src/test/ui/issues/issue-21332.stderr

   1 error[E0053]: method `next` has an incompatible type for trait
   2   --> $DIR/issue-21332.rs:5:5
   3    |
   4 LL |     fn next(&mut self) -> Result<i32, i32> { Ok(7) }
   5    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected enum `Option`, found enum `Result`
   6    |
   7    = note: expected fn pointer `fn(&mut S) -> Option<i32>`
   8               found fn pointer `fn(&mut S) -> Result<i32, i32>`
   9
  10 error: aborting due to previous error
  11
  12 For more information about this error, try `rustc --explain E0053`.