Macro bflag 

macro_rules! bflag {
    (
		$(#[$outer:meta])*
		$vis:vis struct $BFlag:ident: $T:ty
		{
			$(
				$(#[$inner:ident $($args:tt)*])*
				const $Flag:ident = $value:expr;
			)*
		}
		$($t:tt)*
	) => { ... };
    () => { ... };
}