src/tuple_impl.rs

@@ -56,14 +56,15 @@ impl<T> Iterator for TupleBuffer<T>
         }
     }
 
+    #[allow(clippy::unnecessary_lazy_evaluations)] // buffer.len is more complex than usual
     fn size_hint(&self) -> (usize, Option<usize>) {
         let buffer = &self.buf.as_ref()[self.cur..];
         let len = if buffer.is_empty() {
             0
         } else {
             buffer.iter()
                   .position(Option::is_none)
-                  .unwrap_or(buffer.len())
+                  .unwrap_or_else(|| buffer.len())
         };
         (len, Some(len))
     }