In Section 6.5 (“Iter”), the return type is hard to infer

[evelon]

The issue introduced in #189 still persists.

The return type of into_iter is shown like this in the standard library documentation:

fn into_iter(self) -> <&'a Vec<T, A> as IntoIterator>::IntoIter ⓘ
Creates an iterator from a value. Read more

It is simply impossible to infer the concrete return type std::slice::Iter from this signature for a learner working through these exercises.

This exercise, possibly including section 6.4 (“Iterators”), should probably be moved to a later stage.

[gkoundry]

I've having the same issue. I don't think it is really possible to complete exercise 6.5 without the material covering lifetimes in exercise 6.6

[Greenheart]

As of Rust 1.89, the recommended solution for 05_iter also results in a warning:

// Results in warn(mismatched_lifetime_syntaxes):
std::slice::Iter<Ticket>

// Works, because of the explicit lifetime:
std::slice::Iter<'_, Ticket>

I also think this could be resolved by introducing lifetimes earlier, for example by moving 6.4 and 6.5 to after 6.6.