tests/ui/lint/issue-109152.stderr

   1 error: `Iterator::map` call that discard the iterator's values
   2   --> $DIR/issue-109152.rs:5:21
   3    |
   4 LL |     vec![42].iter().map(drop);
   5    |                     ^^^^----^
   6    |                     |   |
   7    |                     |   this function returns `()`, which is likely not what you wanted
   8    |                     |   called `Iterator::map` with callable that returns `()`
   9    |                     after this call to map, the resulting iterator is `impl Iterator<Item = ()>`, which means the only information carried by the iterator is the number of items
  10    |
  11    = note: `Iterator::map`, like many of the methods on `Iterator`, gets executed lazily, meaning that its effects won't be visible until it is iterated
  12 note: the lint level is defined here
  13   --> $DIR/issue-109152.rs:1:9
  14    |
  15 LL | #![deny(map_unit_fn)]
  16    |         ^^^^^^^^^^^
  17 help: you might have meant to use `Iterator::for_each`
  18    |
  19 LL |     vec![42].iter().for_each(drop);
  20    |                     ~~~~~~~~
  21
  22 error: aborting due to 1 previous error
  23