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[SR-5628] inout argument of closure passed to generic function inferred as immutable #48198

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werediver opened this issue Aug 4, 2017 · 3 comments
Closed

[SR-5628] inout argument of closure passed to generic function inferred as immutable #48198

werediver opened this issue Aug 4, 2017 · 3 comments
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@xedin
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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 4.0 type checker Area → compiler: Semantic analysis

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@werediver
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Previous ID SR-5628
Radar rdar://problem/33725301
Original Reporter @werediver
Type Bug
Status Resolved
Resolution Done
Environment

Swift 4.0 (swiftlang-900.0.54.11 clang-900.0.31), Xcode 9.0 beta 4 9M189t, Mac OS X 10.12.5 16F73

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, 4.0Regression, TypeChecker
Assignee @xedin
Priority Medium

md5: 5f0a2256dc0a8c39b3a35e83526a0562

relates to:

  • SR-3520 Generic function taking closure with inout parameter can result in a variety of compiler errors or EXC_BAD_ACCESS

Issue Description:

Swift 4.0 compiler bundled with Xcode 9 beta 4 9M189t

$ sudo xcode-select -s /Applications/Xcode-9b4.app/ # Xcode 9.0 beta 4 9M189t
$ swift --version
Apple Swift version 4.0 (swiftlang-900.0.54.11 clang-900.0.31)
Target: x86_64-apple-macosx10.9

fails on this sample

$ cat mut.swift 
func mut<T, U>(_ some: T, _ body: (inout T) -> U) -> U {
    var _some = some
    return body(&_some)
}

let a = 1
mut(a) { $0 += 1; print($0) }

as shown below

$ swiftc mut.swift 
mut.swift:7:13: error: left side of mutating operator isn't mutable: '$0' is immutable
mut(a) { $0 += 1; print($0) }
         ~~ ^

This behavior is also reproducible in an Xcode Playground.
The issue is related to generic functions only. The following code does not produce any errors.

func muti(_ some: Int, _ body: (inout Int) -> ()) -> () {
    var _some = some
    return body(&_some)
}

let a = 1
muti(a) { $0 += 1; print($0) }

Swift 3.1 compiler bundled with Xcode 8.3.2 8E2002

$ sudo xcode-select -s /Applications/Xcode.app # Xcode 8.3.2 8E2002
$ swift --version
Apple Swift version 3.1 (swiftlang-802.0.53 clang-802.0.42)
Target: x86_64-apple-macosx10.9

compiles the problematic sample without any complains

$ swiftc mut.swift 
$ ./mut
2

This seems to be related to SR-3520, so this can be a regression.
@belkadan
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belkadan commented Aug 4, 2017

Thanks, Raman!

@swift-ci create

@rudkx
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rudkx commented Mar 7, 2018

@xedin I think you may have fixed this, do you recall?

It doesn't reproduce for me anymore.

@xedin
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xedin commented Mar 7, 2018

@rudkx Yes, this should be fixed by #12072 and it's follow-up PRs which address corner cases.

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

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 4.0 type checker Area → compiler: Semantic analysis
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5 participants
@xedin @rudkx @belkadan @werediver @AnthonyLatsis