{"ast_node_type":"variable","tokens":[{"end":96,"kind":"keyword","start":0,"text":"let"}]}
        let hidden_ty = hidden_tys[&trait_projection.def_id].instantiate(tcx, impl_opaque_args);
        let impl_opaque_args = trait_projection.args.rebase_onto(tcx, trait_m.def_id, impl_m_args);