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[SR-13019] Bad compiler error on generic constraint of associated types #55464

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stephencelis opened this issue Jun 15, 2020 · 1 comment
Closed

[SR-13019] Bad compiler error on generic constraint of associated types #55464

stephencelis opened this issue Jun 15, 2020 · 1 comment
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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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@stephencelis
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Previous ID SR-13019
Radar None
Original Reporter @stephencelis
Type Bug
Status Resolved
Resolution Duplicate
Environment

Swift 5.2

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

md5: a78cb98ba468d48de6fb3f5ad2387bb0

duplicates:

  • SR-10752 Trouble with Generic Constraints and Associated Types

Issue Description:

This should compile, but doesn't:

struct T<A> {
  func f<C>(_ c: C) -> A
    where C: Collection, C.SubSequence == A, A.SubSequence == A
  {
    fatalError()
  }
}

Errors:

'SubSequence' is not a member type of 'A'

While this might produce a redundant warning, the error is wrong. This is related to a bug I opened over a year ago that is sadly still open today 🙁

https://bugs.swift.org/browse/SR-10752
@slavapestov
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This is fixed in the RequirementMachine implementation and I already have a regression test for the older dupe.

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