rust-lang / rust-lang/rustfmt

Off-by-one somewhere in chain formatting?

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#3,016 1 comment 1 reaction 0 assignees View on GitHub

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A-call-chains I-poor-formatting P-low
Dominant language
Rust
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Avg merge
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Merged PRs (30d)
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Description

rustfmt 0.99.4-nightly (1c40881 2018-08-27)

fn main() {
    // This is fine (exactly 100 characters):
    let something = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
        bbbbbbbbbbb,
        ccccccccc,
        dddd,
    );

    // This is fine (99 characters):
    let something = a.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
        bbbbbbbbbbb,
        ccccccccc,
        dddd,
    );

    // This is also fine (100 characters), but rustfmt wants to reformat it:
    let something = a.aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
        bbbbbbbbbbb,
        ccccccccc,
        dddd,
    );
}

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Research direction

No source file or test is named. First reproduce the behavior with the supplied Rust snippet and compare rustfmt's handling of the three chained expressions; trace the chain-formatting logic and add a regression test showing that the exactly 100-character case remains unchanged.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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