{"ast_node_type":"other","tokens":[{"end":39,"kind":"keyword","start":0,"text":"//"}]}
    // here rather than using ReErased.
    // FIXME: Consider wrapping the hidden type in an existential `Binder` and instantiating it
    let hidden_ty = tcx.type_of(def_id.to_def_id()).instantiate(tcx, args);