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[SR-7563] Generic class with AnyObject constraint won't except protocol that also has AnyObject constraint #50105

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swift-ci opened this issue Apr 28, 2018 · 1 comment
Closed

[SR-7563] Generic class with AnyObject constraint won't except protocol that also has AnyObject constraint #50105

swift-ci opened this issue Apr 28, 2018 · 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

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@swift-ci
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Previous ID SR-7563
Radar None
Original Reporter kdawgwilk (JIRA User)
Type Bug
Status Resolved
Resolution Duplicate

Attachment: Download

Environment

Xcode 9.3

macOS 10.13.4

Swift 4.1

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

md5: a05c1124d8c541ab8b4de70686ccfd12

duplicates:

  • SR-55 non-@objc protocol existentials do not conform to their own protocol type

Issue Description:

This feels like it should be possible but maybe I am just being naive?

import Foundation

class A<ClassDelegate: AnyObject> {
    weak var delegate: ClassDelegate?
}

protocol P: AnyObject {}

class B: A<P> {}

![](Screen Shot 2018-04-28 at 12.13.34 PM.png)
@belkadan
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belkadan commented May 1, 2018

This is correct behavior: a protocol value carries with it both the underlying class reference and the information about how the class conforms to the protocol (the witness table). This isn't compatible with the representation of AnyObject.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@belkadan @swift-ci