Is there a way to make this formal, like in the code, making the compiler complain when you try to use these features?

I'm not a c++ user but i'm pretty sure you should be able to pull-off a macro to do that ; in c you could alias the lib for something that breaks + alert ; I don't know how I would integrate such additional compiler checks in rust for other kinds of rules however - it's interesting to think about

It is relatively easy to check these things with static analyzers, if nothing else.

It’s a bit different, but WebKit uses Clangs static analysis.

Kythe can be used for that