Macro impl_transitive_lock_order 

macro_rules! impl_transitive_lock_order {
    ($before:ty => $after:ty) => { ... };
}

Implements LockAfter<L> transitively.

This:

impl_transitive_lock_order!(A => B);

expands to this:

impl<L> LockAfter<L> for B
where
    A: LockAfter<L>,
    B: LockAfter<A>,
{
}