Indicates that the compiler should generate an error message when an event is emitted out of order. 指示当事件没有按照顺序发出时,编译器应生成错误信息。
In particular, if the definition and declaration agree as to parameter list but differ as to return type, the compiler will issue a warning or error message indicating the discrepancy. 特别地,如果函数定义和函数声明的形参列表一致,但返回类型不一致,编译器会发出警告或出错信息来指出这种差异。