Change filtermap test to use sum instead of fold

Author: seanchen1991

src/iter/plumbing/README.md

@@ -70,7 +70,7 @@ a very simple consumer because it doesn't need to thread any state
 between items at all.)
 
 Now, the `for_each` call will pass this consumer to the base iterator,
-which is the `flat_map`. It will do by calling the `drive_unindexed`
+which is the `flat_map`. It will do this by calling the `drive_unindexed`
 method on the `ParallelIterator` trait. `drive_unindexed` basically
 says "produce items for this iterator and feed them to this consumer";
 it only works for unindexed consumers.

src/iter/test.rs

@@ -845,7 +845,7 @@ pub fn check_sum_filtermap_ints() {
     let seq_sum_evens = a
         .iter()
         .filter_map(|&x| if (x & 1) == 0 { Some(x as f32) } else { None })
-        .fold(0.0, |a, b| a + b);
+        .sum();
     assert_eq!(par_sum_evens, seq_sum_evens);
 }
 
@@ -2104,4 +2104,4 @@ fn check_update() {
     v.par_iter_mut().update(|v| v.push(0)).for_each(|_| ());
 
     assert_eq!(v, vec![vec![1, 0], vec![3, 2, 1, 0]]);
-}
+}