use libthreema_macros::concat_fixed_bytes; fn main() { let a = [1u8; 4]; let b = [4u16; 2]; let _result: [u8; 4] = concat_fixed_bytes!(b); // b is a u16 array let _result: [u8; 8] = concat_fixed_bytes!(a, b); // b is a u16 array }