{"ast_node_type":"other","tokens":[{"end":65,"kind":"keyword","start":0,"text":"ty::Alias(ty::Opaque,"}]}
                ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })
            ty_op: |ty| match *ty.kind() {
                    if self.can_define_opaque_ty(def_id) && !ty.has_escaping_bound_vars() =>