Poor formatting of macro_rules rhs with consecutive top-level blocks

[dtolnay]

Rustfmt turns this input:

macro_rules! repro {
    () => {
        {
            let _guard = ();
        }
        {
            let _guard = ();
        }
    };
}

into this output:

macro_rules! repro {
    () => {{
        let _guard = ();
    }
    {
        let _guard = ();
    }};
}

I believe the original is clearer.

[dtolnay]

Relevant-looking code:

https://github.com/rust-lang-nursery/rustfmt/blob/a92a1cb51283bc6861bb1bb33b2b34c36b5d16bd/src/macros.rs#L1216

Mentioning @RReverser who implemented this in #2393.

[RReverser]

Sorry I missed this! I agree this should be fixed, has_block_body heuristic is far from perfect for this case.

[ytmimi]

Macro bodies are left unchanged when format_macro_bodies=false

linking tracking issue for format_macro_bodies #3355