C++20引入了is_invocable，用于判定某个可执行类型(函数，lambda，函数对象等）的函数签名

1.is_invocable/is_invocable_v检查函数参数类型

#include <type_traits>
#include <iostream>
using namespace std;auto func1(char) -> int (*)()
{return nullptr;
}int func2(int, int)
{return 1;
}int main()
{cout<<is_invocable<decltype(func1), char>::value<<endl;    //输出1cout<<is_invocable<decltype(func1), int>::value<<endl;     //输出1cout<<is_invocable<decltype(func1), void>::value<<endl;    //输出0cout<<is_invocable_v<decltype(func2), int, int><<endl;     //输出1cout<<is_invocable_v<decltype(func2), int, char><<endl;    //输出1cout<<is_invocable_v<decltype(func2)><<endl;               //输出0cout<<is_invocable_v<decltype(func2), void><<endl;/        //输出0return 0;
}