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  1. Swift
  2. SR-11128

Protocol stubs include __consuming and __owned

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    Details

    • Type: Bug
    • Status: Open
    • Priority: Medium
    • Resolution: Unresolved
    • Component/s: Compiler
    • Labels:
    • Environment:

      Reproduced in Xcode 11 beta 3 and Swift Development Snapshot 2019-07-11 (a)

      Description

      When Swift offers to apply protocol stubs in Xcode, the fix-it produced may include the __consuming and __owned modifiers, which are not currently a supported part of the language and are not intended to be used in most conformances even once they are officially added.

      Steps To Reproduce:
      Although this is a compiler bug, the printed form of compiler diagnostics doesn't display fix-its in sufficient detail to easily demonstrate it. It's most easily reproduced in an Xcode with an appropriate toolchain:

      1. Create a new Xcode project with this code in a Swift source file:

      struct MyType: Hashable {
        typealias Element = Int
      }
      extension MyType: SetAlgebra {}
      

      2. Build it.
      3. Click the error badge on the extension line, then click the “Fix” button to apply the fix-it.

      Results:
      Some of the stubbed declarations include __consuming and/or __owned modifiers, such as:

      __consuming func union(_ other: __owned MyType) -> MyType
      

      I would not expect Swift to suggest these modifiers, since they aren’t officially part of the language. Instead I would expect it to drop these keywords:

      func union(_ other: MyType) -> MyType
      

      Even after we fully support move-only types, I would expect the protocol stubs for a non-move-only conformance to remove unnecessary move-only–related modifiers so that users don't need to worry about this complexity.

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            • Assignee:
              Unassigned
              Reporter:
              brentdax Brent Royal-Gordon
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              Dates

              • Created:
                Updated: