identity
pub trait IdentityUtil<A: ?Sized, B: ?Sized>: Identity<A, B> { type Inverse: ?Sized + Identity<B, A>; }
type Inverse: ?Sized + Identity<B, A>
impl<A: ?Sized, B: ?Sized, Ev: ?Sized + Identity<A, B>> IdentityUtil<A, B> for Ev