fix: trait default-body placeholder overwrites real signature, breaking deriving - #83
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…ng deriving
The parser emits two TraitItem::Method entries for a method with both
a signature and a default body: the signature (TypeKind::Named) and a
placeholder (TypeKind::Hole). The skip guard in register_trait_methods
tested for TypeKind::Named("_") which never matched TypeKind::Hole,
so the placeholder overwrote the real signature with an unquantified
type variable. The first call site pinned it; the second failed with
'type mismatch'. This also broke deriving for any trait with a default
body at 2+ types.
Fix: match TypeKind::Hole in the skip guard. Two regression tests.
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Bug: Trait method with default body is monomorphic
The parser emits two
TraitItem::Methodentries for a method with both a signature and a default body. The skip guard inregister_trait_methodstested forTypeKind::Named("_")which never matchedTypeKind::Hole(the actual placeholder type), so the placeholder overwrote the real signature with an unquantified type variable shared across all call sites.Impact: First call site pins the type; second fails with "type mismatch". Also breaks
derivingfor any trait with a default body at 2+ types — a headline feature.Fix: Match
TypeKind::Holein the skip guard (one-line fix ininfer.rs).Tests: 2 regression tests — one for trait default body, one for deriving at multiple types. All 23 regress tests pass.