Groups with Delimiter::None not (really) preserved

[steffahn]

Is this a bug in this crate or in rustc? (Or intended behavior?)

use rust_2018::rust_2018;

macro_rules! foo {
    ($e:expr) => {
        bar!{$e * 2}
    }
}
macro_rules! bar {
    ($e:expr) => {
        ($e, rust_2018!($e))
    };
}

fn main() {
    dbg!(foo!(5+5));
    // [src/main.rs:18] foo!(5 + 5) = (
    //     20,
    //     15,
    // )
}

[m-ou-se]

That's a known bug in Rustc, unfortunately:

rust-lang/rust#67062
rust-lang/rust#74036

[m-ou-se]

(This issue was also encountered in assert2. That crate now replaces all None delimiters by regular parenthesis as a workaround: de-vri-es/assert2-rs@2344cf1)