Ref:

Usually, you don't have to write out the full type of an iterator. But here, I need to.

This won't compile, because

fn fetch_next_field(pos: &mut Vec::Iter<'_, u8>) -> Option<String> 

which yields the error message

error[E0107]: missing generics for struct `Vec`
help: add missing generic argument
|
| fn fetch_next_field(pos: &mut Vec<T>::Iter<'_, u8>) -> Option<String>{
|                                  +++

Which seems reasonable enough. But if I put u8 in for T, the error message changes to

|
2 | fn fetch_next_field(pos: &mut Vec::Iter<', u8>) -> Option{
| ^^^^^^^^^^^^^^^^^^^^^
|
help: if there were a trait named Example with associated type Iter implemented for Vec<u8>, you could use the fully-qualified path
|
2 - fn fetch_next_field(pos: &mut Vec::Iter<', u8>) -> Option{
2 + fn fetch_next_field(pos: &mut <Vec as Example>::Iter<'_, u8>) -> Option{
|

as if Vec doesn't implement Iter.

What is the correct type for that iterator?

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