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[SR-12913] Associated type inference crash: "Conflicting type witness deductions" #55359

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dan-zheng opened this issue May 31, 2020 · 2 comments · Fixed by #59357
Closed

[SR-12913] Associated type inference crash: "Conflicting type witness deductions" #55359

dan-zheng opened this issue May 31, 2020 · 2 comments · Fixed by #59357
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@AnthonyLatsis
Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself conditional conformances Feature → protocol → conformances: conditional conformances crash Bug: A crash, i.e., an abnormal termination of software

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@dan-zheng
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Previous ID SR-12913
Radar rdar://problem/63819460
Original Reporter @dan-zheng
Type Bug
Environment

swift-DEVELOPMENT-SNAPSHOT-2020-05-26-a

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, AssociatedTypeInference, CompilerCrash
Assignee None
Priority Medium

md5: 017a8020317d94098be933346fbf2e7d

Issue Description:

Reproducer not minimized. I tried minimizing it to a single file but wasn't yet successful, sorry.

import _Differentiation

protocol DifferentiableCollection: Differentiable & Collection {
  associatedtype TangentVector
}
extension Array: DifferentiableCollection {}
$ swift crash.swift
Assertion failed: (Conformance->getTypeWitnessUncached(assocType) .getWitnessType() ->isEqual(type) && "Conflicting type witness deductions"), function recordTypeWitness, file /Users/danielzheng/swift-debug/swift/lib/Sema/TypeCheckProtocol.cpp, line 2685.
Stack dump:
...
1.  Swift version 5.3-dev (LLVM 2e4f104624, Swift 50b4fcc97d)
2.  While evaluating request TypeCheckSourceFileRequest(source_file "crash.swift")
3.  While type-checking extension of Array (at crash.swift:6:1)
4.  While type-checking protocol conformance to 'DifferentiableCollection' (at crash.swift:3:1) for type 'Array<Element>'
0  swift                    0x000000010a280808 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  swift                    0x000000010a27f788 llvm::sys::RunSignalHandlers() + 248
2  swift                    0x000000010a280dfd SignalHandler(int) + 285
3  libsystem_platform.dylib 0x00007fff6d6115fd _sigtramp + 29
4  libsystem_platform.dylib 000000000000000000 _sigtramp + 18446603338681084448
5  libsystem_c.dylib        0x00007fff6d4e7808 abort + 120
6  libsystem_c.dylib        0x00007fff6d4e6ac6 err + 0
7  swift                    0x000000010a692ab3 swift::ConformanceChecker::recordTypeWitness(swift::AssociatedTypeDecl*, swift::Type, swift::TypeDecl*) (.cold.1) + 35
8  swift                    0x0000000106a5b881 swift::ConformanceChecker::recordTypeWitness(swift::AssociatedTypeDecl*, swift::Type, swift::TypeDecl*) + 81
9  swift                    0x0000000106a5c0f0 swift::ConformanceChecker::recordTypeWitness(swift::AssociatedTypeDecl*, swift::Type, swift::TypeDecl*) + 2240
10 swift                    0x0000000106a5f615 swift::ConformanceChecker::resolveTypeWitnessViaLookup(swift::AssociatedTypeDecl*) + 869
11 swift                    0x0000000106a7f5ea swift::AssociatedTypeInference::solve(swift::ConformanceChecker&) + 282
12 swift                    0x0000000106a7fe1f swift::ConformanceChecker::resolveTypeWitnesses() + 271
@typesanitizer
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@swift-ci create

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@AnthonyLatsis AnthonyLatsis self-assigned this Jun 7, 2022
@AnthonyLatsis
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Apparently minimal:

protocol P {
  associatedtype A
}
protocol Q: P {
  associatedtype A
}

struct S<T> {}

extension S: P where T: P {
  typealias A = Int
}
extension S: Q {}

@AnthonyLatsis AnthonyLatsis added conditional conformances Feature → protocol → conformances: conditional conformances and removed associated type inference labels Jun 7, 2022
@AnthonyLatsis AnthonyLatsis mentioned this issue Jun 10, 2022
Merged
@AnthonyLatsis AnthonyLatsis added the crash Bug: A crash, i.e., an abnormal termination of software label Dec 12, 2022
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@AnthonyLatsis AnthonyLatsis

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself conditional conformances Feature → protocol → conformances: conditional conformances crash Bug: A crash, i.e., an abnormal termination of software
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@dan-zheng @typesanitizer @AnthonyLatsis