Macro int_uint 

macro_rules! int_uint {
    ($NAME:ident, $A:ty, $B:ty) => { ... };
}

Conn<i_N, u_M> widening or same-width cross-sign (bits(i_N) ≤ bits(u_M)).

ceil clips negatives to 0 then upcasts (lossless on the non-negative half by the bit-width constraint); inner saturates targets above i_N::MAX down to i_N::MAX.