Fix wasm-gc externref trait-object cast path#6
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bikallem wants to merge 1 commit intomoonbitlang:mainfrom
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Fix wasm-gc externref trait-object cast path#6bikallem wants to merge 1 commit intomoonbitlang:mainfrom
bikallem wants to merge 1 commit intomoonbitlang:mainfrom
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Fixes moonbitlang/moonbit-docs#1123. The wasm-gc backend was emitting invalid cast sequences when trait-object conversion involved #external values across supertrait chains. This change adds a Pidentity lowering path in clam_of_core and tightens Pcast lowering to avoid redundant casts and preserve source/target type intent. In wasm_of_clam_gc, Lcast now handles Ref_extern<->Ref_any with the dedicated conversion ops (Extern_convert_any / Any_convert_extern) instead of generic ref_cast where needed.
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Pull request overview
Fixes wasm-gc reference casting for trait-object paths when #external (externref) values cross supertrait chains, avoiding invalid Wasm validation due to mismatched ref kinds.
Changes:
- Emit
extern.convert_any/any.convert_externforLcastbetweenRef_externandRef_anyinstead of using genericref.cast. - Lower
%identityand tighten%castlowering soLcastis only emitted when source/target ltypes differ (and ensure casts operate on vars viabind). - Adjust stub type validation to allow function-typed stub parameters under the
Wasm_gctarget.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
src/wasm_of_clam_gc.ml |
Special-cases Lcast between externref/anyref using dedicated Wasm GC conversion ops. |
src/clam_of_core.ml |
Adds explicit %identity lowering and avoids emitting redundant Lcast when ltypes are equal. |
src/typeutil.ml |
Changes stub type checking behavior for function types when targeting Wasm_gc. |
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Summary
Fixes the wasm-gc cast path for trait objects when
#external(externref) values flow across supertrait chains.What changed
clam_of_core: add explicitPidentitylowering and tightenPcastlowering so casts are emitted only when source/target ltypes differ.wasm_of_clam_gc: handleLcastbetweenRef_externandRef_anywith dedicated ops (Extern_convert_any/Any_convert_extern) instead of genericref_castin those cases.Why
Issue report shows invalid wasm validation/instantiation due to mismatch in casted ref kinds for
#external-> trait object conversion.Fixes moonbitlang/moonbit-docs#1123.