rust-lang / rust-lang/rustfmt

Comma gets duplicated in a macro params, obstructed by inline comments

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A-comments A-macros C-bug I-invalid-code
Dominant language
Rust
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Merged PRs (30d)
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Description

This is somewhat similar to #6759 but seem to have a different cause as this is a macro param bug

fn main() {
    println!("Magic one to two commas -->" /**/, /**/);
}

Running cargo fmt on this adds another comma after the last /**/:

fn main() {
    println!("Magic one to two commas -->" /**/, /**/,);
}

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Research direction

Reproduce the issue with the Rust snippet and trace rustfmt's handling of macro parameters containing inline comments. Add a regression test for the duplicate comma and verify that formatting preserves the original comma count.

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
45/100

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