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[SR-7601] @objc protocol methods cannot return Self #50143

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nicklockwood opened this issue May 4, 2018 · 6 comments
Closed

[SR-7601] @objc protocol methods cannot return Self #50143

nicklockwood opened this issue May 4, 2018 · 6 comments

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@nicklockwood
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nicklockwood commented May 4, 2018

Previous ID SR-7601
Radar None
Original Reporter @nicklockwood
Type Improvement
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Improvement
Assignee @theblixguy
Priority Medium

md5: d02438d6b1525db5cf95f2cfc2d82dd3

Issue Description:

In Swift, the following is permitted:

protocol Foo {
    static func makeFoo() -> Self
}

But if the protocol is marked as @objc, it generates the warning "Method cannot be a member of an @objc protocol because its result type cannot be represented in Objective-C"

However, adding Self as a return type to a protocol method doesn't usually treat Self as an associatedType requirement, so it's not clear why a protocol method returning Self can't be represented in Objective-C.

The equivalent Objective-C code is permitted and works as you'd expect:

@protocol Foo
+ (instancetype)makeFoo;
@end

@interface Bar: NSObject<Foo>
@end

@implementation Bar
+ (instancetype)makeFoo { return [[self alloc] init]; }
@end
@belkadan
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belkadan commented May 4, 2018

@DougGregor, @rjmccall, do you know the reason for this?

@rjmccall
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rjmccall commented May 4, 2018

I don't think there's any good reason for it; it seems to me that we could absolutely expose it as `instancetype`.

@DougGregor
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DougGregor commented May 4, 2018

I agree; there's no reason for this restriction in an Objective-C protocol.

@Dante-Broggi
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Dante-Broggi commented Aug 30, 2018

This still happens in the swift-DEVELOPMENT-SNAPSHOT-2018-08-26.

@theblixguy
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theblixguy commented Jan 20, 2019

PR: #22006

@theblixguy
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theblixguy commented Jan 23, 2019

@Dante-Broggi @nicklockwood: Fixed on master.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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