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[SR-2115] unused variable unreported by compiler #44723

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swift-ci opened this issue Jul 19, 2016 · 12 comments
Closed

[SR-2115] unused variable unreported by compiler #44723

swift-ci opened this issue Jul 19, 2016 · 12 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself good first issue Good for newcomers

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Previous ID SR-2115
Radar None
Original Reporter erica (JIRA User)
Type Bug
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, StarterBug
Assignee KingOfBrian (JIRA)
Priority Medium

md5: 9c3041434c2dac44b9c1f658849c7920

Issue Description:

for i in sequence(first: 0, next: {
    print($0)
    let value = $0 + 5
    return value <= 100 ? value : nil
}) {}
@swift-ci
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Comment by erica sadun (JIRA)

The compiler should emit a warning / fixit for "i" as it is never used

@belkadan
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I can't remember, but we might have done this deliberately because some people don't like having to write _ in their for-loops.

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Comment by erica sadun (JIRA)

Even if deliberate, it still strikes me as wrong. Variable is never used.

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swift-ci commented Dec 5, 2016

Comment by emlai (JIRA)

This seems to have been fixed. I get "Immutable value 'i' was never used; consider replacing with '_' or removing it" for the above code in Swift 3.0.2 preview 1.

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swift-ci commented Dec 5, 2016

Comment by erica sadun (JIRA)

I don't see errors or warnings in Xcode 8.2 beta 2 or in Xcode 8.1

@belkadan
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belkadan commented Dec 5, 2016

Ah, I see the warning if the loop is within a function body, but not at top-level in a script mode file.

@belkadan
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belkadan commented Dec 5, 2016

(so it does make sense to treat it as a bug)

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belkadan commented Dec 5, 2016

Tagging as StarterBug because it's probably just figuring out the conditions under which this warning is and is not emitted and then changing them.

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swift-ci commented Dec 5, 2016

Comment by erica sadun (JIRA)

When I moved the loop from the global scope of main.swift (maxOS, command line project) into a function, it warned.

Should warn at global scope too.

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Comment by Brian (JIRA)

VarDeclUsageChecker was only running on AbstractFunctionDecl – I added a check to TopLevelCodeDecl too.

#6971

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Comment by Brian (JIRA)

Take 2: #7023

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swift-ci commented Feb 2, 2017

Comment by Brian (JIRA)

This behavior was fixed and should be available in Swift 4.0.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself good first issue Good for newcomers
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@belkadan @swift-ci