Needlessly large expansion when using '@' sign to bind names to certain patterns

[kaikalii]

I have a struct like this:

struct Foo {
    val: u32,
    kinda_long_field_name: bool,
}

I want to do a match on a value of type Result<Foo, _>, which I think should probably be formatted like this:

#[rustfmt::skip]
match foo {
    Ok(f @ Foo {
        kinda_long_field_name: false,
        ..
    }) => {},
    Ok(Foo {
        val,
        kinda_long_field_name,
    }) => {},
    Err(()) => {},
}

However, it gets weirdly formatted to this:

match foo {
    Ok(
        f
        @ Foo {
            kinda_long_field_name: false,
            ..
        },
    ) => {}
    Ok(Foo {
        val,
        kinda_long_field_name,
    }) => {}
    Err(()) => {}
}

...which I think is kind of odd behavior.

I know that '@' and this kind of name-to-pattern binding is pretty niche and uncommon, but I think it should probably still format in a nice way.

[calebcartwright]

Thanks for reaching out @kaikalii!

This is a duplicate of #4031 and has already been fixed. It should be included in the next release of rustfmt, but if you need the fix more urgently you could consider building rustfmt from source in the interim.