Only evaluate function if needed

Author: phimuemue

src/group_map.rs

@@ -15,8 +15,8 @@ pub fn into_group_map<I, K, V>(iter: I) -> HashMap<K, Vec<V>>
     let mut lookup = HashMap::new();
 
     for (key, val) in iter {
-        lookup.entry(key).or_insert(Vec::new()).push(val);
+        lookup.entry(key).or_insert_with(Vec::new).push(val);
     }
 
     lookup
-}
+}

src/tuple_impl.rs

@@ -62,7 +62,7 @@ impl<T> Iterator for TupleBuffer<T>
         } else {
             buffer.iter()
                   .position(|x| x.is_none())
-                  .unwrap_or(buffer.len())
+                  .unwrap_or_else(|| buffer.len())
         };
         (len, Some(len))
     }