Simplify private scheme
diff --git a/src/data.rs b/src/data.rs
index 36f82c6..1b1b928 100644
--- a/src/data.rs
+++ b/src/data.rs
@@ -73,7 +73,7 @@
     /// [`Field`]: struct.Field.html
     pub fn iter(&self) -> punctuated::Iter<Field> {
         match *self {
-            Fields::Unit => private::<punctuated::Iter<Field>>::empty(),
+            Fields::Unit => private::empty_punctuated_iter(),
             Fields::Named(ref f) => f.named.iter(),
             Fields::Unnamed(ref f) => f.unnamed.iter(),
         }
@@ -86,7 +86,7 @@
     /// [`Field`]: struct.Field.html
     pub fn iter_mut(&mut self) -> punctuated::IterMut<Field> {
         match *self {
-            Fields::Unit => private::<punctuated::IterMut<Field>>::empty(),
+            Fields::Unit => private::empty_punctuated_iter_mut(),
             Fields::Named(ref mut f) => f.named.iter_mut(),
             Fields::Unnamed(ref mut f) => f.unnamed.iter_mut(),
         }