[SR-7674] Compiler crash while working on a type erasurer #50214
Labels
associated type inference
bug
A deviation from expected or documented behavior. Also: expected but undesirable behavior.
compiler
The Swift compiler in itself
conformances
Feature → protocol: protocol conformances
declarations
Feature: declarations
protocol
Feature → type declarations: Protocol declarations
swift 5.9
type checker
Area → compiler: Semantic analysis
typealias
Feature → type declarations: `typealias` declarations
unexpected error
Bug: Unexpected error
Comments
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Comment by Guido Marucci Blas (JIRA) OK I found a work-around, instead of declaring private let performEffect: (EffectType) -> EffectResultProducer I declare it without using the typealias inherited from the protocol comformance to private let performEffect: (EffectType) -> SignalProducer<Result<EffectResponseType, EffectErrorType>, NoError>and it compiled. Maybe something clashing when trying to expand the typealias? |
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Comment by Guido Marucci Blas (JIRA) Here are swift build crash output for Swift version in Xcode 9.3 and latest 4.2 snapshot. I've also attached a project that reproduces the issue. Apple Swift version 4.1 (swiftlang-902.0.48 clang-902.0.37.1) Apple Swift version 4.2-dev (LLVM ae60dc0632, Clang 91ee593a0d, Swift 9f28451) |
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Comment by Guido Marucci Blas (JIRA) Here is a twitter thread were I discussed this in case there some replies that can help with this issue -> https://twitter.com/guidomb/status/995810518735753218 |
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@slavapestov, @rudkx, sound familiar? |
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I need to come up with a stand-alone test case, but the problem might even be with associated type inference. |
AnthonyLatsis
added
the
crash
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I hit this today in our codebase: |
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Now that I look at it, this may be a different issue. If we look at |
AnthonyLatsis
added
type checker
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Apparently this no longer crashes, but still unexpectedly errors out due to what feels like a circularity between associated type inference and type alias resolution. Reduced: protocol P {
associatedtype A
typealias Alias = A
func req(_: Alias)
}
struct Conformer<A>: P {
func nonReq(_: Alias) {}
func req(_: Alias) {} // error: reference to invalid type alias 'Alias' of type 'Conformer<A>'
}Funnily enough the error can be hacked around by swapping Tested with Swift 5.9-dev (c1d5118). |
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Attachment: Download
Environment
Xcode Version 9.3 (9E145)
macOS Version 10.13.4 (17E202)
ReactiveSwift 3.1.0 revision 46fb4d4a8285286e54929add1d12f384675895c6
Result 3.2.4 revision 7477584259bfce2560a19e06ad9f71db441fff11
Additional Detail from JIRA
md5: b6710c796fab2d8226271de84635e7dc
Issue Description:
The following code generates a compiler crash
Compiler output:
The text was updated successfully, but these errors were encountered: