1 error[E0053]: method `next` has an incompatible type for trait
2 --> $DIR/issue-21332.rs:5:27
4 LL | fn next(&mut self) -> Result<i32, i32> { Ok(7) }
7 | expected enum `Option`, found enum `Result`
8 | help: change the output type to match the trait: `Option<i32>`
10 = note: expected fn pointer `fn(&mut S) -> Option<i32>`
11 found fn pointer `fn(&mut S) -> Result<i32, i32>`
13 error: aborting due to previous error
15 For more information about this error, try `rustc --explain E0053`.