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[SR-13135] Type inference regression in Swift 5.3/Xcode 12 Beta #55581

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swift-ci opened this issue Jul 2, 2020 · 3 comments
Closed

[SR-13135] Type inference regression in Swift 5.3/Xcode 12 Beta #55581

swift-ci opened this issue Jul 2, 2020 · 3 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis

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@swift-ci
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swift-ci commented Jul 2, 2020

Previous ID SR-13135
Radar rdar://problem/65088975
Original Reporter DeeSee (JIRA User)
Type Bug
Status Resolved
Resolution Done
Environment

Xcode 12 Beta 1/macOS Catalina 10.15.5 (19F101)

Additional Detail from JIRA
Votes 4
Component/s Compiler
Labels Bug, TypeChecker
Assignee DeeSee (JIRA)
Priority Medium

md5: de79c846cf09afec4f64b77b416ac261

Issue Description:

Consider this code sample:

private struct Foo {
  var bar: [Int] = []
}

let baz: Int? = nil

func foo<T: Equatable>(
  _ a: @autoclosure () throws -> T,
  _ b: @autoclosure () throws -> T
) {}

foo(Foo().bar, [baz])

It runs perfectly fine in Xcode 11.5 playground, while Xcode 12 Beta 1 outputs the following error:

error: test.playground:11:17: error: cannot convert value of type 'Int?' to expected element type 'Array<Int>.ArrayLiteralElement' (aka 'Int')
foo(Foo().bar, [baz])

Please note that @autoclosure attribute for foo's parameters is a required precondition for this issue.
@typesanitizer
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Seems like covariance in the return type is not working properly for autoclosures? Here's a slightly reduced example:

let x : [Int] = []
let y: Int? = nil
func f<T>(_: @autoclosure () -> T, _: @autoclosure () -> T) {}
f(x, [y])

Thanks for reporting with a small example! 🙂

@typesanitizer
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@swift-ci create

@xedin
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xedin commented Jul 6, 2020

Fixed by #32724 Please use next available nightly build of master to verify and close.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis
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