Fix remove use of fuse at tuple_windows

Author: aobatact

src/tuple_impl.rs

@@ -139,7 +139,7 @@ pub struct TupleWindows<I, T>
     where I: Iterator<Item = T::Item>,
           T: HomogeneousTuple
 {
-    iter: Fuse<I>,
+    iter: I,
     last: Option<T>,
 }
 
@@ -151,7 +151,7 @@ pub fn tuple_windows<I, T>(iter: I) -> TupleWindows<I, T>
 {
     TupleWindows {
         last : None,
-        iter : iter.fuse(),
+        iter,
     }
 }
 
@@ -166,25 +166,24 @@ impl<I, T> Iterator for TupleWindows<I, T>
         if T::num_items() == 1 {
             return T::collect_from_iter_no_buf(&mut self.iter)
         }
-        if let Some(ref mut last) = self.last {
-            if let Some(new) = self.iter.next() {
+        if let Some(new) = self.iter.next() {
+            if let Some(ref mut last) = self.last {
                 last.left_shift_push(new);
-                return Some(last.clone());
-            }
-        } else {
-            use std::iter::once;
-            if let Some(item) = self.iter.next() {
-                let iter = once(item).chain(&mut self.iter);
+                Some(last.clone())
+            } else {
+                use std::iter::once;
+                let iter = once(new).chain(&mut self.iter);
                 self.last = T::collect_from_iter_no_buf(iter);
-                return self.last.clone();
+                self.last.clone()
             }
+        } else {
+            None
         }
-        None
     }
 }
 
 impl<I, T> FusedIterator for TupleWindows<I, T>
-    where I: Iterator<Item = T::Item>,
+    where I: FusedIterator<Item = T::Item>,
           T: HomogeneousTuple + Clone,
           T::Item: Clone
 {}