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[SR-13112] assignment to enum instance should deinitialize associated values on all optimization levels #55558

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tayloraswift opened this issue Jun 29, 2020 · 1 comment
Closed

[SR-13112] assignment to enum instance should deinitialize associated values on all optimization levels #55558

tayloraswift opened this issue Jun 29, 2020 · 1 comment
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior.

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@tayloraswift
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Previous ID SR-13112
Radar None
Original Reporter @Kelvin13
Type Bug
Status Resolved
Resolution Invalid
Environment

$ swift --version
Swift version 5.2-dev (LLVM 4cd92ac, Swift 79716ef)
Target: x86_64-unknown-linux-gnu

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

md5: 43a01c2ae7a5e2ac494c04e32d0d72d5

Issue Description:

currently, the following test program prints `false` on normal settings, and `true` when compiled with `-O`

related discussion: https://forums.swift.org/t/why-isn-t-isuniquelyreferenced-working-here/37949/4?u=taylorswift

final
class C 
{
    init() 
    {
    }
}
enum E
{
    case empty 
    case c(C)
}

func foo()  
{
    var e:E = .c(.init())
    switch e 
    {
    case .c(var c):
        e = .empty
        print(isKnownUniquelyReferenced(&c))
    default:
        break
    }
}

foo()
@rjmccall
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I'm going to close this one; it's acceptable for `isKnownUniquelyReferenced` to change from `false` to `true` under optimization as a general matter. Whether `switch` should guarantee to not separately keep the switch value alive in unoptimized builds is better tracked as SE-13114.

@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.
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@rjmccall @tayloraswift