src/test/ui/issues/issue-23966.stderr

   1 error[E0277]: expected a `FnMut<(_, char)>` closure, found `()`
   2   --> $DIR/issue-23966.rs:2:32
   3    |
   4 LL |     "".chars().fold(|_, _| (), ());
   5    |                ----            ^^ expected an `FnMut<(_, char)>` closure, found `()`
   6    |                |
   7    |                required by a bound introduced by this call
   8    |
   9    = help: the trait `FnMut<(_, char)>` is not implemented for `()`
  10 note: required by a bound in `fold`
  11   --> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
  12    |
  13 LL |         F: FnMut(B, Self::Item) -> B,
  14    |            ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `fold`
  15
  16 error: aborting due to previous error
  17
  18 For more information about this error, try `rustc --explain E0277`.