rustfmt removes labels of block if inside macro invocation, which will break the code

[anatawa12]

Rustfmt would remove 'block: inside rustfnmt_test0, which will break break 'block Ok(0) line.

For reference, rustfnmt_test1 code won't be broken. this issue only happens with rust.

macro_rules! test_macro {
    (|$transaction: ident| $body: expr) => {{
        let $transaction = some_value;
        let _ = $body;
    }};
}

pub async fn rustfnmt_test0(condition: &bool) {
    test_macro!(|transaction| 'block: {
        if condition {
            break 'block Ok(0);
        }

        todo!()
    });
}

pub async fn rustfnmt_test1(condition: &bool) {
    let x = |transaction| 'block: {
        if condition {
            break 'block Ok(0);
        }

        todo!()
    };
}

rustfmt 1.8.0-beta (0277061b9a 2025-02-01)

[ytmimi]

Thanks for the report! I didn't even realize you could add a label to a closure's block body. Should be easy enough to fix if we pass the entire block expression (body) to rewrite_closure_block instead of just the block. The block doesn't have information about the label.

rustfmt/src/closures.rs

Line 75 in 054efdd

rewrite_closure_block(block, &prefix, context, body_shape)

- rewrite_closure_block(block, &prefix, context, body_shape)
+ rewrite_closure_block(body, &prefix, context, body_shape)