Update drain_filter docs.

Author: mbrubeck

src/map.rs

@@ -584,13 +584,13 @@ impl<K, V, S> HashMap<K, V, S> {
         }
     }
 
-    /// Drains elements which are false under the given predicate,
+    /// Drains elements which are true under the given predicate,
     /// and returns an iterator over the removed items.
     ///
-    /// In other words, move all pairs `(k, v)` such that `f(&k,&mut v)` returns `false` out
+    /// In other words, move all pairs `(k, v)` such that `f(&k,&mut v)` returns `true` out
     /// into another iterator.
     ///
-    /// When the returned DrainedFilter is dropped, the elements that don't satisfy
+    /// When the returned DrainedFilter is dropped, any remaining elements that satisfy
     /// the predicate are dropped from the table.
     ///
     /// # Examples

src/set.rs

@@ -352,13 +352,13 @@ impl<T, S> HashSet<T, S> {
         self.map.retain(|k, _| f(k));
     }
 
-    /// Drains elements which are false under the given predicate,
+    /// Drains elements which are true under the given predicate,
     /// and returns an iterator over the removed items.
     ///
-    /// In other words, move all elements `e` such that `f(&e)` returns `false` out
+    /// In other words, move all elements `e` such that `f(&e)` returns `true` out
     /// into another iterator.
     ///
-    /// When the returned DrainedFilter is dropped, the elements that don't satisfy
+    /// When the returned DrainedFilter is dropped, any remaining elements that satisfy
     /// the predicate are dropped from the set.
     ///
     /// # Examples