Evaluation order is unspecified in C++, whereas it is well-specified in Rust. This makes things easier to reason about in Rust, but does give the optimizer less wiggle room.
In code like `a(b(d),c(e))`, I think it could be relevant. You would want different code based on the size of `b(d)`, `c(e)`, `d`, and `e`. If you must evaluate b before c, that would eliminate some possible arrangements.
Specifically, if `e` and `b(d)` are huge, you probably would want to evaluate `c(e)` first and then `b(d)`.