Macro impl_doc_allocator_for 

macro_rules! impl_doc_allocator_for {
    ($ty:ty) => { ... };
}

Implements pretty::DocAllocator<'a, A> for a local types that already implement HasAllocator<'a, A>.

Usage: impl_doc_allocator_for!(MyType);

Notes:

• Types must be local to your crate (orphan rule).