I came across this sentence in The Rust Programming Language:
: calling the 'next' method on an iterator changes internal state that the iterator uses to keep track of where it is in the sequence.
It seems to me like the state needs an article in the main clause. On the other hand
I'm drinking a water that isn't sparkly.
sounds fine to me, even with the article omitted. Am I wrong in thinking the former case is grammatically incorrect? If not, what differentiates the two cases?