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0652bb7abe
The newly-introduced associated type `AsyncSequence.Failure` must always be equivalent to the `Failure` type of the `AsyncIteratorProtocol`. If the `AsyncSequence` type itself defines a nested `Failure` type (say, for another purpose), associated type inference would pick it and reject the `AsyncSequence`, causing a source compatibility problem. Work around the issue in two ways. First, always infer the type witness for `AsyncSequence.Failure` from the type witness for `AsyncIteratorProtocol.Failure`, so they can't be out of sync. This means that we'll never even consider a nested `Failure` type in the `AsyncSequence`-conforming type. This hack only applies prior to Swift 6. Second, when we have inferred a `Failure` type and there is already something else called `Failure` within that same nominal type, don't print the inferred typelias into a module interface because it will cause a conflict. Fixes rdar://123543633.
55 lines
1.9 KiB
Swift
55 lines
1.9 KiB
Swift
// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s -module-name conformances
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// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -module-name conformances
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// RUN: %FileCheck %s < %t.swiftinterface
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// REQUIRES: concurrency, OS=macosx
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// CHECK: @available(
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// CHECK-NEXT: public struct SequenceAdapte
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@available(SwiftStdlib 5.1, *)
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public struct SequenceAdapter<Base: AsyncSequence>: AsyncSequence {
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// CHECK-LABEL: public struct AsyncIterator
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// CHECK: @available{{.*}}macOS 10.15
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// CHECK-NEXT: public typealias Element = Base.Element
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// CHECK: @available(
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// CHECK-NEXT: public typealias Failure = Base.Failure
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public typealias Element = Base.Element
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public struct AsyncIterator: AsyncIteratorProtocol {
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public mutating func next() async rethrows -> Base.Element? { nil }
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}
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// CHECK-LABEL: public func makeAsyncIterator
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public func makeAsyncIterator() -> AsyncIterator { AsyncIterator() }
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// CHECK: @available(
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// CHECK-NEXT: public typealias Failure = Base.Failure
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}
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// CHECK: @available(
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// CHECK-NEXT: public struct OtherSequenceAdapte
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@available(SwiftStdlib 5.1, *)
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public struct OtherSequenceAdapter<Base: AsyncSequence>: AsyncSequence {
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// CHECK: public typealias Element = Base.Element
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// CHECK-NOT: public typealias Failure
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// CHECK: public struct Failure
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// CHECK-LABEL: public struct AsyncIterator
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// CHECK: @available{{.*}}macOS 10.15
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// CHECK: @available(
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// CHECK-NEXT: public typealias Failure = Base.Failure
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public typealias Element = Base.Element
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public struct Failure: Error { }
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// CHECK-NOT: public typealias Failure
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public struct AsyncIterator: AsyncIteratorProtocol {
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public mutating func next() async rethrows -> Base.Element? { nil }
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}
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// CHECK: public func makeAsyncIterator
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public func makeAsyncIterator() -> AsyncIterator { AsyncIterator() }
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// CHECK-NOT: public typealias Failure
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}
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