Macro moore::node_ref_group

macro_rules! node_ref_group {
    ($ name : ident : $ ($ var : ident ($ ty : ty),) +) => { ... };
    (MATCHES $ value : expr, $ ($ lhs : pat => $ rhs : expr), +) => { ... };
}

Create a new group of node references.

This is a simple enum that contains variants for each of the references. Implements From for the various references, and Into<NodeId>.