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[SR-13215] Default implementation of dynamic member lookup subscript in protocol extension causes segfault 11 #55655

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swift-ci opened this issue Jul 14, 2020 · 2 comments
Closed

[SR-13215] Default implementation of dynamic member lookup subscript in protocol extension causes segfault 11 #55655

swift-ci opened this issue Jul 14, 2020 · 2 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software type checker Area → compiler: Semantic analysis

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@swift-ci
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Previous ID SR-13215
Radar None
Original Reporter marcusrossel (JIRA User)
Type Bug
Status Resolved
Resolution Duplicate
Environment

  • Xcode version Version 11.5 (11E608c)

  • macOS 10.15.5 (19F101)

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

md5: 767161678d25ac02a65f85ea6bb6b8dc

duplicates:

  • SR-12425 Swift 5.2 Regression: Segfault when type of dynamic member key path doesn't match instance type

Issue Description:

This code snippet causes the compiler to fail with a Segmentation fault 11:

@dynamicMemberLookup
protocol FuzzyDecodable: Decodable {
  associatedtype CodingKeys: CodingKey, RawRepresentable where CodingKeys.RawValue == String
  subscript<T>(dynamicMember keyPath: KeyPath<Self, T>) -> T { get set }
  init(from decoder: Decoder) throws
}

extension FuzzyDecodable {
  subscript<T>(dynamicMember keyPath: KeyPath<Self, T>) -> T {
    get { self[keyPath: keyPath] }
    set { self[keyPath: keyPath] = newValue }
  }
}
@theblixguy
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This seems to be fixed on Xcode 12 beta and it no longer crashes. You now get the following diagnostic:

<source>:11:15: error: cannot assign through subscript: 'keyPath' is a read-only key path
    set { self[keyPath: keyPath] = newValue }
          ~~~~^~~~~~~~~~~~~~~~~~

Your subscript needs to take either a WritableKeyPath or ReferenceWritableKeyPath depending on whether you're working with value types or reference types.

@LucianoPAlmeida
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@theblixguy I think this is the same problem as SR-12425 and SR-12626, so maybe could be resolved as a dupe.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@AnthonyLatsis AnthonyLatsis added the crash Bug: A crash, i.e., an abnormal termination of software label Dec 12, 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 crash Bug: A crash, i.e., an abnormal termination of software type checker Area → compiler: Semantic analysis
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@theblixguy @LucianoPAlmeida @swift-ci @AnthonyLatsis