is `iterate` allowed to return something other than a `Tuple{Any, Any}`, when it does not return a `Nothing`?

[nsajko]

Apparently it's sometimes desirable to have iterate return a collection type other than Tuple{Any, Any}. While the interfaces seem to allow this as coded, the documentation does not. Should the docs be updated?

AFAIK, it is permitted for any two-element struct to be returned (such as NamedTuple or Pair), as long as it implements indexing corresponding to fields

Okay, then I guess we probably need to update the docstring for iterate (https://docs.julialang.org/en/v1.13-dev/base/collections/#Base.iterate) too..

xref #59142

[nsajko]

Relevant docs:

• doc string: https://docs.julialang.org/en/v1.13-dev/base/collections/#Base.iterate

• interfaces page: https://docs.julialang.org/en/v1.13-dev/manual/interfaces/#man-interface-iteration

[mbauman]

Ref #25464. But it's true, that really just assumes a struct with at least two fields. But I would imagine many other iterator wrappers hardcode Tuple.

[JeffBezanson]

I am fine with requiring a tuple, as documented now. Are there any examples where returning something else is genuinely useful?