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[Requirement machine] Ignore unavailable conformances on superclass constraints.

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When determining whether a superclass conforms to a particular protocol,
skip unavailable conformances. This way, we don't minimize away a
constraint that might only apply to subclasses of the specified
superclass.

Fixes rdar://91853658.
This commit is contained in:
Doug Gregor
2022-05-27 11:32:44 -07:00
parent f7f0a541cb
commit c9c50b4ae0
12 changed files with 88 additions and 38 deletions
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20
lib/AST/Module.cpp
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@@ -1015,7 +1015,9 @@ ModuleDecl::lookupExistentialConformance(Type type, ProtocolDecl *protocol) {
// If the existential is class-constrained, the class might conform
// concretely.
if (auto superclass = layout.explicitSuperclass) {
if (auto result = lookupConformance(superclass, protocol))
if (auto result = lookupConformance(
superclass, protocol, /*allowMissing=*/false,
/*allowUnavailable=*/false))
return result;
}
@@ -1071,7 +1073,8 @@ ProtocolConformanceRef ProtocolConformanceRef::forMissingOrInvalid(
ProtocolConformanceRef ModuleDecl::lookupConformance(Type type,
ProtocolDecl *protocol,
bool allowMissing) {
bool allowMissing,
bool allowUnavailable) {
// If we are recursively checking for implicit conformance of a nominal
// type to Sendable, fail without evaluating this request. This
// squashes cycles.
@@ -1088,13 +1091,18 @@ ProtocolConformanceRef ModuleDecl::lookupConformance(Type type,
auto result = evaluateOrDefault(
getASTContext().evaluator, request, ProtocolConformanceRef::forInvalid());
// If we aren't supposed to allow missing conformances through for this
// protocol, replace the result with an "invalid" result.
// If we aren't supposed to allow missing conformances but we have one,
// replace the result with an "invalid" result.
if (!allowMissing &&
shouldCreateMissingConformances(type, protocol) &&
result.hasMissingConformance(this))
return ProtocolConformanceRef::forInvalid();
// If we aren't supposed to allow unavailable conformances but we have one,
// replace the result with an "invalid" result.
if (!allowUnavailable && result.hasUnavailableConformance())
return ProtocolConformanceRef::forInvalid();
return result;
}
@@ -1248,7 +1256,9 @@ LookupConformanceInModuleRequest::evaluate(
// able to be resolved by a substitution that makes the archetype
// concrete.
if (auto super = archetype->getSuperclass()) {
if (auto inheritedConformance = mod->lookupConformance(super, protocol)) {
if (auto inheritedConformance = mod->lookupConformance(
super, protocol, /*allowMissing=*/false,
/*allowUnavailable=*/false)) {
return ProtocolConformanceRef(ctx.getInheritedConformance(
type, inheritedConformance.getConcrete()));
}