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[SR-11139] guard's else doesn't recognize variable == nil as validating non optional nil value in it #53535

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swift-ci opened this issue Jul 15, 2019 · 1 comment
Closed

[SR-11139] guard's else doesn't recognize variable == nil as validating non optional nil value in it #53535

swift-ci opened this issue Jul 15, 2019 · 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 feature A feature request or implementation

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@swift-ci
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Previous ID SR-11139
Radar None
Original Reporter idomo (JIRA User)
Type Bug
Status Resolved
Resolution Won't Do
Environment

Swift 5, xCode 11.0 beta 3 (11M362v)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, LanguageFeatureRequest
Assignee idomo (JIRA)
Priority Medium

md5: 205361b48a935095ef57dba1655e44b7

Issue Description:

When writing something like:

guard error == nil else { return print(error) }

The error in the else, is assumed to be nil for the compiler and it gives me this warning:

Expression implicitly coerced from 'Error?' to 'Any'

Well, if I've checked that error is nil in the guard body, the else means that error != nil, so the value should be treated as an unwrapped value.
@belkadan
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Swift doesn't do arbitrary type refinement like this, at least partially because it only works for immutable names. If you're working with a local variable, mutable class instance property, or mutable global, you wouldn't be able to rely on that refinement. Use if let here instead.

@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. compiler The Swift compiler in itself feature A feature request or implementation
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@belkadan @swift-ci