We have a compile time problem, and this is basically the cure.

Intuitively, people imagine CTFE is expensive (and it kinda is), but really, the reason our compile times are bad is template instantiation.

This DIP single-handedly fixes compile-time issues in programs I've written by reducing template instantiations by near-100%, in particular, the expensive ones; recursive instantiations, usually implementing some form of static map.

This is an RFC on a draft, but I'd like to submit it with a reference implementation soon.

Stefan Koch has helped me with a reference implementation, which has so far gone surprisingly smoothly, and has shown 50x improvement in compile times in some artificial tests.

I expect much greater improvements in situations where recursive template expansion reaches a practical threshold due to quadratic resource consumption used by recursive expansions (junk template instantiations, and explosive symbol name lengths).

This should also drastically reduce compiler memory consumption in meta-programming heavy applications.

In addition to that, it's simple, terse, and reduces program logic indirection via 'utility' template definitions, which I find improves readability substantially.