macro_rules! step_nonzero_impls {
{
[$( $narrower:ident ),+] <= usize < [$( $wider:ident ),+]
} => { ... };
}macro_rules! step_nonzero_impls {
{
[$( $narrower:ident ),+] <= usize < [$( $wider:ident ),+]
} => { ... };
}