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[SR-12789] 'τ_0_0' in conformance type-checking diagnostics #55234

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dan-zheng opened this issue May 11, 2020 · 0 comments
Closed

[SR-12789] 'τ_0_0' in conformance type-checking diagnostics #55234

dan-zheng opened this issue May 11, 2020 · 0 comments
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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@dan-zheng
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Previous ID SR-12789
Radar None
Original Reporter @dan-zheng
Type Bug
Status Resolved
Resolution Duplicate
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, TypeChecker
Assignee None
Priority Medium

md5: 7296f7255bcb329049148f6bb5f67e5c

duplicates:

  • SR-12759 Heisenbug in Witness Matching Because of Leaked Type Variables

Issue Description:

protocol Protocol {
  associatedtype Assoc
  func foo()
}
extension Protocol where Assoc == Self {
  func foo() {}
}

extension Float: Protocol {
  typealias Assoc = Float
}

struct Foo<T> {
  var x: T
}
extension Foo: Protocol {
  typealias Assoc = Float
}
$ swift tau.swift
tau.swift:16:1: error: type 'Foo<T>' does not conform to protocol 'Protocol'
extension Foo: Protocol {
^
tau.swift:6:8: note: candidate would match if 'Foo<T>' was the same type as 'Foo<τ_0_0>.Assoc' (aka 'Float')
  func foo() {}
       ^
tau.swift:3:8: note: protocol requires function 'foo()' with type '() -> ()'; do you want to add a stub?
  func foo()
       ^
@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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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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@dan-zheng