Macro define_impl_bitmask 

macro_rules! define_impl_bitmask {
    (
        impl $struct:ident < $($impl_lifetime:lifetime),* > ;
        $mask_getter:ident : $mask_getter_ty:ty = { $get_mask:expr }
        test_mod = $test_mod:ident;
        $(
            $( #[$attr:meta] )*
            => $getter:ident = $mask_constant:ident;
        )*
    ) => { ... };
}

Defines getters for a bitmask

mask_constants must be unsigned integers with exactly one bit set to 1