Yes, Rust move semantics are designed to make passing things like strings and collections cheap. Only the stack-allocated part must be copied. But passing stack-heavy objects (think std::array) can still be expensive without elision guarantees, so some elision rules could be useful even though they don’t affect semantics and would be allowed anyway by the as-if rule. People shouldn’t feel the need to pass by reference just for performance reasons, especially given that it introduces syntactic noise at call site unlike in C++. OTOH I guess inlining makes the point moot in many cases.