{"ast_node_type":"other","tokens":[{"end":74,"kind":"keyword","start":0,"text":"///"}]}
///     the second occurrence of `T` is not a subtree of *any* local type.
///     - similarly, `FundamentalPair<LocalType<T>, T>` is bad, because
///     - however, `LocalType<Vec<T>>` is OK, because `T` is a subtree of