Swift 6 runtime/Compile Crash with AsyncIteratorProcotol TypedThrow #74292
Labels
bug
A deviation from expected or documented behavior. Also: expected but undesirable behavior.
crash
Bug: A crash, i.e., an abnormal termination of software
typed throws
Feature → error handling → throws & rethrows: Typed throws
Comments
pbk20191
added
bug
pbk20191
changed the title
|
There is compile time crash with rethrow Protocol and TypedFailure. This happens in Xcode 16.0 beta swift 6 public protocol TypedAsyncIteratorProtocol<Element, Failure> {
associatedtype Element
associatedtype Failure: Error
typealias TetraFailure = Failure
@inlinable
mutating func next(isolation actor: isolated (any Actor)?) async throws(Failure) -> Element?
}
extension AsyncMapSequence.Iterator: TypedAsyncIteratorProtocol where Base.AsyncIterator: TypedAsyncIteratorProtocol {
@_implements(TypedAsyncIteratorProtocol, next(isolation:))
mutating public func tetraNext(isolation actor: isolated (any Actor)?) async throws(Base.AsyncIterator.TetraFailure) -> Self.Element? {
if #available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *) {
return try await nextValue(isolation: actor)
} else {
return try await nextMapValue()
}
}
}
@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
extension AsyncIteratorProtocol {
@usableFromInline
mutating internal func nextValue(isolation actor: isolated (any Actor)?) async throws(Failure) -> Self.Element? {
try await next(isolation: actor)
}
}
extension AsyncMapSequence.Iterator {
mutating func nextMapValue() async rethrows -> sending Self.Element? {
try await next()
}
}
This is the stack trace |
hborla
added
typed throws
|
Not sure if this is another incarnation of the same issue, or a related-but-different one, but it's also possible to skirt the availability checks more directly: protocol HasAsyncSequenceTraits {
associatedtype Base: AsyncSequence
associatedtype Failure
@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
associatedtype _Witness = Never where Base.Failure == Failure
}
enum AsyncSequenceTraits<Base: AsyncSequence>: HasAsyncSequenceTraits {}
typealias FailureOf<S: AsyncSequence> = AsyncSequenceTraits<S>.Failure
// absurd: would allow you to "extract" the Failure associatedtype at runtime
// despite that info not being present in ABI
func extractFailureType(of sequence: any AsyncSequence) -> Error.Type {
func helper<S: AsyncSequence>(_ sequence: S) -> Error.Type {
FailureOf<S>.self
}
return helper(sequence)
} |
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Description
AsyncIteratorProtocol has inconsistence behavior with protocol witness table. which cause Runtime crash.
Sometime
EXC_BAD_ACCESSReproduction
declare own AsyncIteratorProtocol
Stack dump
Expected behavior
Not crash in runtime and should run normally.
Environment
Xcode 16.0 beta swift 6
Additional information
No response
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