error: avoid using `collect()` when not needed
  --> $DIR/needless_collect.rs:16:28
   |
16 |     let len = sample.iter().collect::<Vec<_>>().len();
   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`
   |
   = note: `-D clippy::needless-collect` implied by `-D warnings`

error: avoid using `collect()` when not needed
  --> $DIR/needless_collect.rs:17:21
   |
17 |     if sample.iter().collect::<Vec<_>>().is_empty() {
   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.next().is_none()`

error: avoid using `collect()` when not needed
  --> $DIR/needless_collect.rs:20:27
   |
20 |     sample.iter().cloned().collect::<Vec<_>>().contains(&1);
   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.any(|&x| x == 1)`

error: avoid using `collect()` when not needed
  --> $DIR/needless_collect.rs:21:34
   |
21 |     sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`

error: aborting due to 4 previous errors