Use concepts instead of SFINAE in bitset_extensions

Use concepts to test GCC intrinsics precence, instead of SFINAE

src/core/util/bitset_extensions.h

@@ -39,13 +39,10 @@ static std::vector<unsigned long long> const kBytes{0xff,
 constexpr static size_t kNumBytes = 8;
 constexpr static size_t kWidth = 64;
 
-// std::vector::operator[] is constexpr only since GCC 12
-// (see https://en.cppreference.com/w/cpp/compiler_support)
-// FIXME(senichenkov): check old versions of other compilers
-#if defined(__GNUC__) && (__GNUC__ < 12)
-#define CONSTEXPR_IF_VECTOR_IS_CONSTEXPR /* Ignore */
+#if (__cpp_lib_constexpr_vector == 201907L)
+#define CONSTEXPR_IF_VECTOR_IS_CONSTEXPR constexpr
 #else
-#define CONSTEXPR_IF_VECTOR_IS_CONSTEXPR conxtexpr
+#define CONSTEXPR_IF_VECTOR_IS_CONSTEXPR /* Ignore */
 #endif
 
 CONSTEXPR_IF_VECTOR_IS_CONSTEXPR unsigned char GetByte(unsigned long long val, size_t byte_num);
@@ -54,26 +51,8 @@ size_t FindFirstFixedWidth(std::bitset<kWidth> const&);
 
 size_t FindNextFixedWidth(std::bitset<kWidth> const&, size_t pos);
 
-/// @brief Test if T has method _Find_next using SFINAE
-template <typename T>
-struct TestBitset {
-private:
-    typedef char yes[1];
-    typedef char no[2];
-
-    template <typename Tp>
-    static yes& Test(decltype(&Tp::_Find_next));
-
-    template <typename Tp>
-    static no& Test(...);
-
-public:
-    static bool const kValue = sizeof(Test<T>(nullptr)) == sizeof(yes);
-};
-
-/// @brief Test if T has method _Find_next
-template <typename T>
-constexpr bool kTestBitsetV = TestBitset<T>::kValue;
+template <typename Bitset>
+concept HasFindFirst = requires(Bitset bs) { bs._Find_first(); };
 
 /// @brief Wrapper for std::bitset to iterate through set bits using temporary
 /// boost::dynamic_bitset.
@@ -129,27 +108,27 @@ class BitsetIterator : public IBitsetIterator {
 }  // namespace bitset_extensions
 
 /// @brief Call bs._Find_first if it's availible, use custom implementation otherwise
-template <size_t S, typename std::enable_if<bitset_extensions::kTestBitsetV<std::bitset<S>>,
-                                            bool>::type = true>
+template <size_t S>
+    requires bitset_extensions::HasFindFirst<std::bitset<S>>
 inline size_t FindFirst(std::bitset<S> const& bs) noexcept {
     return bs._Find_first();
 }
 
 /// @brief Call bs._Find_first if it's availible, use custom implementation otherwise
-template <size_t S, typename = std::enable_if_t<!bitset_extensions::kTestBitsetV<std::bitset<S>>>>
+template <size_t S>
 inline size_t FindFirst(std::bitset<S> const& bs) noexcept {
     return bitset_extensions::FindFirstFixedWidth(bs);
 }
 
 /// @brief Call bs._Find_next if it's availible, use custom implementation otherwise
-template <size_t S, typename std::enable_if<bitset_extensions::kTestBitsetV<std::bitset<S>>,
-                                            bool>::type = true>
+template <size_t S>
+    requires bitset_extensions::HasFindFirst<std::bitset<S>>
 inline size_t FindNext(std::bitset<S> const& bs, size_t pos) noexcept {
     return bs._Find_next(pos);
 }
 
 /// @brief Call bs._Find_next if it's availible, use custom implementation otherwise
-template <size_t S, typename = std::enable_if_t<!bitset_extensions::kTestBitsetV<std::bitset<S>>>>
+template <size_t S>
 inline size_t FindNext(std::bitset<S> const& bs, size_t pos) noexcept {
     if constexpr (S == 64) {
         return bitset_extensions::FindNextFixedWidth(bs, pos);
@@ -163,8 +142,8 @@ inline size_t FindNext(std::bitset<S> const& bs, size_t pos) noexcept {
 
 /// @brief If _Find_next is availible, copy every set bit, else copy biset to dynamic_bitset
 /// through string representation. Bitset is shifted 1 bit left.
-template <size_t S, typename std::enable_if<bitset_extensions::kTestBitsetV<std::bitset<S>>,
-                                            bool>::type = true>
+template <size_t S>
+    requires bitset_extensions::HasFindFirst<std::bitset<S>>
 inline boost::dynamic_bitset<> CreateShiftedDynamicBitset(std::bitset<S> const& bs,
                                                           std::size_t size = S) noexcept {
     boost::dynamic_bitset<> dyn_bitset(size);
@@ -176,7 +155,7 @@ inline boost::dynamic_bitset<> CreateShiftedDynamicBitset(std::bitset<S> const&
 
 /// @brief If _Find_next is availible, copy every set bit, else copy biset to dynamic_bitset
 /// through string representation. Bitset is shifted 1 bit left.
-template <size_t S, typename = std::enable_if_t<!bitset_extensions::kTestBitsetV<std::bitset<S>>>>
+template <size_t S>
 inline boost::dynamic_bitset<> CreateShiftedDynamicBitset(std::bitset<S> const& bs,
                                                           std::size_t size = S) noexcept {
     size_t start = S - size - 1;
@@ -185,15 +164,15 @@ inline boost::dynamic_bitset<> CreateShiftedDynamicBitset(std::bitset<S> const&
 
 /// @brief If _Find_next is availible, create std::bitset set-bits-iterator, else
 /// boost::dynamic_bitset set-bits-iterator
-template <size_t S, typename std::enable_if<bitset_extensions::kTestBitsetV<std::bitset<S>>,
-                                            bool>::type = true>
+template <size_t S>
+    requires bitset_extensions::HasFindFirst<std::bitset<S>>
 inline std::unique_ptr<IBitsetIterator> MakeBitsetIterator(std::bitset<S> const& bs) {
     return std::make_unique<bitset_extensions::BitsetIterator<S>>(bs);
 }
 
 /// @brief If _Find_next is availible, create std::bitset set-bits-iterator, else
 /// boost::dynamic_bitset set-bits-iterator
-template <size_t S, typename = std::enable_if_t<!bitset_extensions::kTestBitsetV<std::bitset<S>>>>
+template <size_t S>
 inline std::unique_ptr<IBitsetIterator> MakeBitsetIterator(std::bitset<S> const& bs) {
     return std::make_unique<bitset_extensions::DynamicBitsetIterator<S>>(bs);
 }