ImportC: confusing failed conversion from K&R variadics to empty parameter list

[dkorpel]

https://forum.dlang.org/post/xhdzoofhirdhfgsgndvq@forum.dlang.org

Officially an empty parameter list in C is f(void), but it's easily conflated with the modern way f(), which currently gives an uninformative message:

--- test_kr_callback.d
import kr_callback;

extern (C) int callback() {
    return 42;
}

void main()
{
    run(&callback); // cannot pass argument `& callback` of type `extern (C) int function()` to parameter `extern (C) int function() fn`
}


--- kr_callback.c
typedef int(*fp)();

int run(fp fn) {
    return fn();
}