[RFC] Named macro capture groups

[tgross35]

This RFC proposes optional names for repetition groups in macros:

macro_rules! foo {
    ( $group1( $a:ident ),+ ) => {
        $group1( println!("{}", $a); )+
    }
}

Rendered

Small Pre-RFC: https://internals.rust-lang.org/t/pre-rfc-named-capture-groups-for-macros/20883