有以下类定义
#include <iostream> using namespace std; class shape { public: virtual int area() = 0; }; class rectangle :public shape { public: int a, b; void setLength(int x, int y) { a = x; b = y; } int area() { return a * b; } };若有语句定义rectangle r; r.setLength(3,5); 则编译时无语法错误的语句是( )