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Fix @_implements type resolution diagnostics #81421

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Merged
merged 1 commit into from
May 12, 2025
Merged

Fix @_implements type resolution diagnostics #81421

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21 changes: 19 additions & 2 deletions lib/Sema/TypeCheckAttr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4281,8 +4281,25 @@ void AttributeChecker::visitImplementsAttr(ImplementsAttr *attr) {
ProtocolDecl *PD = attr->getProtocol(DC);

if (!PD) {
diagnose(attr->getLocation(), diag::implements_attr_non_protocol_type)
.highlight(attr->getProtocolTypeRepr()->getSourceRange());
// `ImplementsAttr::getProtocol()` returns `nullptr` both when a type fails
// to resolve, and when it resolves to something other than a protocol.
// Due to layering concerns, it doesn't resolve in a way that emits
// diagnostics.
//
// Distinguish between these situations by trying to resolve the type again.
// If it doesn't resolve, TypeResolution will have diagnosed the problem; if
// it does, it must have resolved to a non-protocol, so emit a diagnostic to
// that effect.
TypeResolutionOptions options(TypeResolverContext::None);
auto resolvedType = TypeResolution::resolveContextualType(
attr->getProtocolTypeRepr(), DC, options,
// Unbound generics and placeholders are not allowed within this attr.
/*unboundTyOpener*/ nullptr, /*placeholderHandler*/ nullptr,
/*packElementOpener*/ nullptr);

if (resolvedType && !resolvedType->hasError())
diagnose(attr->getLocation(), diag::implements_attr_non_protocol_type)
.highlight(attr->getProtocolTypeRepr()->getSourceRange());
return;
}

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4 changes: 4 additions & 0 deletions test/attr/attr_implements_bad_types.swift
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Expand Up @@ -21,5 +21,9 @@ struct S0 : NeedsF0 { // expected-error {{type 'S0' does not conform to protoco
@_implements(Equatable, ==(_:_:)) // expected-error {{containing type 'S0' does not conform to protocol 'Equatable'}}
static func gg2(x:S0, y:S0) -> Bool {
}

@_implements(NonexistentType, ff3()) // expected-error {{cannot find type 'NonexistentType' in scope}}
func gg3() {
}
}