undestanding of template metaprogramming techniques, you constantly find yourself bumping into glass walls, diagnostics are REALLY bad, "write usual C++ code, just in constexpr" doesn't work IMHO, and it still forces you to write all kinds of wrappers, helpers, static_XXX analogs of standard containers and so on.

Thanks for your attention!

https://redd.it/1pc53b2
@r_cpp