Delete unnecessary member types in bitset and add SFINAE

Author: winner245

libcxx/include/__bit_reference

@@ -23,6 +23,7 @@
 #include <__memory/pointer_traits.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/is_constant_evaluated.h>
+#include <__type_traits/void_t.h>
 #include <__utility/swap.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -42,8 +43,14 @@ struct __has_storage_type {
   static const bool value = false;
 };
 
-template <typename _Cp>
+template <class, class>
 struct __size_difference_type_traits {
+  using difference_type = ptrdiff_t;
+  using size_type       = size_t;
+};
+
+template <class _Cp>
+struct __size_difference_type_traits<_Cp, __void_t<typename _Cp::difference_type, typename _Cp::size_type> > {
   using difference_type = typename _Cp::difference_type;
   using size_type       = typename _Cp::size_type;
 };
@@ -595,9 +602,9 @@ inline _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cr, false> swap_ranges(
 template <class _Cp>
 struct __bit_array {
   using difference_type _LIBCPP_NODEBUG   = typename __size_difference_type_traits<_Cp>::difference_type;
-  using __storage_type _LIBCPP_NODEBUG   = typename _Cp::__storage_type;
+  using __storage_type _LIBCPP_NODEBUG    = typename _Cp::__storage_type;
   using __storage_pointer _LIBCPP_NODEBUG = typename _Cp::__storage_pointer;
-  using iterator _LIBCPP_NODEBUG         = typename _Cp::iterator;
+  using iterator _LIBCPP_NODEBUG          = typename _Cp::iterator;
 
   static const unsigned __bits_per_word = _Cp::__bits_per_word;
   static const unsigned _Np             = 4;

libcxx/include/__fwd/bit_reference.h

@@ -20,7 +20,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 template <class _Cp, bool _IsConst, typename _Cp::__storage_type = 0>
 class __bit_iterator;
 
-template <typename _Cp>
+template <class, class = void>
 struct __size_difference_type_traits;
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/include/bitset

@@ -169,17 +169,9 @@ struct __has_storage_type<__bitset<_N_words, _Size> > {
   static const bool value = true;
 };
 
-template <size_t _N_words, size_t _Size>
-struct __size_difference_type_traits<std::__bitset<_N_words, _Size> > {
-  using difference_type = typename std::__bitset<_N_words, _Size>::__difference_type;
-  using size_type       = typename std::__bitset<_N_words, _Size>::__size_type;
-};
-
 template <size_t _N_words, size_t _Size>
 class __bitset {
 public:
-  typedef ptrdiff_t __difference_type;
-  typedef size_t __size_type;
   typedef size_t __storage_type;
 
 protected:
@@ -440,8 +432,6 @@ inline size_t __bitset<_N_words, _Size>::__hash_code() const _NOEXCEPT {
 template <size_t _Size>
 class __bitset<1, _Size> {
 public:
-  typedef ptrdiff_t __difference_type;
-  typedef size_t __size_type;
   typedef size_t __storage_type;
 
 protected:
@@ -557,8 +547,6 @@ inline size_t __bitset<1, _Size>::__hash_code() const _NOEXCEPT {
 template <>
 class __bitset<0, 0> {
 public:
-  typedef ptrdiff_t __difference_type;
-  typedef size_t __size_type;
   typedef size_t __storage_type;
 
 protected:

libcxx/test/std/utilities/template.bitset/bitset.members/nonstdmem.uglified.compile.pass.cpp

@@ -24,12 +24,9 @@ struct my_base {
   typedef int* iterator;
   typedef const int* const_iterator;
   typedef my_base base;
-<<<<<<< HEAD
   typedef const int& const_reference;
-=======
   typedef std::ptrdiff_t difference_type;
   typedef std::size_t size_type;
->>>>>>> 620da4a790b5 (Fix ambiguity due to non-uglified member typedefs)
 };
 
 template <std::size_t N>
@@ -94,4 +91,3 @@ static_assert(std::is_same<my_derived<32>::size_type, std::size_t>::value, "");
 static_assert(std::is_same<my_derived<48>::size_type, std::size_t>::value, "");
 static_assert(std::is_same<my_derived<64>::size_type, std::size_t>::value, "");
 static_assert(std::is_same<my_derived<96>::size_type, std::size_t>::value, "");
->>>>>>> 620da4a790b5 (Fix ambiguity due to non-uglified member typedefs)