It should be `v.into_iter()`, and that distinction matters because of ownership / move semantics.
It just so happens that for most collections, `IntoIter` is also defined for references to them, which typically gives you the same behavior that `.iter()` would give.
It just so happens that for most collections, `IntoIter` is also defined for references to them, which typically gives you the same behavior that `.iter()` would give.