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wasmparser: share the function subtyping check - #2765
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The operator validator's `is_func_subtype` (used for stack-switching handlers) and `Matches for WithRecGroup<&FuncType>` each spelled out the contravariant-params / covariant-results rule. Pull it into one `func_signature_matches` that takes the value types as iterators plus an `x <: y` predicate, so the type-section path keeps pairing each value with its rec group and the operator validator keeps going through `WasmModuleResources::is_subtype`. Closes bytecodealliance#2480
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Closes #2480.
OperatorValidator::is_func_subtypeandMatches for WithRecGroup<&FuncType>both spelled out the params-contravariant / results-covariant rule. This moves it into onefunc_signature_matchesinmatches.rs, which takes each side's params and results as iterators plus anx <: ypredicate for single value types. That covers the difference between the two callers:Matches::matches;on/switchhandler checks) still compares canonical types throughWasmModuleResources::is_subtype, and keeps passing ad hoc(params, results)slices, so it doesn't need aFuncType.The variance comment moved with the logic, unchanged. No behaviour change intended.
To make sure both callers are actually exercised, I flipped each one's predicate in turn: the type-section side breaks 7 tests in the cli suite (gc subtypes, type-subtyping,
stack-switching/validation_gc.wast, ...) and the operator side breaks 2 (stack-switching/validation_gc.wast,folding/fold-stack-switching-gc.wast). With the change as is,cargo test --all, the cli suite (916), clippy, rustfmt and the wasmparser--no-default-features/x86_64-unknown-nonechecks from CI all pass.