Add missing require in iterator_spec

[asterite]

Without it, the spec can't be run standalone.

[Fryguy]

Aside, I've had this problem in my personal code, and I'm wondering if there's a way for the compiler to catch this? I can't think of a way, personally, but it would be extremely useful if these kinds of things just failed up front.

[asterite]

Yes: specify at the top of each file the requires/imports needed for the file to type-check. That is, make it more similar to JS and Python, and not like Ruby. But of course that's a huge change to the language, and it brings a lot of verboseness.

[Fryguy]

Right, exactly - I can't see how it can be done without a deeper language level change. It happens so infrequently, and the fix is usually so simple, so it seems not worth it.

[straight-shoota]

This concrete practical problem mostly matters for files that can be used as entry points of a program. This is common for spec files, but apart from that, it's very rare (and other entry points are usually well tested).

You could run something like this to check if each spec file compiles on its own:

find spec -name '*_spec.cr' -exec crystal spec {} \;