Macro type_trait 

type_trait!() { /* proc-macro */ }

Generates a TyType trait (has type Ty) with a generic TyUsingType impl given a type name Ty.

type_trait!(Ty);
struct Test;
impl_TyUsingType!(<u8> Test);
fn main() {
  let x: <Test as TyType>::Ty = 5u8;
}