Use core::convert::Infallible instead of our own Uninhabited type (#12115)

* Use `core::convert::Infallible` instead of our own `Uninhabited` type

I didn't realize that the standard library already had an uninhabited type
available for us to reuse.

* Actually remove the uninhabited module and its re-exports

Author: fitzgen

crates/wasmtime/src/runtime.rs

@@ -53,7 +53,6 @@ pub(crate) mod trampoline;
 pub(crate) mod trap;
 pub(crate) mod type_registry;
 pub(crate) mod types;
-pub(crate) mod uninhabited;
 pub(crate) mod v128;
 pub(crate) mod values;
 pub(crate) mod vm;
@@ -100,8 +99,6 @@ pub use types::*;
 pub use v128::V128;
 pub use values::*;
 
-pub(crate) use uninhabited::*;
-
 #[cfg(feature = "pooling-allocator")]
 pub use vm::{PoolConcurrencyLimitError, PoolingAllocatorMetrics};
 

crates/wasmtime/src/runtime/component/concurrent_disabled.rs

@@ -1,8 +1,8 @@
-use crate::Uninhabited;
 use crate::component::Val;
 use crate::component::func::{ComponentType, LiftContext, LowerContext};
 use crate::runtime::vm::VMStore;
 use anyhow::{Result, anyhow};
+use core::convert::Infallible;
 use core::future::Future;
 use core::marker::PhantomData;
 use core::pin::pin;
@@ -56,7 +56,7 @@ pub(crate) fn lower_error_context_to_index<U>(
     should_have_failed_validation("use of `error-context`")
 }
 
-pub struct ErrorContext(Uninhabited);
+pub struct ErrorContext(Infallible);
 
 impl ErrorContext {
     pub(crate) fn into_val(self) -> Val {
@@ -81,7 +81,7 @@ impl ErrorContext {
 }
 
 pub struct StreamReader<P> {
-    uninhabited: Uninhabited,
+    uninhabited: Infallible,
     _phantom: PhantomData<P>,
 }
 
@@ -108,7 +108,7 @@ impl<P> StreamReader<P> {
 }
 
 pub struct FutureReader<P> {
-    uninhabited: Uninhabited,
+    uninhabited: Infallible,
     _phantom: PhantomData<P>,
 }
 

crates/wasmtime/src/runtime/func.rs

@@ -1,5 +1,4 @@
 use crate::prelude::*;
-use crate::runtime::Uninhabited;
 use crate::runtime::vm::{
     self, InterpreterRef, SendSyncPtr, StoreBox, VMArrayCallHostFuncContext,
     VMCommonStackInformation, VMContext, VMFuncRef, VMFunctionImport, VMOpaqueContext,
@@ -12,6 +11,7 @@ use crate::{
     StoreContext, StoreContextMut, Val, ValRaw, ValType,
 };
 use alloc::sync::Arc;
+use core::convert::Infallible;
 use core::ffi::c_void;
 #[cfg(feature = "async")]
 use core::future::Future;
@@ -77,7 +77,7 @@ use wasmtime_environ::VMSharedTypeIndex;
 /// ```
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct NoFunc {
-    _inner: Uninhabited,
+    _inner: Infallible,
 }
 
 impl NoFunc {

crates/wasmtime/src/runtime/gc/disabled/rooting.rs

@@ -1,9 +1,9 @@
 use crate::runtime::vm::{GcStore, VMGcRef};
 use crate::{
     AsContext, AsContextMut, GcRef, Result, RootedGcRef,
-    runtime::Uninhabited,
     store::{AutoAssertNoGc, StoreOpaque},
 };
+use core::convert::Infallible;
 use core::fmt::{self, Debug};
 use core::hash::{Hash, Hasher};
 use core::marker;
@@ -48,7 +48,7 @@ impl RootSet {
 /// This type is disabled because the `gc` cargo feature was not enabled at
 /// compile time.
 pub struct Rooted<T: GcRef> {
-    pub(crate) inner: Uninhabited,
+    pub(crate) inner: Infallible,
     _phantom: marker::PhantomData<T>,
 }
 
@@ -122,7 +122,7 @@ pub struct RootScope<C>
 where
     C: AsContextMut,
 {
-    inner: Uninhabited,
+    inner: Infallible,
     _phantom: marker::PhantomData<C>,
 }
 
@@ -161,7 +161,7 @@ pub struct OwnedRooted<T>
 where
     T: GcRef,
 {
-    pub(crate) inner: Uninhabited,
+    pub(crate) inner: Infallible,
     _phantom: marker::PhantomData<T>,
 }
 

crates/wasmtime/src/runtime/gc/noextern.rs

@@ -1,7 +1,8 @@
 use crate::{
-    HeapType, Ref, RefType, Result, Uninhabited, Val, ValRaw, ValType, WasmTy,
+    HeapType, Ref, RefType, Result, Val, ValRaw, ValType, WasmTy,
     store::{AutoAssertNoGc, StoreOpaque},
 };
+use core::convert::Infallible;
 use core::mem::MaybeUninit;
 
 /// A reference to the abstract `noextern` heap value.
@@ -64,7 +65,7 @@ use core::mem::MaybeUninit;
 /// ```
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct NoExtern {
-    _inner: Uninhabited,
+    _inner: Infallible,
 }
 
 impl NoExtern {

crates/wasmtime/src/runtime/gc/none_ref.rs

@@ -1,7 +1,8 @@
 use crate::{
-    HeapType, Ref, RefType, Result, Uninhabited, Val, ValRaw, ValType, WasmTy,
+    HeapType, Ref, RefType, Result, Val, ValRaw, ValType, WasmTy,
     store::{AutoAssertNoGc, StoreOpaque},
 };
+use core::convert::Infallible;
 use core::mem::MaybeUninit;
 
 /// A reference to the abstract `none` heap value.
@@ -64,7 +65,7 @@ use core::mem::MaybeUninit;
 /// ```
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct NoneRef {
-    _inner: Uninhabited,
+    _inner: Infallible,
 }
 
 impl NoneRef {

crates/wasmtime/src/runtime/store.rs

@@ -106,8 +106,9 @@ use crate::trampoline::VMHostGlobalContext;
 use crate::{Engine, Module, Val, ValRaw, module::ModuleRegistry};
 #[cfg(feature = "gc")]
 use crate::{ExnRef, Rooted};
-use crate::{Global, Instance, Table, Uninhabited};
+use crate::{Global, Instance, Table};
 use alloc::sync::Arc;
+use core::convert::Infallible;
 use core::fmt;
 use core::marker;
 use core::mem::{self, ManuallyDrop, MaybeUninit};
@@ -384,7 +385,7 @@ enum CallHookInner<T: 'static> {
         reason = "forcing, regardless of cfg, the type param to be used"
     )]
     ForceTypeParameterToBeUsed {
-        uninhabited: Uninhabited,
+        uninhabited: Infallible,
         _marker: marker::PhantomData<T>,
     },
 }

crates/wasmtime/src/runtime/uninhabited.rs

@@ -23,15 +23,15 @@ pub(crate) type f64x2 = core::arch::x86_64::__m128d;
 #[cfg(not(all(target_arch = "x86_64", target_feature = "sse")))]
 #[expect(non_camel_case_types, reason = "matching wasm conventions")]
 #[derive(Copy, Clone)]
-pub(crate) struct i8x16(crate::uninhabited::Uninhabited);
+pub(crate) struct i8x16(core::convert::Infallible);
 #[cfg(not(all(target_arch = "x86_64", target_feature = "sse")))]
 #[expect(non_camel_case_types, reason = "matching wasm conventions")]
 #[derive(Copy, Clone)]
-pub(crate) struct f32x4(crate::uninhabited::Uninhabited);
+pub(crate) struct f32x4(core::convert::Infallible);
 #[cfg(not(all(target_arch = "x86_64", target_feature = "sse")))]
 #[expect(non_camel_case_types, reason = "matching wasm conventions")]
 #[derive(Copy, Clone)]
-pub(crate) struct f64x2(crate::uninhabited::Uninhabited);
+pub(crate) struct f64x2(core::convert::Infallible);
 
 use crate::StoreContextMut;
 use crate::prelude::*;

crates/wasmtime/src/runtime/vm.rs

@@ -4,16 +4,16 @@
 //! `Option<Thing>` is also zero-sized so there should be no runtime cost for
 //! having these structures plumbed around.
 
-use crate::runtime::Uninhabited;
 use crate::runtime::vm::{VMContext, VMOpaqueContext};
 use crate::{Engine, ValRaw};
+use core::convert::Infallible;
 use core::marker;
 use core::mem;
 use core::ptr::NonNull;
 use wasmtime_unwinder::Unwind;
 
 pub struct Interpreter {
-    empty: Uninhabited,
+    empty: Infallible,
 }
 
 const _: () = assert!(mem::size_of::<Interpreter>() == 0);
@@ -34,7 +34,7 @@ impl Interpreter {
 }
 
 pub struct InterpreterRef<'a> {
-    empty: Uninhabited,
+    empty: Infallible,
     _marker: marker::PhantomData<&'a mut Interpreter>,
 }