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[SR-7939] Spurious Warning when down casting to [String] #50474

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swift-ci opened this issue Jun 8, 2018 · 1 comment
Closed

[SR-7939] Spurious Warning when down casting to [String] #50474

swift-ci opened this issue Jun 8, 2018 · 1 comment
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@swift-ci
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swift-ci commented Jun 8, 2018

Previous ID SR-7939
Radar None
Original Reporter rauhul (JIRA User)
Type Bug
Status Resolved
Resolution Duplicate
Environment

Version 10.0 beta (10L176w)

Toolchain: Swift Development Snapshot 2018-06-07 (a)

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

md5: bebede5cb57c798cb1074f352feab4f5

duplicates:

  • SR-7906 assigning cast value to implicitly unwrapped Optional causes (bogus?) warning

Issue Description:

The following code should not produce a warning, but does

guard let symbols = _shortStandaloneWeekdaySymbols else {
    let cfSymbols = CFDateFormatterCopyProperty(_cfObject, kCFDateFormatterShortStandaloneWeekdaySymbols) as! NSArray
    return cfSymbols.allObjects as! [String] // produces warning
}

swift-corelibs-foundation/Foundation/DateFormatter.swift:399: Treating a forced downcast to '[String]' as optional will never produce 'nil'

replacing the offending line with the following removes the warning

return (cfSymbols.allObjects as? [String])!
@belkadan
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belkadan commented Jun 9, 2018

The piece that's missing here is that the result type is an IUO. We've had a few other reports of this; I'll find the dup(s) later.

@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
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@belkadan @swift-ci