diff --git a/src/ctx.rs b/src/ctx.rs
index 6c8d9cbbb7..01063857e0 100644
--- a/src/ctx.rs
+++ b/src/ctx.rs
@@ -1,6 +1,6 @@
-use super::fdentry::FdEntry;
-use super::host;
-use super::sys::{dev_null, errno_from_host};
+use crate::fdentry::FdEntry;
+use crate::sys::{dev_null, errno_from_host};
+use crate::{host, Result};
 use std::borrow::Borrow;
 use std::collections::HashMap;
 use std::ffi::CString;
@@ -16,7 +16,7 @@ pub struct WasiCtxBuilder {
 
 impl WasiCtxBuilder {
     /// Builder for a new `WasiCtx`.
-    pub fn new() -> Result<Self, host::__wasi_errno_t> {
+    pub fn new() -> Result<Self> {
         let mut builder = Self {
             fds: HashMap::new(),
             preopens: HashMap::new(),
@@ -31,35 +31,32 @@ impl WasiCtxBuilder {
         Ok(builder)
     }
 
-    pub fn args<S: AsRef<str>>(
-        mut self,
-        args: impl Iterator<Item = S>,
-    ) -> Result<Self, host::__wasi_errno_t> {
-        let args: Result<Vec<CString>, _> = args
+    pub fn args<S: AsRef<str>>(mut self, args: impl Iterator<Item = S>) -> Result<Self> {
+        let args: Result<Vec<CString>> = args
             .map(|arg| CString::new(arg.as_ref()).map_err(|_| host::__WASI_ENOTCAPABLE))
             .collect();
         self.args = args?;
         Ok(self)
     }
 
-    pub fn arg(mut self, arg: &str) -> Result<Self, host::__wasi_errno_t> {
+    pub fn arg(mut self, arg: &str) -> Result<Self> {
         self.args
             .push(CString::new(arg).map_err(|_| host::__WASI_ENOTCAPABLE)?);
         Ok(self)
     }
 
-    pub fn inherit_stdio(mut self) -> Result<Self, host::__wasi_errno_t> {
+    pub fn inherit_stdio(mut self) -> Result<Self> {
         self.fds.insert(0, FdEntry::duplicate_stdin()?);
         self.fds.insert(1, FdEntry::duplicate_stdout()?);
         self.fds.insert(2, FdEntry::duplicate_stderr()?);
         Ok(self)
     }
 
-    pub fn inherit_env(self) -> Result<Self, host::__wasi_errno_t> {
+    pub fn inherit_env(self) -> Result<Self> {
         self.envs(std::env::vars())
     }
 
-    pub fn env<S: AsRef<str>>(mut self, k: S, v: S) -> Result<Self, host::__wasi_errno_t> {
+    pub fn env<S: AsRef<str>>(mut self, k: S, v: S) -> Result<Self> {
         self.env.insert(
             CString::new(k.as_ref()).map_err(|_| host::__WASI_ENOTCAPABLE)?,
             CString::new(v.as_ref()).map_err(|_| host::__WASI_ENOTCAPABLE)?,
@@ -70,8 +67,8 @@ impl WasiCtxBuilder {
     pub fn envs<S: AsRef<str>, T: Borrow<(S, S)>>(
         mut self,
         envs: impl Iterator<Item = T>,
-    ) -> Result<Self, host::__wasi_errno_t> {
-        let env: Result<HashMap<CString, CString>, _> = envs
+    ) -> Result<Self> {
+        let env: Result<HashMap<CString, CString>> = envs
             .map(|t| {
                 let (k, v) = t.borrow();
                 let k = CString::new(k.as_ref()).map_err(|_| host::__WASI_ENOTCAPABLE);
@@ -91,7 +88,7 @@ impl WasiCtxBuilder {
         self
     }
 
-    pub fn build(mut self) -> Result<WasiCtx, host::__wasi_errno_t> {
+    pub fn build(mut self) -> Result<WasiCtx> {
         // startup code starts looking at fd 3 for preopens
         let mut preopen_fd = 3;
         for (guest_path, dir) in self.preopens {
@@ -147,7 +144,7 @@ impl WasiCtx {
     /// - Environment variables are inherited from the host process.
     ///
     /// To override these behaviors, use `WasiCtxBuilder`.
-    pub fn new<S: AsRef<str>>(args: impl Iterator<Item = S>) -> Result<Self, host::__wasi_errno_t> {
+    pub fn new<S: AsRef<str>>(args: impl Iterator<Item = S>) -> Result<Self> {
         WasiCtxBuilder::new()
             .and_then(|ctx| ctx.args(args))
             .and_then(|ctx| ctx.inherit_stdio())
@@ -160,7 +157,7 @@ impl WasiCtx {
         fd: host::__wasi_fd_t,
         rights_base: host::__wasi_rights_t,
         rights_inheriting: host::__wasi_rights_t,
-    ) -> Result<&FdEntry, host::__wasi_errno_t> {
+    ) -> Result<&FdEntry> {
         if let Some(fe) = self.fds.get(&fd) {
             Self::validate_rights(fe, rights_base, rights_inheriting).and(Ok(fe))
         } else {
@@ -173,7 +170,7 @@ impl WasiCtx {
         fd: host::__wasi_fd_t,
         rights_base: host::__wasi_rights_t,
         rights_inheriting: host::__wasi_rights_t,
-    ) -> Result<&mut FdEntry, host::__wasi_errno_t> {
+    ) -> Result<&mut FdEntry> {
         if let Some(fe) = self.fds.get_mut(&fd) {
             Self::validate_rights(fe, rights_base, rights_inheriting).and(Ok(fe))
         } else {
@@ -185,7 +182,7 @@ impl WasiCtx {
         fe: &FdEntry,
         rights_base: host::__wasi_rights_t,
         rights_inheriting: host::__wasi_rights_t,
-    ) -> Result<(), host::__wasi_errno_t> {
+    ) -> Result<()> {
         if !fe.rights_base & rights_base != 0 || !fe.rights_inheriting & rights_inheriting != 0 {
             Err(host::__WASI_ENOTCAPABLE)
         } else {
@@ -193,10 +190,7 @@ impl WasiCtx {
         }
     }
 
-    pub fn insert_fd_entry(
-        &mut self,
-        fe: FdEntry,
-    ) -> Result<host::__wasi_fd_t, host::__wasi_errno_t> {
+    pub fn insert_fd_entry(&mut self, fe: FdEntry) -> Result<host::__wasi_fd_t> {
         // never insert where stdio handles usually are
         let mut fd = 3;
         while self.fds.contains_key(&fd) {
diff --git a/src/fdentry.rs b/src/fdentry.rs
index c3842caf6b..a2baadbceb 100644
--- a/src/fdentry.rs
+++ b/src/fdentry.rs
@@ -1,10 +1,9 @@
-use super::host;
 use crate::sys::{errno_from_host, fdentry_impl};
+use crate::{host, Result};
 
-use std::fs;
-use std::io;
 use std::mem::ManuallyDrop;
 use std::path::PathBuf;
+use std::{fs, io};
 
 #[derive(Debug)]
 pub enum Descriptor {
@@ -39,7 +38,7 @@ impl Drop for FdObject {
 }
 
 impl FdEntry {
-    pub fn from(file: fs::File) -> Result<Self, host::__wasi_errno_t> {
+    pub fn from(file: fs::File) -> Result<Self> {
         fdentry_impl::determine_type_and_access_rights(&file).map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
@@ -54,13 +53,13 @@ impl FdEntry {
         )
     }
 
-    pub fn duplicate(file: &fs::File) -> Result<Self, host::__wasi_errno_t> {
+    pub fn duplicate(file: &fs::File) -> Result<Self> {
         file.try_clone()
             .map_err(|err| err.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
             .and_then(Self::from)
     }
 
-    pub fn duplicate_stdin() -> Result<Self, host::__wasi_errno_t> {
+    pub fn duplicate_stdin() -> Result<Self> {
         fdentry_impl::determine_type_and_access_rights(&io::stdin()).map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
@@ -75,7 +74,7 @@ impl FdEntry {
         )
     }
 
-    pub fn duplicate_stdout() -> Result<Self, host::__wasi_errno_t> {
+    pub fn duplicate_stdout() -> Result<Self> {
         fdentry_impl::determine_type_and_access_rights(&io::stdout()).map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
@@ -90,7 +89,7 @@ impl FdEntry {
         )
     }
 
-    pub fn duplicate_stderr() -> Result<Self, host::__wasi_errno_t> {
+    pub fn duplicate_stderr() -> Result<Self> {
         fdentry_impl::determine_type_and_access_rights(&io::stderr()).map(
             |(file_type, rights_base, rights_inheriting)| Self {
                 fd_object: FdObject {
diff --git a/src/host.rs b/src/host.rs
index fac60f1cd4..a45d98555c 100644
--- a/src/host.rs
+++ b/src/host.rs
@@ -3,7 +3,7 @@
 //! still largely reflects that.
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
-
+use crate::Result;
 use std::{io, slice, str};
 
 pub type void = ::std::os::raw::c_void;
@@ -499,7 +499,7 @@ pub unsafe fn iovec_to_host_mut<'a>(iovec: &'a mut __wasi_iovec_t) -> io::IoSlic
 ///
 /// NB WASI spec requires bytes to be valid UTF-8. Otherwise,
 /// `__WASI_EILSEQ` error is returned.
-pub fn path_from_slice<'a>(s: &'a [u8]) -> Result<&'a str, __wasi_errno_t> {
+pub fn path_from_slice<'a>(s: &'a [u8]) -> Result<&'a str> {
     str::from_utf8(s).map_err(|_| __WASI_EILSEQ)
 }
 
@@ -507,7 +507,7 @@ pub fn path_from_slice<'a>(s: &'a [u8]) -> Result<&'a str, __wasi_errno_t> {
 ///
 /// NB WASI spec requires bytes to be valid UTF-8. Otherwise,
 /// `__WASI_EILSEQ` error is returned.
-pub fn path_from_vec<S: Into<Vec<u8>>>(s: S) -> Result<String, __wasi_errno_t> {
+pub fn path_from_vec<S: Into<Vec<u8>>>(s: S) -> Result<String> {
     String::from_utf8(s.into()).map_err(|_| __WASI_EILSEQ)
 }
 
diff --git a/src/hostcalls/mod.rs b/src/hostcalls/mod.rs
index 925fcc4a2f..f09011901b 100644
--- a/src/hostcalls/mod.rs
+++ b/src/hostcalls/mod.rs
@@ -6,8 +6,10 @@ pub use self::fs::*;
 pub use self::misc::*;
 pub use self::sock::*;
 
-fn return_enc_errno(errno: super::host::__wasi_errno_t) -> super::wasm32::__wasi_errno_t {
-    let errno = super::memory::enc_errno(errno);
-    log::trace!("    -> errno={}", super::wasm32::strerror(errno));
+use crate::{host, memory, wasm32};
+
+fn return_enc_errno(errno: host::__wasi_errno_t) -> wasm32::__wasi_errno_t {
+    let errno = memory::enc_errno(errno);
+    log::trace!("    -> errno={}", wasm32::strerror(errno));
     errno
 }
diff --git a/src/lib.rs b/src/lib.rs
index de7e9298cc..5703d88058 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -31,3 +31,5 @@ pub mod wasm32;
 
 pub use ctx::{WasiCtx, WasiCtxBuilder};
 pub use sys::preopen_dir;
+
+pub(crate) type Result<T> = std::result::Result<T, self::host::__wasi_errno_t>;
diff --git a/src/memory.rs b/src/memory.rs
index 22128a4bda..ef504ac2d5 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -1,22 +1,11 @@
 //! Functions to go back and forth between WASI types in host and wasm32 representations.
 #![allow(unused)]
-use crate::{host, wasm32};
+use crate::{host, wasm32, Result};
 use std::convert::TryFrom;
 use std::mem::{align_of, size_of};
-use std::ptr;
-use std::slice;
+use std::{ptr, slice};
 
-macro_rules! bail_errno {
-    ( $errno:ident ) => {
-        return Err(host::$errno);
-    };
-}
-
-fn dec_ptr(
-    memory: &[u8],
-    ptr: wasm32::uintptr_t,
-    len: usize,
-) -> Result<*const u8, host::__wasi_errno_t> {
+fn dec_ptr(memory: &[u8], ptr: wasm32::uintptr_t, len: usize) -> Result<*const u8> {
     // check for overflow
     let checked_len = (ptr as usize).checked_add(len).ok_or(host::__WASI_EFAULT)?;
 
@@ -27,11 +16,7 @@ fn dec_ptr(
         .map(|mem| mem.as_ptr())
 }
 
-fn dec_ptr_mut(
-    memory: &mut [u8],
-    ptr: wasm32::uintptr_t,
-    len: usize,
-) -> Result<*mut u8, host::__wasi_errno_t> {
+fn dec_ptr_mut(memory: &mut [u8], ptr: wasm32::uintptr_t, len: usize) -> Result<*mut u8> {
     // check for overflow
     let checked_len = (ptr as usize).checked_add(len).ok_or(host::__WASI_EFAULT)?;
 
@@ -42,13 +27,10 @@ fn dec_ptr_mut(
         .map(|mem| mem.as_mut_ptr())
 }
 
-fn dec_ptr_to<'memory, T>(
-    memory: &'memory [u8],
-    ptr: wasm32::uintptr_t,
-) -> Result<&'memory T, host::__wasi_errno_t> {
+fn dec_ptr_to<'memory, T>(memory: &'memory [u8], ptr: wasm32::uintptr_t) -> Result<&'memory T> {
     // check that the ptr is aligned
     if ptr as usize % align_of::<T>() != 0 {
-        bail_errno!(__WASI_EINVAL);
+        return Err(host::__WASI_EINVAL);
     }
 
     dec_ptr(memory, ptr, size_of::<T>()).map(|p| unsafe { &*(p as *const T) })
@@ -57,31 +39,24 @@ fn dec_ptr_to<'memory, T>(
 fn dec_ptr_to_mut<'memory, T>(
     memory: &'memory mut [u8],
     ptr: wasm32::uintptr_t,
-) -> Result<&'memory mut T, host::__wasi_errno_t> {
+) -> Result<&'memory mut T> {
     // check that the ptr is aligned
     if ptr as usize % align_of::<T>() != 0 {
-        bail_errno!(__WASI_EINVAL);
+        return Err(host::__WASI_EINVAL);
     }
 
     dec_ptr_mut(memory, ptr, size_of::<T>()).map(|p| unsafe { &mut *(p as *mut T) })
 }
 
-pub fn dec_pointee<T>(memory: &[u8], ptr: wasm32::uintptr_t) -> Result<T, host::__wasi_errno_t> {
+pub fn dec_pointee<T>(memory: &[u8], ptr: wasm32::uintptr_t) -> Result<T> {
     dec_ptr_to::<T>(memory, ptr).map(|p| unsafe { ptr::read(p) })
 }
 
-pub fn enc_pointee<T>(
-    memory: &mut [u8],
-    ptr: wasm32::uintptr_t,
-    t: T,
-) -> Result<(), host::__wasi_errno_t> {
+pub fn enc_pointee<T>(memory: &mut [u8], ptr: wasm32::uintptr_t, t: T) -> Result<()> {
     dec_ptr_to_mut::<T>(memory, ptr).map(|p| unsafe { ptr::write(p, t) })
 }
 
-fn check_slice_of<T>(
-    ptr: wasm32::uintptr_t,
-    len: wasm32::size_t,
-) -> Result<(usize, usize), host::__wasi_errno_t> {
+fn check_slice_of<T>(ptr: wasm32::uintptr_t, len: wasm32::size_t) -> Result<(usize, usize)> {
     // check alignment, and that length doesn't overflow
     if ptr as usize % align_of::<T>() != 0 {
         return Err(host::__WASI_EINVAL);
@@ -100,7 +75,7 @@ pub fn dec_slice_of<'memory, T>(
     memory: &'memory [u8],
     ptr: wasm32::uintptr_t,
     len: wasm32::size_t,
-) -> Result<&'memory [T], host::__wasi_errno_t> {
+) -> Result<&'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) })
@@ -110,17 +85,13 @@ pub fn dec_slice_of_mut<'memory, T>(
     memory: &'memory mut [u8],
     ptr: wasm32::uintptr_t,
     len: wasm32::size_t,
-) -> Result<&'memory mut [T], host::__wasi_errno_t> {
+) -> Result<&'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) })
 }
 
-pub fn enc_slice_of<T>(
-    memory: &mut [u8],
-    slice: &[T],
-    ptr: wasm32::uintptr_t,
-) -> Result<(), host::__wasi_errno_t> {
+pub fn enc_slice_of<T>(memory: &mut [u8], slice: &[T], ptr: wasm32::uintptr_t) -> Result<()> {
     // check alignment
     if ptr as usize % align_of::<T>() != 0 {
         return Err(host::__WASI_EINVAL);
@@ -147,10 +118,7 @@ macro_rules! dec_enc_scalar {
             host::$ty::from_le(x)
         }
 
-        pub fn $dec_byref(
-            memory: &mut [u8],
-            ptr: wasm32::uintptr_t,
-        ) -> Result<host::$ty, host::__wasi_errno_t> {
+        pub fn $dec_byref(memory: &mut [u8], ptr: wasm32::uintptr_t) -> Result<host::$ty> {
             dec_pointee::<wasm32::$ty>(memory, ptr).map($dec)
         }
 
@@ -158,11 +126,7 @@ macro_rules! dec_enc_scalar {
             x.to_le()
         }
 
-        pub fn $enc_byref(
-            memory: &mut [u8],
-            ptr: wasm32::uintptr_t,
-            x: host::$ty,
-        ) -> Result<(), host::__wasi_errno_t> {
+        pub fn $enc_byref(memory: &mut [u8], ptr: wasm32::uintptr_t, x: host::$ty) -> Result<()> {
             enc_pointee::<wasm32::$ty>(memory, ptr, $enc(x))
         }
     };
@@ -171,7 +135,7 @@ macro_rules! dec_enc_scalar {
 pub fn dec_ciovec(
     memory: &[u8],
     ciovec: &wasm32::__wasi_ciovec_t,
-) -> Result<host::__wasi_ciovec_t, host::__wasi_errno_t> {
+) -> Result<host::__wasi_ciovec_t> {
     let len = dec_usize(ciovec.buf_len);
     Ok(host::__wasi_ciovec_t {
         buf: dec_ptr(memory, ciovec.buf, len)? as *const host::void,
@@ -183,15 +147,12 @@ pub fn dec_ciovec_slice(
     memory: &[u8],
     ptr: wasm32::uintptr_t,
     len: wasm32::size_t,
-) -> Result<Vec<host::__wasi_ciovec_t>, host::__wasi_errno_t> {
+) -> Result<Vec<host::__wasi_ciovec_t>> {
     let slice = dec_slice_of::<wasm32::__wasi_ciovec_t>(memory, ptr, len)?;
     slice.iter().map(|iov| dec_ciovec(memory, iov)).collect()
 }
 
-pub fn dec_iovec(
-    memory: &[u8],
-    iovec: &wasm32::__wasi_iovec_t,
-) -> Result<host::__wasi_iovec_t, host::__wasi_errno_t> {
+pub fn dec_iovec(memory: &[u8], iovec: &wasm32::__wasi_iovec_t) -> Result<host::__wasi_iovec_t> {
     let len = dec_usize(iovec.buf_len);
     Ok(host::__wasi_iovec_t {
         buf: dec_ptr(memory, iovec.buf, len)? as *mut host::void,
@@ -203,7 +164,7 @@ pub fn dec_iovec_slice(
     memory: &[u8],
     ptr: wasm32::uintptr_t,
     len: wasm32::size_t,
-) -> Result<Vec<host::__wasi_iovec_t>, host::__wasi_errno_t> {
+) -> Result<Vec<host::__wasi_iovec_t>> {
     let slice = dec_slice_of::<wasm32::__wasi_iovec_t>(memory, ptr, len)?;
     slice.iter().map(|iov| dec_iovec(memory, iov)).collect()
 }
@@ -215,6 +176,7 @@ dec_enc_scalar!(
     enc_clockid,
     enc_clockid_byref
 );
+
 dec_enc_scalar!(
     __wasi_errno_t,
     dec_errno,
@@ -222,6 +184,7 @@ dec_enc_scalar!(
     enc_errno,
     enc_errno_byref
 );
+
 dec_enc_scalar!(
     __wasi_exitcode_t,
     dec_exitcode,
@@ -229,7 +192,9 @@ dec_enc_scalar!(
     enc_exitcode,
     enc_exitcode_byref
 );
+
 dec_enc_scalar!(__wasi_fd_t, dec_fd, dec_fd_byref, enc_fd, enc_fd_byref);
+
 dec_enc_scalar!(
     __wasi_fdflags_t,
     dec_fdflags,
@@ -237,6 +202,7 @@ dec_enc_scalar!(
     enc_fdflags,
     enc_fdflags_byref
 );
+
 dec_enc_scalar!(
     __wasi_device_t,
     dec_device,
@@ -244,6 +210,7 @@ dec_enc_scalar!(
     enc_device,
     enc_device_byref
 );
+
 dec_enc_scalar!(
     __wasi_inode_t,
     dec_inode,
@@ -251,6 +218,7 @@ dec_enc_scalar!(
     enc_inode,
     enc_inode_byref
 );
+
 dec_enc_scalar!(
     __wasi_linkcount_t,
     dec_linkcount,
@@ -275,7 +243,7 @@ pub fn dec_filestat(filestat: wasm32::__wasi_filestat_t) -> host::__wasi_filesta
 pub fn dec_filestat_byref(
     memory: &mut [u8],
     filestat_ptr: wasm32::uintptr_t,
-) -> Result<host::__wasi_filestat_t, host::__wasi_errno_t> {
+) -> Result<host::__wasi_filestat_t> {
     dec_pointee::<wasm32::__wasi_filestat_t>(memory, filestat_ptr).map(dec_filestat)
 }
 
@@ -296,7 +264,7 @@ pub fn enc_filestat_byref(
     memory: &mut [u8],
     filestat_ptr: wasm32::uintptr_t,
     host_filestat: host::__wasi_filestat_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     let filestat = enc_filestat(host_filestat);
     enc_pointee::<wasm32::__wasi_filestat_t>(memory, filestat_ptr, filestat)
 }
@@ -313,7 +281,7 @@ pub fn dec_fdstat(fdstat: wasm32::__wasi_fdstat_t) -> host::__wasi_fdstat_t {
 pub fn dec_fdstat_byref(
     memory: &mut [u8],
     fdstat_ptr: wasm32::uintptr_t,
-) -> Result<host::__wasi_fdstat_t, host::__wasi_errno_t> {
+) -> Result<host::__wasi_fdstat_t> {
     dec_pointee::<wasm32::__wasi_fdstat_t>(memory, fdstat_ptr).map(dec_fdstat)
 }
 
@@ -331,7 +299,7 @@ pub fn enc_fdstat_byref(
     memory: &mut [u8],
     fdstat_ptr: wasm32::uintptr_t,
     host_fdstat: host::__wasi_fdstat_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     let fdstat = enc_fdstat(host_fdstat);
     enc_pointee::<wasm32::__wasi_fdstat_t>(memory, fdstat_ptr, fdstat)
 }
@@ -343,6 +311,7 @@ dec_enc_scalar!(
     enc_filedelta,
     enc_filedelta_byref
 );
+
 dec_enc_scalar!(
     __wasi_filesize_t,
     dec_filesize,
@@ -375,9 +344,7 @@ dec_enc_scalar!(
     enc_oflags_byref
 );
 
-pub fn dec_prestat(
-    prestat: wasm32::__wasi_prestat_t,
-) -> Result<host::__wasi_prestat_t, host::__wasi_errno_t> {
+pub fn dec_prestat(prestat: wasm32::__wasi_prestat_t) -> Result<host::__wasi_prestat_t> {
     match prestat.pr_type {
         wasm32::__WASI_PREOPENTYPE_DIR => {
             let u = host::__wasi_prestat_t___wasi_prestat_u {
@@ -397,13 +364,11 @@ pub fn dec_prestat(
 pub fn dec_prestat_byref(
     memory: &mut [u8],
     prestat_ptr: wasm32::uintptr_t,
-) -> Result<host::__wasi_prestat_t, host::__wasi_errno_t> {
+) -> Result<host::__wasi_prestat_t> {
     dec_pointee::<wasm32::__wasi_prestat_t>(memory, prestat_ptr).and_then(dec_prestat)
 }
 
-pub fn enc_prestat(
-    prestat: host::__wasi_prestat_t,
-) -> Result<wasm32::__wasi_prestat_t, host::__wasi_errno_t> {
+pub fn enc_prestat(prestat: host::__wasi_prestat_t) -> Result<wasm32::__wasi_prestat_t> {
     match prestat.pr_type {
         host::__WASI_PREOPENTYPE_DIR => {
             let u = wasm32::__wasi_prestat_t___wasi_prestat_u {
@@ -424,7 +389,7 @@ pub fn enc_prestat_byref(
     memory: &mut [u8],
     prestat_ptr: wasm32::uintptr_t,
     host_prestat: host::__wasi_prestat_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     let prestat = enc_prestat(host_prestat)?;
     enc_pointee::<wasm32::__wasi_prestat_t>(memory, prestat_ptr, prestat)
 }
@@ -436,6 +401,7 @@ dec_enc_scalar!(
     enc_rights,
     enc_rights_byref
 );
+
 dec_enc_scalar!(
     __wasi_timestamp_t,
     dec_timestamp,
@@ -464,7 +430,7 @@ pub fn enc_usize_byref(
     memory: &mut [u8],
     usize_ptr: wasm32::uintptr_t,
     host_usize: usize,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     enc_pointee::<wasm32::size_t>(memory, usize_ptr, enc_usize(host_usize))
 }
 
@@ -510,7 +476,7 @@ dec_enc_scalar!(
 
 pub fn dec_subscription(
     subscription: &wasm32::__wasi_subscription_t,
-) -> Result<host::__wasi_subscription_t, host::__wasi_errno_t> {
+) -> Result<host::__wasi_subscription_t> {
     let userdata = dec_userdata(subscription.userdata);
     let type_ = dec_eventtype(subscription.type_);
     let u_orig = subscription.u;
diff --git a/src/sys/mod.rs b/src/sys/mod.rs
index ec7071ff38..dcad0ea7fc 100644
--- a/src/sys/mod.rs
+++ b/src/sys/mod.rs
@@ -1,4 +1,4 @@
-use super::host;
+use crate::host;
 use cfg_if::cfg_if;
 
 cfg_if! {
diff --git a/src/sys/unix/fdentry_impl.rs b/src/sys/unix/fdentry_impl.rs
index 2367ff4f7c..9be3954021 100644
--- a/src/sys/unix/fdentry_impl.rs
+++ b/src/sys/unix/fdentry_impl.rs
@@ -1,7 +1,6 @@
 use crate::fdentry::Descriptor;
-use crate::host;
 use crate::sys::errno_from_host;
-
+use crate::{host, Result};
 use std::io;
 use std::os::unix::prelude::{AsRawFd, FileTypeExt, FromRawFd, RawFd};
 
@@ -18,14 +17,11 @@ impl AsRawFd for Descriptor {
 
 pub(crate) fn determine_type_and_access_rights<Fd: AsRawFd>(
     fd: &Fd,
-) -> Result<
-    (
-        host::__wasi_filetype_t,
-        host::__wasi_rights_t,
-        host::__wasi_rights_t,
-    ),
-    host::__wasi_errno_t,
-> {
+) -> Result<(
+    host::__wasi_filetype_t,
+    host::__wasi_rights_t,
+    host::__wasi_rights_t,
+)> {
     let (file_type, mut rights_base, rights_inheriting) = determine_type_rights(fd)?;
 
     use nix::fcntl::{fcntl, OFlag, F_GETFL};
@@ -46,14 +42,11 @@ pub(crate) fn determine_type_and_access_rights<Fd: AsRawFd>(
 
 pub(crate) fn determine_type_rights<Fd: AsRawFd>(
     fd: &Fd,
-) -> Result<
-    (
-        host::__wasi_filetype_t,
-        host::__wasi_rights_t,
-        host::__wasi_rights_t,
-    ),
-    host::__wasi_errno_t,
-> {
+) -> Result<(
+    host::__wasi_filetype_t,
+    host::__wasi_rights_t,
+    host::__wasi_rights_t,
+)> {
     let (file_type, rights_base, rights_inheriting) = {
         // we just make a `File` here for convenience; we don't want it to close when it drops
         let file =
diff --git a/src/sys/unix/host_impl.rs b/src/sys/unix/host_impl.rs
index 461e433748..fa7601a054 100644
--- a/src/sys/unix/host_impl.rs
+++ b/src/sys/unix/host_impl.rs
@@ -2,7 +2,7 @@
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
 #![allow(dead_code)]
-use crate::{host, memory, wasm32};
+use crate::{host, memory, wasm32, Result};
 use std::ffi::OsStr;
 use std::os::unix::prelude::OsStrExt;
 
@@ -196,9 +196,7 @@ pub fn nix_from_filetype(sflags: host::__wasi_filetype_t) -> nix::sys::stat::SFl
     nix_sflags
 }
 
-pub fn filestat_from_nix(
-    filestat: nix::sys::stat::FileStat,
-) -> Result<host::__wasi_filestat_t, host::__wasi_errno_t> {
+pub fn filestat_from_nix(filestat: nix::sys::stat::FileStat) -> Result<host::__wasi_filestat_t> {
     use std::convert::TryFrom;
 
     let filetype = nix::sys::stat::SFlag::from_bits_truncate(filestat.st_mode);
@@ -220,9 +218,7 @@ pub fn filestat_from_nix(
 }
 
 #[cfg(target_os = "linux")]
-pub fn dirent_from_host(
-    host_entry: &nix::libc::dirent,
-) -> Result<wasm32::__wasi_dirent_t, host::__wasi_errno_t> {
+pub fn dirent_from_host(host_entry: &nix::libc::dirent) -> Result<wasm32::__wasi_dirent_t> {
     let mut entry = unsafe { std::mem::zeroed::<wasm32::__wasi_dirent_t>() };
     let d_namlen = unsafe { std::ffi::CStr::from_ptr(host_entry.d_name.as_ptr()) }
         .to_bytes()
@@ -238,9 +234,7 @@ pub fn dirent_from_host(
 }
 
 #[cfg(not(target_os = "linux"))]
-pub fn dirent_from_host(
-    host_entry: &nix::libc::dirent,
-) -> Result<wasm32::__wasi_dirent_t, host::__wasi_errno_t> {
+pub fn dirent_from_host(host_entry: &nix::libc::dirent) -> Result<wasm32::__wasi_dirent_t> {
     let mut entry = unsafe { std::mem::zeroed::<wasm32::__wasi_dirent_t>() };
     entry.d_ino = memory::enc_inode(host_entry.d_ino);
     entry.d_next = memory::enc_dircookie(host_entry.d_seekoff);
@@ -253,6 +247,6 @@ pub fn dirent_from_host(
 ///
 /// NB WASI spec requires OS string to be valid UTF-8. Otherwise,
 /// `__WASI_EILSEQ` error is returned.
-pub fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String, host::__wasi_errno_t> {
+pub fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String> {
     host::path_from_slice(s.as_ref().as_bytes()).map(String::from)
 }
diff --git a/src/sys/unix/hostcalls_impl/fs.rs b/src/sys/unix/hostcalls_impl/fs.rs
index 37e70ee267..6b65d828e5 100644
--- a/src/sys/unix/hostcalls_impl/fs.rs
+++ b/src/sys/unix/hostcalls_impl/fs.rs
@@ -6,7 +6,7 @@ use crate::fdentry::FdEntry;
 use crate::sys::errno_from_host;
 use crate::sys::fdentry_impl::determine_type_rights;
 use crate::sys::host_impl;
-use crate::{host, wasm32};
+use crate::{host, wasm32, Result};
 use nix::libc::{self, c_long, c_void, off_t};
 use std::ffi::CString;
 use std::fs::File;
@@ -17,16 +17,12 @@ pub(crate) fn fd_pread(
     file: &File,
     buf: &mut [u8],
     offset: host::__wasi_filesize_t,
-) -> Result<usize, host::__wasi_errno_t> {
+) -> Result<usize> {
     file.read_at(buf, offset)
         .map_err(|e| e.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
 }
 
-pub(crate) fn fd_pwrite(
-    file: &File,
-    buf: &[u8],
-    offset: host::__wasi_filesize_t,
-) -> Result<usize, host::__wasi_errno_t> {
+pub(crate) fn fd_pwrite(file: &File, buf: &[u8], offset: host::__wasi_filesize_t) -> Result<usize> {
     file.write_at(buf, offset)
         .map_err(|e| e.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
 }
@@ -35,7 +31,7 @@ pub(crate) fn fd_renumber(
     wasi_ctx: &mut WasiCtx,
     from: host::__wasi_fd_t,
     to: host::__wasi_fd_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     let fe_from = match wasi_ctx.fds.get(&from) {
         Some(fe_from) => fe_from,
         None => return Err(host::__WASI_EBADF),
@@ -68,7 +64,7 @@ pub(crate) fn fd_seek(
     fd_entry: &FdEntry,
     offset: host::__wasi_filedelta_t,
     whence: host::__wasi_whence_t,
-) -> Result<u64, host::__wasi_errno_t> {
+) -> Result<u64> {
     use nix::unistd::{lseek, Whence};
     let nwhence = match whence {
         host::__WASI_WHENCE_CUR => Whence::SeekCur,
@@ -85,7 +81,7 @@ pub(crate) fn fd_seek(
     }
 }
 
-pub(crate) fn fd_tell(fd_entry: &FdEntry) -> Result<u64, host::__wasi_errno_t> {
+pub(crate) fn fd_tell(fd_entry: &FdEntry) -> Result<u64> {
     use nix::unistd::{lseek, Whence};
 
     let rawfd = fd_entry.fd_object.descriptor.as_raw_fd();
@@ -95,9 +91,7 @@ pub(crate) fn fd_tell(fd_entry: &FdEntry) -> Result<u64, host::__wasi_errno_t> {
     }
 }
 
-pub(crate) fn fd_fdstat_get(
-    fd_entry: &FdEntry,
-) -> Result<host::__wasi_fdflags_t, host::__wasi_errno_t> {
+pub(crate) fn fd_fdstat_get(fd_entry: &FdEntry) -> Result<host::__wasi_fdflags_t> {
     use nix::fcntl::{fcntl, OFlag, F_GETFL};
 
     let rawfd = fd_entry.fd_object.descriptor.as_raw_fd();
@@ -110,7 +104,7 @@ pub(crate) fn fd_fdstat_get(
 pub(crate) fn fd_fdstat_set_flags(
     fd_entry: &FdEntry,
     fdflags: host::__wasi_fdflags_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     let rawfd = fd_entry.fd_object.descriptor.as_raw_fd();
     let nix_flags = host_impl::nix_from_fdflags(fdflags);
     match nix::fcntl::fcntl(rawfd, nix::fcntl::F_SETFL(nix_flags)) {
@@ -124,7 +118,7 @@ pub(crate) fn fd_advise(
     advice: host::__wasi_advice_t,
     offset: host::__wasi_filesize_t,
     len: host::__wasi_filesize_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     #[cfg(target_os = "linux")]
     {
         let host_advice = match advice {
@@ -164,7 +158,7 @@ pub(crate) fn path_create_directory(
     ctx: &WasiCtx,
     dirfd: host::__wasi_fd_t,
     path: &str,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::libc::mkdirat;
 
     let (dir, path) = match path_get(
@@ -196,7 +190,7 @@ pub(crate) fn path_link(
     new_path: &str,
     source_rights: host::__wasi_rights_t,
     target_rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::libc::linkat;
     let (old_dir, old_path) = match path_get(ctx, old_dirfd, 0, old_path, source_rights, 0, false) {
         Ok((dir, path)) => (dir, path),
@@ -238,7 +232,7 @@ pub(crate) fn path_open(
     mut needed_base: host::__wasi_rights_t,
     mut needed_inheriting: host::__wasi_rights_t,
     fs_flags: host::__wasi_fdflags_t,
-) -> Result<FdEntry, host::__wasi_errno_t> {
+) -> Result<FdEntry> {
     use nix::errno::Errno;
     use nix::fcntl::{openat, AtFlags, OFlag};
     use nix::sys::stat::{fstatat, Mode, SFlag};
@@ -354,7 +348,7 @@ pub(crate) fn fd_readdir(
     fd_entry: &FdEntry,
     host_buf: &mut [u8],
     cookie: host::__wasi_dircookie_t,
-) -> Result<usize, host::__wasi_errno_t> {
+) -> Result<usize> {
     use libc::{dirent, fdopendir, memcpy, readdir_r, seekdir};
 
     let rawfd = fd_entry.fd_object.descriptor.as_raw_fd();
@@ -415,7 +409,7 @@ pub(crate) fn path_readlink(
     path: &str,
     rights: host::__wasi_rights_t,
     buf: &mut [u8],
-) -> Result<usize, host::__wasi_errno_t> {
+) -> Result<usize> {
     use nix::errno::Errno;
 
     let (dir, path) = match path_get(wasi_ctx, dirfd, 0, path, rights, 0, false) {
@@ -459,7 +453,7 @@ pub(crate) fn path_rename(
     new_dirfd: host::__wasi_fd_t,
     new_path: &str,
     new_rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::libc::renameat;
 
     let (old_dir, old_path) = match path_get(wasi_ctx, old_dirfd, 0, old_path, old_rights, 0, false)
@@ -490,9 +484,7 @@ pub(crate) fn path_rename(
     }
 }
 
-pub(crate) fn fd_filestat_get(
-    fd_entry: &FdEntry,
-) -> Result<host::__wasi_filestat_t, host::__wasi_errno_t> {
+pub(crate) fn fd_filestat_get(fd_entry: &FdEntry) -> Result<host::__wasi_filestat_t> {
     use nix::sys::stat::fstat;
 
     let rawfd = fd_entry.fd_object.descriptor.as_raw_fd();
@@ -507,7 +499,7 @@ pub(crate) fn fd_filestat_set_times(
     st_atim: host::__wasi_timestamp_t,
     mut st_mtim: host::__wasi_timestamp_t,
     fst_flags: host::__wasi_fstflags_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::sys::time::{TimeSpec, TimeValLike};
 
     if fst_flags & host::__WASI_FILESTAT_SET_MTIM_NOW != 0 {
@@ -553,7 +545,7 @@ pub(crate) fn fd_filestat_set_times(
 pub(crate) fn fd_filestat_set_size(
     fd_entry: &FdEntry,
     st_size: host::__wasi_filesize_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::unistd::ftruncate;
 
     let rawfd = fd_entry.fd_object.descriptor.as_raw_fd();
@@ -565,7 +557,7 @@ pub(crate) fn path_filestat_get(
     dirfd: host::__wasi_fd_t,
     dirflags: host::__wasi_lookupflags_t,
     path: &str,
-) -> Result<host::__wasi_filestat_t, host::__wasi_errno_t> {
+) -> Result<host::__wasi_filestat_t> {
     use nix::fcntl::AtFlags;
     use nix::sys::stat::fstatat;
 
@@ -601,7 +593,7 @@ pub(crate) fn path_filestat_set_times(
     st_atim: host::__wasi_timestamp_t,
     mut st_mtim: host::__wasi_timestamp_t,
     fst_flags: host::__wasi_fstflags_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::sys::time::{TimeSpec, TimeValLike};
 
     let (dir, path) = match path_get(wasi_ctx, dirfd, dirflags, &path, rights, 0, false) {
@@ -661,7 +653,7 @@ pub(crate) fn path_symlink(
     rights: host::__wasi_rights_t,
     old_path: &str,
     new_path: &str,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::libc::symlinkat;
 
     let (dir, new_path) = match path_get(wasi_ctx, dirfd, 0, new_path, rights, 0, false) {
@@ -690,7 +682,7 @@ pub(crate) fn path_unlink_file(
     dirfd: host::__wasi_fd_t,
     path: &str,
     rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::errno;
     use nix::libc::unlinkat;
 
@@ -741,7 +733,7 @@ pub(crate) fn path_remove_directory(
     dirfd: host::__wasi_fd_t,
     path: &str,
     rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     use nix::errno;
     use nix::libc::{unlinkat, AT_REMOVEDIR};
 
diff --git a/src/sys/unix/hostcalls_impl/fs_helpers.rs b/src/sys/unix/hostcalls_impl/fs_helpers.rs
index 0cb7d40e69..539b965807 100644
--- a/src/sys/unix/hostcalls_impl/fs_helpers.rs
+++ b/src/sys/unix/hostcalls_impl/fs_helpers.rs
@@ -3,9 +3,9 @@
 
 use crate::ctx::WasiCtx;
 use crate::fdentry::Descriptor;
-use crate::host;
 use crate::sys::errno_from_host;
 use crate::sys::host_impl;
+use crate::{host, Result};
 use nix::libc::{self, c_long};
 use std::fs::File;
 use std::path::{Component, Path};
@@ -21,7 +21,7 @@ pub(crate) fn path_get(
     needed_base: host::__wasi_rights_t,
     needed_inheriting: host::__wasi_rights_t,
     needs_final_component: bool,
-) -> Result<(File, String), host::__wasi_errno_t> {
+) -> Result<(File, String)> {
     const MAX_SYMLINK_EXPANSIONS: usize = 128;
 
     if path.contains("\0") {
@@ -186,7 +186,7 @@ pub(crate) fn path_get(
     }
 }
 
-fn openat(dirfd: &File, path: &str) -> Result<File, host::__wasi_errno_t> {
+fn openat(dirfd: &File, path: &str) -> Result<File> {
     use nix::fcntl::{self, OFlag};
     use nix::sys::stat::Mode;
     use std::os::unix::prelude::{AsRawFd, FromRawFd};
@@ -201,7 +201,7 @@ fn openat(dirfd: &File, path: &str) -> Result<File, host::__wasi_errno_t> {
     .map_err(|e| host_impl::errno_from_nix(e.as_errno().unwrap()))
 }
 
-fn readlinkat(dirfd: &File, path: &str) -> Result<String, host::__wasi_errno_t> {
+fn readlinkat(dirfd: &File, path: &str) -> Result<String> {
     use nix::fcntl;
     use std::os::unix::prelude::AsRawFd;
 
diff --git a/src/sys/unix/hostcalls_impl/misc.rs b/src/sys/unix/hostcalls_impl/misc.rs
index 4d3852390c..27edac64d4 100644
--- a/src/sys/unix/hostcalls_impl/misc.rs
+++ b/src/sys/unix/hostcalls_impl/misc.rs
@@ -2,16 +2,13 @@
 #![allow(unused_unsafe)]
 use crate::memory::*;
 use crate::sys::host_impl;
-use crate::{host, wasm32};
-
+use crate::{host, wasm32, Result};
 use nix::convert_ioctl_res;
 use nix::libc::{self, c_int};
 use std::cmp;
 use std::time::SystemTime;
 
-pub(crate) fn clock_res_get(
-    clock_id: host::__wasi_clockid_t,
-) -> Result<host::__wasi_timestamp_t, host::__wasi_errno_t> {
+pub(crate) fn clock_res_get(clock_id: host::__wasi_clockid_t) -> Result<host::__wasi_timestamp_t> {
     // convert the supported clocks to the libc types, or return EINVAL
     let clock_id = match clock_id {
         host::__WASI_CLOCK_REALTIME => libc::CLOCK_REALTIME,
@@ -45,9 +42,7 @@ pub(crate) fn clock_res_get(
         })
 }
 
-pub(crate) fn clock_time_get(
-    clock_id: host::__wasi_clockid_t,
-) -> Result<host::__wasi_timestamp_t, host::__wasi_errno_t> {
+pub(crate) fn clock_time_get(clock_id: host::__wasi_clockid_t) -> Result<host::__wasi_timestamp_t> {
     // convert the supported clocks to the libc types, or return EINVAL
     let clock_id = match clock_id {
         host::__WASI_CLOCK_REALTIME => libc::CLOCK_REALTIME,
@@ -73,9 +68,9 @@ pub(crate) fn clock_time_get(
 }
 
 pub(crate) fn poll_oneoff(
-    input: Vec<Result<host::__wasi_subscription_t, host::__wasi_errno_t>>,
+    input: Vec<Result<host::__wasi_subscription_t>>,
     output_slice: &mut [wasm32::__wasi_event_t],
-) -> Result<wasm32::size_t, host::__wasi_errno_t> {
+) -> Result<wasm32::size_t> {
     let timeout = input
         .iter()
         .filter_map(|event| match event {
@@ -152,7 +147,7 @@ nix::ioctl_read_bad!(fionread, nix::libc::FIONREAD, c_int);
 
 fn wasi_clock_to_relative_ns_delay(
     wasi_clock: host::__wasi_subscription_t___wasi_subscription_u___wasi_subscription_u_clock_t,
-) -> Result<u128, host::__wasi_errno_t> {
+) -> Result<u128> {
     if wasi_clock.flags != wasm32::__WASI_SUBSCRIPTION_CLOCK_ABSTIME {
         return Ok(wasi_clock.timeout as u128);
     }
diff --git a/src/sys/unix/mod.rs b/src/sys/unix/mod.rs
index f634561680..0e39f63cb4 100644
--- a/src/sys/unix/mod.rs
+++ b/src/sys/unix/mod.rs
@@ -2,16 +2,16 @@ pub(crate) mod fdentry_impl;
 pub(crate) mod host_impl;
 pub(crate) mod hostcalls_impl;
 
-use crate::host;
 use crate::sys::errno_from_host;
+use crate::{host, Result};
 use std::fs::File;
 use std::path::Path;
 
-pub(crate) fn dev_null() -> Result<File, host::__wasi_errno_t> {
+pub(crate) fn dev_null() -> Result<File> {
     File::open("/dev/null")
         .map_err(|err| err.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
 }
 
-pub fn preopen_dir<P: AsRef<Path>>(path: P) -> Result<File, host::__wasi_errno_t> {
+pub fn preopen_dir<P: AsRef<Path>>(path: P) -> Result<File> {
     File::open(path).map_err(|err| err.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
 }
diff --git a/src/sys/windows/fdentry_impl.rs b/src/sys/windows/fdentry_impl.rs
index e8d6acbd84..0a0bfdaf0f 100644
--- a/src/sys/windows/fdentry_impl.rs
+++ b/src/sys/windows/fdentry_impl.rs
@@ -1,7 +1,6 @@
 use super::host_impl;
 use crate::fdentry::Descriptor;
-use crate::host;
-
+use crate::{host, Result};
 use std::fs::File;
 use std::io;
 use std::os::windows::prelude::{AsRawHandle, FromRawHandle, RawHandle};
@@ -19,14 +18,11 @@ impl AsRawHandle for Descriptor {
 
 pub(crate) fn determine_type_and_access_rights<Handle: AsRawHandle>(
     handle: &Handle,
-) -> Result<
-    (
-        host::__wasi_filetype_t,
-        host::__wasi_rights_t,
-        host::__wasi_rights_t,
-    ),
-    host::__wasi_errno_t,
-> {
+) -> Result<(
+    host::__wasi_filetype_t,
+    host::__wasi_rights_t,
+    host::__wasi_rights_t,
+)> {
     use winx::file::{get_file_access_rights, AccessRight};
 
     let (file_type, mut rights_base, rights_inheriting) = determine_type_rights(handle)?;
@@ -54,14 +50,11 @@ pub(crate) fn determine_type_and_access_rights<Handle: AsRawHandle>(
 
 pub(crate) fn determine_type_rights<Handle: AsRawHandle>(
     handle: &Handle,
-) -> Result<
-    (
-        host::__wasi_filetype_t,
-        host::__wasi_rights_t,
-        host::__wasi_rights_t,
-    ),
-    host::__wasi_errno_t,
-> {
+) -> Result<(
+    host::__wasi_filetype_t,
+    host::__wasi_rights_t,
+    host::__wasi_rights_t,
+)> {
     let (file_type, rights_base, rights_inheriting) = {
         let file_type =
             winx::file::get_file_type(handle.as_raw_handle()).map_err(host_impl::errno_from_win)?;
diff --git a/src/sys/windows/host_impl.rs b/src/sys/windows/host_impl.rs
index 065868f2b7..b591774c62 100644
--- a/src/sys/windows/host_impl.rs
+++ b/src/sys/windows/host_impl.rs
@@ -2,7 +2,7 @@
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
 #![allow(unused)]
-use crate::host;
+use crate::{host, Result};
 use std::ffi::OsStr;
 use std::os::windows::ffi::OsStrExt;
 
@@ -108,7 +108,7 @@ pub fn win_from_oflags(
 ///
 /// NB WASI spec requires OS string to be valid UTF-8. Otherwise,
 /// `__WASI_EILSEQ` error is returned.
-pub fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String, host::__wasi_errno_t> {
+pub fn path_from_host<S: AsRef<OsStr>>(s: S) -> Result<String> {
     let vec: Vec<u16> = s.as_ref().encode_wide().collect();
     String::from_utf16(&vec).map_err(|_| host::__WASI_EILSEQ)
 }
diff --git a/src/sys/windows/hostcalls_impl/fs.rs b/src/sys/windows/hostcalls_impl/fs.rs
index 671b7c9954..bf3b042c90 100644
--- a/src/sys/windows/hostcalls_impl/fs.rs
+++ b/src/sys/windows/hostcalls_impl/fs.rs
@@ -3,10 +3,10 @@
 use super::fs_helpers::*;
 use crate::ctx::WasiCtx;
 use crate::fdentry::FdEntry;
-use crate::host;
 use crate::sys::errno_from_host;
 use crate::sys::fdentry_impl::determine_type_rights;
 use crate::sys::host_impl;
+use crate::{host, Result};
 use std::fs::File;
 use std::io::{self, Seek, SeekFrom};
 use std::os::windows::fs::FileExt;
@@ -36,16 +36,12 @@ pub(crate) fn fd_pread(
     file: &File,
     buf: &mut [u8],
     offset: host::__wasi_filesize_t,
-) -> Result<usize, host::__wasi_errno_t> {
+) -> Result<usize> {
     read_at(file, buf, offset)
         .map_err(|err| err.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
 }
 
-pub(crate) fn fd_pwrite(
-    file: &File,
-    buf: &[u8],
-    offset: host::__wasi_filesize_t,
-) -> Result<usize, host::__wasi_errno_t> {
+pub(crate) fn fd_pwrite(file: &File, buf: &[u8], offset: host::__wasi_filesize_t) -> Result<usize> {
     write_at(file, buf, offset)
         .map_err(|err| err.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
 }
@@ -54,7 +50,7 @@ pub(crate) fn fd_renumber(
     wasi_ctx: &mut WasiCtx,
     from: host::__wasi_fd_t,
     to: host::__wasi_fd_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("fd_renumber")
 }
 
@@ -62,17 +58,15 @@ pub(crate) fn fd_seek(
     fd_entry: &FdEntry,
     offset: host::__wasi_filedelta_t,
     whence: host::__wasi_whence_t,
-) -> Result<u64, host::__wasi_errno_t> {
+) -> Result<u64> {
     unimplemented!("fd_seek")
 }
 
-pub(crate) fn fd_tell(fd_entry: &FdEntry) -> Result<u64, host::__wasi_errno_t> {
+pub(crate) fn fd_tell(fd_entry: &FdEntry) -> Result<u64> {
     unimplemented!("fd_tell")
 }
 
-pub(crate) fn fd_fdstat_get(
-    fd_entry: &FdEntry,
-) -> Result<host::__wasi_fdflags_t, host::__wasi_errno_t> {
+pub(crate) fn fd_fdstat_get(fd_entry: &FdEntry) -> Result<host::__wasi_fdflags_t> {
     use winx::file::AccessRight;
 
     let raw_handle = fd_entry.fd_object.descriptor.as_raw_handle();
@@ -85,7 +79,7 @@ pub(crate) fn fd_fdstat_get(
 pub(crate) fn fd_fdstat_set_flags(
     fd_entry: &FdEntry,
     fdflags: host::__wasi_fdflags_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("fd_fdstat_set_flags")
 }
 
@@ -94,7 +88,7 @@ pub(crate) fn fd_advise(
     advice: host::__wasi_advice_t,
     offset: host::__wasi_filesize_t,
     len: host::__wasi_filesize_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("fd_advise")
 }
 
@@ -102,7 +96,7 @@ pub(crate) fn path_create_directory(
     ctx: &WasiCtx,
     dirfd: host::__wasi_fd_t,
     path: &str,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("path_create_directory")
 }
 
@@ -114,7 +108,7 @@ pub(crate) fn path_link(
     new_path: &str,
     source_rights: host::__wasi_rights_t,
     target_rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("path_link")
 }
 
@@ -129,7 +123,7 @@ pub(crate) fn path_open(
     mut needed_base: host::__wasi_rights_t,
     mut needed_inheriting: host::__wasi_rights_t,
     fs_flags: host::__wasi_fdflags_t,
-) -> Result<FdEntry, host::__wasi_errno_t> {
+) -> Result<FdEntry> {
     use winx::file::{AccessRight, CreationDisposition, FlagsAndAttributes, ShareMode};
 
     let mut win_rights = AccessRight::READ_CONTROL;
@@ -200,7 +194,7 @@ pub(crate) fn fd_readdir(
     fd_entry: &FdEntry,
     host_buf: &mut [u8],
     cookie: host::__wasi_dircookie_t,
-) -> Result<usize, host::__wasi_errno_t> {
+) -> Result<usize> {
     unimplemented!("fd_readdir")
 }
 
@@ -210,7 +204,7 @@ pub(crate) fn path_readlink(
     path: &str,
     rights: host::__wasi_rights_t,
     buf: &mut [u8],
-) -> Result<usize, host::__wasi_errno_t> {
+) -> Result<usize> {
     unimplemented!("path_readlink")
 }
 
@@ -222,13 +216,11 @@ pub(crate) fn path_rename(
     new_dirfd: host::__wasi_fd_t,
     new_path: &str,
     new_rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("path_rename")
 }
 
-pub(crate) fn fd_filestat_get(
-    fd_entry: &FdEntry,
-) -> Result<host::__wasi_filestat_t, host::__wasi_errno_t> {
+pub(crate) fn fd_filestat_get(fd_entry: &FdEntry) -> Result<host::__wasi_filestat_t> {
     unimplemented!("fd_filestat_get")
 }
 
@@ -237,14 +229,14 @@ pub(crate) fn fd_filestat_set_times(
     st_atim: host::__wasi_timestamp_t,
     mut st_mtim: host::__wasi_timestamp_t,
     fst_flags: host::__wasi_fstflags_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("fd_filestat_set_times")
 }
 
 pub(crate) fn fd_filestat_set_size(
     fd_entry: &FdEntry,
     st_size: host::__wasi_filesize_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("fd_filestat_set_size")
 }
 
@@ -253,7 +245,7 @@ pub(crate) fn path_filestat_get(
     dirfd: host::__wasi_fd_t,
     dirflags: host::__wasi_lookupflags_t,
     path: &str,
-) -> Result<host::__wasi_filestat_t, host::__wasi_errno_t> {
+) -> Result<host::__wasi_filestat_t> {
     unimplemented!("path_filestat_get")
 }
 
@@ -266,7 +258,7 @@ pub(crate) fn path_filestat_set_times(
     st_atim: host::__wasi_timestamp_t,
     mut st_mtim: host::__wasi_timestamp_t,
     fst_flags: host::__wasi_fstflags_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("path_filestat_set_times")
 }
 
@@ -276,7 +268,7 @@ pub(crate) fn path_symlink(
     rights: host::__wasi_rights_t,
     old_path: &str,
     new_path: &str,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("path_symlink")
 }
 
@@ -285,7 +277,7 @@ pub(crate) fn path_unlink_file(
     dirfd: host::__wasi_fd_t,
     path: &str,
     rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("path_unlink_file")
 }
 
@@ -294,6 +286,6 @@ pub(crate) fn path_remove_directory(
     dirfd: host::__wasi_fd_t,
     path: &str,
     rights: host::__wasi_rights_t,
-) -> Result<(), host::__wasi_errno_t> {
+) -> Result<()> {
     unimplemented!("path_remove_directory")
 }
diff --git a/src/sys/windows/hostcalls_impl/fs_helpers.rs b/src/sys/windows/hostcalls_impl/fs_helpers.rs
index 53db390705..7e6a409056 100644
--- a/src/sys/windows/hostcalls_impl/fs_helpers.rs
+++ b/src/sys/windows/hostcalls_impl/fs_helpers.rs
@@ -3,9 +3,9 @@
 
 use crate::ctx::WasiCtx;
 use crate::fdentry::Descriptor;
-use crate::host;
 use crate::sys::errno_from_host;
 use crate::sys::host_impl;
+use crate::{host, Result};
 use std::fs::File;
 use std::os::windows::prelude::{AsRawHandle, FromRawHandle};
 use std::path::{Component, Path};
@@ -19,7 +19,7 @@ pub(crate) fn path_get(
     needed_base: host::__wasi_rights_t,
     needed_inheriting: host::__wasi_rights_t,
     needs_final_component: bool,
-) -> Result<(File, String), host::__wasi_errno_t> {
+) -> Result<(File, String)> {
     if path.contains("\0") {
         // if contains NUL, return EILSEQ
         return Err(host::__WASI_EILSEQ);
diff --git a/src/sys/windows/hostcalls_impl/misc.rs b/src/sys/windows/hostcalls_impl/misc.rs
index 2daac48ab6..f920957753 100644
--- a/src/sys/windows/hostcalls_impl/misc.rs
+++ b/src/sys/windows/hostcalls_impl/misc.rs
@@ -3,25 +3,21 @@
 #![allow(unused)]
 use crate::memory::*;
 use crate::sys::host_impl;
-use crate::{host, wasm32};
+use crate::{host, wasm32, Result};
 
 use wasi_common_cbindgen::wasi_common_cbindgen;
 
-pub(crate) fn clock_res_get(
-    clock_id: host::__wasi_clockid_t,
-) -> Result<host::__wasi_timestamp_t, host::__wasi_errno_t> {
+pub(crate) fn clock_res_get(clock_id: host::__wasi_clockid_t) -> Result<host::__wasi_timestamp_t> {
     unimplemented!("clock_res_get")
 }
 
-pub(crate) fn clock_time_get(
-    clock_id: host::__wasi_clockid_t,
-) -> Result<host::__wasi_timestamp_t, host::__wasi_errno_t> {
+pub(crate) fn clock_time_get(clock_id: host::__wasi_clockid_t) -> Result<host::__wasi_timestamp_t> {
     unimplemented!("clock_time_get")
 }
 
 pub(crate) fn poll_oneoff(
-    input: Vec<Result<host::__wasi_subscription_t, host::__wasi_errno_t>>,
+    input: Vec<Result<host::__wasi_subscription_t>>,
     output_slice: &mut [wasm32::__wasi_event_t],
-) -> Result<wasm32::size_t, host::__wasi_errno_t> {
+) -> Result<wasm32::size_t> {
     unimplemented!("poll_oneoff")
 }
diff --git a/src/sys/windows/mod.rs b/src/sys/windows/mod.rs
index 3e8b24f019..02e562c067 100644
--- a/src/sys/windows/mod.rs
+++ b/src/sys/windows/mod.rs
@@ -2,16 +2,16 @@ pub(crate) mod fdentry_impl;
 pub(crate) mod host_impl;
 pub(crate) mod hostcalls_impl;
 
-use crate::host;
 use crate::sys::errno_from_host;
+use crate::{host, Result};
 use std::fs::File;
 use std::path::Path;
 
-pub(crate) fn dev_null() -> Result<File, host::__wasi_errno_t> {
+pub(crate) fn dev_null() -> Result<File> {
     File::open("NUL").map_err(|err| err.raw_os_error().map_or(host::__WASI_EIO, errno_from_host))
 }
 
-pub fn preopen_dir<P: AsRef<Path>>(path: P) -> Result<File, host::__wasi_errno_t> {
+pub fn preopen_dir<P: AsRef<Path>>(path: P) -> Result<File> {
     use std::fs::OpenOptions;
     use std::os::windows::fs::OpenOptionsExt;
     use winapi::um::winbase::FILE_FLAG_BACKUP_SEMANTICS;