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[SR-9595] Unexpected error when type checking constrained associated types #52042

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rxwei opened this issue Jan 3, 2019 · 5 comments
Closed

[SR-9595] Unexpected error when type checking constrained associated types #52042

rxwei opened this issue Jan 3, 2019 · 5 comments
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@slavapestov
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis

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@rxwei
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rxwei commented Jan 3, 2019

Previous ID SR-9595
Radar rdar://problem/75329340
Original Reporter @rxwei
Type Bug
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, TypeChecker
Assignee @slavapestov
Priority Medium

md5: 566220f9d77423bbecc919b4912e7ab1

relates to:

  • TF-213 [AD] Fix Differentiable protocol generic signature bug

Issue Description:

I expect the following to compile:

protocol Q {
  associatedtype Assoc
}

protocol P {
  associatedtype T : P, Q where T.Assoc : FloatingPoint, T == U.U
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
}

... but the compiler produces a ton of warnings that don't really make sense.

sr9595.swift:6:22: warning: redundant conformance constraint 'Self.T': 'P'
  associatedtype T : P, Q where T.Assoc : FloatingPoint, T == U.U
                     ^
sr9595.swift:7:22: note: conformance constraint 'Self.T.T': 'P' implied here
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
                     ^
sr9595.swift:6:25: warning: redundant conformance constraint 'Self.T': 'Q'
  associatedtype T : P, Q where T.Assoc : FloatingPoint, T == U.U
                        ^
sr9595.swift:7:22: note: conformance constraint 'Self.T.T': 'Q' implied here
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
                     ^
sr9595.swift:6:41: warning: redundant conformance constraint 'Self.T.Assoc': 'FloatingPoint'
  associatedtype T : P, Q where T.Assoc : FloatingPoint, T == U.U
                                        ^
sr9595.swift:7:22: note: conformance constraint 'Self.T.T.Assoc': 'FloatingPoint' implied here
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
                     ^
sr9595.swift:7:25: warning: redundant conformance constraint 'Self.U': 'Q'
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
                        ^
sr9595.swift:7:22: note: conformance constraint 'Self.U': 'Q' implied here
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
                     ^
sr9595.swift:7:41: warning: redundant conformance constraint 'Self.U.Assoc': 'FloatingPoint'
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
                                        ^
sr9595.swift:7:22: note: conformance constraint 'Self.U.Assoc': 'FloatingPoint' implied here
  associatedtype U : P, Q where U.Assoc : FloatingPoint, U == T.U
                     ^
@belkadan
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belkadan commented Jan 7, 2019

cc @DougGregor, @slavapestov

@dan-zheng
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@DougGregor: you said that this is a generic signature minimization bug.
Could you please give some pointers towards debugging/fixing this issue in lib/AST/GenericSignatureBuilder.cpp? That would be much appreciated.

@slavapestov
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@swift-ci create

@slavapestov
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Nice test case!

@slavapestov
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#42113

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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@slavapestov slavapestov

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis
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@slavapestov @belkadan @rxwei @dan-zheng