Add a feature flag for GC in the component model (#2165)

* Add a feature flag for GC in the component model

This is the first baby step towards integrating support for Wasm GC into the
component model and its canonical ABI.

* update test expectations

Author: fitzgen

crates/wasmparser/src/features.rs

@@ -139,7 +139,7 @@ define_wasm_features! {
     /// has any associated constants. When `features` are disabled all values
     /// for proposals are fixed at compile time to their defaults.
     #[derive(Hash, Debug, Copy, Clone, Eq, PartialEq)]
-    pub struct WasmFeatures: u32 {
+    pub struct WasmFeatures: u64 {
         /// The WebAssembly `mutable-global` proposal.
         pub mutable_global: MUTABLE_GLOBAL(1) = true;
         /// The WebAssembly `saturating-float-to-int` proposal.
@@ -259,6 +259,11 @@ define_wasm_features! {
         /// Corresponds to the 🔧 character in
         /// <https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md>.
         pub cm_fixed_size_list: CM_FIXED_SIZE_LIST(1 << 31) = false;
+        /// Support for Wasm GC in the component model proposal.
+        ///
+        /// Corresponds to the 🛸 character in
+        /// <https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md>.
+        pub cm_gc: CM_GC(1 << 32) = false;
     }
 }
 

tests/cli/validate-unknown-features.wat.stderr

@@ -1,4 +1,4 @@
 error: invalid value 'unknown' for '--features <FEATURES>': unknown feature `unknown`
-Valid features: mutable-global, saturating-float-to-int, sign-extension, reference-types, multi-value, bulk-memory, simd, relaxed-simd, threads, shared-everything-threads, tail-call, floats, multi-memory, exceptions, memory64, extended-const, component-model, function-references, memory-control, gc, custom-page-sizes, legacy-exceptions, gc-types, stack-switching, wide-arithmetic, cm-values, cm-nested-names, cm-async, cm-async-stackful, cm-async-builtins, cm-error-context, cm-fixed-size-list, mvp, wasm1, wasm2, wasm3, all
+Valid features: mutable-global, saturating-float-to-int, sign-extension, reference-types, multi-value, bulk-memory, simd, relaxed-simd, threads, shared-everything-threads, tail-call, floats, multi-memory, exceptions, memory64, extended-const, component-model, function-references, memory-control, gc, custom-page-sizes, legacy-exceptions, gc-types, stack-switching, wide-arithmetic, cm-values, cm-nested-names, cm-async, cm-async-stackful, cm-async-builtins, cm-error-context, cm-fixed-size-list, cm-gc, mvp, wasm1, wasm2, wasm3, all
 
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