Using to_iter instead of iter leads to unhelpful errors in iterators1

[MathsStan]

The hint for iterators1 leads to the trait.Iterator documentation, where many of the examples use the to_iter method for obtaining the iterator. The compiler errors when using this method are unfriendly, and it is not clear that the iter method exists.

The simplest solution in my mind is to add a use of my_fav_fruits after the assert statements, to compel the compiler to throw an error about the array being consumed if using to_iter instead of iter.