Hello grauzone,
I would even go so far to say, that dmd should automatically follow all imports and compile them in one go. This would be faster than having a separate responsefile step, because the source code needs to be analyzed only once. To prevent compilation of imported library headers, the compiler could provide a new include switch for library code. Modules inside "library" include paths wouldn't be compiled.
Adding that without a way to turn it off would kill D in some cases. I have a project where DMD uses up >30% of the available address space compiling one module. If I was forced to compile all modules at once, it might not work, end of story.
That said, for many cases, I don't see a problem with having that feature available.
