{"ast_node_type":"variable","tokens":[{"end":59,"kind":"keyword","start":0,"text":"let"}]}
            let op_ty = op_arg.node.ty(self.mir, bx.tcx());
        let extra_args = bx.tcx().mk_type_list_from_iter(extra_args.iter().map(|op_arg| {
            self.monomorphize(op_ty)