Implement first D-specific optimization pass: -simplify-drtcalls. It uses the machinery of the standard -simplify-libcalls pass, but optimizes calls to the D runtime instead of calls to C libraries. At the moment, these optimizations are implemented by this pass: - Avoid the runtime call for `arr.length = newlen` if it can determine that the new length isn't longer than the old one. - Ditto for `cast(T[]) arr` if it will clearly always succeed. (e.g. if the length of the original array is zero, or if the old element size is a multiple of the new element size)

interface Inter
{
    int func();
}

extern(C) int printf(char*, ...);

class InterClass : Inter
{
    int func()
    {
        return printf("InterClass.func()\n");
    }
}

alias int delegate() dg_t;

void main()
{
    scope c = new InterClass;

    {
    Inter i = cast(Inter)c;
        {
        dg_t dg = &i.func;
            {
            int j = dg();
            }
        }
    }
}