The reasoning is to know what you're creating. Yes, iterators can probably also benefit from auto. But the concrete bug that prompted some introspection into wh

The reasoning is to know what you're creating. Yes, iterators can probably also benefit from auto. But the concrete bug that prompted some introspection into what the rule should be was: void mutate(Foo &foo); ... for(auto foo : manyFoos) mutate(foo); If manyFoos is Foo[], then the auto type is Foo, rather than Foo& and you're mutating a copy. The goal is to not get screwed by the type inference, so unless you can defend why it's obvious that the type is what it is, don't use auto. An auto that you need to ask the IDE for it's concrete type is a strong code smell.