Here's something that doesn't seem to be very simple or possible in D - "function" macros which can be used at the global scope, unlike regular functions which can't be.

Take the following macros in COM and directx:

#define MAKE_HRESULT(sev,fac,code) \
((HRESULT) (((unsigned long)(sev)<<31) | ((unsigned long)(fac)<<16) | ((unsigned long)(code))) )

#define _FACD3D 0x876

#define MAKE_D3DHRESULT( code ) MAKE_HRESULT( 1, _FACD3D, code )

#define D3DERR_WRONGTEXTUREFORMAT MAKE_D3DHRESULT(2072)

This defines a constant, D3DERR_WRONGTEXTUREFORMAT with some complicated value that you'd normally not be able to come up with without help from the macros.

Converting to D, however, leaves you with:

HRESULT MAKE_HRESULT(int sev, int fac, int code) { return (sev << 31) | (fac << 16) | code; }
HRESULT MAKE_D3DHRESULT(int code) { return MAKE_HRESULT(1, _FACD3D, code);

const HRESULT D3DERR_WRONGTEXTUREFORMAT=MAKE_D3DHRESULT(2072);

Which, at global scope, of course gives you an error about it not being a constant expression. You can't call functions at global scope.

I've tried doing this with a mixin, but it doesn't seem possible to define a variable with a mixed-in name within a mixin.

Of course, it would be possible to run the original C++ file through the preprocessor to get the big ugly error codes, but this still doesn't solve the overall problem.