wasmparser: require result equivalence for (on $t switch) handler#2564
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The `resume`/`resume_throw` handler clause `(on $tag switch)` was accepted when the switch tag's result types were merely a *subtype* of the resumed continuation's results. This is unsound, and does not follow the spec: the handler judgment has no subsumption rule, so `(on tu switch) : t*` together with the required `hdl : t2*` forces `t* = t2*`. The two result vectors must be equivalent, not just related by subtyping. V8 and Binaryen already check for equivalence.
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The
resume/resume_throwhandler clause(on $tag switch)was accepted when the switch tag's result types were merely a subtype of the resumed continuation's results. This is unsound, and does not follow the spec: the handler judgment has no subsumption rule, so(on tu switch) : t*together with the requiredhdl : t2*forcest* = t2*. The two result vectors must be equivalent, not just related by subtyping.V8 and Binaryen already check for equivalence (see v8/v8@cf215c5).