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[Sema][GSB] Fix crash on cond conformances with invalid req #17284

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[Sema][GSB] Fix crash on cond conformances with invalid req #17284

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19 changes: 14 additions & 5 deletions lib/AST/GenericSignatureBuilder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4721,12 +4721,21 @@ ConstraintResult GenericSignatureBuilder::addTypeRequirement(
// type that makes sense to use here, but, in practice, all
// getLookupConformanceFns used in here don't use that parameter anyway.
auto dependentType = CanType();
auto conformance =
getLookupConformanceFn()(dependentType, subjectType, proto->getDecl());

// FIXME: diagnose if there's no conformance.
if (conformance) {
addConditionalRequirements(*this, *conformance, inferForModule);
auto D = getGenericParams().front()->getDecl();
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Hm, I think this could do with some explanation: is this new code trying to deduce if we're in a circular situation, where the requirement is referring to the "original" type (the one for which we're building the generic signature)? And these few lines are trying to work out that original type?

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Yes, I am proceeding with the conformance lookup if the subject type has a null decl context or isn't a nominal type declaration context, or otherwise isn't the type we're extending or declaring. Simply put, I am just making sure not to look up conformances if the base type of the subject and the current context match.

auto DC = D ? D->getDeclContext() : nullptr;
auto NTD = DC ? DC->getAsNominalTypeOrNominalTypeExtensionContext()
: nullptr;
auto subjectNTD = subjectType->getAnyNominal();

if (!NTD || !subjectNTD || NTD != subjectNTD) {
auto conformance =
getLookupConformanceFn()(dependentType, subjectType,
proto->getDecl());
// FIXME: diagnose if there's no conformance.
if (conformance) {
addConditionalRequirements(*this, *conformance, inferForModule);
}
}
}
}
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17 changes: 17 additions & 0 deletions test/decl/ext/generic.swift
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Expand Up @@ -144,6 +144,23 @@ extension GenericClass where Self : P3 { }
// expected-error@-1{{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'GenericClass'?}} {{30-34=GenericClass}}
// expected-error@-2{{type 'GenericClass<T>' in conformance requirement does not refer to a generic parameter or associated type}}

protocol Prot1 {}
protocol Prot2 {}
protocol Prot3 {}
protocol Prot4 {}
protocol Prot5 {}

extension GenericClass: Prot1 where T: Prot1 {}
extension GenericClass: Prot2 where Self: Prot1 {}
// expected-error@-1 {{'Self' is only available in a protocol or as the result of a method in a class; did you mean 'GenericClass'?}}
// expected-error@-2 {{type 'GenericClass<T>' in conformance requirement does not refer to a generic parameter or associated type}}
extension GenericClass: Prot3 where GenericClass<T>: Prot1 {}
// expected-error @-1 {{type 'GenericClass<T>' in conformance requirement does not refer to a generic parameter or associated type}}
extension GenericClass: Prot4 where GenericClass<Int>: Prot1 {}
// expected-error @-1 {{type 'GenericClass<Int>' in conformance requirement does not refer to a generic parameter or associated type}}
extension GenericClass: Prot5 where GenericClass: Prot5 {}
// expected-error @-1 {{type 'GenericClass<T>' in conformance requirement does not refer to a generic parameter or associated type}}

protocol P4 {
associatedtype T
init(_: T)
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