我正在尝试在flow中定义功能签名。我希望以下代码抛出错误，但我没有收到任何错误？
// function that applied a function to an array - just for numbers
const arrayMath = (func: () => number, arr: Array<number>):Array<Number> => arr.map(func);
// would expect this function to work OK with arrayMath
const square = (num: number): number => num * num;
// would expect this function to fail with arrayMath
const concatX = (str: string): string => `${str}X`;
// flow is not giving me an error here..
arrayMath(concatX, [1, 2, 3]);