Macro gca 

macro_rules! gca {
    ($($arg:tt)*) => { ... };
}

🔬This is a nightly-only experimental API. (min_generic_const_args #132980)

Creates a new style directly represented const argument.

const BAR<const N: usize>: usize = gca!(N);
const FOO<const N: usize>: usize = gca!(BAR::<N>);