{"ast_node_type":"other","tokens":[{"end":41,"kind":"keyword","start":0,"text":"opaque_type_key:"}]}
    opaque_type_key: OpaqueTypeKey<'tcx>,
    member_constraints: &mut MemberConstraintSet<'tcx, ty::RegionVid>,
    OpaqueHiddenType { span, ty: hidden_ty }: OpaqueHiddenType<'tcx>,