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[SR-4536] Useless diagnostic unwrapping weak self in closure #47113

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NachoSoto opened this issue Apr 7, 2017 · 5 comments
Closed

[SR-4536] Useless diagnostic unwrapping weak self in closure #47113

NachoSoto opened this issue Apr 7, 2017 · 5 comments
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@NachoSoto
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation

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@NachoSoto
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Previous ID SR-4536
Radar rdar://problem/31511959
Original Reporter @NachoSoto
Type Bug
Status Resolved
Resolution Done
Environment

  • Swift version 3.1 (swiftlang-802.0.48 clang-802.0.38)

  • Swift version 4.0 (swiftlang-900.0.59 clang-900.0.34.2)

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

md5: e28f8bd1ca54953bce648738e911d723

Issue Description:

Code:

class C {
    func f() {
        let _: () -> Void = { [weak self] in
            guard let self = self else { return }
            print(self)
        }
    }
}

Expected result:

It works, just like this works:

class C {
    func f() {
        let a = NSObject()
        
        let _: () -> Void = { [weak a] in
            guard let a = a else { return }
            print(a)
        }
    }
}

Actual result:

3 useless diagnostics:

  • Cannot convert value of type 'C?' to expected argument type '_OptionalNilComparisonType'

  • Pattern matching in a condition requires the 'case' keyword

  • Expression implicitly coerced from 'C?' to Any
@jckarter
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jckarter commented Apr 7, 2017

@swift-ci create

@belkadan
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These are terrible diagnostics, but it's worth noting that "self" is a keyword, not a normal variable name. (There's been requests to add support for this syntax anyway, though.)

@NachoSoto
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> These are terrible diagnostics, but it's worth noting that "self" is a keyword, not a normal variable name.

That seems like a language implementation detail 😛 it behaves as a variable in many situations. But I see what you're saying.

@NachoSoto
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Still an issue in Swift 4.0

@xedin
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xedin commented Feb 5, 2020

Tried first snippet with master/5.2 and it type-checks correctly now. I think support for weak self has been recently implemented in the compiler. Please verify using master and/or 5.2 snapshot.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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@NachoSoto NachoSoto

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself diagnostics QoI Bug: Diagnostics Quality of Implementation
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@xedin @jckarter @NachoSoto @belkadan