From fa98f0bc91c4c29c7a70db4370bf9d9e43c752f5 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Wed, 17 Feb 2021 13:42:41 -0800
Subject: [PATCH] Fix wiggle tests

---
 crates/wasi-common/WASI                     |   2 +-
 crates/wiggle/generate/src/funcs.rs         |  20 ++-
 crates/wiggle/generate/src/lib.rs           |  17 ++-
 crates/wiggle/generate/src/module_trait.rs  |   2 +
 crates/wiggle/generate/src/types/variant.rs |   4 +-
 crates/wiggle/tests/arrays.rs               |  14 +--
 crates/wiggle/tests/arrays.witx             |  24 ++--
 crates/wiggle/tests/atoms.rs                |   4 +-
 crates/wiggle/tests/atoms.witx              |   5 +-
 crates/wiggle/tests/errno.witx              |   2 +-
 crates/wiggle/tests/errors.rs               |  18 +--
 crates/wiggle/tests/excuse.witx             |   2 +-
 crates/wiggle/tests/flags.rs                |   4 +-
 crates/wiggle/tests/flags.witx              |   5 +-
 crates/wiggle/tests/handles.rs              |   6 +-
 crates/wiggle/tests/handles.witx            |   5 +-
 crates/wiggle/tests/ints.rs                 |   8 +-
 crates/wiggle/tests/ints.witx               |  13 +-
 crates/wiggle/tests/keywords.rs             |   6 +-
 crates/wiggle/tests/keywords_union.witx     |   8 +-
 crates/wiggle/tests/pointers.rs             |   7 +-
 crates/wiggle/tests/pointers.witx           |   2 +-
 crates/wiggle/tests/strings.rs              |   6 +-
 crates/wiggle/tests/strings.witx            |   9 +-
 crates/wiggle/tests/structs.rs              |  12 +-
 crates/wiggle/tests/structs.witx            |  31 +++--
 crates/wiggle/tests/typenames.witx          |  76 +++++------
 crates/wiggle/tests/union.rs                |   8 +-
 crates/wiggle/tests/union.witx              |  21 ++--
 crates/wiggle/tests/wasi.rs                 |   2 +-
 crates/wiggle/tests/wasi.witx               | 132 ++++++++------------
 31 files changed, 236 insertions(+), 239 deletions(-)

diff --git a/crates/wasi-common/WASI b/crates/wasi-common/WASI
index 7c4fd252d0..3b684dd2fc 160000
--- a/crates/wasi-common/WASI
+++ b/crates/wasi-common/WASI
@@ -1 +1 @@
-Subproject commit 7c4fd252d0841488de4a6e724e600f1561797387
+Subproject commit 3b684dd2fcbf87e9854cf6a5c66651ca15e619e3
diff --git a/crates/wiggle/generate/src/funcs.rs b/crates/wiggle/generate/src/funcs.rs
index 8e164f878b..187178e8b6 100644
--- a/crates/wiggle/generate/src/funcs.rs
+++ b/crates/wiggle/generate/src/funcs.rs
@@ -55,6 +55,7 @@ pub fn define_func(
     let mod_name = &module.name.as_str();
     let func_name = &func.name.as_str();
     quote! {
+        #[allow(unreachable_code)] // deals with warnings in noreturn functions
         pub fn #ident(
             ctx: &#ctx_type,
             memory: &dyn #rt::GuestMemory,
@@ -215,7 +216,7 @@ impl witx::Bindgen for Rust<'_> {
                 if func.results.len() > 0 {
                     results.push(quote!(ret));
                 } else if func.noreturn {
-                    self.src.extend(quote!(return Err(ret)));
+                    self.src.extend(quote!(return Err(ret);));
                 }
             }
 
@@ -250,7 +251,9 @@ impl witx::Bindgen for Rust<'_> {
 
             Instruction::VariantPayload => results.push(quote!(e)),
 
-            Instruction::Return { amt: 0 } => {}
+            Instruction::Return { amt: 0 } => {
+                self.src.extend(quote!(return Ok(())));
+            }
             Instruction::Return { amt: 1 } => {
                 let val = operands.pop().unwrap();
                 self.src.extend(quote!(return Ok(#val)));
@@ -278,6 +281,17 @@ impl witx::Bindgen for Rust<'_> {
                 });
             }
 
+            Instruction::Load { ty } => {
+                let ptr = operands.pop().unwrap();
+                let wrap_err = wrap_err(&format!("read {}", ty.name.as_str()));
+                let pointee_type = self.names.type_(&ty.name);
+                results.push(quote! {
+                    #rt::GuestPtr::<#pointee_type>::new(memory, #ptr as u32)
+                        .read()
+                        .map_err(#wrap_err)?
+                });
+            }
+
             Instruction::HandleFromI32 { ty } => {
                 let val = operands.pop().unwrap();
                 let ty = self.names.type_(&ty.name);
@@ -294,7 +308,7 @@ impl witx::Bindgen for Rust<'_> {
 
             // Conversions with matching bit-widths but different signededness
             // use `as` since we're basically just reinterpreting the bits.
-            Instruction::U32FromI32 => {
+            Instruction::U32FromI32 | Instruction::UsizeFromI32 => {
                 let val = operands.pop().unwrap();
                 results.push(quote!(#val as u32));
             }
diff --git a/crates/wiggle/generate/src/lib.rs b/crates/wiggle/generate/src/lib.rs
index 3eb359bc67..2e172633df 100644
--- a/crates/wiggle/generate/src/lib.rs
+++ b/crates/wiggle/generate/src/lib.rs
@@ -6,8 +6,9 @@ mod module_trait;
 mod names;
 mod types;
 
+use heck::ShoutySnakeCase;
 use lifetimes::anon_lifetime;
-use proc_macro2::TokenStream;
+use proc_macro2::{Literal, TokenStream};
 use quote::quote;
 
 pub use config::Config;
@@ -24,6 +25,19 @@ pub fn generate(doc: &witx::Document, names: &Names, errs: &ErrorTransform) -> T
 
     let types = doc.typenames().map(|t| define_datatype(&names, &t));
 
+    let constants = doc.constants().map(|c| {
+        let name = quote::format_ident!(
+            "{}_{}",
+            c.ty.as_str().to_shouty_snake_case(),
+            c.name.as_str().to_shouty_snake_case()
+        );
+        let ty = names.type_(&c.ty);
+        let value = Literal::u64_unsuffixed(c.value);
+        quote! {
+            pub const #name: #ty = #value;
+        }
+    });
+
     let guest_error_methods = doc.error_types().map(|t| {
         let typename = names.type_ref(&t, anon_lifetime());
         let err_method = names.guest_error_conversion_method(&t);
@@ -69,6 +83,7 @@ pub fn generate(doc: &witx::Document, names: &Names, errs: &ErrorTransform) -> T
             use std::convert::TryFrom;
 
             #(#types)*
+            #(#constants)*
             #guest_error_conversion
             #user_error_conversion
         }
diff --git a/crates/wiggle/generate/src/module_trait.rs b/crates/wiggle/generate/src/module_trait.rs
index 92e503ddda..30dae00076 100644
--- a/crates/wiggle/generate/src/module_trait.rs
+++ b/crates/wiggle/generate/src/module_trait.rs
@@ -9,6 +9,8 @@ use witx::Module;
 pub fn passed_by_reference(ty: &witx::Type) -> bool {
     match ty {
         witx::Type::Pointer(_) | witx::Type::ConstPointer(_) | witx::Type::List(_) => true,
+        witx::Type::Record(r) => r.bitflags_repr().is_none(),
+        witx::Type::Variant(v) => !v.is_enum(),
         _ => false,
     }
 }
diff --git a/crates/wiggle/generate/src/types/variant.rs b/crates/wiggle/generate/src/types/variant.rs
index 6568228ded..93df4edb1d 100644
--- a/crates/wiggle/generate/src/types/variant.rs
+++ b/crates/wiggle/generate/src/types/variant.rs
@@ -65,6 +65,7 @@ pub(super) fn define_variant(names: &Names, name: &witx::Id, v: &witx::Variant)
         }
     });
 
+    let mut extra_derive = quote!();
     let enum_try_from = if v.cases.iter().all(|c| c.tref.is_none()) {
         let tryfrom_repr_cases = v.cases.iter().enumerate().map(|(i, c)| {
             let variant_name = names.enum_variant(&c.name);
@@ -72,6 +73,7 @@ pub(super) fn define_variant(names: &Names, name: &witx::Id, v: &witx::Variant)
             quote!(#n => Ok(#ident::#variant_name))
         });
         let abi_ty = names.wasm_type(v.tag_repr.into());
+        extra_derive = quote!(, Copy);
         quote! {
             impl TryFrom<#tag_ty> for #ident {
                 type Error = #rt::GuestError;
@@ -97,7 +99,7 @@ pub(super) fn define_variant(names: &Names, name: &witx::Id, v: &witx::Variant)
     let (enum_lifetime, extra_derive) = if v.needs_lifetime() {
         (quote!(<'a>), quote!())
     } else {
-        (quote!(), quote!(, PartialEq))
+        (quote!(), quote!(, PartialEq #extra_derive))
     };
 
     quote! {
diff --git a/crates/wiggle/tests/arrays.rs b/crates/wiggle/tests/arrays.rs
index b796a212d7..f5e577ba29 100644
--- a/crates/wiggle/tests/arrays.rs
+++ b/crates/wiggle/tests/arrays.rs
@@ -105,7 +105,7 @@ impl ReduceExcusesExcercise {
             self.return_ptr_loc.ptr as i32,
         );
 
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "reduce excuses errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "reduce excuses errno");
 
         let expected = *self
             .excuse_values
@@ -183,7 +183,7 @@ impl PopulateExcusesExcercise {
             self.array_ptr_loc.ptr as i32,
             self.elements.len() as i32,
         );
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "populate excuses errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "populate excuses errno");
 
         let arr: GuestPtr<'_, [GuestPtr<'_, types::Excuse>]> =
             host_memory.ptr((self.array_ptr_loc.ptr, self.elements.len() as u32));
@@ -309,7 +309,7 @@ impl SumElementsExercise {
             self.start_ix as i32,
             self.return_loc.ptr as i32,
         );
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "sum_of_element errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "sum_of_element errno");
         let result_ptr = host_memory.ptr::<i32>(self.return_loc.ptr);
         let result = result_ptr.read().expect("read result");
 
@@ -330,7 +330,7 @@ impl SumElementsExercise {
         );
         assert_eq!(
             res,
-            Ok(types::Errno::InvalidArg.into()),
+            Ok(types::Errno::InvalidArg as i32),
             "out of bounds sum_of_element errno"
         );
 
@@ -346,7 +346,7 @@ impl SumElementsExercise {
         if self.start_ix <= self.end_ix {
             assert_eq!(
                 res,
-                Ok(types::Errno::Ok.into()),
+                Ok(types::Errno::Ok as i32),
                 "expected ok sum_of_elements errno"
             );
             let result_ptr = host_memory.ptr::<i32>(self.return_loc.ptr);
@@ -367,7 +367,7 @@ impl SumElementsExercise {
         } else {
             assert_eq!(
                 res,
-                Ok(types::Errno::InvalidArg.into()),
+                Ok(types::Errno::InvalidArg as i32),
                 "expected error out-of-bounds sum_of_elements"
             );
         }
@@ -384,7 +384,7 @@ impl SumElementsExercise {
         );
         assert_eq!(
             res,
-            Ok(types::Errno::InvalidArg.into()),
+            Ok(types::Errno::InvalidArg as i32),
             "out of bounds sum_of_elements errno"
         );
     }
diff --git a/crates/wiggle/tests/arrays.witx b/crates/wiggle/tests/arrays.witx
index 4b6a1f14c5..3522fc4096 100644
--- a/crates/wiggle/tests/arrays.witx
+++ b/crates/wiggle/tests/arrays.witx
@@ -1,36 +1,36 @@
 (use "errno.witx")
 (use "excuse.witx")
 
-(typename $const_excuse_array (array (@witx const_pointer $excuse)))
-(typename $excuse_array (array (@witx pointer $excuse)))
+(typename $const_excuse_array (list (@witx const_pointer $excuse)))
+(typename $excuse_array (list (@witx pointer $excuse)))
 
 (module $arrays
   (@interface func (export "reduce_excuses")
     (param $excuses $const_excuse_array)
-    (result $error $errno)
-    (result $reduced $excuse)
+    (result $error (expected $excuse (error $errno)))
   )
   (@interface func (export "populate_excuses")
     (param $excuses $excuse_array)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 )
 
 (typename $pair_ints
-  (struct
+  (record
     (field $first s32)
     (field $second s32)))
 
+(typename $s32 s32)
+
 (module $array_traversal
   (@interface func (export "sum_of_element")
-    (param $elements (array $pair_ints))
+    (param $elements (list $pair_ints))
     (param $index (@witx usize))
-    (result $error $errno)
-    (result $sum s32))
+    (result $error (expected $s32 (error $errno))))
 
   (@interface func (export "sum_of_elements")
-    (param $elements (array $pair_ints))
+    (param $elements (list $pair_ints))
     (param $start (@witx usize))
     (param $end (@witx usize))
-    (result $error $errno)
-    (result $sum s32)))
+    (result $error (expected $s32 (error $errno))))
+)
diff --git a/crates/wiggle/tests/atoms.rs b/crates/wiggle/tests/atoms.rs
index f2da4827a8..b39bec5b15 100644
--- a/crates/wiggle/tests/atoms.rs
+++ b/crates/wiggle/tests/atoms.rs
@@ -34,7 +34,7 @@ impl IntFloatExercise {
 
         let e = atoms::int_float_args(&ctx, &host_memory, self.an_int as i32, self.an_float);
 
-        assert_eq!(e, Ok(types::Errno::Ok.into()), "int_float_args error");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "int_float_args error");
     }
 
     pub fn strat() -> BoxedStrategy<Self> {
@@ -72,7 +72,7 @@ impl DoubleIntExercise {
             .ptr::<types::AliasToFloat>(self.return_loc.ptr)
             .read()
             .expect("failed to read return");
-        assert_eq!(e, Ok(types::Errno::Ok.into()), "errno");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "errno");
         assert_eq!(return_val, (self.input as f32) * 2.0, "return val");
     }
 
diff --git a/crates/wiggle/tests/atoms.witx b/crates/wiggle/tests/atoms.witx
index 932d7c9ffd..87144fc3ee 100644
--- a/crates/wiggle/tests/atoms.witx
+++ b/crates/wiggle/tests/atoms.witx
@@ -6,9 +6,8 @@
   (@interface func (export "int_float_args")
     (param $an_int u32)
     (param $an_float f32)
-    (result $error $errno))
+    (result $error (expected (error $errno))))
   (@interface func (export "double_int_return_float")
     (param $an_int u32)
-    (result $error $errno)
-    (result $doubled_it $alias_to_float))
+    (result $error (expected $alias_to_float (error $errno))))
 )
diff --git a/crates/wiggle/tests/errno.witx b/crates/wiggle/tests/errno.witx
index 36ee67622e..845e2389ed 100644
--- a/crates/wiggle/tests/errno.witx
+++ b/crates/wiggle/tests/errno.witx
@@ -1,5 +1,5 @@
 (typename $errno
-    (enum u32
+    (enum (@witx tag u32)
         ;;; Success
         $ok
         ;;; Invalid argument
diff --git a/crates/wiggle/tests/errors.rs b/crates/wiggle/tests/errors.rs
index 4252962469..53d39a233d 100644
--- a/crates/wiggle/tests/errors.rs
+++ b/crates/wiggle/tests/errors.rs
@@ -17,11 +17,11 @@ mod convert_just_errno {
     // trivial function.
     wiggle::from_witx!({
         witx_literal: "
-(typename $errno (enum u8 $ok $invalid_arg $picket_line))
+(typename $errno (enum (@witx tag u8) $ok $invalid_arg $picket_line))
 (module $one_error_conversion
   (@interface func (export \"foo\")
      (param $strike u32)
-     (result $err $errno)))
+     (result $err (expected (error $errno)))))
     ",
         ctx: WasiCtx,
         errors: { errno => RichError },
@@ -68,7 +68,7 @@ mod convert_just_errno {
         let r0 = one_error_conversion::foo(&ctx, &host_memory, 0);
         assert_eq!(
             r0,
-            Ok(i32::from(types::Errno::Ok)),
+            Ok(types::Errno::Ok as i32),
             "Expected return value for strike=0"
         );
         assert!(ctx.log.borrow().is_empty(), "No error log for strike=0");
@@ -77,7 +77,7 @@ mod convert_just_errno {
         let r1 = one_error_conversion::foo(&ctx, &host_memory, 1);
         assert_eq!(
             r1,
-            Ok(i32::from(types::Errno::PicketLine)),
+            Ok(types::Errno::PicketLine as i32),
             "Expected return value for strike=1"
         );
         assert_eq!(
@@ -90,7 +90,7 @@ mod convert_just_errno {
         let r2 = one_error_conversion::foo(&ctx, &host_memory, 2);
         assert_eq!(
             r2,
-            Ok(i32::from(types::Errno::InvalidArg)),
+            Ok(types::Errno::InvalidArg as i32),
             "Expected return value for strike=2"
         );
         assert_eq!(
@@ -120,15 +120,15 @@ mod convert_multiple_error_types {
     // Additionally, test that the function "baz" marked noreturn always returns a wiggle::Trap.
     wiggle::from_witx!({
         witx_literal: "
-(typename $errno (enum u8 $ok $invalid_arg $picket_line))
-(typename $errno2 (enum u8 $ok $too_much_coffee))
+(typename $errno (enum (@witx tag u8) $ok $invalid_arg $picket_line))
+(typename $errno2 (enum (@witx tag u8) $ok $too_much_coffee))
 (module $two_error_conversions
   (@interface func (export \"foo\")
      (param $strike u32)
-     (result $err $errno))
+     (result $err (expected (error $errno))))
   (@interface func (export \"bar\")
      (param $drink u32)
-     (result $err $errno2))
+     (result $err (expected (error $errno2))))
   (@interface func (export \"baz\")
      (param $drink u32)
      (@witx noreturn)))
diff --git a/crates/wiggle/tests/excuse.witx b/crates/wiggle/tests/excuse.witx
index 14a927164e..1aacc92709 100644
--- a/crates/wiggle/tests/excuse.witx
+++ b/crates/wiggle/tests/excuse.witx
@@ -1,5 +1,5 @@
 (typename $excuse
-  (enum u8
+  (enum (@witx tag u8)
      $dog_ate
      $traffic
      $sleeping))
diff --git a/crates/wiggle/tests/flags.rs b/crates/wiggle/tests/flags.rs
index 1a2bb0019f..b97285a94a 100644
--- a/crates/wiggle/tests/flags.rs
+++ b/crates/wiggle/tests/flags.rs
@@ -75,11 +75,11 @@ impl ConfigureCarExercise {
         let res = flags::configure_car(
             &ctx,
             &host_memory,
-            self.old_config.into(),
+            self.old_config.bits() as i32,
             self.other_config_by_ptr.ptr as i32,
             self.return_ptr_loc.ptr as i32,
         );
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "configure car errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "configure car errno");
 
         let res_config = host_memory
             .ptr::<types::CarConfig>(self.return_ptr_loc.ptr)
diff --git a/crates/wiggle/tests/flags.witx b/crates/wiggle/tests/flags.witx
index b46f73d5b5..98dbf911e9 100644
--- a/crates/wiggle/tests/flags.witx
+++ b/crates/wiggle/tests/flags.witx
@@ -1,7 +1,7 @@
 (use "errno.witx")
 
 (typename $car_config
-  (flags u8
+  (flags (@witx repr u8)
     $automatic
     $awd
     $suv))
@@ -10,7 +10,6 @@
   (@interface func (export "configure_car")
     (param $old_config $car_config)
     (param $old_config_by_ptr (@witx const_pointer $car_config))
-    (result $error $errno)
-    (result $new_config $car_config)
+    (result $error (expected $car_config (error $errno)))
   )
 )
diff --git a/crates/wiggle/tests/handles.rs b/crates/wiggle/tests/handles.rs
index 4ad9085a42..d562e0bb14 100644
--- a/crates/wiggle/tests/handles.rs
+++ b/crates/wiggle/tests/handles.rs
@@ -37,7 +37,7 @@ impl HandleExercise {
 
         let e = handle_examples::fd_create(&ctx, &host_memory, self.return_loc.ptr as i32);
 
-        assert_eq!(e, Ok(types::Errno::Ok.into()), "fd_create error");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "fd_create error");
 
         let h_got: u32 = host_memory
             .ptr(self.return_loc.ptr)
@@ -48,13 +48,13 @@ impl HandleExercise {
 
         let e = handle_examples::fd_consume(&ctx, &host_memory, h_got as i32);
 
-        assert_eq!(e, Ok(types::Errno::Ok.into()), "fd_consume error");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "fd_consume error");
 
         let e = handle_examples::fd_consume(&ctx, &host_memory, h_got as i32 + 1);
 
         assert_eq!(
             e,
-            Ok(types::Errno::InvalidArg.into()),
+            Ok(types::Errno::InvalidArg as i32),
             "fd_consume invalid error"
         );
     }
diff --git a/crates/wiggle/tests/handles.witx b/crates/wiggle/tests/handles.witx
index 69c1b0546e..6991d9dc22 100644
--- a/crates/wiggle/tests/handles.witx
+++ b/crates/wiggle/tests/handles.witx
@@ -4,9 +4,8 @@
 
 (module $handle_examples
   (@interface func (export "fd_create")
-    (result $error $errno)
-    (result $fd $fd))
+    (result $error (expected $fd (error $errno))))
   (@interface func (export "fd_consume")
     (param $fd $fd)
-    (result $error $errno))
+    (result $error (expected (error $errno))))
 )
diff --git a/crates/wiggle/tests/ints.rs b/crates/wiggle/tests/ints.rs
index 82d04a4a00..d09615cca6 100644
--- a/crates/wiggle/tests/ints.rs
+++ b/crates/wiggle/tests/ints.rs
@@ -12,7 +12,7 @@ impl_errno!(types::Errno, types::GuestErrorConversion);
 
 impl<'a> ints::Ints for WasiCtx<'a> {
     fn cookie_cutter(&self, init_cookie: types::Cookie) -> Result<types::Bool, types::Errno> {
-        let res = if init_cookie == types::Cookie::START {
+        let res = if init_cookie == types::COOKIE_START {
             types::Bool::True
         } else {
             types::Bool::False
@@ -50,10 +50,10 @@ impl CookieCutterExercise {
         let res = ints::cookie_cutter(
             &ctx,
             &host_memory,
-            self.cookie.into(),
+            self.cookie as i64,
             self.return_ptr_loc.ptr as i32,
         );
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "cookie cutter errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "cookie cutter errno");
 
         let is_cookie_start = host_memory
             .ptr::<types::Bool>(self.return_ptr_loc.ptr)
@@ -66,7 +66,7 @@ impl CookieCutterExercise {
             } else {
                 false
             },
-            self.cookie == types::Cookie::START,
+            self.cookie == types::COOKIE_START,
             "returned Bool should test if input was Cookie::START",
         );
     }
diff --git a/crates/wiggle/tests/ints.witx b/crates/wiggle/tests/ints.witx
index 09dc62f5ec..2ad73600a2 100644
--- a/crates/wiggle/tests/ints.witx
+++ b/crates/wiggle/tests/ints.witx
@@ -1,18 +1,13 @@
 (use "errno.witx")
 
-(typename $cookie
-  (int u64
-    (const $start 0)))
+(typename $cookie u64)
+(@witx const $cookie $start 0)
 
-(typename $bool
-  (enum u8
-    $false
-    $true))
+(typename $bool bool)
 
 (module $ints
   (@interface func (export "cookie_cutter")
     (param $init_cookie $cookie)
-    (result $error $errno)
-    (result $is_start $bool)
+    (result $error (expected $bool (error $errno)))
   )
 )
diff --git a/crates/wiggle/tests/keywords.rs b/crates/wiggle/tests/keywords.rs
index bc1ee4edce..1aa84e188a 100644
--- a/crates/wiggle/tests/keywords.rs
+++ b/crates/wiggle/tests/keywords.rs
@@ -8,7 +8,7 @@ mod enum_test {
     wiggle::from_witx!({
         witx_literal:
             "(typename $self
-                 (enum u8
+                 (enum (@witx tag u8)
                      $self
                      $2big
                  )
@@ -35,7 +35,7 @@ mod module_trait_fn_and_arg_test {
     });
     impl<'a> self_::Self_ for WasiCtx<'a> {
         #[allow(unused_variables)]
-        fn fn_(&self, use_: u32, virtual_: u32) -> Result<(), ()> {
+        fn fn_(&self, use_: u32, virtual_: u32) {
             unimplemented!();
         }
     }
@@ -46,7 +46,7 @@ mod struct_test {
     wiggle::from_witx!({
         witx_literal:
             "(typename $self
-                 (struct
+                 (record
                      (field $become s32)
                      (field $mut s32)
                  )
diff --git a/crates/wiggle/tests/keywords_union.witx b/crates/wiggle/tests/keywords_union.witx
index 14d29b70dd..7e3dcf99bf 100644
--- a/crates/wiggle/tests/keywords_union.witx
+++ b/crates/wiggle/tests/keywords_union.witx
@@ -1,15 +1,15 @@
 (typename $union
-  (enum u8
+  (enum (@witx tag u8)
     $self
     $power
   )
 )
 
 (typename $self
-  (union $union
+  (variant (@witx tag $union)
     ;; A union variant that will expand to a strict keyword `Self`.
-    (field $self (@witx pointer f32))
+    (case $self (@witx pointer f32))
     ;; Oh it's true, that there's power in a union!
-    (field $power (@witx pointer f32))
+    (case $power (@witx pointer f32))
   )
 )
diff --git a/crates/wiggle/tests/pointers.rs b/crates/wiggle/tests/pointers.rs
index 5bc2719480..ebae550fc3 100644
--- a/crates/wiggle/tests/pointers.rs
+++ b/crates/wiggle/tests/pointers.rs
@@ -152,12 +152,12 @@ impl PointersAndEnumsExercise {
         let e = pointers::pointers_and_enums(
             &ctx,
             &host_memory,
-            self.input1.into(),
+            self.input1 as i32,
             self.input2_loc.ptr as i32,
             self.input3_loc.ptr as i32,
             self.input4_ptr_loc.ptr as i32,
         );
-        assert_eq!(e, Ok(types::Errno::Ok.into()), "errno");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "errno");
 
         // Implementation of pointers_and_enums writes input3 to the input2_loc:
         let written_to_input2_loc: i32 = host_memory
@@ -166,8 +166,7 @@ impl PointersAndEnumsExercise {
             .expect("input2 ref");
 
         assert_eq!(
-            written_to_input2_loc,
-            self.input3.into(),
+            written_to_input2_loc, self.input3 as i32,
             "pointers_and_enums written to input2"
         );
 
diff --git a/crates/wiggle/tests/pointers.witx b/crates/wiggle/tests/pointers.witx
index 9a73a37520..f5243b667e 100644
--- a/crates/wiggle/tests/pointers.witx
+++ b/crates/wiggle/tests/pointers.witx
@@ -7,5 +7,5 @@
     (param $an_excuse_by_reference (@witx pointer $excuse))
     (param $a_lamer_excuse (@witx const_pointer $excuse))
     (param $two_layers_of_excuses (@witx pointer (@witx const_pointer $excuse)))
-    (result $error $errno))
+    (result $error (expected (error $errno))))
 )
diff --git a/crates/wiggle/tests/strings.rs b/crates/wiggle/tests/strings.rs
index a55917e4df..0caeb73782 100644
--- a/crates/wiggle/tests/strings.rs
+++ b/crates/wiggle/tests/strings.rs
@@ -88,7 +88,7 @@ impl HelloStringExercise {
             self.test_word.len() as i32,
             self.return_ptr_loc.ptr as i32,
         );
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "hello string errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "hello string errno");
 
         let given = host_memory
             .ptr::<u32>(self.return_ptr_loc.ptr)
@@ -209,7 +209,7 @@ impl MultiStringExercise {
             self.c.len() as i32,
             self.return_ptr_loc.ptr as i32,
         );
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "multi string errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "multi string errno");
 
         let given = host_memory
             .ptr::<u32>(self.return_ptr_loc.ptr)
@@ -287,7 +287,7 @@ impl OverlappingStringExercise {
             a_len - self.offset_c as i32,
             self.return_ptr_loc.ptr as i32,
         );
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "multi string errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "multi string errno");
 
         let given = host_memory
             .ptr::<u32>(self.return_ptr_loc.ptr)
diff --git a/crates/wiggle/tests/strings.witx b/crates/wiggle/tests/strings.witx
index b3531e87bb..918c1b327a 100644
--- a/crates/wiggle/tests/strings.witx
+++ b/crates/wiggle/tests/strings.witx
@@ -1,16 +1,17 @@
 (use "errno.witx")
+
+(typename $ret u32)
+
 (module $strings
   (@interface func (export "hello_string")
     (param $a_string string)
-    (result $error $errno)
-    (result $total_bytes u32)
+    (result $error (expected $ret (error $errno)))
   )
 
   (@interface func (export "multi_string")
     (param $a string)
     (param $b string)
     (param $c string)
-    (result $error $errno)
-    (result $total_bytes u32)
+    (result $error (expected $ret (error $errno)))
   )
 )
diff --git a/crates/wiggle/tests/structs.rs b/crates/wiggle/tests/structs.rs
index 9e92f1b86e..537ac0afb5 100644
--- a/crates/wiggle/tests/structs.rs
+++ b/crates/wiggle/tests/structs.rs
@@ -118,7 +118,7 @@ impl SumOfPairExercise {
             self.return_loc.ptr as i32,
         );
 
-        assert_eq!(sum_err, Ok(types::Errno::Ok.into()), "sum errno");
+        assert_eq!(sum_err, Ok(types::Errno::Ok as i32), "sum errno");
 
         let return_val: i64 = host_memory
             .ptr(self.return_loc.ptr)
@@ -218,7 +218,7 @@ impl SumPairPtrsExercise {
 
         assert_eq!(
             res,
-            Ok(types::Errno::Ok.into()),
+            Ok(types::Errno::Ok as i32),
             "sum of pair of ptrs errno"
         );
 
@@ -299,7 +299,7 @@ impl SumIntAndPtrExercise {
             self.return_loc.ptr as i32,
         );
 
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "sum of int and ptr errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "sum of int and ptr errno");
 
         let doubled: i64 = host_memory
             .ptr(self.return_loc.ptr)
@@ -338,7 +338,7 @@ impl ReturnPairInts {
 
         let err = structs::return_pair_ints(&ctx, &host_memory, self.return_loc.ptr as i32);
 
-        assert_eq!(err, Ok(types::Errno::Ok.into()), "return struct errno");
+        assert_eq!(err, Ok(types::Errno::Ok as i32), "return struct errno");
 
         let return_struct: types::PairInts = host_memory
             .ptr(self.return_loc.ptr)
@@ -420,7 +420,7 @@ impl ReturnPairPtrsExercise {
 
         assert_eq!(
             res,
-            Ok(types::Errno::Ok.into()),
+            Ok(types::Errno::Ok as i32),
             "return pair of ptrs errno"
         );
 
@@ -530,7 +530,7 @@ impl SumArrayExercise {
         );
 
         // should be no error - if hostcall did a GuestError it should eprintln it.
-        assert_eq!(res, Ok(types::Errno::Ok.into()), "reduce excuses errno");
+        assert_eq!(res, Ok(types::Errno::Ok as i32), "reduce excuses errno");
 
         // Sum is inputs upcasted to u16
         let expected: u16 = self.inputs.iter().map(|v| *v as u16).sum();
diff --git a/crates/wiggle/tests/structs.witx b/crates/wiggle/tests/structs.witx
index 2a64b125f9..16f5ced8ec 100644
--- a/crates/wiggle/tests/structs.witx
+++ b/crates/wiggle/tests/structs.witx
@@ -2,49 +2,46 @@
 (use "errno.witx")
 
 (typename $pair_ints
-  (struct
+  (record
     (field $first s32)
     (field $second s32)))
 
 (typename $pair_int_ptrs
-  (struct
+  (record
     (field $first (@witx const_pointer s32))
     (field $second (@witx const_pointer s32))))
 
 (typename $pair_int_and_ptr
-  (struct
+  (record
     (field $first (@witx const_pointer s32))
     (field $second s32)))
 
-(typename $some_bytes (array u8))
+(typename $some_bytes (list u8))
 
 (typename $struct_of_array
-  (struct
+  (record
     (field $arr $some_bytes)))
 
+(typename $s64 s64)
+(typename $u16 u16)
+
 (module $structs
   (@interface func (export "sum_of_pair")
     (param $an_pair $pair_ints)
-    (result $error $errno)
-    (result $doubled s64))
+    (result $error (expected $s64 (error $errno))))
   (@interface func (export "sum_of_pair_of_ptrs")
     (param $an_pair $pair_int_ptrs)
-    (result $error $errno)
-    (result $doubled s64))
+    (result $error (expected $s64 (error $errno))))
   (@interface func (export "sum_of_int_and_ptr")
     (param $an_pair $pair_int_and_ptr)
-    (result $error $errno)
-    (result $double s64))
+    (result $error (expected $s64 (error $errno))))
   (@interface func (export "return_pair_ints")
-    (result $error $errno)
-    (result $an_pair $pair_ints))
+    (result $error (expected $pair_ints (error $errno))))
   (@interface func (export "return_pair_of_ptrs")
     (param $first (@witx const_pointer s32))
     (param $second (@witx const_pointer s32))
-    (result $error $errno)
-    (result $an_pair $pair_int_ptrs))
+    (result $error (expected $pair_int_ptrs (error $errno))))
   (@interface func (export "sum_array")
     (param $an_arr $struct_of_array)
-    (result $error $errno)
-    (result $doubled u16))
+    (result $error (expected $u16 (error $errno))))
 )
diff --git a/crates/wiggle/tests/typenames.witx b/crates/wiggle/tests/typenames.witx
index 1351fc4e13..df60c5c34e 100644
--- a/crates/wiggle/tests/typenames.witx
+++ b/crates/wiggle/tests/typenames.witx
@@ -15,7 +15,7 @@
 
 ;;; Identifiers for clocks.
 (typename $clockid
-  (enum u32
+  (enum (@witx tag u32)
     ;;; The clock measuring real time. Time value zero corresponds with
     ;;; 1970-01-01T00:00:00Z.
     $realtime
@@ -36,7 +36,7 @@
 ;;; API; some are used in higher-level library layers, and others are provided
 ;;; merely for alignment with POSIX.
 (typename $errno
-  (enum u16
+  (enum (@witx tag u16)
     ;;; No error occurred. System call completed successfully.
     $success
     ;;; Argument list too long.
@@ -196,7 +196,7 @@
 
 ;;; File descriptor rights, determining which actions may be performed.
 (typename $rights
-  (flags u64
+  (flags (@witx repr u64)
     ;;; The right to invoke `fd_datasync`.
     ;;
     ;;; If `path_open` is set, includes the right to invoke
@@ -278,7 +278,7 @@
 
 ;;; A region of memory for scatter/gather reads.
 (typename $iovec
-  (struct
+  (record
     ;;; The address of the buffer to be filled.
     (field $buf (@witx pointer u8))
     ;;; The length of the buffer to be filled.
@@ -288,7 +288,7 @@
 
 ;;; A region of memory for scatter/gather writes.
 (typename $ciovec
-  (struct
+  (record
     ;;; The address of the buffer to be written.
     (field $buf (@witx const_pointer u8))
     ;;; The length of the buffer to be written.
@@ -296,15 +296,15 @@
   )
 )
 
-(typename $iovec_array (array $iovec))
-(typename $ciovec_array (array $ciovec))
+(typename $iovec_array (list $iovec))
+(typename $ciovec_array (list $ciovec))
 
 ;;; Relative offset within a file.
 (typename $filedelta s64)
 
 ;;; The position relative to which to set the offset of the file descriptor.
 (typename $whence
-  (enum u8
+  (enum (@witx tag u8)
     ;;; Seek relative to start-of-file.
     $set
     ;;; Seek relative to current position.
@@ -327,7 +327,7 @@
 
 ;;; The type of a file descriptor or file.
 (typename $filetype
-  (enum u8
+  (enum (@witx tag u8)
     ;;; The type of the file descriptor or file is unknown or is different from any of the other types specified.
     $unknown
     ;;; The file descriptor or file refers to a block device inode.
@@ -349,7 +349,7 @@
 
 ;;; A directory entry.
 (typename $dirent
-  (struct
+  (record
     ;;; The offset of the next directory entry stored in this directory.
     (field $d_next $dircookie)
     ;;; The serial number of the file referred to by this directory entry.
@@ -363,7 +363,7 @@
 
 ;;; File or memory access pattern advisory information.
 (typename $advice
-  (enum u8
+  (enum (@witx tag u8)
     ;;; The application has no advice to give on its behavior with respect to the specified data.
     $normal
     ;;; The application expects to access the specified data sequentially from lower offsets to higher offsets.
@@ -381,7 +381,7 @@
 
 ;;; File descriptor flags.
 (typename $fdflags
-  (flags u16
+  (flags (@witx repr u16)
     ;;; Append mode: Data written to the file is always appended to the file's end.
     $append
     ;;; Write according to synchronized I/O data integrity completion. Only the data stored in the file is synchronized.
@@ -399,7 +399,7 @@
 
 ;;; File descriptor attributes.
 (typename $fdstat
-  (struct
+  (record
     ;;; File type.
     (field $fs_filetype $filetype)
     ;;; File descriptor flags.
@@ -418,7 +418,7 @@
 
 ;;; Which file time attributes to adjust.
 (typename $fstflags
-  (flags u16
+  (flags (@witx repr u16)
     ;;; Adjust the last data access timestamp to the value stored in `filestat::atim`.
     $atim
     ;;; Adjust the last data access timestamp to the time of clock `clockid::realtime`.
@@ -432,7 +432,7 @@
 
 ;;; Flags determining the method of how paths are resolved.
 (typename $lookupflags
-  (flags u32
+  (flags (@witx repr u32)
     ;;; As long as the resolved path corresponds to a symbolic link, it is expanded.
     $symlink_follow
   )
@@ -440,7 +440,7 @@
 
 ;;; Open flags used by `path_open`.
 (typename $oflags
-  (flags u16
+  (flags (@witx repr u16)
     ;;; Create file if it does not exist.
     $creat
     ;;; Fail if not a directory.
@@ -457,7 +457,7 @@
 
 ;;; File attributes.
 (typename $filestat
-  (struct
+  (record
     ;;; Device ID of device containing the file.
     (field $dev $device)
     ;;; File serial number.
@@ -483,7 +483,7 @@
 
 ;;; Type of a subscription to an event or its occurrence.
 (typename $eventtype
-  (enum u8
+  (enum (@witx tag u8)
     ;;; The time value of clock `subscription_clock::id` has
     ;;; reached timestamp `subscription_clock::timeout`.
     $clock
@@ -499,7 +499,7 @@
 ;;; The state of the file descriptor subscribed to with
 ;;; `eventtype::fd_read` or `eventtype::fd_write`.
 (typename $eventrwflags
-  (flags u16
+  (flags (@witx repr u16)
     ;;; The peer of this socket has closed or disconnected.
     $fd_readwrite_hangup
   )
@@ -508,7 +508,7 @@
 ;;; The contents of an $event when type is `eventtype::fd_read` or
 ;;; `eventtype::fd_write`.
 (typename $event_fd_readwrite
-  (struct
+  (record
     ;;; The number of bytes available for reading or writing.
     (field $nbytes $filesize)
     ;;; The state of the file descriptor.
@@ -518,7 +518,7 @@
 
 ;;; An event that occurred.
 (typename $event
-  (struct
+  (record
     ;;; User-provided value that got attached to `subscription::userdata`.
     (field $userdata $userdata)
     ;;; If non-zero, an error that occurred while processing the subscription request.
@@ -534,7 +534,7 @@
 ;;; Flags determining how to interpret the timestamp provided in
 ;;; `subscription_clock::timeout`.
 (typename $subclockflags
-  (flags u16
+  (flags (@witx repr u16)
     ;;; If set, treat the timestamp provided in
     ;;; `subscription_clock::timeout` as an absolute timestamp of clock
     ;;; `subscription_clock::id`. If clear, treat the timestamp
@@ -546,7 +546,7 @@
 
 ;;; The contents of a `subscription` when type is `eventtype::clock`.
 (typename $subscription_clock
-  (struct
+  (record
     ;;; The clock against which to compare the timestamp.
     (field $id $clockid)
     ;;; The absolute or relative timestamp.
@@ -562,7 +562,7 @@
 ;;; The contents of a `subscription` when type is type is
 ;;; `eventtype::fd_read` or `eventtype::fd_write`.
 (typename $subscription_fd_readwrite
-  (struct
+  (record
     ;;; The file descriptor on which to wait for it to become ready for reading or writing.
     (field $file_descriptor $fd)
   )
@@ -570,16 +570,16 @@
 
 ;;; The contents of a `subscription`.
 (typename $subscription_u
-  (union $eventtype
-    (field $clock $subscription_clock)
-    (field $fd_read  $subscription_fd_readwrite)
-    (field $fd_write $subscription_fd_readwrite)
+  (union (@witx tag $eventtype)
+    $subscription_clock
+    $subscription_fd_readwrite
+    $subscription_fd_readwrite
   )
 )
 
 ;;; Subscription to an event.
 (typename $subscription
-  (struct
+  (record
     ;;; User-provided value that is attached to the subscription in the
     ;;; implementation and returned through `event::userdata`.
     (field $userdata $userdata)
@@ -593,7 +593,7 @@
 
 ;;; Signal condition.
 (typename $signal
-  (enum u8
+  (enum (@witx tag u8)
     ;;; No signal. Note that POSIX has special semantics for `kill(pid, 0)`,
     ;;; so this value is reserved.
     $none
@@ -606,7 +606,7 @@
     ;;; Terminal quit signal.
     ;;; Action: Terminates the process.
     $quit
-    ;;; Illegal instruction.
+    ;;; Illegal inrecordion.
     ;;; Action: Terminates the process.
     $ill
     ;;; Trace/breakpoint trap.
@@ -692,7 +692,7 @@
 
 ;;; Flags provided to `sock_recv`.
 (typename $riflags
-  (flags u16
+  (flags (@witx repr u16)
     ;;; Returns the message without removing it from the socket's receive queue.
     $recv_peek
     ;;; On byte-stream sockets, block until the full amount of data can be returned.
@@ -702,7 +702,7 @@
 
 ;;; Flags returned by `sock_recv`.
 (typename $roflags
-  (flags u16
+  (flags (@witx repr u16)
     ;;; Returned by `sock_recv`: Message data has been truncated.
     $recv_data_truncated
   )
@@ -714,7 +714,7 @@
 
 ;;; Which channels on a socket to shut down.
 (typename $sdflags
-  (flags u8
+  (flags (@witx repr u8)
     ;;; Disables further receive operations.
     $rd
     ;;; Disables further send operations.
@@ -724,7 +724,7 @@
 
 ;;; Identifiers for preopened capabilities.
 (typename $preopentype
-  (enum u8
+  (enum (@witx tag u8)
     ;;; A pre-opened directory.
     $dir
   )
@@ -732,7 +732,7 @@
 
 ;;; The contents of a $prestat when type is `preopentype::dir`.
 (typename $prestat_dir
-  (struct
+  (record
     ;;; The length of the directory name for use with `fd_prestat_dir_name`.
     (field $pr_name_len $size)
   )
@@ -740,7 +740,7 @@
 
 ;;; Information about a pre-opened capability.
 (typename $prestat
-  (union $preopentype
-    (field $dir $prestat_dir)
+  (union (@witx tag $preopentype)
+    $prestat_dir
   )
 )
diff --git a/crates/wiggle/tests/union.rs b/crates/wiggle/tests/union.rs
index 22a9f967ec..04a1f4cce0 100644
--- a/crates/wiggle/tests/union.rs
+++ b/crates/wiggle/tests/union.rs
@@ -108,7 +108,7 @@ impl GetTagExercise {
         let ctx = WasiCtx::new();
         let host_memory = HostMemory::new();
 
-        let discriminant: u8 = reason_tag(&self.input).into();
+        let discriminant = reason_tag(&self.input) as u8;
         host_memory
             .ptr(self.input_loc.ptr)
             .write(discriminant)
@@ -133,7 +133,7 @@ impl GetTagExercise {
             self.return_loc.ptr as i32,
         );
 
-        assert_eq!(e, Ok(types::Errno::Ok.into()), "get_tag errno");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "get_tag errno");
 
         let return_val: types::Excuse = host_memory
             .ptr(self.return_loc.ptr)
@@ -185,7 +185,7 @@ impl ReasonMultExercise {
         let ctx = WasiCtx::new();
         let host_memory = HostMemory::new();
 
-        let discriminant: u8 = reason_tag(&self.input).into();
+        let discriminant = reason_tag(&self.input) as u8;
         host_memory
             .ptr(self.input_loc.ptr)
             .write(discriminant)
@@ -217,7 +217,7 @@ impl ReasonMultExercise {
             self.multiply_by as i32,
         );
 
-        assert_eq!(e, Ok(types::Errno::Ok.into()), "reason_mult errno");
+        assert_eq!(e, Ok(types::Errno::Ok as i32), "reason_mult errno");
 
         match self.input {
             types::Reason::DogAte(f) => {
diff --git a/crates/wiggle/tests/union.witx b/crates/wiggle/tests/union.witx
index d76f150ddd..0559666b8a 100644
--- a/crates/wiggle/tests/union.witx
+++ b/crates/wiggle/tests/union.witx
@@ -5,27 +5,26 @@
 ;; Fight for the full product of your labor!
 
 (typename $reason
-  (union $excuse
-    (field $dog_ate f32)
-    (field $traffic s32)
-    (empty $sleeping)))
+  (variant (@witx tag $excuse)
+    (case $dog_ate f32)
+    (case $traffic s32)
+    (case $sleeping)))
 
 (typename $reason_mut
-  (union $excuse
-    (field $dog_ate (@witx pointer f32))
-    (field $traffic (@witx pointer s32))
-    (empty $sleeping)))
+  (variant (@witx tag $excuse)
+    (case $dog_ate (@witx pointer f32))
+    (case $traffic (@witx pointer s32))
+    (case $sleeping)))
 
 (module $union_example
   (@interface func (export "get_tag")
     (param $r $reason)
-    (result $error $errno)
-    (result $t $excuse)
+    (result $error (expected $excuse (error $errno)))
   )
 
   (@interface func (export "reason_mult")
     (param $r $reason_mut)
     (param $multiply_by u32)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 )
diff --git a/crates/wiggle/tests/wasi.rs b/crates/wiggle/tests/wasi.rs
index 07b56db62a..95c1461526 100644
--- a/crates/wiggle/tests/wasi.rs
+++ b/crates/wiggle/tests/wasi.rs
@@ -322,7 +322,7 @@ impl<'a> crate::wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx<'a> {
         unimplemented!("poll_oneoff")
     }
 
-    fn proc_exit(&self, _rval: types::Exitcode) -> std::result::Result<(), ()> {
+    fn proc_exit(&self, _rval: types::Exitcode) -> wiggle::Trap {
         unimplemented!("proc_exit")
     }
 
diff --git a/crates/wiggle/tests/wasi.witx b/crates/wiggle/tests/wasi.witx
index 98cd947878..df3c670f3e 100644
--- a/crates/wiggle/tests/wasi.witx
+++ b/crates/wiggle/tests/wasi.witx
@@ -17,15 +17,13 @@
   (@interface func (export "args_get")
     (param $argv (@witx pointer (@witx pointer u8)))
     (param $argv_buf (@witx pointer u8))
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
   ;;; Return command-line argument data sizes.
   (@interface func (export "args_sizes_get")
-    (result $error $errno)
-    ;;; The number of arguments.
-    (result $argc $size)
-    ;;; The size of the argument string data.
-    (result $argv_buf_size $size)
+    ;;; Returns the number of arguments and the size of the argument string
+    ;;; data, or an error.
+    (result $error (expected (tuple $size $size) (error $errno)))
   )
 
   ;;; Read environment variable data.
@@ -33,15 +31,13 @@
   (@interface func (export "environ_get")
     (param $environ (@witx pointer (@witx pointer u8)))
     (param $environ_buf (@witx pointer u8))
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
   ;;; Return environment variable data sizes.
   (@interface func (export "environ_sizes_get")
-    (result $error $errno)
-    ;;; The number of environment variable arguments.
-    (result $environc $size)
-    ;;; The size of the environment variable data.
-    (result $environ_buf_size $size)
+    ;;; Returns the number of environment variable arguments and the size of the
+    ;;; environment variable data.
+    (result $error (expected (tuple $size $size) (error $errno)))
   )
 
   ;;; Return the resolution of a clock.
@@ -51,9 +47,8 @@
   (@interface func (export "clock_res_get")
     ;;; The clock for which to return the resolution.
     (param $id $clockid)
-    (result $error $errno)
-    ;;; The resolution of the clock.
-    (result $resolution $timestamp)
+    ;;; The resolution of the clock, or an error if one happened.
+    (result $error (expected $timestamp (error $errno)))
   )
   ;;; Return the time value of a clock.
   ;;; Note: This is similar to `clock_gettime` in POSIX.
@@ -62,9 +57,8 @@
     (param $id $clockid)
     ;;; The maximum lag (exclusive) that the returned time value may have, compared to its actual value.
     (param $precision $timestamp)
-    (result $error $errno)
     ;;; The time value of the clock.
-    (result $time $timestamp)
+    (result $error (expected $timestamp (error $errno)))
   )
 
   ;;; Provide file advisory information on a file descriptor.
@@ -77,7 +71,7 @@
     (param $len $filesize)
     ;;; The advice.
     (param $advice $advice)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Force the allocation of space in a file.
@@ -88,30 +82,29 @@
     (param $offset $filesize)
     ;;; The length of the area that is allocated.
     (param $len $filesize)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Close a file descriptor.
   ;;; Note: This is similar to `close` in POSIX.
   (@interface func (export "fd_close")
     (param $fd $fd)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Synchronize the data of a file to disk.
   ;;; Note: This is similar to `fdatasync` in POSIX.
   (@interface func (export "fd_datasync")
     (param $fd $fd)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Get the attributes of a file descriptor.
   ;;; Note: This returns similar flags to `fsync(fd, F_GETFL)` in POSIX, as well as additional fields.
   (@interface func (export "fd_fdstat_get")
     (param $fd $fd)
-    (result $error $errno)
     ;;; The buffer where the file descriptor's attributes are stored.
-    (result $stat $fdstat)
+    (result $error (expected $fdstat (error $errno)))
   )
 
   ;;; Adjust the flags associated with a file descriptor.
@@ -120,7 +113,7 @@
     (param $fd $fd)
     ;;; The desired values of the file descriptor flags.
     (param $flags $fdflags)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Adjust the rights associated with a file descriptor.
@@ -130,15 +123,14 @@
     ;;; The desired rights of the file descriptor.
     (param $fs_rights_base $rights)
     (param $fs_rights_inheriting $rights)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Return the attributes of an open file.
   (@interface func (export "fd_filestat_get")
     (param $fd $fd)
-    (result $error $errno)
     ;;; The buffer where the file's attributes are stored.
-    (result $buf $filestat)
+    (result $error (expected $filestat (error $errno)))
   )
 
   ;;; Adjust the size of an open file. If this increases the file's size, the extra bytes are filled with zeros.
@@ -147,7 +139,7 @@
     (param $fd $fd)
     ;;; The desired file size.
     (param $size $filesize)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Adjust the timestamps of an open file or directory.
@@ -160,7 +152,7 @@
     (param $mtim $timestamp)
     ;;; A bitmask indicating which timestamps to adjust.
     (param $fst_flags $fstflags)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Read from a file descriptor, without using and updating the file descriptor's offset.
@@ -171,17 +163,15 @@
     (param $iovs $iovec_array)
     ;;; The offset within the file at which to read.
     (param $offset $filesize)
-    (result $error $errno)
     ;;; The number of bytes read.
-    (result $nread $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Return a description of the given preopened file descriptor.
   (@interface func (export "fd_prestat_get")
     (param $fd $fd)
-    (result $error $errno)
     ;;; The buffer where the description is stored.
-    (result $buf $prestat)
+    (result $error (expected $prestat (error $errno)))
   )
 
   ;;; Return a description of the given preopened file descriptor.
@@ -190,7 +180,7 @@
     ;;; A buffer into which to write the preopened directory name.
     (param $path (@witx pointer u8))
     (param $path_len $size)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Write to a file descriptor, without using and updating the file descriptor's offset.
@@ -201,9 +191,8 @@
     (param $iovs $ciovec_array)
     ;;; The offset within the file at which to write.
     (param $offset $filesize)
-    (result $error $errno)
     ;;; The number of bytes written.
-    (result $nwritten $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Read from a file descriptor.
@@ -212,15 +201,14 @@
     (param $fd $fd)
     ;;; List of scatter/gather vectors to which to store data.
     (param $iovs $iovec_array)
-    (result $error $errno)
     ;;; The number of bytes read.
-    (result $nread $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Read directory entries from a directory.
   ;;; When successful, the contents of the output buffer consist of a sequence of
-  ;;; directory entries. Each directory entry consists of a dirent_t object,
-  ;;; followed by dirent_t::d_namlen bytes holding the name of the directory
+  ;;; directory entries. Each directory entry consists of a `dirent` object,
+  ;;; followed by `dirent::d_namlen` bytes holding the name of the directory
   ;;; entry.
   ;;
   ;;; This function fills the output buffer as much as possible, potentially
@@ -234,9 +222,8 @@
     (param $buf_len $size)
     ;;; The location within the directory to start reading
     (param $cookie $dircookie)
-    (result $error $errno)
     ;;; The number of bytes stored in the read buffer. If less than the size of the read buffer, the end of the directory has been reached.
-    (result $bufused $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Atomically replace a file descriptor by renumbering another file descriptor.
@@ -253,7 +240,7 @@
     (param $fd $fd)
     ;;; The file descriptor to overwrite.
     (param $to $fd)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Move the offset of a file descriptor.
@@ -264,25 +251,23 @@
     (param $offset $filedelta)
     ;;; The base from which the offset is relative.
     (param $whence $whence)
-    (result $error $errno)
     ;;; The new offset of the file descriptor, relative to the start of the file.
-    (result $newoffset $filesize)
+    (result $error (expected $filesize (error $errno)))
   )
 
   ;;; Synchronize the data and metadata of a file to disk.
   ;;; Note: This is similar to `fsync` in POSIX.
   (@interface func (export "fd_sync")
     (param $fd $fd)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Return the current offset of a file descriptor.
   ;;; Note: This is similar to `lseek(fd, 0, SEEK_CUR)` in POSIX.
   (@interface func (export "fd_tell")
     (param $fd $fd)
-    (result $error $errno)
     ;;; The current offset of the file descriptor, relative to the start of the file.
-    (result $offset $filesize)
+    (result $error (expected $filesize (error $errno)))
   )
 
   ;;; Write to a file descriptor.
@@ -291,9 +276,7 @@
     (param $fd $fd)
     ;;; List of scatter/gather vectors from which to retrieve data.
     (param $iovs $ciovec_array)
-    (result $error $errno)
-    ;;; The number of bytes written.
-    (result $nwritten $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Create a directory.
@@ -302,7 +285,7 @@
     (param $fd $fd)
     ;;; The path at which to create the directory.
     (param $path string)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Return the attributes of a file or directory.
@@ -313,9 +296,8 @@
     (param $flags $lookupflags)
     ;;; The path of the file or directory to inspect.
     (param $path string)
-    (result $error $errno)
     ;;; The buffer where the file's attributes are stored.
-    (result $buf $filestat)
+    (result $error (expected $filestat (error $errno)))
   )
 
   ;;; Adjust the timestamps of a file or directory.
@@ -332,7 +314,7 @@
     (param $mtim $timestamp)
     ;;; A bitmask indicating which timestamps to adjust.
     (param $fst_flags $fstflags)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Create a hard link.
@@ -347,7 +329,7 @@
     (param $new_fd $fd)
     ;;; The destination path at which to create the hard link.
     (param $new_path string)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Open a file or directory.
@@ -377,11 +359,10 @@
     ;;; descriptor itself, while the *inheriting* rights are rights that apply to
     ;;; file descriptors derived from it.
     (param $fs_rights_base $rights)
-    (param $fs_rights_inherting $rights)
+    (param $fs_rights_inheriting $rights)
     (param $fdflags $fdflags)
-    (result $error $errno)
     ;;; The file descriptor of the file that has been opened.
-    (result $opened_fd $fd)
+    (result $error (expected $fd (error $errno)))
   )
 
   ;;; Read the contents of a symbolic link.
@@ -393,9 +374,8 @@
     ;;; The buffer to which to write the contents of the symbolic link.
     (param $buf (@witx pointer u8))
     (param $buf_len $size)
-    (result $error $errno)
     ;;; The number of bytes placed in the buffer.
-    (result $bufused $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Remove a directory.
@@ -405,7 +385,7 @@
     (param $fd $fd)
     ;;; The path to a directory to remove.
     (param $path string)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Rename a file or directory.
@@ -418,7 +398,7 @@
     (param $new_fd $fd)
     ;;; The destination path to which to rename the file or directory.
     (param $new_path string)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Create a symbolic link.
@@ -429,7 +409,7 @@
     (param $fd $fd)
     ;;; The destination path at which to create the symbolic link.
     (param $new_path string)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
 
@@ -440,7 +420,7 @@
     (param $fd $fd)
     ;;; The path to a file to unlink.
     (param $path string)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Concurrently poll for the occurrence of a set of events.
@@ -451,9 +431,8 @@
     (param $out (@witx pointer $event))
     ;;; Both the number of subscriptions and events.
     (param $nsubscriptions $size)
-    (result $error $errno)
     ;;; The number of events stored.
-    (result $nevents $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Terminate the process normally. An exit code of 0 indicates successful
@@ -462,6 +441,7 @@
   (@interface func (export "proc_exit")
     ;;; The exit code returned by the process.
     (param $rval $exitcode)
+    (@witx noreturn)
   )
 
   ;;; Send a signal to the process of the calling thread.
@@ -469,13 +449,13 @@
   (@interface func (export "proc_raise")
     ;;; The signal condition to trigger.
     (param $sig $signal)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Temporarily yield execution of the calling thread.
   ;;; Note: This is similar to `sched_yield` in POSIX.
   (@interface func (export "sched_yield")
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Write high-quality random data into a buffer.
@@ -488,7 +468,7 @@
     ;;; The buffer to fill with random data.
     (param $buf (@witx pointer u8))
     (param $buf_len $size)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 
   ;;; Receive a message from a socket.
@@ -500,11 +480,8 @@
     (param $ri_data $iovec_array)
     ;;; Message flags.
     (param $ri_flags $riflags)
-    (result $error $errno)
-    ;;; Number of bytes stored in ri_data.
-    (result $ro_datalen $size)
-    ;;; Message flags.
-    (result $ro_flags $roflags)
+    ;;; Number of bytes stored in ri_data and message flags.
+    (result $error (expected (tuple $size $roflags) (error $errno)))
   )
 
   ;;; Send a message on a socket.
@@ -516,9 +493,8 @@
     (param $si_data $ciovec_array)
     ;;; Message flags.
     (param $si_flags $siflags)
-    (result $error $errno)
     ;;; Number of bytes transmitted.
-    (result $so_datalen $size)
+    (result $error (expected $size (error $errno)))
   )
 
   ;;; Shut down socket send and receive channels.
@@ -527,6 +503,6 @@
     (param $fd $fd)
     ;;; Which channels on the socket to shut down.
     (param $how $sdflags)
-    (result $error $errno)
+    (result $error (expected (error $errno)))
   )
 )