Remove useless types declaration
Let the compiler infer the types
@@ -398,8 +398,10 @@ pub trait ParallelIterator: Sized + Send {
///
/// ```
/// use rayon::prelude::*;
- /// let x: Vec<Vec<i32>> = vec![vec![1, 2], vec![3, 4]];
- /// let y: Vec<i32> = x.into_par_iter().flatten().collect();
+ ///
+ /// let x: Vec<Vec<_>> = vec![vec![1, 2], vec![3, 4]];
+ /// let y: Vec<_> = x.into_par_iter().flatten().collect();
+ ///
/// assert_eq!(y, vec![1, 2, 3, 4]);
/// ```
fn flatten(self) -> Flatten<Self>
