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Merge pull request #59357 from AnthonyLatsis/cond-conf-overridden-assoc
ConformanceChecker: Don't record a type witness for an overridden associated type if...
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Diff for: ‎lib/Sema/TypeCheckProtocol.cpp

+31-1
Original file line numberDiff line numberDiff line change
@@ -3449,8 +3449,38 @@ void ConformanceChecker::recordTypeWitness(AssociatedTypeDecl *assocType,
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!overriddenConformance.isConcrete())
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continue;
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auto overriddenRootConformance =
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auto *overriddenRootConformance =
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overriddenConformance.getConcrete()->getRootNormalConformance();
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auto *overriddenRootConformanceDC =
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overriddenRootConformance->getDeclContext();
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// Don't record a type witness for an overridden associated type if the
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// conformance to the corresponding inherited protocol
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// - originates in a superclass
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// - originates in a different module
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// - and the current conformance have mismatching conditional requirements
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// This can turn out badly in two ways:
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// - Foremost, we must not *alter* conformances originating in superclasses
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// or other modules. In other cases, we may hit an assertion in an attempt
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// to overwrite an already recorded type witness with a different one.
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// For example, the recorded type witness may be invalid, whereas the
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// other one---valid, and vice versa.
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// - If the current conformance is more restrictive, this type witness may
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// not be a viable candidate for the overridden associated type.
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if (overriddenRootConformanceDC->getSelfNominalTypeDecl() !=
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DC->getSelfNominalTypeDecl())
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continue;
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if (overriddenRootConformanceDC->getParentModule() != DC->getParentModule())
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continue;
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auto currConformanceSig = DC->getGenericSignatureOfContext();
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auto overriddenConformanceSig =
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overriddenRootConformanceDC->getGenericSignatureOfContext();
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if (currConformanceSig.getCanonicalSignature() !=
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overriddenConformanceSig.getCanonicalSignature())
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continue;
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ConformanceChecker(getASTContext(), overriddenRootConformance,
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GlobalMissingWitnesses)
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.recordTypeWitness(overridden, type, typeDecl);

Diff for: ‎test/decl/protocol/associated_type_overrides_conformances.swift

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,138 @@
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// RUN: %target-typecheck-verify-swift
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func assertTypeWitnessForP1_A<T: P1, U>(in: T.Type, is: U.Type) where T.A == U {}
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func assertTypeWitnessForP2_A<T: P2, U>(in: T.Type, is: U.Type) where T.A == U {}
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protocol P1 {
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associatedtype A
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// expected-note@-1 2 {{protocol requires nested type 'A'; do you want to add it?}}
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// expected-note@-2 2 {{multiple matching types named 'A'}}
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}
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protocol P2: P1 {
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associatedtype A
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// expected-note@-1 2 {{protocol requires nested type 'A'; do you want to add it?}}
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// expected-note@-2 2 {{multiple matching types named 'A'}}
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}
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// Conformance to P1 checked first and more restrictive.
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struct S1<T> {}
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extension S1: P1 where T == Never { // expected-error {{type 'S1<T>' does not conform to protocol 'P1'}}
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typealias A = Int // expected-note {{possibly intended match}}
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}
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extension S1: P2 {
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// expected-error@-1 {{type 'S1<T>' does not conform to protocol 'P2'}}
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// expected-error@-2 {{'P2' requires the types 'T' and 'Never' be equivalent}}
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// expected-note@-3 {{requirement specified as 'T' == 'Never'}}
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// expected-note@-4 {{requirement from conditional conformance of 'S1<T>' to 'P1'}}
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typealias A = Bool // expected-note {{possibly intended match}}
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}
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struct S2<T> {}
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extension S2: P1 where T == Never {
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typealias A = Int
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}
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extension S2: P2 {} // expected-error {{type 'S2<T>' does not conform to protocol 'P2'}}
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struct S3<T> {}
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extension S3: P1 where T == Never {}
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extension S3: P2 {
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// expected-error@-1 {{type 'S3<T>' does not conform to protocol 'P2'}}
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// expected-error@-2 {{'P2' requires the types 'T' and 'Never' be equivalent}}
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// expected-note@-3 {{requirement specified as 'T' == 'Never'}}
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// expected-note@-4 {{requirement from conditional conformance of 'S3<T>' to 'P1'}}
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typealias A = Int
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}
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// Conformance to P1 checked first and less restrictive.
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struct S4<T> {}
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extension S4: P1 {
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typealias A = Int // expected-note {{possibly intended match}}
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}
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extension S4: P2 where T == Never { // expected-error {{type 'S4<T>' does not conform to protocol 'P2'}}
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typealias A = Bool // expected-note {{possibly intended match}}
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}
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struct S5<T> {}
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extension S5: P1 {
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typealias A = Int
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}
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extension S5: P2 where T == Never {}
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struct S6<T> {}
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extension S6: P1 {} // expected-error {{type 'S6<T>' does not conform to protocol 'P1'}}
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extension S6: P2 where T == Never {
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typealias A = Bool
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}
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// Conformance to P2 checked first and more restrictive.
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struct S7<T> {}
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extension S7: P2 where T == Never { // expected-error {{type 'S7<T>' does not conform to protocol 'P2'}}
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typealias A = Bool // expected-note {{possibly intended match}}
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}
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extension S7: P1 {
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typealias A = Int // expected-note {{possibly intended match}}
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}
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struct S8<T> {}
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extension S8: P2 where T == Never {}
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extension S8: P1 {
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typealias A = Int
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}
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struct S9<T> {}
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extension S9: P2 where T == Never {
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typealias A = Bool
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}
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extension S9: P1 {} // expected-error {{type 'S9<T>' does not conform to protocol 'P1'}}
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// Conformance to P2 checked first and less restrictive.
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struct S10<T> {}
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extension S10: P2 {
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// expected-error@-1 {{type 'S10<T>' does not conform to protocol 'P2'}}
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// expected-error@-2 {{'P2' requires the types 'T' and 'Never' be equivalent}}
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// expected-note@-3 {{requirement specified as 'T' == 'Never'}}
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// expected-note@-4 {{requirement from conditional conformance of 'S10<T>' to 'P1'}}
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typealias A = Bool // expected-note {{possibly intended match}}
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}
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extension S10: P1 where T == Never { // expected-error {{type 'S10<T>' does not conform to protocol 'P1'}}
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typealias A = Int // expected-note {{possibly intended match}}
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}
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struct S11<T> {}
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extension S11: P2 {} // expected-error {{type 'S11<T>' does not conform to protocol 'P2'}}
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extension S11: P1 where T == Never {
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typealias A = Int
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}
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struct S12<T> {}
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extension S12: P2 {
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// expected-error@-1 {{type 'S12<T>' does not conform to protocol 'P2'}}
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// expected-error@-2 {{'P2' requires the types 'T' and 'Never' be equivalent}}
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// expected-note@-3 {{requirement specified as 'T' == 'Never'}}
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// expected-note@-4 {{requirement from conditional conformance of 'S12<T>' to 'P1'}}
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typealias A = Int
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}
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extension S12: P1 where T == Never {}
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// Inherited conformances.
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class Base1 {}
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class Derived1: Base1 {}
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extension Base1: P1 {
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typealias A = Bool
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}
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extension Derived1: P2 {
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typealias A = Int
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}
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assertTypeWitnessForP1_A(in: Base1.self, is: Bool.self)
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assertTypeWitnessForP2_A(in: Derived1.self, is: Bool.self)
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class Base2 {}
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class Derived2: Base2 {}
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extension Derived2: P2 {
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typealias A = Int
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}
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extension Base2: P1 {
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typealias A = Bool
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}
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assertTypeWitnessForP1_A(in: Base2.self, is: Bool.self)
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assertTypeWitnessForP2_A(in: Derived2.self, is: Bool.self)

Diff for: ‎test/decl/protocol/associated_type_overrides_conformances_cross_module.swift

+27
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@@ -0,0 +1,27 @@
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// RUN: %empty-directory(%t)
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// RUN: %target-swift-frontend -D M -emit-module -module-name M -parse-as-library -o %t %s
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// RUN: %target-typecheck-verify-swift -I %t
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#if M
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public protocol P {
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associatedtype A
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}
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public struct S: P {
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public typealias A = Int
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}
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#else
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import M
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protocol Q: P {
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associatedtype A // expected-note {{multiple matching types named 'A'}}
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}
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extension S: Q { // expected-error {{type 'S' does not conform to protocol 'Q'}}
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typealias A = Bool // expected-note {{possibly intended match}}
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}
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#endif

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