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[SR-2324] Optional closure type is always considered @escaping #44931

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swift-ci opened this issue Aug 11, 2016 · 6 comments
Closed

[SR-2324] Optional closure type is always considered @escaping #44931

swift-ci opened this issue Aug 11, 2016 · 6 comments
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@swift-ci
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@swift-ci swift-ci commented Aug 11, 2016

Previous ID SR-2324
Radar rdar://problem/27795901
Original Reporter ilijatovilo (JIRA User)
Type Bug
Status Resolved
Resolution Done
Environment

OSX 10.11.6 (15G31)
MacBook Pro (Retina, Mid 2012)
Version 8.0 beta 5 (8S193k)
Toolchain: Swift Development Snapshot 2016-08-07 (a)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee @milseman
Priority Medium

md5: ab4ee203bb7d77d3976562cd10a4342c

is duplicated by:

Issue Description:

The following code snippet doesn't work anymore in the current Swift 3 snapshot:

func takes(anOptionalClosure: (() -> Void)?) {
    if let aClosure = anOptionalClosure {
        aClosure()
    }
}

func takes(aClosure: () -> Void) {
    takes(anOptionalClosure: aClosure)
}

> main.swift:18:30: Cannot convert value of type '() -> Void' to expected argument type '(() -> Void)?'

My guess is that the type checker thinks that `(() -> Void)?` is interpreted as a tuple type. But the parens are only necessary to make the closure optional. Interestingly this only happens with function types. `(String)?` e.g. type checks correctly.

The following snippet works as expected:

func takes(anOptionalClosure: (() -> Void)?) {
    if let aClosure = anOptionalClosure {
        aClosure()
    }
}

// Hint: Added two surrounding parens to the argument type
func takes(aClosure: (() -> Void)) {
    takes(anOptionalClosure: aClosure)
}
@belkadan
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@belkadan belkadan commented Aug 12, 2016

The actual issue here is that optional closures are implicitly @escaping right now.

@belkadan
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@belkadan belkadan commented Aug 12, 2016

@milseman, do we have a JIRA or Radar for this already?

@milseman
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Mannequin

@milseman milseman mannequin commented Aug 12, 2016

Yes, <rdar://problem/27795901>

@swift-ci
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@swift-ci swift-ci commented Sep 7, 2016

Comment by Shawn Erickson (JIRA)

Note I added a comment to SR-2444 which is marked resolved because I assume it is considered a duplicate of this issue. What is described in SR-2444 is problematic still in Xcode 8 GM.

https://bugs.swift.org/browse/SR-2444?focusedCommentId=17861&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-17861

@milseman
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Mannequin

@milseman milseman mannequin commented Sep 19, 2016

Also, rdar://problem/28372774

@milseman
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Mannequin

@milseman milseman mannequin commented Sep 23, 2016

With #4905 produces the correct error message here:

...: error: unexpected note produced: parameter 'aClosure' is implicitly non-escaping
func takes(aClosure: () -> Void) {
           ^
...: error: unexpected error produced: passing non-escaping parameter 'aClosure' to function expecting an @escaping closure
    takes(anOptionalClosure: aClosure)
                             ^

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