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f7bccb0e68
When an extension introduces a conformance that already exists, the type checker will reject the conformance and then ignore it. In cases where the original conformance is in the same module as the type or protocol (but the new, redundant conformance is in some other module), downgrade this error to a warning. This helps with library-evolution cases where a library omitted a particular conformance for one of its own types/protocols in a previous version, then introduces it in a new version. The specific driver for this is the conformance of String to Collection, which affects source compatibility. Fixes rdar://problem/31104415.
33 lines
1.3 KiB
Swift
33 lines
1.3 KiB
Swift
// RUN: rm -rf %t
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// RUN: mkdir -p %t
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// RUN: %target-swift-frontend -emit-module -o %t %S/Inputs/redundant_conformance_A.swift
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// RUN: %target-swift-frontend -emit-module -o %t -I %t %S/Inputs/redundant_conformance_B.swift
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// RUN: %target-typecheck-verify-swift -I %t %s
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import redundant_conformance_A
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import redundant_conformance_B
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extension ConformsToP
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: P1 { // expected-warning{{conformance of 'ConformsToP' to protocol 'P1' was already stated in the type's module 'redundant_conformance_A'}}
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typealias A = Double // expected-note{{type alias 'A' will not be used to satisfy the conformance to 'P1'}}
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func f() -> Double { return 0.0 } // expected-note{{instance method 'f()' will not be used to satisfy the conformance to 'P1'}}
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// expected-note@-1{{found this candidate}}
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}
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extension ConformsToP
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: P2 { // expected-warning{{conformance of 'ConformsToP' to protocol 'P2' was already stated in the protocol's module 'redundant_conformance_B'}}
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}
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extension OtherConformsToP : P1 { // expected-error{{redundant conformance of 'OtherConformsToP' to protocol 'P1'}}
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func f() -> Int { return 0 }
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}
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func testConformsToP(cp1: ConformsToP, ocp1: OtherConformsToP) {
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// Note:
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let _ = cp1.f() // expected-error{{ambiguous use of 'f()'}}
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let _ = ocp1.f() // okay: picks "our" OtherConformsToP.f()
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}
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