{"ast_node_type":"variable","tokens":[{"end":97,"kind":"keyword","start":0,"text":"//"}]}
    // Do NOT let `cb` touch `TraitRef` outside of `TyLoweringContext`. Its substitution contains
    assoc_name: Option<Name>,
    // free `BoundVar`s that need to be shifted and only `TyLoweringContext` knows how to do that