, Path::new(s_path))?;
@@ -83,8 +83,8 @@ pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> Result<String> {
             let dir_path = PathBuf::from(strip_extended_prefix(dir_path));
             let target_path = target_path
                 .strip_prefix(dir_path)
-                .map_err(|_| Error::ENOTCAPABLE)?;
-            let target_path = target_path.to_str().ok_or(Error::EILSEQ)?;
+                .map_err(|_| WasiError::ENOTCAPABLE)?;
+            let target_path = target_path.to_str().ok_or(WasiError::EILSEQ)?;
             return Ok(target_path.to_owned());
         }
         Err(e) => e,
@@ -96,7 +96,7 @@ pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> Result<String> {
                 // strip "/" and check if exists
                 let path = concatenate(dirfd, Path::new(s_path.trim_end_matches('/')))?;
                 if path.exists() && !path.is_dir() {
-                    return Err(Error::ENOTDIR);
+                    return Err(WasiError::ENOTDIR);
                 }
             }
         }
@@ -113,13 +113,13 @@ pub(crate) fn strip_extended_prefix<P: AsRef<OsStr>>(path: P) -> OsString {
     }
 }
 
-pub(crate) fn concatenate<P: AsRef<Path>>(dirfd: &File, path: P) -> Result<PathBuf> {
+pub(crate) fn concatenate<P: AsRef<Path>>(dirfd: &File, path: P) -> WasiResult<PathBuf> {
     use winx::file::get_file_path;
 
     // WASI is not able to deal with absolute paths
     // so error out if absolute
     if path.as_ref().is_absolute() {
-        return Err(Error::ENOTCAPABLE);
+        return Err(WasiError::ENOTCAPABLE);
     }
 
     let dir_path = get_file_path(dirfd)?;
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/misc.rs b/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/misc.rs
index bf8df626cd..395adce4f0 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/misc.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/windows/hostcalls_impl/misc.rs
@@ -4,7 +4,8 @@
 use crate::old::snapshot_0::hostcalls_impl::{ClockEventData, FdEventData};
 use crate::old::snapshot_0::memory::*;
 use crate::old::snapshot_0::sys::host_impl;
-use crate::old::snapshot_0::{wasi, wasi32, Error, Result};
+use crate::old::snapshot_0::wasi::{self, WasiError, WasiResult};
+use crate::old::snapshot_0::wasi32;
 use cpu_time::{ProcessTime, ThreadTime};
 use lazy_static::lazy_static;
 use std::convert::TryInto;
@@ -17,7 +18,9 @@ lazy_static! {
 
 // Timer resolution on Windows is really hard. We may consider exposing the resolution of the respective
 // timers as an associated function in the future.
-pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_res_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     Ok(match clock_id {
         // This is the best that we can do with std::time::SystemTime.
         // Rust uses GetSystemTimeAsFileTime, which is said to have the resolution of
@@ -61,17 +64,19 @@ pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__
         // The best we can do is to hardcode the value from the docs.
         // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getthreadtimes
         wasi::__WASI_CLOCKID_THREAD_CPUTIME_ID => 100,
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     })
 }
 
-pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_time_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     let duration = match clock_id {
         wasi::__WASI_CLOCKID_REALTIME => get_monotonic_time(),
         wasi::__WASI_CLOCKID_MONOTONIC => get_realtime_time()?,
         wasi::__WASI_CLOCKID_PROCESS_CPUTIME_ID => get_proc_cputime()?,
         wasi::__WASI_CLOCKID_THREAD_CPUTIME_ID => get_thread_cputime()?,
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     };
     duration.as_nanos().try_into().map_err(Into::into)
 }
@@ -80,7 +85,7 @@ pub(crate) fn poll_oneoff(
     timeout: Option<ClockEventData>,
     fd_events: Vec<FdEventData>,
     events: &mut Vec<wasi::__wasi_event_t>,
-) -> Result<Vec<wasi::__wasi_event_t>> {
+) -> WasiResult<Vec<wasi::__wasi_event_t>> {
     unimplemented!("poll_oneoff")
 }
 
@@ -94,17 +99,17 @@ fn get_monotonic_time() -> Duration {
     START_MONOTONIC.elapsed()
 }
 
-fn get_realtime_time() -> Result<Duration> {
+fn get_realtime_time() -> WasiResult<Duration> {
     SystemTime::now()
         .duration_since(UNIX_EPOCH)
-        .map_err(|_| Error::EFAULT)
+        .map_err(|_| WasiError::EFAULT)
 }
 
-fn get_proc_cputime() -> Result<Duration> {
+fn get_proc_cputime() -> WasiResult<Duration> {
     Ok(ProcessTime::try_now()?.as_duration())
 }
 
-fn get_thread_cputime() -> Result<Duration> {
+fn get_thread_cputime() -> WasiResult<Duration> {
     Ok(ThreadTime::try_now()?.as_duration())
 }
 
diff --git a/crates/wasi-common/src/old/snapshot_0/sys/windows/mod.rs b/crates/wasi-common/src/old/snapshot_0/sys/windows/mod.rs
index 35d00ac935..7783272946 100644
--- a/crates/wasi-common/src/old/snapshot_0/sys/windows/mod.rs
+++ b/crates/wasi-common/src/old/snapshot_0/sys/windows/mod.rs
@@ -2,13 +2,9 @@ pub(crate) mod fdentry_impl;
 pub(crate) mod host_impl;
 pub(crate) mod hostcalls_impl;
 
-use crate::old::snapshot_0::Result;
 use std::fs::{File, OpenOptions};
+use std::io::Result;
 
 pub(crate) fn dev_null() -> Result<File> {
-    OpenOptions::new()
-        .read(true)
-        .write(true)
-        .open("NUL")
-        .map_err(Into::into)
+    OpenOptions::new().read(true).write(true).open("NUL")
 }
diff --git a/crates/wasi-common/src/old/snapshot_0/wasi.rs b/crates/wasi-common/src/old/snapshot_0/wasi.rs
index 63a08e8c5e..966fed9bbd 100644
--- a/crates/wasi-common/src/old/snapshot_0/wasi.rs
+++ b/crates/wasi-common/src/old/snapshot_0/wasi.rs
@@ -10,6 +10,115 @@ use wig::witx_wasi_types;
 
 witx_wasi_types!("old/snapshot_0" "wasi_unstable");
 
+pub type WasiResult<T> = Result<T, WasiError>;
+
+#[derive(Clone, Copy, Debug, thiserror::Error, Eq, PartialEq)]
+#[repr(u16)]
+#[error("{:?} ({})", self, strerror(*self as __wasi_errno_t))]
+pub enum WasiError {
+    ESUCCESS = __WASI_ERRNO_SUCCESS,
+    E2BIG = __WASI_ERRNO_2BIG,
+    EACCES = __WASI_ERRNO_ACCES,
+    EADDRINUSE = __WASI_ERRNO_ADDRINUSE,
+    EADDRNOTAVAIL = __WASI_ERRNO_ADDRNOTAVAIL,
+    EAFNOSUPPORT = __WASI_ERRNO_AFNOSUPPORT,
+    EAGAIN = __WASI_ERRNO_AGAIN,
+    EALREADY = __WASI_ERRNO_ALREADY,
+    EBADF = __WASI_ERRNO_BADF,
+    EBADMSG = __WASI_ERRNO_BADMSG,
+    EBUSY = __WASI_ERRNO_BUSY,
+    ECANCELED = __WASI_ERRNO_CANCELED,
+    ECHILD = __WASI_ERRNO_CHILD,
+    ECONNABORTED = __WASI_ERRNO_CONNABORTED,
+    ECONNREFUSED = __WASI_ERRNO_CONNREFUSED,
+    ECONNRESET = __WASI_ERRNO_CONNRESET,
+    EDEADLK = __WASI_ERRNO_DEADLK,
+    EDESTADDRREQ = __WASI_ERRNO_DESTADDRREQ,
+    EDOM = __WASI_ERRNO_DOM,
+    EDQUOT = __WASI_ERRNO_DQUOT,
+    EEXIST = __WASI_ERRNO_EXIST,
+    EFAULT = __WASI_ERRNO_FAULT,
+    EFBIG = __WASI_ERRNO_FBIG,
+    EHOSTUNREACH = __WASI_ERRNO_HOSTUNREACH,
+    EIDRM = __WASI_ERRNO_IDRM,
+    EILSEQ = __WASI_ERRNO_ILSEQ,
+    EINPROGRESS = __WASI_ERRNO_INPROGRESS,
+    EINTR = __WASI_ERRNO_INTR,
+    EINVAL = __WASI_ERRNO_INVAL,
+    EIO = __WASI_ERRNO_IO,
+    EISCONN = __WASI_ERRNO_ISCONN,
+    EISDIR = __WASI_ERRNO_ISDIR,
+    ELOOP = __WASI_ERRNO_LOOP,
+    EMFILE = __WASI_ERRNO_MFILE,
+    EMLINK = __WASI_ERRNO_MLINK,
+    EMSGSIZE = __WASI_ERRNO_MSGSIZE,
+    EMULTIHOP = __WASI_ERRNO_MULTIHOP,
+    ENAMETOOLONG = __WASI_ERRNO_NAMETOOLONG,
+    ENETDOWN = __WASI_ERRNO_NETDOWN,
+    ENETRESET = __WASI_ERRNO_NETRESET,
+    ENETUNREACH = __WASI_ERRNO_NETUNREACH,
+    ENFILE = __WASI_ERRNO_NFILE,
+    ENOBUFS = __WASI_ERRNO_NOBUFS,
+    ENODEV = __WASI_ERRNO_NODEV,
+    ENOENT = __WASI_ERRNO_NOENT,
+    ENOEXEC = __WASI_ERRNO_NOEXEC,
+    ENOLCK = __WASI_ERRNO_NOLCK,
+    ENOLINK = __WASI_ERRNO_NOLINK,
+    ENOMEM = __WASI_ERRNO_NOMEM,
+    ENOMSG = __WASI_ERRNO_NOMSG,
+    ENOPROTOOPT = __WASI_ERRNO_NOPROTOOPT,
+    ENOSPC = __WASI_ERRNO_NOSPC,
+    ENOSYS = __WASI_ERRNO_NOSYS,
+    ENOTCONN = __WASI_ERRNO_NOTCONN,
+    ENOTDIR = __WASI_ERRNO_NOTDIR,
+    ENOTEMPTY = __WASI_ERRNO_NOTEMPTY,
+    ENOTRECOVERABLE = __WASI_ERRNO_NOTRECOVERABLE,
+    ENOTSOCK = __WASI_ERRNO_NOTSOCK,
+    ENOTSUP = __WASI_ERRNO_NOTSUP,
+    ENOTTY = __WASI_ERRNO_NOTTY,
+    ENXIO = __WASI_ERRNO_NXIO,
+    EOVERFLOW = __WASI_ERRNO_OVERFLOW,
+    EOWNERDEAD = __WASI_ERRNO_OWNERDEAD,
+    EPERM = __WASI_ERRNO_PERM,
+    EPIPE = __WASI_ERRNO_PIPE,
+    EPROTO = __WASI_ERRNO_PROTO,
+    EPROTONOSUPPORT = __WASI_ERRNO_PROTONOSUPPORT,
+    EPROTOTYPE = __WASI_ERRNO_PROTOTYPE,
+    ERANGE = __WASI_ERRNO_RANGE,
+    EROFS = __WASI_ERRNO_ROFS,
+    ESPIPE = __WASI_ERRNO_SPIPE,
+    ESRCH = __WASI_ERRNO_SRCH,
+    ESTALE = __WASI_ERRNO_STALE,
+    ETIMEDOUT = __WASI_ERRNO_TIMEDOUT,
+    ETXTBSY = __WASI_ERRNO_TXTBSY,
+    EXDEV = __WASI_ERRNO_XDEV,
+    ENOTCAPABLE = __WASI_ERRNO_NOTCAPABLE,
+}
+
+impl WasiError {
+    pub fn as_raw_errno(self) -> __wasi_errno_t {
+        self as __wasi_errno_t
+    }
+}
+
+impl From<std::convert::Infallible> for WasiError {
+    fn from(_err: std::convert::Infallible) -> Self {
+        unreachable!()
+    }
+}
+
+impl From<std::num::TryFromIntError> for WasiError {
+    fn from(_err: std::num::TryFromIntError) -> Self {
+        Self::EOVERFLOW
+    }
+}
+
+impl From<std::str::Utf8Error> for WasiError {
+    fn from(_err: std::str::Utf8Error) -> Self {
+        Self::EILSEQ
+    }
+}
+
 pub(crate) const RIGHTS_ALL: __wasi_rights_t = __WASI_RIGHTS_FD_DATASYNC
     | __WASI_RIGHTS_FD_READ
     | __WASI_RIGHTS_FD_SEEK
diff --git a/crates/wasi-common/src/sys/unix/bsd/host_impl.rs b/crates/wasi-common/src/sys/unix/bsd/host_impl.rs
index 53f0782deb..d2ab148fc6 100644
--- a/crates/wasi-common/src/sys/unix/bsd/host_impl.rs
+++ b/crates/wasi-common/src/sys/unix/bsd/host_impl.rs
@@ -1,12 +1,12 @@
-use crate::{wasi, Result};
+use crate::wasi::{self, WasiResult};
 use std::convert::TryFrom;
 
 pub(crate) const O_RSYNC: yanix::file::OFlag = yanix::file::OFlag::SYNC;
 
-pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> Result<wasi::__wasi_device_t> {
+pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> WasiResult<wasi::__wasi_device_t> {
     wasi::__wasi_device_t::try_from(dev).map_err(Into::into)
 }
 
-pub(crate) fn stino_from_nix(ino: libc::ino_t) -> Result<wasi::__wasi_inode_t> {
+pub(crate) fn stino_from_nix(ino: libc::ino_t) -> WasiResult<wasi::__wasi_inode_t> {
     wasi::__wasi_device_t::try_from(ino).map_err(Into::into)
 }
diff --git a/crates/wasi-common/src/sys/unix/bsd/hostcalls_impl.rs b/crates/wasi-common/src/sys/unix/bsd/hostcalls_impl.rs
index b82b917c1c..9b56bb76a0 100644
--- a/crates/wasi-common/src/sys/unix/bsd/hostcalls_impl.rs
+++ b/crates/wasi-common/src/sys/unix/bsd/hostcalls_impl.rs
@@ -1,8 +1,8 @@
 use crate::hostcalls_impl::PathGet;
-use crate::{Error, Result};
+use crate::wasi::{WasiError, WasiResult};
 use std::os::unix::prelude::AsRawFd;
 
-pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_unlink_file(resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{unlinkat, AtFlag};
     match unsafe {
         unlinkat(
@@ -32,7 +32,7 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
                 } {
                     Ok(stat) => {
                         if FileType::from_stat_st_mode(stat.st_mode) == FileType::Directory {
-                            return Err(Error::EISDIR);
+                            return Err(WasiError::EISDIR);
                         }
                     }
                     Err(err) => {
@@ -47,7 +47,7 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
     }
 }
 
-pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{fstatat, symlinkat, AtFlag};
 
     log::debug!("path_symlink old_path = {:?}", old_path);
@@ -69,7 +69,7 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
                         AtFlag::SYMLINK_NOFOLLOW,
                     )
                 } {
-                    Ok(_) => return Err(Error::EEXIST),
+                    Ok(_) => return Err(WasiError::EEXIST),
                     Err(err) => {
                         log::debug!("path_symlink fstatat error: {:?}", err);
                     }
@@ -81,7 +81,7 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
     }
 }
 
-pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use yanix::file::{fstatat, renameat, AtFlag};
     match unsafe {
         renameat(
@@ -113,9 +113,9 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
                     Ok(_) => {
                         // check if destination contains a trailing slash
                         if resolved_new.path().contains('/') {
-                            return Err(Error::ENOTDIR);
+                            return Err(WasiError::ENOTDIR);
                         } else {
-                            return Err(Error::ENOENT);
+                            return Err(WasiError::ENOENT);
                         }
                     }
                     Err(err) => {
@@ -132,13 +132,13 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
 
 pub(crate) mod fd_readdir_impl {
     use crate::sys::fdentry_impl::OsHandle;
-    use crate::Result;
+    use crate::wasi::WasiResult;
     use std::sync::{Mutex, MutexGuard};
     use yanix::dir::Dir;
 
     pub(crate) fn get_dir_from_os_handle<'a>(
         os_handle: &'a mut OsHandle,
-    ) -> Result<MutexGuard<'a, Dir>> {
+    ) -> WasiResult<MutexGuard<'a, Dir>> {
         let dir = match os_handle.dir {
             Some(ref mut dir) => dir,
             None => {
diff --git a/crates/wasi-common/src/sys/unix/fdentry_impl.rs b/crates/wasi-common/src/sys/unix/fdentry_impl.rs
index 2ba4bd0c13..7a45e28c13 100644
--- a/crates/wasi-common/src/sys/unix/fdentry_impl.rs
+++ b/crates/wasi-common/src/sys/unix/fdentry_impl.rs
@@ -1,5 +1,5 @@
 use crate::fdentry::{Descriptor, OsHandleRef};
-use crate::{sys::unix::sys_impl, wasi, Error, Result};
+use crate::{sys::unix::sys_impl, wasi};
 use std::fs::File;
 use std::io;
 use std::mem::ManuallyDrop;
@@ -33,7 +33,7 @@ pub(crate) fn descriptor_as_oshandle<'lifetime>(
 /// This function is unsafe because it operates on a raw file descriptor.
 pub(crate) unsafe fn determine_type_and_access_rights<Fd: AsRawFd>(
     fd: &Fd,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -57,7 +57,7 @@ pub(crate) unsafe fn determine_type_and_access_rights<Fd: AsRawFd>(
 /// This function is unsafe because it operates on a raw file descriptor.
 pub(crate) unsafe fn determine_type_rights<Fd: AsRawFd>(
     fd: &Fd,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -117,7 +117,7 @@ pub(crate) unsafe fn determine_type_rights<Fd: AsRawFd>(
                     wasi::RIGHTS_SOCKET_BASE,
                     wasi::RIGHTS_SOCKET_INHERITING,
                 ),
-                _ => return Err(Error::EINVAL),
+                _ => return Err(io::Error::from_raw_os_error(libc::EINVAL)),
             }
         } else if ft.is_fifo() {
             log::debug!("Host fd {:?} is a fifo", fd.as_raw_fd());
@@ -128,7 +128,7 @@ pub(crate) unsafe fn determine_type_rights<Fd: AsRawFd>(
             )
         } else {
             log::debug!("Host fd {:?} is unknown", fd.as_raw_fd());
-            return Err(Error::EINVAL);
+            return Err(io::Error::from_raw_os_error(libc::EINVAL));
         }
     };
 
diff --git a/crates/wasi-common/src/sys/unix/host_impl.rs b/crates/wasi-common/src/sys/unix/host_impl.rs
index dea0b106eb..3a3010b1f7 100644
--- a/crates/wasi-common/src/sys/unix/host_impl.rs
+++ b/crates/wasi-common/src/sys/unix/host_impl.rs
@@ -3,92 +3,101 @@
 #![allow(non_snake_case)]
 #![allow(dead_code)]
 use crate::host::FileType;
-use crate::{error::FromRawOsError, helpers, sys::unix::sys_impl, wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
+use crate::{helpers, sys::unix::sys_impl};
 use std::ffi::OsStr;
+use std::io;
 use std::os::unix::prelude::OsStrExt;
 use yanix::file::OFlag;
 
 pub(crate) use sys_impl::host_impl::*;
 
-impl FromRawOsError for Error {
-    fn from_raw_os_error(code: i32) -> Self {
-        match code {
-            libc::EPERM => Self::EPERM,
-            libc::ENOENT => Self::ENOENT,
-            libc::ESRCH => Self::ESRCH,
-            libc::EINTR => Self::EINTR,
-            libc::EIO => Self::EIO,
-            libc::ENXIO => Self::ENXIO,
-            libc::E2BIG => Self::E2BIG,
-            libc::ENOEXEC => Self::ENOEXEC,
-            libc::EBADF => Self::EBADF,
-            libc::ECHILD => Self::ECHILD,
-            libc::EAGAIN => Self::EAGAIN,
-            libc::ENOMEM => Self::ENOMEM,
-            libc::EACCES => Self::EACCES,
-            libc::EFAULT => Self::EFAULT,
-            libc::EBUSY => Self::EBUSY,
-            libc::EEXIST => Self::EEXIST,
-            libc::EXDEV => Self::EXDEV,
-            libc::ENODEV => Self::ENODEV,
-            libc::ENOTDIR => Self::ENOTDIR,
-            libc::EISDIR => Self::EISDIR,
-            libc::EINVAL => Self::EINVAL,
-            libc::ENFILE => Self::ENFILE,
-            libc::EMFILE => Self::EMFILE,
-            libc::ENOTTY => Self::ENOTTY,
-            libc::ETXTBSY => Self::ETXTBSY,
-            libc::EFBIG => Self::EFBIG,
-            libc::ENOSPC => Self::ENOSPC,
-            libc::ESPIPE => Self::ESPIPE,
-            libc::EROFS => Self::EROFS,
-            libc::EMLINK => Self::EMLINK,
-            libc::EPIPE => Self::EPIPE,
-            libc::EDOM => Self::EDOM,
-            libc::ERANGE => Self::ERANGE,
-            libc::EDEADLK => Self::EDEADLK,
-            libc::ENAMETOOLONG => Self::ENAMETOOLONG,
-            libc::ENOLCK => Self::ENOLCK,
-            libc::ENOSYS => Self::ENOSYS,
-            libc::ENOTEMPTY => Self::ENOTEMPTY,
-            libc::ELOOP => Self::ELOOP,
-            libc::ENOMSG => Self::ENOMSG,
-            libc::EIDRM => Self::EIDRM,
-            libc::ENOLINK => Self::ENOLINK,
-            libc::EPROTO => Self::EPROTO,
-            libc::EMULTIHOP => Self::EMULTIHOP,
-            libc::EBADMSG => Self::EBADMSG,
-            libc::EOVERFLOW => Self::EOVERFLOW,
-            libc::EILSEQ => Self::EILSEQ,
-            libc::ENOTSOCK => Self::ENOTSOCK,
-            libc::EDESTADDRREQ => Self::EDESTADDRREQ,
-            libc::EMSGSIZE => Self::EMSGSIZE,
-            libc::EPROTOTYPE => Self::EPROTOTYPE,
-            libc::ENOPROTOOPT => Self::ENOPROTOOPT,
-            libc::EPROTONOSUPPORT => Self::EPROTONOSUPPORT,
-            libc::EAFNOSUPPORT => Self::EAFNOSUPPORT,
-            libc::EADDRINUSE => Self::EADDRINUSE,
-            libc::EADDRNOTAVAIL => Self::EADDRNOTAVAIL,
-            libc::ENETDOWN => Self::ENETDOWN,
-            libc::ENETUNREACH => Self::ENETUNREACH,
-            libc::ENETRESET => Self::ENETRESET,
-            libc::ECONNABORTED => Self::ECONNABORTED,
-            libc::ECONNRESET => Self::ECONNRESET,
-            libc::ENOBUFS => Self::ENOBUFS,
-            libc::EISCONN => Self::EISCONN,
-            libc::ENOTCONN => Self::ENOTCONN,
-            libc::ETIMEDOUT => Self::ETIMEDOUT,
-            libc::ECONNREFUSED => Self::ECONNREFUSED,
-            libc::EHOSTUNREACH => Self::EHOSTUNREACH,
-            libc::EALREADY => Self::EALREADY,
-            libc::EINPROGRESS => Self::EINPROGRESS,
-            libc::ESTALE => Self::ESTALE,
-            libc::EDQUOT => Self::EDQUOT,
-            libc::ECANCELED => Self::ECANCELED,
-            libc::EOWNERDEAD => Self::EOWNERDEAD,
-            libc::ENOTRECOVERABLE => Self::ENOTRECOVERABLE,
-            x => {
-                log::debug!("Unknown errno value: {}", x);
+impl From<io::Error> for WasiError {
+    fn from(err: io::Error) -> Self {
+        match err.raw_os_error() {
+            Some(code) => match code {
+                libc::EPERM => Self::EPERM,
+                libc::ENOENT => Self::ENOENT,
+                libc::ESRCH => Self::ESRCH,
+                libc::EINTR => Self::EINTR,
+                libc::EIO => Self::EIO,
+                libc::ENXIO => Self::ENXIO,
+                libc::E2BIG => Self::E2BIG,
+                libc::ENOEXEC => Self::ENOEXEC,
+                libc::EBADF => Self::EBADF,
+                libc::ECHILD => Self::ECHILD,
+                libc::EAGAIN => Self::EAGAIN,
+                libc::ENOMEM => Self::ENOMEM,
+                libc::EACCES => Self::EACCES,
+                libc::EFAULT => Self::EFAULT,
+                libc::EBUSY => Self::EBUSY,
+                libc::EEXIST => Self::EEXIST,
+                libc::EXDEV => Self::EXDEV,
+                libc::ENODEV => Self::ENODEV,
+                libc::ENOTDIR => Self::ENOTDIR,
+                libc::EISDIR => Self::EISDIR,
+                libc::EINVAL => Self::EINVAL,
+                libc::ENFILE => Self::ENFILE,
+                libc::EMFILE => Self::EMFILE,
+                libc::ENOTTY => Self::ENOTTY,
+                libc::ETXTBSY => Self::ETXTBSY,
+                libc::EFBIG => Self::EFBIG,
+                libc::ENOSPC => Self::ENOSPC,
+                libc::ESPIPE => Self::ESPIPE,
+                libc::EROFS => Self::EROFS,
+                libc::EMLINK => Self::EMLINK,
+                libc::EPIPE => Self::EPIPE,
+                libc::EDOM => Self::EDOM,
+                libc::ERANGE => Self::ERANGE,
+                libc::EDEADLK => Self::EDEADLK,
+                libc::ENAMETOOLONG => Self::ENAMETOOLONG,
+                libc::ENOLCK => Self::ENOLCK,
+                libc::ENOSYS => Self::ENOSYS,
+                libc::ENOTEMPTY => Self::ENOTEMPTY,
+                libc::ELOOP => Self::ELOOP,
+                libc::ENOMSG => Self::ENOMSG,
+                libc::EIDRM => Self::EIDRM,
+                libc::ENOLINK => Self::ENOLINK,
+                libc::EPROTO => Self::EPROTO,
+                libc::EMULTIHOP => Self::EMULTIHOP,
+                libc::EBADMSG => Self::EBADMSG,
+                libc::EOVERFLOW => Self::EOVERFLOW,
+                libc::EILSEQ => Self::EILSEQ,
+                libc::ENOTSOCK => Self::ENOTSOCK,
+                libc::EDESTADDRREQ => Self::EDESTADDRREQ,
+                libc::EMSGSIZE => Self::EMSGSIZE,
+                libc::EPROTOTYPE => Self::EPROTOTYPE,
+                libc::ENOPROTOOPT => Self::ENOPROTOOPT,
+                libc::EPROTONOSUPPORT => Self::EPROTONOSUPPORT,
+                libc::EAFNOSUPPORT => Self::EAFNOSUPPORT,
+                libc::EADDRINUSE => Self::EADDRINUSE,
+                libc::EADDRNOTAVAIL => Self::EADDRNOTAVAIL,
+                libc::ENETDOWN => Self::ENETDOWN,
+                libc::ENETUNREACH => Self::ENETUNREACH,
+                libc::ENETRESET => Self::ENETRESET,
+                libc::ECONNABORTED => Self::ECONNABORTED,
+                libc::ECONNRESET => Self::ECONNRESET,
+                libc::ENOBUFS => Self::ENOBUFS,
+                libc::EISCONN => Self::EISCONN,
+                libc::ENOTCONN => Self::ENOTCONN,
+                libc::ETIMEDOUT => Self::ETIMEDOUT,
+                libc::ECONNREFUSED => Self::ECONNREFUSED,
+                libc::EHOSTUNREACH => Self::EHOSTUNREACH,
+                libc::EALREADY => Self::EALREADY,
+                libc::EINPROGRESS => Self::EINPROGRESS,
+                libc::ESTALE => Self::ESTALE,
+                libc::EDQUOT => Self::EDQUOT,
+                libc::ECANCELED => Self::ECANCELED,
+                libc::EOWNERDEAD => Self::EOWNERDEAD,
+                libc::ENOTRECOVERABLE => Self::ENOTRECOVERABLE,
+                libc::ENOTSUP => Self::ENOTSUP,
+                x => {
+                    log::debug!("Unknown errno value: {}", x);
+                    Self::EIO
+                }
+            },
+            None => {
+                log::debug!("Other I/O error: {}", err);
                 Self::EIO
             }
         }
@@ -152,13 +161,13 @@ pub(crate) fn nix_from_oflags(oflags: wasi::__wasi_oflags_t) -> OFlag {
     nix_flags
 }
 
-pub(crate) fn filestat_from_nix(filestat: libc::stat) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn filestat_from_nix(filestat: libc::stat) -> WasiResult<wasi::__wasi_filestat_t> {
     use std::convert::TryInto;
 
-    fn filestat_to_timestamp(secs: u64, nsecs: u64) -> Result<wasi::__wasi_timestamp_t> {
+    fn filestat_to_timestamp(secs: u64, nsecs: u64) -> WasiResult<wasi::__wasi_timestamp_t> {
         secs.checked_mul(1_000_000_000)
             .and_then(|sec_nsec| sec_nsec.checked_add(nsecs))
-            .ok_or(Error::EOVERFLOW)
+            .ok_or(WasiError::EOVERFLOW)
     }
 
     let filetype = yanix::file::FileType::from_stat_st_mode(filestat.st_mode);
@@ -193,7 +202,7 @@ pub(crate) fn filestat_from_nix(filestat: libc::stat) -> Result<wasi::__wasi_fil
 ///
 /// NB WASI spec requires OS string to be valid UTF-8. Otherwise,
 /// `__WASI_ERRNO_ILSEQ` error is returned.
-pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String> {
+pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> WasiResult<String> {
     helpers::path_from_slice(s.as_ref().as_bytes()).map(String::from)
 }
 
diff --git a/crates/wasi-common/src/sys/unix/hostcalls_impl/fs.rs b/crates/wasi-common/src/sys/unix/hostcalls_impl/fs.rs
index 85ac6bb1c2..abba915480 100644
--- a/crates/wasi-common/src/sys/unix/hostcalls_impl/fs.rs
+++ b/crates/wasi-common/src/sys/unix/hostcalls_impl/fs.rs
@@ -3,8 +3,9 @@
 use crate::fdentry::Descriptor;
 use crate::host::Dirent;
 use crate::hostcalls_impl::PathGet;
-use crate::sys::{fdentry_impl::OsHandle, host_impl, unix::sys_impl};
-use crate::{wasi, Error, Result};
+use crate::sys::fdentry_impl::OsHandle;
+use crate::sys::{host_impl, unix::sys_impl};
+use crate::wasi::{self, WasiError, WasiResult};
 use std::convert::TryInto;
 use std::fs::File;
 use std::os::unix::fs::FileExt;
@@ -16,15 +17,19 @@ pub(crate) fn fd_pread(
     file: &File,
     buf: &mut [u8],
     offset: wasi::__wasi_filesize_t,
-) -> Result<usize> {
+) -> WasiResult<usize> {
     file.read_at(buf, offset).map_err(Into::into)
 }
 
-pub(crate) fn fd_pwrite(file: &File, buf: &[u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+pub(crate) fn fd_pwrite(
+    file: &File,
+    buf: &[u8],
+    offset: wasi::__wasi_filesize_t,
+) -> WasiResult<usize> {
     file.write_at(buf, offset).map_err(Into::into)
 }
 
-pub(crate) fn fd_fdstat_get(fd: &File) -> Result<wasi::__wasi_fdflags_t> {
+pub(crate) fn fd_fdstat_get(fd: &File) -> WasiResult<wasi::__wasi_fdflags_t> {
     unsafe { yanix::fcntl::get_status_flags(fd.as_raw_fd()) }
         .map(host_impl::fdflags_from_nix)
         .map_err(Into::into)
@@ -33,7 +38,7 @@ pub(crate) fn fd_fdstat_get(fd: &File) -> Result<wasi::__wasi_fdflags_t> {
 pub(crate) fn fd_fdstat_set_flags(
     fd: &File,
     fdflags: wasi::__wasi_fdflags_t,
-) -> Result<Option<OsHandle>> {
+) -> WasiResult<Option<OsHandle>> {
     let nix_flags = host_impl::nix_from_fdflags(fdflags);
     unsafe { yanix::fcntl::set_status_flags(fd.as_raw_fd(), nix_flags) }
         .map(|_| None)
@@ -45,7 +50,7 @@ pub(crate) fn fd_advise(
     advice: wasi::__wasi_advice_t,
     offset: wasi::__wasi_filesize_t,
     len: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     use yanix::fadvise::{posix_fadvise, PosixFadviseAdvice};
     let offset = offset.try_into()?;
     let len = len.try_into()?;
@@ -56,17 +61,17 @@ pub(crate) fn fd_advise(
         wasi::__WASI_ADVICE_NOREUSE => PosixFadviseAdvice::NoReuse,
         wasi::__WASI_ADVICE_RANDOM => PosixFadviseAdvice::Random,
         wasi::__WASI_ADVICE_NORMAL => PosixFadviseAdvice::Normal,
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     };
     unsafe { posix_fadvise(file.as_raw_fd(), offset, len, host_advice) }.map_err(Into::into)
 }
 
-pub(crate) fn path_create_directory(base: &File, path: &str) -> Result<()> {
+pub(crate) fn path_create_directory(base: &File, path: &str) -> WasiResult<()> {
     use yanix::file::{mkdirat, Mode};
     unsafe { mkdirat(base.as_raw_fd(), path, Mode::from_bits_truncate(0o777)) }.map_err(Into::into)
 }
 
-pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use yanix::file::{linkat, AtFlag};
     unsafe {
         linkat(
@@ -86,7 +91,7 @@ pub(crate) fn path_open(
     write: bool,
     oflags: wasi::__wasi_oflags_t,
     fs_flags: wasi::__wasi_fdflags_t,
-) -> Result<Descriptor> {
+) -> WasiResult<Descriptor> {
     use yanix::file::{fstatat, openat, AtFlag, FileType, Mode, OFlag};
 
     let mut nix_all_oflags = if read && write {
@@ -136,7 +141,7 @@ pub(crate) fn path_open(
                     } {
                         Ok(stat) => {
                             if FileType::from_stat_st_mode(stat.st_mode) == FileType::Socket {
-                                return Err(Error::ENOTSUP);
+                                return Err(WasiError::ENOTSUP);
                             }
                         }
                         Err(err) => {
@@ -158,7 +163,7 @@ pub(crate) fn path_open(
                     } {
                         Ok(stat) => {
                             if FileType::from_stat_st_mode(stat.st_mode) == FileType::Symlink {
-                                return Err(Error::ELOOP);
+                                return Err(WasiError::ELOOP);
                             }
                         }
                         Err(err) => {
@@ -169,7 +174,7 @@ pub(crate) fn path_open(
                 // FreeBSD returns EMLINK instead of ELOOP when using O_NOFOLLOW on
                 // a symlink.
                 libc::EMLINK if !(nix_all_oflags & OFlag::NOFOLLOW).is_empty() => {
-                    return Err(Error::ELOOP);
+                    return Err(WasiError::ELOOP);
                 }
                 _ => {}
             }
@@ -184,7 +189,7 @@ pub(crate) fn path_open(
     Ok(OsHandle::from(unsafe { File::from_raw_fd(new_fd) }).into())
 }
 
-pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize> {
+pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> WasiResult<usize> {
     use std::cmp::min;
     use yanix::file::readlinkat;
     let read_link = unsafe { readlinkat(resolved.dirfd().as_raw_fd(), resolved.path()) }
@@ -197,7 +202,7 @@ pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize>
     Ok(copy_len)
 }
 
-pub(crate) fn fd_filestat_get(file: &std::fs::File) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn fd_filestat_get(file: &std::fs::File) -> WasiResult<wasi::__wasi_filestat_t> {
     use yanix::file::fstat;
     unsafe { fstat(file.as_raw_fd()) }
         .map_err(Into::into)
@@ -207,7 +212,7 @@ pub(crate) fn fd_filestat_get(file: &std::fs::File) -> Result<wasi::__wasi_files
 pub(crate) fn path_filestat_get(
     resolved: PathGet,
     dirflags: wasi::__wasi_lookupflags_t,
-) -> Result<wasi::__wasi_filestat_t> {
+) -> WasiResult<wasi::__wasi_filestat_t> {
     use yanix::file::{fstatat, AtFlag};
     let atflags = match dirflags {
         0 => AtFlag::empty(),
@@ -224,7 +229,7 @@ pub(crate) fn path_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     use std::time::{Duration, UNIX_EPOCH};
     use yanix::filetime::*;
 
@@ -234,7 +239,7 @@ pub(crate) fn path_filestat_set_times(
     let set_mtim_now = fst_flags & wasi::__WASI_FSTFLAGS_MTIM_NOW != 0;
 
     if (set_atim && set_atim_now) || (set_mtim && set_mtim_now) {
-        return Err(Error::EINVAL);
+        return Err(WasiError::EINVAL);
     }
 
     let symlink_nofollow = wasi::__WASI_LOOKUPFLAGS_SYMLINK_FOLLOW != dirflags;
@@ -265,7 +270,7 @@ pub(crate) fn path_filestat_set_times(
     .map_err(Into::into)
 }
 
-pub(crate) fn path_remove_directory(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_remove_directory(resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{unlinkat, AtFlag};
 
     unsafe {
@@ -281,7 +286,7 @@ pub(crate) fn path_remove_directory(resolved: PathGet) -> Result<()> {
 pub(crate) fn fd_readdir<'a>(
     os_handle: &'a mut OsHandle,
     cookie: wasi::__wasi_dircookie_t,
-) -> Result<impl Iterator<Item = Result<Dirent>> + 'a> {
+) -> WasiResult<impl Iterator<Item = WasiResult<Dirent>> + 'a> {
     use yanix::dir::{DirIter, Entry, EntryExt, SeekLoc};
 
     // Get an instance of `Dir`; this is host-specific due to intricasies
diff --git a/crates/wasi-common/src/sys/unix/hostcalls_impl/fs_helpers.rs b/crates/wasi-common/src/sys/unix/hostcalls_impl/fs_helpers.rs
index 785b553d96..f151feee1a 100644
--- a/crates/wasi-common/src/sys/unix/hostcalls_impl/fs_helpers.rs
+++ b/crates/wasi-common/src/sys/unix/hostcalls_impl/fs_helpers.rs
@@ -1,7 +1,7 @@
 #![allow(non_camel_case_types)]
 #![allow(unused_unsafe)]
 use crate::sys::host_impl;
-use crate::{wasi, Result};
+use crate::wasi::{self, WasiResult};
 use std::fs::File;
 use yanix::file::OFlag;
 
@@ -36,7 +36,7 @@ pub(crate) fn path_open_rights(
     (needed_base, needed_inheriting)
 }
 
-pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
+pub(crate) fn openat(dirfd: &File, path: &str) -> WasiResult<File> {
     use std::os::unix::prelude::{AsRawFd, FromRawFd};
     use yanix::file::{openat, Mode};
 
@@ -54,7 +54,7 @@ pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
     .map_err(Into::into)
 }
 
-pub(crate) fn readlinkat(dirfd: &File, path: &str) -> Result<String> {
+pub(crate) fn readlinkat(dirfd: &File, path: &str) -> WasiResult<String> {
     use std::os::unix::prelude::AsRawFd;
     use yanix::file::readlinkat;
 
diff --git a/crates/wasi-common/src/sys/unix/hostcalls_impl/misc.rs b/crates/wasi-common/src/sys/unix/hostcalls_impl/misc.rs
index 678f335cad..9456d2a69f 100644
--- a/crates/wasi-common/src/sys/unix/hostcalls_impl/misc.rs
+++ b/crates/wasi-common/src/sys/unix/hostcalls_impl/misc.rs
@@ -1,22 +1,24 @@
 #![allow(non_camel_case_types)]
 #![allow(unused_unsafe)]
 use crate::hostcalls_impl::{ClockEventData, FdEventData};
-use crate::{wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
 use std::io;
 use yanix::clock::{clock_getres, clock_gettime, ClockId};
 
-fn wasi_clock_id_to_unix(clock_id: wasi::__wasi_clockid_t) -> Result<ClockId> {
+fn wasi_clock_id_to_unix(clock_id: wasi::__wasi_clockid_t) -> WasiResult<ClockId> {
     // convert the supported clocks to libc types, or return EINVAL
     match clock_id {
         wasi::__WASI_CLOCKID_REALTIME => Ok(ClockId::Realtime),
         wasi::__WASI_CLOCKID_MONOTONIC => Ok(ClockId::Monotonic),
         wasi::__WASI_CLOCKID_PROCESS_CPUTIME_ID => Ok(ClockId::ProcessCPUTime),
         wasi::__WASI_CLOCKID_THREAD_CPUTIME_ID => Ok(ClockId::ThreadCPUTime),
-        _ => Err(Error::EINVAL),
+        _ => Err(WasiError::EINVAL),
     }
 }
 
-pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_res_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     let clock_id = wasi_clock_id_to_unix(clock_id)?;
     let timespec = clock_getres(clock_id)?;
 
@@ -26,18 +28,20 @@ pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__
     (timespec.tv_sec as wasi::__wasi_timestamp_t)
         .checked_mul(1_000_000_000)
         .and_then(|sec_ns| sec_ns.checked_add(timespec.tv_nsec as wasi::__wasi_timestamp_t))
-        .map_or(Err(Error::EOVERFLOW), |resolution| {
+        .map_or(Err(WasiError::EOVERFLOW), |resolution| {
             // a supported clock can never return zero; this case will probably never get hit, but
             // make sure we follow the spec
             if resolution == 0 {
-                Err(Error::EINVAL)
+                Err(WasiError::EINVAL)
             } else {
                 Ok(resolution)
             }
         })
 }
 
-pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_time_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     let clock_id = wasi_clock_id_to_unix(clock_id)?;
     let timespec = clock_gettime(clock_id)?;
 
@@ -46,14 +50,14 @@ pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::_
     (timespec.tv_sec as wasi::__wasi_timestamp_t)
         .checked_mul(1_000_000_000)
         .and_then(|sec_ns| sec_ns.checked_add(timespec.tv_nsec as wasi::__wasi_timestamp_t))
-        .map_or(Err(Error::EOVERFLOW), Ok)
+        .map_or(Err(WasiError::EOVERFLOW), Ok)
 }
 
 pub(crate) fn poll_oneoff(
     timeout: Option<ClockEventData>,
     fd_events: Vec<FdEventData>,
     events: &mut Vec<wasi::__wasi_event_t>,
-) -> Result<()> {
+) -> WasiResult<()> {
     use std::{convert::TryInto, os::unix::prelude::AsRawFd};
     use yanix::poll::{poll, PollFd, PollFlags};
 
@@ -122,12 +126,12 @@ fn poll_oneoff_handle_timeout_event(
 fn poll_oneoff_handle_fd_event<'a>(
     ready_events: impl Iterator<Item = (FdEventData<'a>, yanix::poll::PollFd)>,
     events: &mut Vec<wasi::__wasi_event_t>,
-) -> Result<()> {
+) -> WasiResult<()> {
     use crate::fdentry::Descriptor;
     use std::{convert::TryInto, os::unix::prelude::AsRawFd};
     use yanix::{file::fionread, poll::PollFlags};
 
-    fn query_nbytes(fd: &Descriptor) -> Result<u64> {
+    fn query_nbytes(fd: &Descriptor) -> WasiResult<u64> {
         // fionread may overflow for large files, so use another way for regular files.
         if let Descriptor::OsHandle(os_handle) = fd {
             let meta = os_handle.metadata()?;
diff --git a/crates/wasi-common/src/sys/unix/linux/host_impl.rs b/crates/wasi-common/src/sys/unix/linux/host_impl.rs
index d7a3e46fdb..b1850f9daa 100644
--- a/crates/wasi-common/src/sys/unix/linux/host_impl.rs
+++ b/crates/wasi-common/src/sys/unix/linux/host_impl.rs
@@ -1,11 +1,11 @@
-use crate::{wasi, Result};
+use crate::wasi::{self, WasiResult};
 
 pub(crate) const O_RSYNC: yanix::file::OFlag = yanix::file::OFlag::RSYNC;
 
-pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> Result<wasi::__wasi_device_t> {
+pub(crate) fn stdev_from_nix(dev: libc::dev_t) -> WasiResult<wasi::__wasi_device_t> {
     Ok(wasi::__wasi_device_t::from(dev))
 }
 
-pub(crate) fn stino_from_nix(ino: libc::ino_t) -> Result<wasi::__wasi_inode_t> {
+pub(crate) fn stino_from_nix(ino: libc::ino_t) -> WasiResult<wasi::__wasi_inode_t> {
     Ok(wasi::__wasi_device_t::from(ino))
 }
diff --git a/crates/wasi-common/src/sys/unix/linux/hostcalls_impl.rs b/crates/wasi-common/src/sys/unix/linux/hostcalls_impl.rs
index 308c085d4c..42ea5c8b92 100644
--- a/crates/wasi-common/src/sys/unix/linux/hostcalls_impl.rs
+++ b/crates/wasi-common/src/sys/unix/linux/hostcalls_impl.rs
@@ -1,9 +1,9 @@
 use crate::fdentry::Descriptor;
 use crate::hostcalls_impl::PathGet;
-use crate::Result;
+use crate::wasi::WasiResult;
 use std::os::unix::prelude::AsRawFd;
 
-pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_unlink_file(resolved: PathGet) -> WasiResult<()> {
     use yanix::file::{unlinkat, AtFlag};
     unsafe {
         unlinkat(
@@ -15,7 +15,7 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
     .map_err(Into::into)
 }
 
-pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> WasiResult<()> {
     use yanix::file::symlinkat;
 
     log::debug!("path_symlink old_path = {:?}", old_path);
@@ -25,7 +25,7 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
         .map_err(Into::into)
 }
 
-pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use yanix::file::renameat;
     match (resolved_old.dirfd(), resolved_new.dirfd()) {
         (Descriptor::OsHandle(resolved_old_file), Descriptor::OsHandle(resolved_new_file)) => {
@@ -47,10 +47,10 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
 
 pub(crate) mod fd_readdir_impl {
     use crate::sys::fdentry_impl::OsHandle;
-    use crate::Result;
+    use crate::wasi::WasiResult;
     use yanix::dir::Dir;
 
-    pub(crate) fn get_dir_from_os_handle(os_handle: &mut OsHandle) -> Result<Box<Dir>> {
+    pub(crate) fn get_dir_from_os_handle(os_handle: &mut OsHandle) -> WasiResult<Box<Dir>> {
         // We need to duplicate the fd, because `opendir(3)`:
         //     After a successful call to fdopendir(), fd is used internally by the implementation,
         //     and should not otherwise be used by the application.
diff --git a/crates/wasi-common/src/sys/unix/mod.rs b/crates/wasi-common/src/sys/unix/mod.rs
index b34024676b..abd5160114 100644
--- a/crates/wasi-common/src/sys/unix/mod.rs
+++ b/crates/wasi-common/src/sys/unix/mod.rs
@@ -20,18 +20,14 @@ cfg_if::cfg_if! {
     }
 }
 
-use crate::Result;
 use std::fs::{File, OpenOptions};
+use std::io::Result;
 use std::path::Path;
 
 pub(crate) fn dev_null() -> Result<File> {
-    OpenOptions::new()
-        .read(true)
-        .write(true)
-        .open("/dev/null")
-        .map_err(Into::into)
+    OpenOptions::new().read(true).write(true).open("/dev/null")
 }
 
 pub fn preopen_dir<P: AsRef<Path>>(path: P) -> Result<File> {
-    File::open(path).map_err(Into::into)
+    File::open(path)
 }
diff --git a/crates/wasi-common/src/sys/windows/fdentry_impl.rs b/crates/wasi-common/src/sys/windows/fdentry_impl.rs
index bd1d1e88cf..8776111673 100644
--- a/crates/wasi-common/src/sys/windows/fdentry_impl.rs
+++ b/crates/wasi-common/src/sys/windows/fdentry_impl.rs
@@ -1,5 +1,5 @@
 use crate::fdentry::{Descriptor, OsHandleRef};
-use crate::{wasi, Error, Result};
+use crate::wasi;
 use std::fs::File;
 use std::io;
 use std::mem::ManuallyDrop;
@@ -63,7 +63,7 @@ pub(crate) fn descriptor_as_oshandle<'lifetime>(
 /// This function is unsafe because it operates on a raw file descriptor.
 pub(crate) unsafe fn determine_type_and_access_rights<Handle: AsRawHandle>(
     handle: &Handle,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -96,7 +96,7 @@ pub(crate) unsafe fn determine_type_and_access_rights<Handle: AsRawHandle>(
 /// This function is unsafe because it operates on a raw file descriptor.
 pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
     handle: &Handle,
-) -> Result<(
+) -> io::Result<(
     wasi::__wasi_filetype_t,
     wasi::__wasi_rights_t,
     wasi::__wasi_rights_t,
@@ -114,7 +114,7 @@ pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
         } else if file_type.is_disk() {
             // disk file: file, dir or disk device
             let file = std::mem::ManuallyDrop::new(File::from_raw_handle(handle.as_raw_handle()));
-            let meta = file.metadata().map_err(|_| Error::EINVAL)?;
+            let meta = file.metadata()?;
             if meta.is_dir() {
                 (
                     wasi::__WASI_FILETYPE_DIRECTORY,
@@ -128,7 +128,7 @@ pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
                     wasi::RIGHTS_REGULAR_FILE_INHERITING,
                 )
             } else {
-                return Err(Error::EINVAL);
+                return Err(io::Error::from_raw_os_error(libc::EINVAL));
             }
         } else if file_type.is_pipe() {
             // pipe object: socket, named pipe or anonymous pipe
@@ -139,7 +139,7 @@ pub(crate) unsafe fn determine_type_rights<Handle: AsRawHandle>(
                 wasi::RIGHTS_SOCKET_INHERITING,
             )
         } else {
-            return Err(Error::EINVAL);
+            return Err(io::Error::from_raw_os_error(libc::EINVAL));
         }
     };
     Ok((file_type, rights_base, rights_inheriting))
diff --git a/crates/wasi-common/src/sys/windows/host_impl.rs b/crates/wasi-common/src/sys/windows/host_impl.rs
index ad5ecd4483..cadb7205bf 100644
--- a/crates/wasi-common/src/sys/windows/host_impl.rs
+++ b/crates/wasi-common/src/sys/windows/host_impl.rs
@@ -1,6 +1,6 @@
 //! WASI host types specific to Windows host.
 use crate::host::FileType;
-use crate::{error::FromRawOsError, wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
 use std::convert::TryInto;
 use std::ffi::OsStr;
 use std::fs::{self, File};
@@ -9,34 +9,42 @@ use std::os::windows::ffi::OsStrExt;
 use std::time::{SystemTime, UNIX_EPOCH};
 use winapi::shared::winerror;
 
-impl FromRawOsError for Error {
-    fn from_raw_os_error(code: i32) -> Self {
-        // TODO: implement error mapping between Windows and WASI
-        match code as u32 {
-            winerror::ERROR_SUCCESS => Self::ESUCCESS,
-            winerror::ERROR_BAD_ENVIRONMENT => Self::E2BIG,
-            winerror::ERROR_FILE_NOT_FOUND => Self::ENOENT,
-            winerror::ERROR_PATH_NOT_FOUND => Self::ENOENT,
-            winerror::ERROR_TOO_MANY_OPEN_FILES => Self::ENFILE,
-            winerror::ERROR_ACCESS_DENIED => Self::EACCES,
-            winerror::ERROR_SHARING_VIOLATION => Self::EACCES,
-            winerror::ERROR_PRIVILEGE_NOT_HELD => Self::ENOTCAPABLE, // TODO is this the correct mapping?
-            winerror::ERROR_INVALID_HANDLE => Self::EBADF,
-            winerror::ERROR_INVALID_NAME => Self::ENOENT,
-            winerror::ERROR_NOT_ENOUGH_MEMORY => Self::ENOMEM,
-            winerror::ERROR_OUTOFMEMORY => Self::ENOMEM,
-            winerror::ERROR_DIR_NOT_EMPTY => Self::ENOTEMPTY,
-            winerror::ERROR_NOT_READY => Self::EBUSY,
-            winerror::ERROR_BUSY => Self::EBUSY,
-            winerror::ERROR_NOT_SUPPORTED => Self::ENOTSUP,
-            winerror::ERROR_FILE_EXISTS => Self::EEXIST,
-            winerror::ERROR_BROKEN_PIPE => Self::EPIPE,
-            winerror::ERROR_BUFFER_OVERFLOW => Self::ENAMETOOLONG,
-            winerror::ERROR_NOT_A_REPARSE_POINT => Self::EINVAL,
-            winerror::ERROR_NEGATIVE_SEEK => Self::EINVAL,
-            winerror::ERROR_DIRECTORY => Self::ENOTDIR,
-            winerror::ERROR_ALREADY_EXISTS => Self::EEXIST,
-            _ => Self::ENOTSUP,
+impl From<io::Error> for WasiError {
+    fn from(err: io::Error) -> Self {
+        match err.raw_os_error() {
+            Some(code) => match code as u32 {
+                winerror::ERROR_SUCCESS => Self::ESUCCESS,
+                winerror::ERROR_BAD_ENVIRONMENT => Self::E2BIG,
+                winerror::ERROR_FILE_NOT_FOUND => Self::ENOENT,
+                winerror::ERROR_PATH_NOT_FOUND => Self::ENOENT,
+                winerror::ERROR_TOO_MANY_OPEN_FILES => Self::ENFILE,
+                winerror::ERROR_ACCESS_DENIED => Self::EACCES,
+                winerror::ERROR_SHARING_VIOLATION => Self::EACCES,
+                winerror::ERROR_PRIVILEGE_NOT_HELD => Self::ENOTCAPABLE,
+                winerror::ERROR_INVALID_HANDLE => Self::EBADF,
+                winerror::ERROR_INVALID_NAME => Self::ENOENT,
+                winerror::ERROR_NOT_ENOUGH_MEMORY => Self::ENOMEM,
+                winerror::ERROR_OUTOFMEMORY => Self::ENOMEM,
+                winerror::ERROR_DIR_NOT_EMPTY => Self::ENOTEMPTY,
+                winerror::ERROR_NOT_READY => Self::EBUSY,
+                winerror::ERROR_BUSY => Self::EBUSY,
+                winerror::ERROR_NOT_SUPPORTED => Self::ENOTSUP,
+                winerror::ERROR_FILE_EXISTS => Self::EEXIST,
+                winerror::ERROR_BROKEN_PIPE => Self::EPIPE,
+                winerror::ERROR_BUFFER_OVERFLOW => Self::ENAMETOOLONG,
+                winerror::ERROR_NOT_A_REPARSE_POINT => Self::EINVAL,
+                winerror::ERROR_NEGATIVE_SEEK => Self::EINVAL,
+                winerror::ERROR_DIRECTORY => Self::ENOTDIR,
+                winerror::ERROR_ALREADY_EXISTS => Self::EEXIST,
+                x => {
+                    log::debug!("unknown error value: {}", x);
+                    Self::EIO
+                }
+            },
+            None => {
+                log::debug!("Other I/O error: {}", err);
+                Self::EIO
+            }
         }
     }
 }
@@ -73,15 +81,15 @@ fn change_time(file: &File) -> io::Result<i64> {
     winx::file::change_time(file)
 }
 
-fn systemtime_to_timestamp(st: SystemTime) -> Result<u64> {
+fn systemtime_to_timestamp(st: SystemTime) -> WasiResult<u64> {
     st.duration_since(UNIX_EPOCH)
-        .map_err(|_| Error::EINVAL)? // date earlier than UNIX_EPOCH
+        .map_err(|_| WasiError::EINVAL)? // date earlier than UNIX_EPOCH
         .as_nanos()
         .try_into()
         .map_err(Into::into) // u128 doesn't fit into u64
 }
 
-pub(crate) fn filestat_from_win(file: &File) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn filestat_from_win(file: &File) -> WasiResult<wasi::__wasi_filestat_t> {
     let metadata = file.metadata()?;
     Ok(wasi::__wasi_filestat_t {
         dev: device_id(file)?,
@@ -99,7 +107,7 @@ pub(crate) fn filestat_from_win(file: &File) -> Result<wasi::__wasi_filestat_t>
 ///
 /// NB WASI spec requires OS string to be valid UTF-8. Otherwise,
 /// `__WASI_ERRNO_ILSEQ` error is returned.
-pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String> {
+pub(crate) fn path_from_host<S: AsRef<OsStr>>(s: S) -> WasiResult<String> {
     let vec: Vec<u16> = s.as_ref().encode_wide().collect();
-    String::from_utf16(&vec).map_err(|_| Error::EILSEQ)
+    String::from_utf16(&vec).map_err(|_| WasiError::EILSEQ)
 }
diff --git a/crates/wasi-common/src/sys/windows/hostcalls_impl/fs.rs b/crates/wasi-common/src/sys/windows/hostcalls_impl/fs.rs
index a6e86650e6..6d7030cfb3 100644
--- a/crates/wasi-common/src/sys/windows/hostcalls_impl/fs.rs
+++ b/crates/wasi-common/src/sys/windows/hostcalls_impl/fs.rs
@@ -8,7 +8,7 @@ use crate::hostcalls_impl::{fd_filestat_set_times_impl, PathGet};
 use crate::sys::fdentry_impl::{determine_type_rights, OsHandle};
 use crate::sys::host_impl::{self, path_from_host};
 use crate::sys::hostcalls_impl::fs_helpers::PathGetExt;
-use crate::{wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
 use log::{debug, trace};
 use std::convert::TryInto;
 use std::fs::{File, Metadata, OpenOptions};
@@ -44,16 +44,20 @@ pub(crate) fn fd_pread(
     file: &File,
     buf: &mut [u8],
     offset: wasi::__wasi_filesize_t,
-) -> Result<usize> {
+) -> WasiResult<usize> {
     read_at(file, buf, offset).map_err(Into::into)
 }
 
 // TODO refactor common code with unix
-pub(crate) fn fd_pwrite(file: &File, buf: &[u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+pub(crate) fn fd_pwrite(
+    file: &File,
+    buf: &[u8],
+    offset: wasi::__wasi_filesize_t,
+) -> WasiResult<usize> {
     write_at(file, buf, offset).map_err(Into::into)
 }
 
-pub(crate) fn fd_fdstat_get(fd: &File) -> Result<wasi::__wasi_fdflags_t> {
+pub(crate) fn fd_fdstat_get(fd: &File) -> WasiResult<wasi::__wasi_fdflags_t> {
     let mut fdflags = 0;
 
     let handle = unsafe { fd.as_raw_handle() };
@@ -82,7 +86,7 @@ pub(crate) fn fd_fdstat_get(fd: &File) -> Result<wasi::__wasi_fdflags_t> {
 pub(crate) fn fd_fdstat_set_flags(
     fd: &File,
     fdflags: wasi::__wasi_fdflags_t,
-) -> Result<Option<OsHandle>> {
+) -> WasiResult<Option<OsHandle>> {
     let handle = unsafe { fd.as_raw_handle() };
 
     let access_mode = winx::file::query_access_information(handle)?;
@@ -106,7 +110,7 @@ pub(crate) fn fd_advise(
     advice: wasi::__wasi_advice_t,
     _offset: wasi::__wasi_filesize_t,
     _len: wasi::__wasi_filesize_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     match advice {
         wasi::__WASI_ADVICE_DONTNEED
         | wasi::__WASI_ADVICE_SEQUENTIAL
@@ -114,18 +118,18 @@ pub(crate) fn fd_advise(
         | wasi::__WASI_ADVICE_NOREUSE
         | wasi::__WASI_ADVICE_RANDOM
         | wasi::__WASI_ADVICE_NORMAL => {}
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     }
 
     Ok(())
 }
 
-pub(crate) fn path_create_directory(file: &File, path: &str) -> Result<()> {
+pub(crate) fn path_create_directory(file: &File, path: &str) -> WasiResult<()> {
     let path = concatenate(file, path)?;
     std::fs::create_dir(&path).map_err(Into::into)
 }
 
-pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_link(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     unimplemented!("path_link")
 }
 
@@ -135,7 +139,7 @@ pub(crate) fn path_open(
     write: bool,
     oflags: wasi::__wasi_oflags_t,
     fdflags: wasi::__wasi_fdflags_t,
-) -> Result<Descriptor> {
+) -> WasiResult<Descriptor> {
     use winx::file::{AccessMode, CreationDisposition, Flags};
 
     let is_trunc = oflags & wasi::__WASI_OFLAGS_TRUNC != 0;
@@ -145,7 +149,7 @@ pub(crate) fn path_open(
         // This is because truncation requires `GENERIC_WRITE` access, which will override the removal
         // of the `FILE_WRITE_DATA` permission.
         if fdflags & wasi::__WASI_FDFLAGS_APPEND != 0 {
-            return Err(Error::ENOTSUP);
+            return Err(WasiError::ENOTSUP);
         }
     }
 
@@ -172,11 +176,11 @@ pub(crate) fn path_open(
         Ok(file_type) => {
             // check if we are trying to open a symlink
             if file_type.is_symlink() {
-                return Err(Error::ELOOP);
+                return Err(WasiError::ELOOP);
             }
             // check if we are trying to open a file as a dir
             if file_type.is_file() && oflags & wasi::__WASI_OFLAGS_DIRECTORY != 0 {
-                return Err(Error::ENOTDIR);
+                return Err(WasiError::ENOTDIR);
             }
         }
         Err(err) => match err.raw_os_error() {
@@ -191,7 +195,7 @@ pub(crate) fn path_open(
             }
             None => {
                 log::debug!("Inconvertible OS error: {}", err);
-                return Err(Error::EIO);
+                return Err(WasiError::EIO);
             }
         },
     }
@@ -276,7 +280,7 @@ fn dirent_from_path<P: AsRef<Path>>(
     path: P,
     name: &str,
     cookie: wasi::__wasi_dircookie_t,
-) -> Result<Dirent> {
+) -> WasiResult<Dirent> {
     let path = path.as_ref();
     trace!("dirent_from_path: opening {}", path.to_string_lossy());
 
@@ -325,7 +329,7 @@ fn dirent_from_path<P: AsRef<Path>>(
 pub(crate) fn fd_readdir(
     fd: &File,
     cookie: wasi::__wasi_dircookie_t,
-) -> Result<impl Iterator<Item = Result<Dirent>>> {
+) -> WasiResult<impl Iterator<Item = WasiResult<Dirent>>> {
     use winx::file::get_file_path;
 
     let cookie = cookie.try_into()?;
@@ -361,7 +365,7 @@ pub(crate) fn fd_readdir(
     Ok(iter.skip(cookie))
 }
 
-pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize> {
+pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> WasiResult<usize> {
     use winx::file::get_file_path;
 
     let path = resolved.concatenate()?;
@@ -375,8 +379,8 @@ pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize>
     let dir_path = PathBuf::from(strip_extended_prefix(dir_path));
     let target_path = target_path
         .strip_prefix(dir_path)
-        .map_err(|_| Error::ENOTCAPABLE)
-        .and_then(|path| path.to_str().map(String::from).ok_or(Error::EILSEQ))?;
+        .map_err(|_| WasiError::ENOTCAPABLE)
+        .and_then(|path| path.to_str().map(String::from).ok_or(WasiError::EILSEQ))?;
 
     if buf.len() > 0 {
         let mut chars = target_path.chars();
@@ -398,7 +402,7 @@ pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize>
     }
 }
 
-fn strip_trailing_slashes_and_concatenate(resolved: &PathGet) -> Result<Option<PathBuf>> {
+fn strip_trailing_slashes_and_concatenate(resolved: &PathGet) -> WasiResult<Option<PathBuf>> {
     if resolved.path().ends_with('/') {
         let suffix = resolved.path().trim_end_matches('/');
         concatenate(&resolved.dirfd().as_os_handle(), Path::new(suffix)).map(Some)
@@ -407,7 +411,7 @@ fn strip_trailing_slashes_and_concatenate(resolved: &PathGet) -> Result<Option<P
     }
 }
 
-pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> WasiResult<()> {
     use std::fs;
 
     let old_path = resolved_old.concatenate()?;
@@ -418,12 +422,12 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
     //
     // [std::fs::rename]: https://doc.rust-lang.org/std/fs/fn.rename.html
     if old_path.is_dir() && new_path.is_file() {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
     // Second sanity check: check we're not trying to rename a file into a path
     // ending in a trailing slash.
     if old_path.is_file() && resolved_new.path().ends_with('/') {
-        return Err(Error::ENOTDIR);
+        return Err(WasiError::ENOTDIR);
     }
 
     // TODO handle symlinks
@@ -439,7 +443,7 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
                     // So most likely dealing with new_path == dir.
                     // Eliminate case old_path == file first.
                     if old_path.is_file() {
-                        return Err(Error::EISDIR);
+                        return Err(WasiError::EISDIR);
                     } else {
                         // Ok, let's try removing an empty dir at new_path if it exists
                         // and is a nonempty dir.
@@ -453,7 +457,7 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
                     // a file instead of a dir, and if so, throw ENOTDIR.
                     if let Some(path) = strip_trailing_slashes_and_concatenate(&resolved_old)? {
                         if path.is_file() {
-                            return Err(Error::ENOTDIR);
+                            return Err(WasiError::ENOTDIR);
                         }
                     }
                 }
@@ -464,19 +468,19 @@ pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Resul
         }
         None => {
             log::debug!("Inconvertible OS error: {}", err);
-            Err(Error::EIO)
+            Err(WasiError::EIO)
         }
     }
 }
 
-pub(crate) fn fd_filestat_get(file: &std::fs::File) -> Result<wasi::__wasi_filestat_t> {
+pub(crate) fn fd_filestat_get(file: &std::fs::File) -> WasiResult<wasi::__wasi_filestat_t> {
     host_impl::filestat_from_win(file)
 }
 
 pub(crate) fn path_filestat_get(
     resolved: PathGet,
     dirflags: wasi::__wasi_lookupflags_t,
-) -> Result<wasi::__wasi_filestat_t> {
+) -> WasiResult<wasi::__wasi_filestat_t> {
     let path = resolved.concatenate()?;
     let file = File::open(path)?;
     host_impl::filestat_from_win(&file)
@@ -488,7 +492,7 @@ pub(crate) fn path_filestat_set_times(
     st_atim: wasi::__wasi_timestamp_t,
     mut st_mtim: wasi::__wasi_timestamp_t,
     fst_flags: wasi::__wasi_fstflags_t,
-) -> Result<()> {
+) -> WasiResult<()> {
     use winx::file::AccessMode;
     let path = resolved.concatenate()?;
     let file = OpenOptions::new()
@@ -498,7 +502,7 @@ pub(crate) fn path_filestat_set_times(
     fd_filestat_set_times_impl(&modifiable_fd, st_atim, st_mtim, fst_flags)
 }
 
-pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> WasiResult<()> {
     use std::os::windows::fs::{symlink_dir, symlink_file};
 
     let old_path = concatenate(&resolved.dirfd().as_os_handle(), Path::new(old_path))?;
@@ -520,14 +524,14 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
                 winerror::ERROR_ACCESS_DENIED => {
                     // does the target exist?
                     if new_path.exists() {
-                        return Err(Error::EEXIST);
+                        return Err(WasiError::EEXIST);
                     }
                 }
                 winerror::ERROR_INVALID_NAME => {
                     // does the target without trailing slashes exist?
                     if let Some(path) = strip_trailing_slashes_and_concatenate(&resolved)? {
                         if path.exists() {
-                            return Err(Error::EEXIST);
+                            return Err(WasiError::EEXIST);
                         }
                     }
                 }
@@ -538,12 +542,12 @@ pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
         }
         None => {
             log::debug!("Inconvertible OS error: {}", err);
-            Err(Error::EIO)
+            Err(WasiError::EIO)
         }
     }
 }
 
-pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_unlink_file(resolved: PathGet) -> WasiResult<()> {
     use std::fs;
 
     let path = resolved.concatenate()?;
@@ -573,19 +577,19 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
             }
             None => {
                 log::debug!("Inconvertible OS error: {}", err);
-                Err(Error::EIO)
+                Err(WasiError::EIO)
             }
         }
     } else if file_type.is_dir() {
-        Err(Error::EISDIR)
+        Err(WasiError::EISDIR)
     } else if file_type.is_file() {
         fs::remove_file(path).map_err(Into::into)
     } else {
-        Err(Error::EINVAL)
+        Err(WasiError::EINVAL)
     }
 }
 
-pub(crate) fn path_remove_directory(resolved: PathGet) -> Result<()> {
+pub(crate) fn path_remove_directory(resolved: PathGet) -> WasiResult<()> {
     let path = resolved.concatenate()?;
     std::fs::remove_dir(&path).map_err(Into::into)
 }
diff --git a/crates/wasi-common/src/sys/windows/hostcalls_impl/fs_helpers.rs b/crates/wasi-common/src/sys/windows/hostcalls_impl/fs_helpers.rs
index df77548ce9..7d35a4d95f 100644
--- a/crates/wasi-common/src/sys/windows/hostcalls_impl/fs_helpers.rs
+++ b/crates/wasi-common/src/sys/windows/hostcalls_impl/fs_helpers.rs
@@ -1,7 +1,7 @@
 #![allow(non_camel_case_types)]
 use crate::fdentry::Descriptor;
 use crate::hostcalls_impl::PathGet;
-use crate::{wasi, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
 use std::ffi::{OsStr, OsString};
 use std::fs::File;
 use std::os::windows::ffi::{OsStrExt, OsStringExt};
@@ -9,11 +9,11 @@ use std::path::{Path, PathBuf};
 use winapi::shared::winerror;
 
 pub(crate) trait PathGetExt {
-    fn concatenate(&self) -> Result<PathBuf>;
+    fn concatenate(&self) -> WasiResult<PathBuf>;
 }
 
 impl PathGetExt for PathGet {
-    fn concatenate(&self) -> Result<PathBuf> {
+    fn concatenate(&self) -> WasiResult<PathBuf> {
         match self.dirfd() {
             Descriptor::OsHandle(file) => concatenate(file, Path::new(self.path())),
             Descriptor::VirtualFile(_virt) => {
@@ -55,7 +55,7 @@ pub(crate) fn path_open_rights(
     (needed_base, needed_inheriting)
 }
 
-pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
+pub(crate) fn openat(dirfd: &File, path: &str) -> WasiResult<File> {
     use std::fs::OpenOptions;
     use std::os::windows::fs::OpenOptionsExt;
     use winx::file::Flags;
@@ -72,13 +72,13 @@ pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
     if let Some(code) = err.raw_os_error() {
         log::debug!("openat error={:?}", code);
         if code as u32 == winerror::ERROR_INVALID_NAME {
-            return Err(Error::ENOTDIR);
+            return Err(WasiError::ENOTDIR);
         }
     }
     Err(err.into())
 }
 
-pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> Result<String> {
+pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> WasiResult<String> {
     use winx::file::get_file_path;
 
     let path = concatenate(dirfd, Path::new(s_path))?;
@@ -92,8 +92,8 @@ pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> Result<String> {
             let dir_path = PathBuf::from(strip_extended_prefix(dir_path));
             let target_path = target_path
                 .strip_prefix(dir_path)
-                .map_err(|_| Error::ENOTCAPABLE)?;
-            let target_path = target_path.to_str().ok_or(Error::EILSEQ)?;
+                .map_err(|_| WasiError::ENOTCAPABLE)?;
+            let target_path = target_path.to_str().ok_or(WasiError::EILSEQ)?;
             return Ok(target_path.to_owned());
         }
         Err(e) => e,
@@ -105,7 +105,7 @@ pub(crate) fn readlinkat(dirfd: &File, s_path: &str) -> Result<String> {
                 // strip "/" and check if exists
                 let path = concatenate(dirfd, Path::new(s_path.trim_end_matches('/')))?;
                 if path.exists() && !path.is_dir() {
-                    return Err(Error::ENOTDIR);
+                    return Err(WasiError::ENOTDIR);
                 }
             }
         }
@@ -122,13 +122,13 @@ pub(crate) fn strip_extended_prefix<P: AsRef<OsStr>>(path: P) -> OsString {
     }
 }
 
-pub(crate) fn concatenate<P: AsRef<Path>>(file: &File, path: P) -> Result<PathBuf> {
+pub(crate) fn concatenate<P: AsRef<Path>>(file: &File, path: P) -> WasiResult<PathBuf> {
     use winx::file::get_file_path;
 
     // WASI is not able to deal with absolute paths
     // so error out if absolute
     if path.as_ref().is_absolute() {
-        return Err(Error::ENOTCAPABLE);
+        return Err(WasiError::ENOTCAPABLE);
     }
 
     let dir_path = get_file_path(file)?;
diff --git a/crates/wasi-common/src/sys/windows/hostcalls_impl/misc.rs b/crates/wasi-common/src/sys/windows/hostcalls_impl/misc.rs
index a3b56c00be..cb27e3690f 100644
--- a/crates/wasi-common/src/sys/windows/hostcalls_impl/misc.rs
+++ b/crates/wasi-common/src/sys/windows/hostcalls_impl/misc.rs
@@ -5,7 +5,8 @@ use crate::fdentry::Descriptor;
 use crate::hostcalls_impl::{ClockEventData, FdEventData};
 use crate::memory::*;
 use crate::sys::host_impl;
-use crate::{error::WasiError, wasi, wasi32, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
+use crate::wasi32;
 use cpu_time::{ProcessTime, ThreadTime};
 use lazy_static::lazy_static;
 use log::{debug, error, trace, warn};
@@ -24,9 +25,9 @@ struct StdinPoll {
 
 enum PollState {
     Ready,
-    NotReady,         // it's not ready, but we didn't wait
-    TimedOut,         // it's not ready and a timeout has occurred
-    Error(WasiError), // not using the top-lever Error because it's not Clone
+    NotReady, // it's not ready, but we didn't wait
+    TimedOut, // it's not ready and a timeout has occurred
+    Error(WasiError),
 }
 
 enum WaitMode {
@@ -82,7 +83,7 @@ impl StdinPoll {
             // Linux returns `POLLIN` in both cases, and we imitate this behavior.
             let resp = match std::io::stdin().lock().fill_buf() {
                 Ok(_) => PollState::Ready,
-                Err(e) => PollState::Error(Error::from(e).as_wasi_error()),
+                Err(e) => PollState::Error(WasiError::from(e)),
             };
 
             // Notify the requestor about data in stdin. They may have already timed out,
@@ -108,7 +109,9 @@ lazy_static! {
 
 // Timer resolution on Windows is really hard. We may consider exposing the resolution of the respective
 // timers as an associated function in the future.
-pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_res_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     Ok(match clock_id {
         // This is the best that we can do with std::time::SystemTime.
         // Rust uses GetSystemTimeAsFileTime, which is said to have the resolution of
@@ -152,25 +155,28 @@ pub(crate) fn clock_res_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__
         // The best we can do is to hardcode the value from the docs.
         // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getthreadtimes
         wasi::__WASI_CLOCKID_THREAD_CPUTIME_ID => 100,
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     })
 }
 
-pub(crate) fn clock_time_get(clock_id: wasi::__wasi_clockid_t) -> Result<wasi::__wasi_timestamp_t> {
+pub(crate) fn clock_time_get(
+    clock_id: wasi::__wasi_clockid_t,
+) -> WasiResult<wasi::__wasi_timestamp_t> {
     let duration = match clock_id {
         wasi::__WASI_CLOCKID_REALTIME => get_monotonic_time(),
         wasi::__WASI_CLOCKID_MONOTONIC => get_realtime_time()?,
         wasi::__WASI_CLOCKID_PROCESS_CPUTIME_ID => get_proc_cputime()?,
         wasi::__WASI_CLOCKID_THREAD_CPUTIME_ID => get_thread_cputime()?,
-        _ => return Err(Error::EINVAL),
+        _ => return Err(WasiError::EINVAL),
     };
     duration.as_nanos().try_into().map_err(Into::into)
 }
 
-fn make_rw_event(event: &FdEventData, nbytes: Result<u64>) -> wasi::__wasi_event_t {
-    use crate::error::AsWasiError;
-    let error = nbytes.as_wasi_error();
-    let nbytes = nbytes.unwrap_or_default();
+fn make_rw_event(event: &FdEventData, nbytes: WasiResult<u64>) -> wasi::__wasi_event_t {
+    let (nbytes, error) = match nbytes {
+        Ok(nbytes) => (nbytes, WasiError::ESUCCESS),
+        Err(e) => (u64::default(), e),
+    };
     wasi::__wasi_event_t {
         userdata: event.userdata,
         r#type: event.r#type,
@@ -233,7 +239,7 @@ fn handle_rw_event(event: FdEventData, out_events: &mut Vec<wasi::__wasi_event_t
 
 fn handle_error_event(
     event: FdEventData,
-    error: Error,
+    error: WasiError,
     out_events: &mut Vec<wasi::__wasi_event_t>,
 ) {
     let new_event = make_rw_event(&event, Err(error));
@@ -244,7 +250,7 @@ pub(crate) fn poll_oneoff(
     timeout: Option<ClockEventData>,
     fd_events: Vec<FdEventData>,
     events: &mut Vec<wasi::__wasi_event_t>,
-) -> Result<()> {
+) -> WasiResult<()> {
     use std::fs::Metadata;
     use std::thread;
 
@@ -289,7 +295,7 @@ pub(crate) fn poll_oneoff(
                 let ftype = unsafe { winx::file::get_file_type(os_handle.as_raw_handle()) }?;
                 if ftype.is_unknown() || ftype.is_char() {
                     debug!("poll_oneoff: unsupported file type: {:?}", ftype);
-                    handle_error_event(event, Error::ENOTSUP, events);
+                    handle_error_event(event, WasiError::ENOTSUP, events);
                 } else if ftype.is_disk() {
                     immediate_events.push(event);
                 } else if ftype.is_pipe() {
@@ -349,7 +355,7 @@ pub(crate) fn poll_oneoff(
                 PollState::Ready => handle_rw_event(event, events),
                 PollState::NotReady => {} // not immediately available, so just ignore
                 PollState::TimedOut => handle_timeout_event(timeout.unwrap().0, events),
-                PollState::Error(e) => handle_error_event(event, Error::Wasi(e), events),
+                PollState::Error(e) => handle_error_event(event, e, events),
             }
         }
     }
@@ -365,7 +371,7 @@ pub(crate) fn poll_oneoff(
             }
             None => {
                 error!("Polling only pipes with no timeout not supported on Windows.");
-                return Err(Error::ENOTSUP);
+                return Err(WasiError::ENOTSUP);
             }
         }
     }
@@ -383,17 +389,17 @@ fn get_monotonic_time() -> Duration {
     START_MONOTONIC.elapsed()
 }
 
-fn get_realtime_time() -> Result<Duration> {
+fn get_realtime_time() -> WasiResult<Duration> {
     SystemTime::now()
         .duration_since(UNIX_EPOCH)
-        .map_err(|_| Error::EFAULT)
+        .map_err(|_| WasiError::EFAULT)
 }
 
-fn get_proc_cputime() -> Result<Duration> {
+fn get_proc_cputime() -> WasiResult<Duration> {
     Ok(ProcessTime::try_now()?.as_duration())
 }
 
-fn get_thread_cputime() -> Result<Duration> {
+fn get_thread_cputime() -> WasiResult<Duration> {
     Ok(ThreadTime::try_now()?.as_duration())
 }
 
diff --git a/crates/wasi-common/src/sys/windows/mod.rs b/crates/wasi-common/src/sys/windows/mod.rs
index 398d945323..b9e51e25f8 100644
--- a/crates/wasi-common/src/sys/windows/mod.rs
+++ b/crates/wasi-common/src/sys/windows/mod.rs
@@ -2,16 +2,12 @@ pub(crate) mod fdentry_impl;
 pub(crate) mod host_impl;
 pub(crate) mod hostcalls_impl;
 
-use crate::Result;
 use std::fs::{File, OpenOptions};
+use std::io::Result;
 use std::path::Path;
 
 pub(crate) fn dev_null() -> Result<File> {
-    OpenOptions::new()
-        .read(true)
-        .write(true)
-        .open("NUL")
-        .map_err(Into::into)
+    OpenOptions::new().read(true).write(true).open("NUL")
 }
 
 pub fn preopen_dir<P: AsRef<Path>>(path: P) -> Result<File> {
@@ -28,5 +24,4 @@ pub fn preopen_dir<P: AsRef<Path>>(path: P) -> Result<File> {
         .read(true)
         .attributes(FILE_FLAG_BACKUP_SEMANTICS)
         .open(path)
-        .map_err(Into::into)
 }
diff --git a/crates/wasi-common/src/virtfs.rs b/crates/wasi-common/src/virtfs.rs
index 52e48629aa..50c34177d8 100644
--- a/crates/wasi-common/src/virtfs.rs
+++ b/crates/wasi-common/src/virtfs.rs
@@ -1,6 +1,7 @@
 use crate::host::Dirent;
 use crate::host::FileType;
-use crate::{wasi, wasi32, Error, Result};
+use crate::wasi::{self, WasiError, WasiResult};
+use crate::wasi32;
 use filetime::FileTime;
 use log::trace;
 use std::cell::RefCell;
@@ -44,8 +45,8 @@ pub(crate) trait VirtualFile: MovableFile {
 
     fn try_clone(&self) -> io::Result<Box<dyn VirtualFile>>;
 
-    fn readlinkat(&self, _path: &Path) -> Result<String> {
-        Err(Error::EACCES)
+    fn readlinkat(&self, _path: &Path) -> WasiResult<String> {
+        Err(WasiError::EACCES)
     }
 
     fn openat(
@@ -55,51 +56,51 @@ pub(crate) trait VirtualFile: MovableFile {
         _write: bool,
         _oflags: wasi::__wasi_oflags_t,
         _fd_flags: wasi::__wasi_fdflags_t,
-    ) -> Result<Box<dyn VirtualFile>> {
-        Err(Error::EACCES)
+    ) -> WasiResult<Box<dyn VirtualFile>> {
+        Err(WasiError::EACCES)
     }
 
-    fn remove_directory(&self, _path: &str) -> Result<()> {
-        Err(Error::EACCES)
+    fn remove_directory(&self, _path: &str) -> WasiResult<()> {
+        Err(WasiError::EACCES)
     }
 
-    fn unlink_file(&self, _path: &str) -> Result<()> {
-        Err(Error::EACCES)
+    fn unlink_file(&self, _path: &str) -> WasiResult<()> {
+        Err(WasiError::EACCES)
     }
 
-    fn datasync(&self) -> Result<()> {
-        Err(Error::EINVAL)
+    fn datasync(&self) -> WasiResult<()> {
+        Err(WasiError::EINVAL)
     }
 
-    fn sync(&self) -> Result<()> {
+    fn sync(&self) -> WasiResult<()> {
         Ok(())
     }
 
-    fn create_directory(&self, _path: &Path) -> Result<()> {
-        Err(Error::EACCES)
+    fn create_directory(&self, _path: &Path) -> WasiResult<()> {
+        Err(WasiError::EACCES)
     }
 
     fn readdir(
         &self,
         _cookie: wasi::__wasi_dircookie_t,
-    ) -> Result<Box<dyn Iterator<Item = Result<Dirent>>>> {
-        Err(Error::EBADF)
+    ) -> WasiResult<Box<dyn Iterator<Item = WasiResult<Dirent>>>> {
+        Err(WasiError::EBADF)
     }
 
-    fn write_vectored(&mut self, _iovs: &[io::IoSlice]) -> Result<usize> {
-        Err(Error::EBADF)
+    fn write_vectored(&mut self, _iovs: &[io::IoSlice]) -> WasiResult<usize> {
+        Err(WasiError::EBADF)
     }
 
-    fn pread(&self, _buf: &mut [u8], _offset: u64) -> Result<usize> {
-        Err(Error::EBADF)
+    fn pread(&self, _buf: &mut [u8], _offset: u64) -> WasiResult<usize> {
+        Err(WasiError::EBADF)
     }
 
-    fn pwrite(&self, _buf: &mut [u8], _offset: u64) -> Result<usize> {
-        Err(Error::EBADF)
+    fn pwrite(&self, _buf: &mut [u8], _offset: u64) -> WasiResult<usize> {
+        Err(WasiError::EBADF)
     }
 
-    fn seek(&mut self, _offset: SeekFrom) -> Result<u64> {
-        Err(Error::EBADF)
+    fn seek(&mut self, _offset: SeekFrom) -> WasiResult<u64> {
+        Err(WasiError::EBADF)
     }
 
     fn advise(
@@ -107,36 +108,40 @@ pub(crate) trait VirtualFile: MovableFile {
         _advice: wasi::__wasi_advice_t,
         _offset: wasi::__wasi_filesize_t,
         _len: wasi::__wasi_filesize_t,
-    ) -> Result<()> {
-        Err(Error::EBADF)
+    ) -> WasiResult<()> {
+        Err(WasiError::EBADF)
     }
 
     fn allocate(
         &self,
         _offset: wasi::__wasi_filesize_t,
         _len: wasi::__wasi_filesize_t,
-    ) -> Result<()> {
-        Err(Error::EBADF)
+    ) -> WasiResult<()> {
+        Err(WasiError::EBADF)
     }
 
-    fn filestat_get(&self) -> Result<wasi::__wasi_filestat_t> {
-        Err(Error::EBADF)
+    fn filestat_get(&self) -> WasiResult<wasi::__wasi_filestat_t> {
+        Err(WasiError::EBADF)
     }
 
-    fn filestat_set_times(&self, _atim: Option<FileTime>, _mtim: Option<FileTime>) -> Result<()> {
-        Err(Error::EBADF)
+    fn filestat_set_times(
+        &self,
+        _atim: Option<FileTime>,
+        _mtim: Option<FileTime>,
+    ) -> WasiResult<()> {
+        Err(WasiError::EBADF)
     }
 
-    fn filestat_set_size(&self, _st_size: wasi::__wasi_filesize_t) -> Result<()> {
-        Err(Error::EBADF)
+    fn filestat_set_size(&self, _st_size: wasi::__wasi_filesize_t) -> WasiResult<()> {
+        Err(WasiError::EBADF)
     }
 
-    fn fdstat_set_flags(&mut self, _fdflags: wasi::__wasi_fdflags_t) -> Result<()> {
-        Err(Error::EBADF)
+    fn fdstat_set_flags(&mut self, _fdflags: wasi::__wasi_fdflags_t) -> WasiResult<()> {
+        Err(WasiError::EBADF)
     }
 
-    fn read_vectored(&mut self, _iovs: &mut [io::IoSliceMut]) -> Result<usize> {
-        Err(Error::EBADF)
+    fn read_vectored(&mut self, _iovs: &mut [io::IoSliceMut]) -> WasiResult<usize> {
+        Err(WasiError::EBADF)
     }
 
     fn get_file_type(&self) -> wasi::__wasi_filetype_t;
@@ -157,23 +162,30 @@ pub trait FileContents {
     /// The current number of bytes this `FileContents` describes.
     fn size(&self) -> wasi::__wasi_filesize_t;
     /// Resize to hold `new_size` number of bytes, or error if this is not possible.
-    fn resize(&mut self, new_size: wasi::__wasi_filesize_t) -> Result<()>;
+    fn resize(&mut self, new_size: wasi::__wasi_filesize_t) -> WasiResult<()>;
     /// Write a list of `IoSlice` starting at `offset`. `offset` plus the total size of all `iovs`
     /// is guaranteed to not exceed `max_size`. Implementations must not indicate more bytes have
     /// been written than can be held by `iovs`.
-    fn pwritev(&mut self, iovs: &[io::IoSlice], offset: wasi::__wasi_filesize_t) -> Result<usize>;
+    fn pwritev(
+        &mut self,
+        iovs: &[io::IoSlice],
+        offset: wasi::__wasi_filesize_t,
+    ) -> WasiResult<usize>;
     /// Read from the file from `offset`, filling a list of `IoSlice`. The returend size must not
     /// be more than the capactiy of `iovs`, and must not exceed the limit reported by
     /// `self.max_size()`.
-    fn preadv(&self, iovs: &mut [io::IoSliceMut], offset: wasi::__wasi_filesize_t)
-        -> Result<usize>;
+    fn preadv(
+        &self,
+        iovs: &mut [io::IoSliceMut],
+        offset: wasi::__wasi_filesize_t,
+    ) -> WasiResult<usize>;
     /// Write contents from `buf` to this file starting at `offset`. `offset` plus the length of
     /// `buf` is guaranteed to not exceed `max_size`. Implementations must not indicate more bytes
     /// have been written than the size of `buf`.
-    fn pwrite(&mut self, buf: &[u8], offset: wasi::__wasi_filesize_t) -> Result<usize>;
+    fn pwrite(&mut self, buf: &[u8], offset: wasi::__wasi_filesize_t) -> WasiResult<usize>;
     /// Read from the file at `offset`, filling `buf`. The returned size must not be more than the
     /// capacity of `buf`, and `offset` plus the returned size must not exceed `self.max_size()`.
-    fn pread(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> Result<usize>;
+    fn pread(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> WasiResult<usize>;
 }
 
 impl FileContents for VecFileContents {
@@ -185,8 +197,8 @@ impl FileContents for VecFileContents {
         self.content.len() as wasi::__wasi_filesize_t
     }
 
-    fn resize(&mut self, new_size: wasi::__wasi_filesize_t) -> Result<()> {
-        let new_size: usize = new_size.try_into().map_err(|_| Error::EINVAL)?;
+    fn resize(&mut self, new_size: wasi::__wasi_filesize_t) -> WasiResult<()> {
+        let new_size: usize = new_size.try_into().map_err(|_| WasiError::EINVAL)?;
         self.content.resize(new_size, 0);
         Ok(())
     }
@@ -195,7 +207,7 @@ impl FileContents for VecFileContents {
         &self,
         iovs: &mut [io::IoSliceMut],
         offset: wasi::__wasi_filesize_t,
-    ) -> Result<usize> {
+    ) -> WasiResult<usize> {
         let mut read_total = 0usize;
         for iov in iovs.iter_mut() {
             let read = self.pread(iov, offset)?;
@@ -204,7 +216,11 @@ impl FileContents for VecFileContents {
         Ok(read_total)
     }
 
-    fn pwritev(&mut self, iovs: &[io::IoSlice], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+    fn pwritev(
+        &mut self,
+        iovs: &[io::IoSlice],
+        offset: wasi::__wasi_filesize_t,
+    ) -> WasiResult<usize> {
         let mut write_total = 0usize;
         for iov in iovs.iter() {
             let written = self.pwrite(iov, offset)?;
@@ -213,9 +229,9 @@ impl FileContents for VecFileContents {
         Ok(write_total)
     }
 
-    fn pread(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+    fn pread(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> WasiResult<usize> {
         trace!("     | pread(buf.len={}, offset={})", buf.len(), offset);
-        let offset: usize = offset.try_into().map_err(|_| Error::EINVAL)?;
+        let offset: usize = offset.try_into().map_err(|_| WasiError::EINVAL)?;
 
         let data_remaining = self.content.len().saturating_sub(offset);
 
@@ -228,10 +244,10 @@ impl FileContents for VecFileContents {
         res
     }
 
-    fn pwrite(&mut self, buf: &[u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
-        let offset: usize = offset.try_into().map_err(|_| Error::EINVAL)?;
+    fn pwrite(&mut self, buf: &[u8], offset: wasi::__wasi_filesize_t) -> WasiResult<usize> {
+        let offset: usize = offset.try_into().map_err(|_| WasiError::EINVAL)?;
 
-        let write_end = offset.checked_add(buf.len()).ok_or(Error::EFBIG)?;
+        let write_end = offset.checked_add(buf.len()).ok_or(WasiError::EFBIG)?;
 
         if write_end > self.content.len() {
             self.content.resize(write_end, 0);
@@ -305,9 +321,9 @@ impl VirtualFile for InMemoryFile {
         }))
     }
 
-    fn readlinkat(&self, _path: &Path) -> Result<String> {
+    fn readlinkat(&self, _path: &Path) -> WasiResult<String> {
         // no symlink support, so always say it's invalid.
-        Err(Error::ENOTDIR)
+        Err(WasiError::ENOTDIR)
     }
 
     fn openat(
@@ -317,7 +333,7 @@ impl VirtualFile for InMemoryFile {
         write: bool,
         oflags: wasi::__wasi_oflags_t,
         fd_flags: wasi::__wasi_fdflags_t,
-    ) -> Result<Box<dyn VirtualFile>> {
+    ) -> WasiResult<Box<dyn VirtualFile>> {
         log::trace!(
             "InMemoryFile::openat(path={:?}, read={:?}, write={:?}, oflags={:?}, fd_flags={:?}",
             path,
@@ -333,7 +349,7 @@ impl VirtualFile for InMemoryFile {
                 path
             );
             log::trace!("  return ENOTDIR");
-            return Err(Error::ENOTDIR);
+            return Err(WasiError::ENOTDIR);
         }
 
         if path == Path::new(".") {
@@ -344,24 +360,24 @@ impl VirtualFile for InMemoryFile {
                 None => self.try_clone().map_err(Into::into),
             }
         } else {
-            Err(Error::EACCES)
+            Err(WasiError::EACCES)
         }
     }
 
-    fn remove_directory(&self, _path: &str) -> Result<()> {
-        Err(Error::ENOTDIR)
+    fn remove_directory(&self, _path: &str) -> WasiResult<()> {
+        Err(WasiError::ENOTDIR)
     }
 
-    fn unlink_file(&self, _path: &str) -> Result<()> {
-        Err(Error::ENOTDIR)
+    fn unlink_file(&self, _path: &str) -> WasiResult<()> {
+        Err(WasiError::ENOTDIR)
     }
 
-    fn fdstat_set_flags(&mut self, fdflags: wasi::__wasi_fdflags_t) -> Result<()> {
+    fn fdstat_set_flags(&mut self, fdflags: wasi::__wasi_fdflags_t) -> WasiResult<()> {
         self.fd_flags = fdflags;
         Ok(())
     }
 
-    fn write_vectored(&mut self, iovs: &[io::IoSlice]) -> Result<usize> {
+    fn write_vectored(&mut self, iovs: &[io::IoSlice]) -> WasiResult<usize> {
         trace!("write_vectored(iovs={:?})", iovs);
         let mut data = self.data.borrow_mut();
 
@@ -389,10 +405,10 @@ impl VirtualFile for InMemoryFile {
 
         if let Some(end) = write_start.checked_add(max_size as wasi::__wasi_filesize_t) {
             if end > data.max_size() {
-                return Err(Error::EFBIG);
+                return Err(WasiError::EFBIG);
             }
         } else {
-            return Err(Error::EFBIG);
+            return Err(WasiError::EFBIG);
         }
 
         trace!("     | *write_start={:?}", write_start);
@@ -407,43 +423,43 @@ impl VirtualFile for InMemoryFile {
         Ok(written)
     }
 
-    fn read_vectored(&mut self, iovs: &mut [io::IoSliceMut]) -> Result<usize> {
+    fn read_vectored(&mut self, iovs: &mut [io::IoSliceMut]) -> WasiResult<usize> {
         trace!("read_vectored(iovs={:?})", iovs);
         trace!("     | *read_start={:?}", self.cursor);
         self.data.borrow_mut().preadv(iovs, self.cursor)
     }
 
-    fn pread(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+    fn pread(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> WasiResult<usize> {
         self.data.borrow_mut().pread(buf, offset)
     }
 
-    fn pwrite(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> Result<usize> {
+    fn pwrite(&self, buf: &mut [u8], offset: wasi::__wasi_filesize_t) -> WasiResult<usize> {
         self.data.borrow_mut().pwrite(buf, offset)
     }
 
-    fn seek(&mut self, offset: SeekFrom) -> Result<wasi::__wasi_filesize_t> {
+    fn seek(&mut self, offset: SeekFrom) -> WasiResult<wasi::__wasi_filesize_t> {
         let content_len = self.data.borrow().size();
         match offset {
             SeekFrom::Current(offset) => {
                 let new_cursor = if offset < 0 {
                     self.cursor
                         .checked_sub(offset.wrapping_neg() as u64)
-                        .ok_or(Error::EINVAL)?
+                        .ok_or(WasiError::EINVAL)?
                 } else {
                     self.cursor
                         .checked_add(offset as u64)
-                        .ok_or(Error::EINVAL)?
+                        .ok_or(WasiError::EINVAL)?
                 };
                 self.cursor = std::cmp::min(content_len, new_cursor);
             }
             SeekFrom::End(offset) => {
                 // A negative offset from the end would be past the end of the file,
-                let offset: u64 = offset.try_into().map_err(|_| Error::EINVAL)?;
+                let offset: u64 = offset.try_into().map_err(|_| WasiError::EINVAL)?;
                 self.cursor = content_len.saturating_sub(offset);
             }
             SeekFrom::Start(offset) => {
                 // A negative offset from the end would be before the start of the file.
-                let offset: u64 = offset.try_into().map_err(|_| Error::EINVAL)?;
+                let offset: u64 = offset.try_into().map_err(|_| WasiError::EINVAL)?;
                 self.cursor = std::cmp::min(content_len, offset);
             }
         }
@@ -456,7 +472,7 @@ impl VirtualFile for InMemoryFile {
         advice: wasi::__wasi_advice_t,
         _offset: wasi::__wasi_filesize_t,
         _len: wasi::__wasi_filesize_t,
-    ) -> Result<()> {
+    ) -> WasiResult<()> {
         // we'll just ignore advice for now, unless it's totally invalid
         match advice {
             wasi::__WASI_ADVICE_DONTNEED
@@ -465,7 +481,7 @@ impl VirtualFile for InMemoryFile {
             | wasi::__WASI_ADVICE_NOREUSE
             | wasi::__WASI_ADVICE_RANDOM
             | wasi::__WASI_ADVICE_NORMAL => Ok(()),
-            _ => Err(Error::EINVAL),
+            _ => Err(WasiError::EINVAL),
         }
     }
 
@@ -473,12 +489,12 @@ impl VirtualFile for InMemoryFile {
         &self,
         offset: wasi::__wasi_filesize_t,
         len: wasi::__wasi_filesize_t,
-    ) -> Result<()> {
-        let new_limit = offset.checked_add(len).ok_or(Error::EFBIG)?;
+    ) -> WasiResult<()> {
+        let new_limit = offset.checked_add(len).ok_or(WasiError::EFBIG)?;
         let mut data = self.data.borrow_mut();
 
         if new_limit > data.max_size() {
-            return Err(Error::EFBIG);
+            return Err(WasiError::EFBIG);
         }
 
         if new_limit > data.size() {
@@ -488,15 +504,15 @@ impl VirtualFile for InMemoryFile {
         Ok(())
     }
 
-    fn filestat_set_size(&self, st_size: wasi::__wasi_filesize_t) -> Result<()> {
+    fn filestat_set_size(&self, st_size: wasi::__wasi_filesize_t) -> WasiResult<()> {
         let mut data = self.data.borrow_mut();
         if st_size > data.max_size() {
-            return Err(Error::EFBIG);
+            return Err(WasiError::EFBIG);
         }
         data.resize(st_size)
     }
 
-    fn filestat_get(&self) -> Result<wasi::__wasi_filestat_t> {
+    fn filestat_get(&self) -> WasiResult<wasi::__wasi_filestat_t> {
         let stat = wasi::__wasi_filestat_t {
             dev: 0,
             ino: 0,
@@ -594,9 +610,9 @@ impl VirtualFile for VirtualDir {
         }))
     }
 
-    fn readlinkat(&self, _path: &Path) -> Result<String> {
+    fn readlinkat(&self, _path: &Path) -> WasiResult<String> {
         // Files are not symbolic links or directories, faithfully report ENOTDIR.
-        Err(Error::ENOTDIR)
+        Err(WasiError::ENOTDIR)
     }
 
     fn openat(
@@ -606,7 +622,7 @@ impl VirtualFile for VirtualDir {
         write: bool,
         oflags: wasi::__wasi_oflags_t,
         fd_flags: wasi::__wasi_fdflags_t,
-    ) -> Result<Box<dyn VirtualFile>> {
+    ) -> WasiResult<Box<dyn VirtualFile>> {
         log::trace!(
             "VirtualDir::openat(path={:?}, read={:?}, write={:?}, oflags={:?}, fd_flags={:?}",
             path,
@@ -631,7 +647,7 @@ impl VirtualFile for VirtualDir {
 
         // openat may have been passed a path with a trailing slash, but files are mapped to paths
         // with trailing slashes normalized out.
-        let file_name = path.file_name().ok_or(Error::EINVAL)?;
+        let file_name = path.file_name().ok_or(WasiError::EINVAL)?;
         let mut entries = self.entries.borrow_mut();
         let entry_count = entries.len();
         match entries.entry(Path::new(file_name).to_path_buf()) {
@@ -640,7 +656,7 @@ impl VirtualFile for VirtualDir {
                 if (oflags & creat_excl_mask) == creat_excl_mask {
                     log::trace!("VirtualDir::openat was passed oflags CREAT|EXCL, but the file {:?} exists.", file_name);
                     log::trace!("  return EEXIST");
-                    return Err(Error::EEXIST);
+                    return Err(WasiError::EEXIST);
                 }
 
                 if (oflags & wasi::__WASI_OFLAGS_DIRECTORY) != 0
@@ -651,7 +667,7 @@ impl VirtualFile for VirtualDir {
                         file_name
                     );
                     log::trace!("  return ENOTDIR");
-                    return Err(Error::ENOTDIR);
+                    return Err(WasiError::ENOTDIR);
                 }
 
                 e.get().try_clone().map_err(Into::into)
@@ -663,7 +679,7 @@ impl VirtualFile for VirtualDir {
                     // would have with `usize`. The limit is the full `u32` range minus two so we
                     // can reserve "self" and "parent" cookie values.
                     if entry_count >= (std::u32::MAX - RESERVED_ENTRY_COUNT) as usize {
-                        return Err(Error::ENOSPC);
+                        return Err(WasiError::ENOSPC);
                     }
 
                     log::trace!(
@@ -676,26 +692,26 @@ impl VirtualFile for VirtualDir {
                     file.set_parent(Some(self.try_clone().expect("can clone self")));
                     v.insert(file).try_clone().map_err(Into::into)
                 } else {
-                    Err(Error::EACCES)
+                    Err(WasiError::EACCES)
                 }
             }
         }
     }
 
-    fn remove_directory(&self, path: &str) -> Result<()> {
+    fn remove_directory(&self, path: &str) -> WasiResult<()> {
         let trimmed_path = path.trim_end_matches('/');
         let mut entries = self.entries.borrow_mut();
         match entries.entry(Path::new(trimmed_path).to_path_buf()) {
             Entry::Occupied(e) => {
                 // first, does this name a directory?
                 if e.get().get_file_type() != wasi::__WASI_FILETYPE_DIRECTORY {
-                    return Err(Error::ENOTDIR);
+                    return Err(WasiError::ENOTDIR);
                 }
 
                 // Okay, but is the directory empty?
                 let iter = e.get().readdir(wasi::__WASI_DIRCOOKIE_START)?;
                 if iter.skip(RESERVED_ENTRY_COUNT as usize).next().is_some() {
-                    return Err(Error::ENOTEMPTY);
+                    return Err(WasiError::ENOTEMPTY);
                 }
 
                 // Alright, it's an empty directory. We can remove it.
@@ -711,19 +727,19 @@ impl VirtualFile for VirtualDir {
                     "VirtualDir::remove_directory failed to remove {}, no such entry",
                     trimmed_path
                 );
-                Err(Error::ENOENT)
+                Err(WasiError::ENOENT)
             }
         }
     }
 
-    fn unlink_file(&self, path: &str) -> Result<()> {
+    fn unlink_file(&self, path: &str) -> WasiResult<()> {
         let trimmed_path = path.trim_end_matches('/');
 
         // Special case: we may be unlinking this directory itself if path is `"."`. In that case,
         // fail with EISDIR, since this is a directory. Alternatively, we may be unlinking `".."`,
         // which is bound the same way, as this is by definition contained in a directory.
         if trimmed_path == "." || trimmed_path == ".." {
-            return Err(Error::EISDIR);
+            return Err(WasiError::EISDIR);
         }
 
         let mut entries = self.entries.borrow_mut();
@@ -731,7 +747,7 @@ impl VirtualFile for VirtualDir {
             Entry::Occupied(e) => {
                 // Directories must be removed through `remove_directory`, not `unlink_file`.
                 if e.get().get_file_type() == wasi::__WASI_FILETYPE_DIRECTORY {
-                    return Err(Error::EISDIR);
+                    return Err(WasiError::EISDIR);
                 }
 
                 let removed = e.remove_entry();
@@ -746,15 +762,15 @@ impl VirtualFile for VirtualDir {
                     "VirtualDir::unlink_file failed to remove {}, no such entry",
                     trimmed_path
                 );
-                Err(Error::ENOENT)
+                Err(WasiError::ENOENT)
             }
         }
     }
 
-    fn create_directory(&self, path: &Path) -> Result<()> {
+    fn create_directory(&self, path: &Path) -> WasiResult<()> {
         let mut entries = self.entries.borrow_mut();
         match entries.entry(path.to_owned()) {
-            Entry::Occupied(_) => Err(Error::EEXIST),
+            Entry::Occupied(_) => Err(WasiError::EEXIST),
             Entry::Vacant(v) => {
                 if self.writable {
                     let new_dir = Box::new(VirtualDir::new(true));
@@ -762,26 +778,26 @@ impl VirtualFile for VirtualDir {
                     v.insert(new_dir);
                     Ok(())
                 } else {
-                    Err(Error::EACCES)
+                    Err(WasiError::EACCES)
                 }
             }
         }
     }
 
-    fn write_vectored(&mut self, _iovs: &[io::IoSlice]) -> Result<usize> {
-        Err(Error::EBADF)
+    fn write_vectored(&mut self, _iovs: &[io::IoSlice]) -> WasiResult<usize> {
+        Err(WasiError::EBADF)
     }
 
     fn readdir(
         &self,
         cookie: wasi::__wasi_dircookie_t,
-    ) -> Result<Box<dyn Iterator<Item = Result<Dirent>>>> {
+    ) -> WasiResult<Box<dyn Iterator<Item = WasiResult<Dirent>>>> {
         struct VirtualDirIter {
             start: u32,
             entries: Rc<RefCell<HashMap<PathBuf, Box<dyn VirtualFile>>>>,
         }
         impl Iterator for VirtualDirIter {
-            type Item = Result<Dirent>;
+            type Item = WasiResult<Dirent>;
 
             fn next(&mut self) -> Option<Self::Item> {
                 log::trace!("VirtualDirIter::next continuing from {}", self.start);
@@ -850,7 +866,7 @@ impl VirtualFile for VirtualDir {
         }))
     }
 
-    fn filestat_get(&self) -> Result<wasi::__wasi_filestat_t> {
+    fn filestat_get(&self) -> WasiResult<wasi::__wasi_filestat_t> {
         let stat = wasi::__wasi_filestat_t {
             dev: 0,
             ino: 0,
diff --git a/crates/wasi-common/src/wasi.rs b/crates/wasi-common/src/wasi.rs
index e418546a07..385541a0cf 100644
--- a/crates/wasi-common/src/wasi.rs
+++ b/crates/wasi-common/src/wasi.rs
@@ -10,6 +10,115 @@ use wig::witx_wasi_types;
 
 witx_wasi_types!("snapshot" "wasi_snapshot_preview1");
 
+pub type WasiResult<T> = Result<T, WasiError>;
+
+#[derive(Clone, Copy, Debug, thiserror::Error, Eq, PartialEq)]
+#[repr(u16)]
+#[error("{:?} ({})", self, strerror(*self as __wasi_errno_t))]
+pub enum WasiError {
+    ESUCCESS = __WASI_ERRNO_SUCCESS,
+    E2BIG = __WASI_ERRNO_2BIG,
+    EACCES = __WASI_ERRNO_ACCES,
+    EADDRINUSE = __WASI_ERRNO_ADDRINUSE,
+    EADDRNOTAVAIL = __WASI_ERRNO_ADDRNOTAVAIL,
+    EAFNOSUPPORT = __WASI_ERRNO_AFNOSUPPORT,
+    EAGAIN = __WASI_ERRNO_AGAIN,
+    EALREADY = __WASI_ERRNO_ALREADY,
+    EBADF = __WASI_ERRNO_BADF,
+    EBADMSG = __WASI_ERRNO_BADMSG,
+    EBUSY = __WASI_ERRNO_BUSY,
+    ECANCELED = __WASI_ERRNO_CANCELED,
+    ECHILD = __WASI_ERRNO_CHILD,
+    ECONNABORTED = __WASI_ERRNO_CONNABORTED,
+    ECONNREFUSED = __WASI_ERRNO_CONNREFUSED,
+    ECONNRESET = __WASI_ERRNO_CONNRESET,
+    EDEADLK = __WASI_ERRNO_DEADLK,
+    EDESTADDRREQ = __WASI_ERRNO_DESTADDRREQ,
+    EDOM = __WASI_ERRNO_DOM,
+    EDQUOT = __WASI_ERRNO_DQUOT,
+    EEXIST = __WASI_ERRNO_EXIST,
+    EFAULT = __WASI_ERRNO_FAULT,
+    EFBIG = __WASI_ERRNO_FBIG,
+    EHOSTUNREACH = __WASI_ERRNO_HOSTUNREACH,
+    EIDRM = __WASI_ERRNO_IDRM,
+    EILSEQ = __WASI_ERRNO_ILSEQ,
+    EINPROGRESS = __WASI_ERRNO_INPROGRESS,
+    EINTR = __WASI_ERRNO_INTR,
+    EINVAL = __WASI_ERRNO_INVAL,
+    EIO = __WASI_ERRNO_IO,
+    EISCONN = __WASI_ERRNO_ISCONN,
+    EISDIR = __WASI_ERRNO_ISDIR,
+    ELOOP = __WASI_ERRNO_LOOP,
+    EMFILE = __WASI_ERRNO_MFILE,
+    EMLINK = __WASI_ERRNO_MLINK,
+    EMSGSIZE = __WASI_ERRNO_MSGSIZE,
+    EMULTIHOP = __WASI_ERRNO_MULTIHOP,
+    ENAMETOOLONG = __WASI_ERRNO_NAMETOOLONG,
+    ENETDOWN = __WASI_ERRNO_NETDOWN,
+    ENETRESET = __WASI_ERRNO_NETRESET,
+    ENETUNREACH = __WASI_ERRNO_NETUNREACH,
+    ENFILE = __WASI_ERRNO_NFILE,
+    ENOBUFS = __WASI_ERRNO_NOBUFS,
+    ENODEV = __WASI_ERRNO_NODEV,
+    ENOENT = __WASI_ERRNO_NOENT,
+    ENOEXEC = __WASI_ERRNO_NOEXEC,
+    ENOLCK = __WASI_ERRNO_NOLCK,
+    ENOLINK = __WASI_ERRNO_NOLINK,
+    ENOMEM = __WASI_ERRNO_NOMEM,
+    ENOMSG = __WASI_ERRNO_NOMSG,
+    ENOPROTOOPT = __WASI_ERRNO_NOPROTOOPT,
+    ENOSPC = __WASI_ERRNO_NOSPC,
+    ENOSYS = __WASI_ERRNO_NOSYS,
+    ENOTCONN = __WASI_ERRNO_NOTCONN,
+    ENOTDIR = __WASI_ERRNO_NOTDIR,
+    ENOTEMPTY = __WASI_ERRNO_NOTEMPTY,
+    ENOTRECOVERABLE = __WASI_ERRNO_NOTRECOVERABLE,
+    ENOTSOCK = __WASI_ERRNO_NOTSOCK,
+    ENOTSUP = __WASI_ERRNO_NOTSUP,
+    ENOTTY = __WASI_ERRNO_NOTTY,
+    ENXIO = __WASI_ERRNO_NXIO,
+    EOVERFLOW = __WASI_ERRNO_OVERFLOW,
+    EOWNERDEAD = __WASI_ERRNO_OWNERDEAD,
+    EPERM = __WASI_ERRNO_PERM,
+    EPIPE = __WASI_ERRNO_PIPE,
+    EPROTO = __WASI_ERRNO_PROTO,
+    EPROTONOSUPPORT = __WASI_ERRNO_PROTONOSUPPORT,
+    EPROTOTYPE = __WASI_ERRNO_PROTOTYPE,
+    ERANGE = __WASI_ERRNO_RANGE,
+    EROFS = __WASI_ERRNO_ROFS,
+    ESPIPE = __WASI_ERRNO_SPIPE,
+    ESRCH = __WASI_ERRNO_SRCH,
+    ESTALE = __WASI_ERRNO_STALE,
+    ETIMEDOUT = __WASI_ERRNO_TIMEDOUT,
+    ETXTBSY = __WASI_ERRNO_TXTBSY,
+    EXDEV = __WASI_ERRNO_XDEV,
+    ENOTCAPABLE = __WASI_ERRNO_NOTCAPABLE,
+}
+
+impl WasiError {
+    pub fn as_raw_errno(self) -> __wasi_errno_t {
+        self as __wasi_errno_t
+    }
+}
+
+impl From<std::convert::Infallible> for WasiError {
+    fn from(_err: std::convert::Infallible) -> Self {
+        unreachable!()
+    }
+}
+
+impl From<std::num::TryFromIntError> for WasiError {
+    fn from(_err: std::num::TryFromIntError) -> Self {
+        Self::EOVERFLOW
+    }
+}
+
+impl From<std::str::Utf8Error> for WasiError {
+    fn from(_err: std::str::Utf8Error) -> Self {
+        Self::EILSEQ
+    }
+}
+
 pub(crate) const RIGHTS_ALL: __wasi_rights_t = __WASI_RIGHTS_FD_DATASYNC
     | __WASI_RIGHTS_FD_READ
     | __WASI_RIGHTS_FD_SEEK
diff --git a/crates/wasi-common/wig/src/hostcalls.rs b/crates/wasi-common/wig/src/hostcalls.rs
index df7d813f1d..938ca5a2e0 100644
--- a/crates/wasi-common/wig/src/hostcalls.rs
+++ b/crates/wasi-common/wig/src/hostcalls.rs
@@ -92,8 +92,7 @@ fn generate_wrappers(func: &witx::InterfaceFunc, old: bool) -> TokenStream {
         quote! {
             let ret = #call
                 .err()
-                .unwrap_or(super::Error::ESUCCESS)
-                .as_wasi_error();
+                .unwrap_or(super::wasi::WasiError::ESUCCESS);
             log::trace!("     | errno={}", ret);
             ret.as_raw_errno()
         }