{"ast_node_type":"other","tokens":[{"end":68,"kind":"keyword","start":0,"text":"sig.inputs().skip_binder().get(0).and_then(|first|"}]}
                sig.inputs().skip_binder().get(0).and_then(|first| {
                let sig = self.tcx.fn_sig(assoc.def_id).instantiate_identity();
                    // if the type of first arg is the same as the current impl type, we should take the first arg into assoc function