Iterators claim to be first-class but aren't. And "zero-cost" iterators that are only zero-cost if you don't value your own time spent debugging them. I've been able to crash the compiler when trying to write what in Python is idiomatic "itertools-y" code. And whenever I complain about this, someone pops up to recommend some third party iteration library. Which is part of the problem; I shouldn't need a third party library full of terrifying-looking macros just to write lazy iterators. They don't live up to what the docs promise, which is a real shame.

If they made iterators work how they seem they should work, I would come right back to Nim. It does so many things right but this one thing is a dealbreaker for me. The UFCS is practically begging me to chain lazy iterators together but actually trying it is like stepping on a rake.