I understand not having first-class iterators; Rust traits encourage using option/iterator combinator methods rather than imperative code, which I find unclear

I understand not having first-class iterators; Rust traits encourage using option/iterator combinator methods rather than imperative code, which I find unclear in nearly all cases (though iterator reduce() is better at finding the min/max of a sequence, since you don't have to initialize the counter to a sentinel value). I was discussing the use of coroutines for building iterators, for example implementing the next function for a recursive filesystem glob or B-tree map iterator or database table join, which I find miserable and bug-prone to write by hand.