Interestingly since you can't pass an allocator to an operator call, there is some extra guarantee around whether a hypothetical overloaded operator can allocat

Interestingly since you can't pass an allocator to an operator call, there is some extra guarantee around whether a hypothetical overloaded operator can allocate. If you implement it for a vector type which doesn't contain an allocator reference, then you're sure that any operators won't allocate.