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[SR-9837] Optional<T>.none -> Optional<U>.none casting regression in generic context #52251

hamishknight opened this issue Feb 1, 2019 · 2 comments


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@hamishknight hamishknight commented Feb 1, 2019

Previous ID SR-9837
Radar rdar://problem/47743688
Original Reporter @hamishknight
Type Bug
Status Resolved
Resolution Done

Apple Swift version 5.0-dev (LLVM eb302e257f, Clang a113643bc4, Swift 646034c)
Target: x86_64-apple-darwin18.2.0

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, 5.0Regression, Runtime
Assignee @hamishknight
Priority Medium

md5: ec7bbde0897708940075adc9253e1aca

Issue Description:

In Swift 4.2 the following cast correctly succeeds:

func test<T>(_ type: T.Type) -> T? {
  return Any?.none as? T

print(test(Bool?.self)) // Optional(nil)

However, as discovered on the forums, in Swift 5 it incorrectly fails and prints nil instead. This does appear to be fixed on master, but we should add a test case.

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@belkadan belkadan commented Feb 1, 2019

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@jckarter jckarter commented Feb 12, 2019

@mikeash took a look, and it looks like this is fixed in the most recent Swift 5 snapshots.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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3 participants