This is a spin-off of bug 5069
(On request of yebblies too).

This is a wrong D2 program:


import std.c.stdlib: qsort;
import std.c.stdio: printf;
int compare(const void *a, const void *b) {
    return *cast(int*)a - *cast(int*)b;
}
void main () {
    int[] values = [40, 10, 100, 90, 20, 25];
    for (int n = 0; n < 6; n++)
        printf ("%d ", values[n]);
    printf("\n");
    qsort(values.ptr, 6, int.sizeof, &compare);
    for (int n = 0; n < 6; n++)
        printf ("%d ", values[n]);
    printf("\n");
}



With dmd 2.055head it prints:

test.d(11): Error: function core.stdc.stdlib.qsort (void* base, uint nmemb, uint size, int C function(in const(void*), in const(void*)) compar) is not callable using argument types (int*,int,uint,int function(in const(void*), in const(void*)))
test.d(11): Error: cannot implicitly convert expression (& compare) of type int function(in const(void*), in const(void*)) to int C function(in const(void*), in const(void*))


I'd like it to print:
int extern(C) function(in const(void*), in const(void*))

Instead of:
int C function(in const(void*), in const(void*))

Because it's easy to miss a single C in the noise of the error message, and because it's closer to the code that you actually have to write.


Even better is to produce a single error message, reducing the clutter:

test.d(11): Error: cannot implicitly convert expression (&compare) of type int function(in const(void*), in const(void*)) to int extern(C) function(in const(void*), in const(void*))