Apply suggestions from code review

Co-authored-by: Louis Dionne <[email protected]>

Author: huixie90

libcxx/include/__iterator/product_iterator.h

@@ -6,8 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP___PRODUCT_ITERATOR_H
-#define _LIBCPP___PRODUCT_ITERATOR_H
+#ifndef _LIBCPP___ITERATOR_PRODUCT_ITERATOR_H
+#define _LIBCPP___ITERATOR_PRODUCT_ITERATOR_H
 
 // Product iterators are iterators that contain two or more underlying iterators.
 //
@@ -66,4 +66,4 @@ using __product_iterator_element_t _LIBCPP_NODEBUG =
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP___PRODUCT_ITERATOR_H
+#endif // _LIBCPP___ITERATOR_PRODUCT_ITERATOR_H

libcxx/include/__ranges/zip_view.h

@@ -252,7 +252,7 @@ class zip_view<_Views...>::__iterator : public __zip_view_iterator_category_base
 
   friend class zip_view<_Views...>;
 
-  using __is_zip_view_iterator _LIBCPP_NODEBUG = true_type;
+  static constexpr bool __is_zip_view_iterator = true;
 
   friend struct __product_iterator_traits<__iterator>;