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Suggest potentially missing value in empty conditional expression arms with inferred type #99525

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#99539
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Suggest potentially missing value in empty conditional expression arms with inferred type#99525
#99539
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compiler-errors
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A-diagnosticsArea: Messages for errors, warnings, and lintsD-papercutDiagnostics: An error or lint that needs small tweaks.P-lowLow priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Description

@estebank
estebank
opened on Jul 20, 2022

When given

fn d(opt_str: Option<String>) {
    let s = if let Some(s) = opt_str {
        //~^ ERROR mismatched types
    } else {
        String::new()
    };
}

we should mention that s might be missing in the if branch of the expression, like we do for

fn d(opt_str: Option<String>) {
    let s: String = if let Some(s) = opt_str {
        //~^ ERROR mismatched types
    } else {
        String::new()
    };
}

#98784 (comment)

Activity

  1. estebank
    added
    A-diagnosticsArea: Messages for errors, warnings, and lints
    P-lowLow priority
    T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
    D-papercutDiagnostics: An error or lint that needs small tweaks.
    on Jul 20, 2022

  2. compiler-errors commented on Jul 20, 2022

    @compiler-errors
    compiler-errors
    on Jul 20, 2022
    Contributor

    Actually this aligns perfectly with a refactoring of IfExpressionCause I was looking at last night...

  3. compiler-errors commented on Jul 20, 2022

    @compiler-errors
    compiler-errors
    on Jul 20, 2022
    Contributor

    Since we already suggest removing semicolon bidirectionally i.e. if a { b; } else { c } and if a { b } else { c; }, we should be able to do the same with the return binding suggestion too.

    @rustbot claim

  4. rustbot
    assigned
    compiler-errors
    on Jul 20, 2022
  5. Dylan-DPC
    added 2 commits that reference this issue on Jul 22, 2022

    Rollup merge of rust-lang#99539 - compiler-errors:bidirectional-block…

    36478ef

    Rollup merge of rust-lang#99539 - compiler-errors:bidirectional-block…

    92bebac
  6. bors
    closed this as completedin 92bebacon Jul 22, 2022
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A-diagnosticsArea: Messages for errors, warnings, and lintsD-papercutDiagnostics: An error or lint that needs small tweaks.P-lowLow priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

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