{"ast_node_type":"variable","tokens":[{"end":53,"kind":"keyword","start":0,"text":"let"}]}
                    let first_ty = first.peel_refs();
                    // if the type of first arg is the same as the current impl type, we should take the first arg into assoc function
                    if first_ty == self_ty || first_ty == self.tcx.types.self_param {