replace by_ref with internal iteration

Author: hellow554

src/adaptors/mod.rs

@@ -1027,14 +1027,18 @@ impl<I, F> Iterator for Positions<I, F>
     type Item = usize;
 
     fn next(&mut self) -> Option<Self::Item> {
-        for v in self.iter.by_ref() {
-            let i = self.count;
-            self.count = i + 1;
-            if (self.f)(v) {
-                return Some(i);
+        // let's help the borrow checker a little bit :)
+        let count = &mut self.count;
+        let f = &mut self.f;
+        self.iter.find_map(|v| {
+            let i = *count;
+            *count = i + 1;
+            if f(v) {
+                Some(i)
+            } else {
+                None
             }
-        }
-        None
+        })
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {

src/lib.rs

@@ -1748,12 +1748,7 @@ pub trait Itertools : Iterator {
     fn find_position<P>(&mut self, mut pred: P) -> Option<(usize, Self::Item)>
         where P: FnMut(&Self::Item) -> bool
     {
-        for (index, elt) in self.enumerate() {
-            if pred(&elt) {
-                return Some((index, elt));
-            }
-        }
-        None
+        self.enumerate().find(|x| pred(&x.1))
     }
     /// Find the value of the first element satisfying a predicate or return the last element, if any.
     ///

src/unique_impl.rs

@@ -57,13 +57,17 @@ impl<I, V, F> Iterator for UniqueBy<I, V, F>
     type Item = I::Item;
 
     fn next(&mut self) -> Option<Self::Item> {
-        for v in self.iter.by_ref() {
-            let key = (self.f)(&v);
-            if self.used.insert(key, ()).is_none() {
-                return Some(v);
+        // let's help the borrow checker a little bit :)
+        let used = &mut self.used;
+        let f = &mut self.f;
+        self.iter.find_map(|v| {
+            let key = f(&v);
+            if used.insert(key, ()).is_none() {
+                Some(v)
+            } else {
+                None
             }
-        }
-        None
+        })
     }
 
     #[inline]
@@ -107,14 +111,16 @@ impl<I> Iterator for Unique<I>
     type Item = I::Item;
 
     fn next(&mut self) -> Option<Self::Item> {
-        for v in self.iter.iter.by_ref() {
-            if let Entry::Vacant(entry) = self.iter.used.entry(v) {
+        let used = &mut self.iter.used;
+        self.iter.iter.find_map(|v| {
+            if let Entry::Vacant(entry) = used.entry(v) {
                 let elt = entry.key().clone();
                 entry.insert(());
-                return Some(elt);
+                Some(elt)
+            } else {
+                None
             }
-        }
-        None
+        })
     }
 
     #[inline]