[kibwen]

> Perhaps control flow isn't the right term, maybe non-trivial would be better?

Indeed, there are plenty of valid reasons to be wary of operator overloading, such as the risk that someone might insert a network call into your vector addition. There's some precedence from C++ in calling an operator invocation "trivial" when it hasn't been user-defined, in general I might go further and say that a good overloaded operator is "well-behaved" when it not only has a non-surprising implementation (e.g. no side-effects) but also its function is congruent with the specific chosen operator (so no overloading bitshift for iostreams).