类似以下内容：
#include <functional>
int main()
{
std::function<int(int)> func = [](int x){return x;};
int* Fptr(int) = &func; //error
}
我得到的错误是
temp.cpp: In function ‘int main()’:
temp.cpp:6:15: warning: declaration of ‘int* Fptr(int)’ has ‘extern’ and is initialized
int* Fptr(int) = &func; //error
^
temp.cpp:6:20: error: invalid pure specifier (only ‘= 0’ is allowed) before ‘func’
int* Fptr(int) = &func; //error
^
temp.cpp:6:20: error: function ‘int* Fptr(int)’ is initialized like a variable
