If you have a constant expression like 1 + 2 in your code you can evaluate it at compile time once and avoid computing it at runtime. You can do that with control flow and much more complex language constructs in C++. If you want to know more about that look into C++ template meta programming, constexpr, and constval.

it means rust is cool as fuck

Overengineered mess

I think the closest to an actual answer you will find are the cpp core guidelines.