Function concat_bindings 

pub const fn concat_bindings<const N: usize>(
    parts: &[&'static [(&'static str, &'static str)]],
) -> [(&'static str, &'static str); N]

The bindings of several commands, joined into one array.

const because a binding table is a static a test reads without running anything, and a slice cannot be concatenated in a const initializer without somewhere to put the result. N is the sum of the parts’ lengths, which a generated caller computes from the same consts.