fix clippy::while_let_on_iterator

Author: hellow554

src/adaptors/mod.rs

@@ -1032,7 +1032,7 @@ impl<I, F> Iterator for Positions<I, F>
     type Item = usize;
 
     fn next(&mut self) -> Option<Self::Item> {
-        while let Some(v) = self.iter.next() {
+        for v in self.iter.by_ref() {
             let i = self.count;
             self.count = i + 1;
             if (self.f)(v) {

src/unique_impl.rs

@@ -57,7 +57,7 @@ impl<I, V, F> Iterator for UniqueBy<I, V, F>
     type Item = I::Item;
 
     fn next(&mut self) -> Option<Self::Item> {
-        while let Some(v) = self.iter.next() {
+        for v in self.iter.by_ref() {
             let key = (self.f)(&v);
             if self.used.insert(key, ()).is_none() {
                 return Some(v);
@@ -107,7 +107,7 @@ impl<I> Iterator for Unique<I>
     type Item = I::Item;
 
     fn next(&mut self) -> Option<Self::Item> {
-        while let Some(v) = self.iter.iter.next() {
+        for v in self.iter.iter.by_ref() {
             if let Entry::Vacant(entry) = self.iter.used.entry(v) {
                 let elt = entry.key().clone();
                 entry.insert(());