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>.