error: you are collecting an iterator to check its length
 --> $DIR/needless_collect.rs:5:15
  |
5 |     let len = sample.iter().collect::<Vec<_>>().len();
  |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `sample.iter().count()`
  |
  = note: `-D needless-collect` implied by `-D warnings`

error: you are collecting an iterator to check if it is empty
 --> $DIR/needless_collect.rs:6:8
  |
6 |     if sample.iter().collect::<Vec<_>>().is_empty() {
  |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `sample.iter().any(|_| true)`

error: you are collecting an iterator to check if contains an element
 --> $DIR/needless_collect.rs:9:5
  |
9 |     sample.iter().cloned().collect::<Vec<_>>().contains(&1);
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider replacing with: `sample.iter().cloned().any(|&x| x == 1)`

error: aborting due to 3 previous errors