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[SR-12530] Faulty compiler error when passing keypath to property wrapper in Swift 5.2 #54973

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swift-ci opened this issue Apr 6, 2020 · 4 comments
Closed

[SR-12530] Faulty compiler error when passing keypath to property wrapper in Swift 5.2 #54973

swift-ci opened this issue Apr 6, 2020 · 4 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 5.2

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@swift-ci
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swift-ci commented Apr 6, 2020

Previous ID SR-12530
Radar rdar://problem/61911117
Original Reporter xy (JIRA User)
Type Bug
Status Resolved
Resolution Done

Attachment: Download

Additional Detail from JIRA
Votes 2
Component/s Compiler
Labels Bug, 5.2Regression
Assignee xy (JIRA)
Priority Medium

md5: 08076328c000c9215ccfcb5afab360f0

Issue Description:

The Problem:

The below code compiles fine on Swift 5.1 compiler, however Swift 5.2 introduced a bug in the compiler. Now it fails to compile, with the error "Key path cannot refer to static member 'bar'"

@propertyWrapper
struct Wrap<R, V> {
    var val: V 
    var wrappedValue: V {
        get { val }
        set { val = newValue }
    }
    init(_ key: WritableKeyPath<R,V>, val: V) {
        self.val = val
    }
}

struct Foo {
    @Wrap(\Foo.bar, val: 1) var bar: Int
}

Current Workaround

The following compiles in 5.2 with no errors and works fine:

struct Foo {
    static let barKeyPath: WritableKeyPath<Foo, Int> = \.bar
    @Wrap(barKeyPath, val: 1) var bar: Int
}

This is not an acceptable workaround though due to how many places we would need to use it. As a result this bug makes Swift 5.2 unusable for us. Please fix soon, thanks.
@weissi
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weissi commented Apr 7, 2020

@swift-ci create

@theblixguy
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Works fine on master. Can you verify using the latest trunk snapshot?

@swift-ci
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swift-ci commented May 3, 2020

Comment by Thomas Dekker (JIRA)

This issue is also really quite breaking for me. I use KeyPaths to neatly match the property within a meta model for a database without a lot of boilerplate.

The issue only occurs if a KeyPath is used with the initializer of the property wrapper of that same property. See my attachment for an example. It occurs in Xcode 11.4.1 using Swift 5.2.

However, I did test this using the Swift Snapshot 2020-04-30 with Xcode 11.4.1. This DOES work correctly. It seems this has already been fixed, but not released.

@hborla
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hborla commented Jul 2, 2020

This is fixed in Swift 5.3. Could you please verify with Xcode 12 beta 1? Thank you!

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 5.2
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@weissi @theblixguy @hborla @swift-ci @AnthonyLatsis