rust-lang / rust-lang/rustfmt

Illegally adds comma to macro invocation

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A-macros C-bug
Dominant language
Rust
Stars
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Forks
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Avg merge
2d 13h
Merged PRs (30d)
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Description

Rustfmt adds a comma to the following and causes a compiler error.

macro_rules! idx {
    ($(#[$attr:meta])* $vis:vis struct $name:ident; $metadata:ident) => {
        $(#[$attr])*
        $vis struct $name(usize);
    };
}

idx!(
    #[derive(Debug)]
    pub struct FooIdx; // rustfmt adds a comma here
    Meta
);

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Research direction

Start by reproducing the Rust macro invocation shown in the issue and inspect rustfmt's handling of this macro syntax. Done means rustfmt no longer inserts a comma after the struct declaration, and the formatted output still compiles.

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
Clearly specified
Newbie friendliness
45/100

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