C Compiler okay with different arity in function pointer declaration

Question

I am new to C and am confused why the compiler is totally okay with the following code snippet where I am casting the foo function pointer to other function pointers with different arities. This means that a single void * parameter in a function pointer declaration can be cast to any number of parameters? Can some one please help me understand why this is no problem in C?

// 
#include <stdio.h>

int main() {
    // function pointer declaration
    void *(*foo)(void *);
    // castings
    (int *(*)(int *, int *))foo;
    (int *(*)(float *, int *, char **))foo;
    (int *(*)(int, int))foo;
    return 0;
}