Python cryptography, Rust, and Gentoo

And it is, mechanically. Semantically, it is *not* a simple thing. These kinds of issues are what Rust is aiming to tackle as a whole.

Could once_cell or lazy_static be added to the stdlib? Sure. Why not yet? Maybe the API isn't sufficiently nailed down, soundness cases considered, etc. enough for the stdlib. Until then, crates.io is a handy place for these things to mature *while getting real world (ab)use*.

Some context for the C++ side of things. Improvements living in some random P paper on the ISO C++ standard committee mailings isn't going to get battle-hardened by anyone other than the author without the heroic work of making it available on existing language specs (e.g., Eric Neibler's Ranges library). This kind of stuff is nigh impossible with language features too. There is still errata coming in for `for (auto i : expr)` for crying out loud because this is undefined behavior:

std::vector<std::string> func();
// ...
for (auto i : func()[0]) // oops, you're iterating on a temporary that just got destructed
{}