Infinite compilation with templates

Question

This question is just out of curiosity. In recursive templates if we forget to put one particular specialization, then compiler will do large number of iterations and then s

Answer 1

If I understand your question correctly, you want the compiler to recognise that it will never stop iterating. Besides just stopping after a fixed number of nesting types, what you want is provably impossible: If I see it correctly you can express any turing-machine in this fashion (at least the templates in D are turing complete).

So if you can build a compiler that recognises that it will nest types forever before actually trying to, you decide the halting problem which is undecidable for turing-machines.

However, I could very well be mistaken that you can put any computation in the parameter-list (but simulating a register-machine appears to be possible, as we can encode all registers in a separate integer template parameter (yes, int is finite, but quite large, which makes it practically unbounded)).