Unnecessary collect() on iterable to Vec RS-P1006

Collecting Iterator to Vec has the possible cost of forcing allocation, hence instead directly using the iterator is more efficient quite often, if the Vec is unnecessary.

Consider replacing,

• .collect::<Vec<_>>().len() with .count().
• .collect::<Vec<_>>().is_empty() with .next().is_none().

Bad practice

(0..5).collect::<Vec<_>>().len()

Recommended

(0..5).count()