[PATCH] [libcxx] Delay evaluation of __make_tuple_types to prevent blowing the max template instantiation depth. Fixes Bug #18345

[Eric Fiselier]

I haven't actually considered that. I'm actually leaning towards making `__tuple_constructible_imp` (and similar) lazy to prevent compile errors where possible. Either way I think I'll prototype something similar to your suggestion to see if it helps compile times.

However I'm more interested in improving `__make_tuple_types` since it is evaluated multiple times before `__tuple_constructible_imp`.

http://reviews.llvm.org/D4467