Rust for safety

The reason a compiler will choose one order of evaluation over another, when the order is unspecified, is to generate better code. When optimization is off, some compilers will choose a right-to-left order (I think MSVC did at one time), others left to right. With optimization on, if evaluating A before B would require register spills that would not be required if B is evaluated first, B would be evaluated first, and the code runs faster.