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