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In the included test case, conformance checking of Wrapper : B would pick up typealias Foo as a witness for the associated type B.Foo. However, this typealias Foo is defined in a constrained extension where T : A, and the underlying type references the associated type A.Foo on T. The resulting substitution is invalid when the conformance Wrapper : B is used in a context where T does not conform to A. Instead, we should ignore this typealias entirely, since it appears in an unusable constrained extension. Fixes <rdar://problem/60219705>, <https://bugs.swift.org/browse/SR-12327>, <https://bugs.swift.org/browse/SR-12663>.
49 lines
1.3 KiB
Swift
49 lines
1.3 KiB
Swift
// RUN: %target-typecheck-verify-swift
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protocol P {}
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struct S<T> {}
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class C : P {}
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extension S where T : P { // expected-note {{where 'T' = 'T'}}
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typealias A = Int
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typealias B<U> = S<U>
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}
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extension S where T == Float { // expected-note {{requirement specified as 'T' == 'Float' [with T = Int]}}
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typealias C = Int
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}
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class A<T, U> {}
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extension A where T == [U], U: P {
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typealias S1 = Int
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}
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extension A where T == [U], U == Int {
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// expected-note@-1 {{requirement specified as 'T' == '[Int]' [with T = [String]]}}
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typealias S2 = Int
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}
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class B<U> : A<[U], U> {}
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_ = B<C>.S1() // Ok
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_ = B<Int>.S2() // Ok
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_ = B<Float>.S1() // expected-error {{type 'Float' does not conform to protocol 'P'}}
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_ = B<String>.S2()
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// expected-error@-1 {{'A<T, U>.S2' (aka 'Int') requires the types '[String]' and '[Int]' be equivalent}}
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_ = S<C>.A() // Ok
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_ = S<Int>.A() // expected-error {{type 'Int' does not conform to protocol 'P'}}
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_ = S<String>.B<Int>() // expected-error {{type 'String' does not conform to protocol 'P'}}
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_ = S<Int>.C() // expected-error {{'S<T>.C' (aka 'Int') requires the types 'Int' and 'Float' be equivalent}}
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func foo<T>(_ s: S<T>.Type) {
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_ = s.A() // expected-error {{referencing type alias 'A' on 'S' requires that 'T' conform to 'P'}}
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}
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func bar<T: P>(_ s: S<T>.Type) {
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_ = s.A() // Ok
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}
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