rustfmt thinks that a pattern matching is a closure

[real-felix]

When formatting this code:

fn is_something(foo: Foo, bar: Bar) -> bool {
    matches!((legacy_required_finality, signature_weight),
        | (LegacyRequiredFinality::Any, Insufficient | Weak | Strict)
        | (LegacyRequiredFinality::Weak, Weak | Strict)
        | (LegacyRequiredFinality::Strict, Strict)
    )
}

It is written like that:

fn is_something(foo: Foo, bar: Bar) -> bool {
    matches!((legacy_required_finality, signature_weight), |(
        LegacyRequiredFinality::Any,
        Insufficient | Weak | Strict,
    )| (
        LegacyRequiredFinality::Weak,
        Weak | Strict
    ) | (
        LegacyRequiredFinality::Strict,
        Strict
    ))
}

I think that rustfmt sees it as a closure.

I tried to reproduce with a simpler example, but it doesn't work. I think it comes from diverse things, like the fact there is a tuple.

[ytmimi]

Thanks for reaching out. Confirming I can reproduce this using rustfmt 1.5.2-nightly (34f9ca28 2023-02-16). I also believe your assumption about this being parsed as a closure is correct.

The issue here is that rustfmt doesn't currently have any special case handling for the matches! macro, however I just looked into it and I believe #5554 would resolve this issue. I've updated the PR to include a test case for this issue.