Improve readability of SFINAE for std::__fill_n

Author: winner245

libcxx/include/__algorithm/fill_n.h

@@ -37,8 +37,8 @@ template <class _OutputIterator,
           class _Tp
 #ifndef _LIBCPP_CXX03_LANG
           ,
-          __enable_if_t<_Or< _Not<__is_segmented_iterator<_OutputIterator> >,
-                             _Not<__has_random_access_local_iterator<_OutputIterator> > >::value,
+          __enable_if_t<!_And<__is_segmented_iterator<_OutputIterator>,
+                              __has_random_access_local_iterator<_OutputIterator> >::value,
                         int> = 0
 #endif
           >
@@ -53,9 +53,8 @@ __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value) {
 template < class _OutputIterator,
            class _Size,
            class _Tp,
-           __enable_if_t<__is_segmented_iterator<_OutputIterator>::value &&
-                             __has_random_access_iterator_category<
-                                 typename __segmented_iterator_traits<_OutputIterator>::__local_iterator>::value,
+           __enable_if_t<_And<__is_segmented_iterator<_OutputIterator>,
+                              __has_random_access_local_iterator<_OutputIterator> >::value,
                          int> = 0>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _OutputIterator
 __fill_n(_OutputIterator __first, _Size __n, const _Tp& __value) {