Macro cargo::macros::compact_debug

macro_rules! compact_debug {
    (
        impl fmt::Debug for $ty:ident {
            fn fmt(&$this:ident, f: &mut fmt::Formatter) -> fmt::Result {
                let (default, default_name) = $e:expr;
                [debug_the_fields($($field:ident)*)]
            }
        }
    ) => { ... };
}