[libcxx-commits] [libcxx] [libc++] P1789R3: Library Support for Expansion Statements (PR #167184)

[Victor Chernyakin via libcxx-commits]

================
@@ -67,6 +72,30 @@ _LIBCPP_HIDE_FROM_ABI constexpr void __for_each_index_sequence(index_sequence<_I
 }
 #    endif // _LIBCPP_STD_VER >= 20
 
+#    if _LIBCPP_STD_VER >= 26
+// structured binding support for integer_sequence
+template <typename _Tp, _Tp... _Indices>
+struct tuple_size<integer_sequence<_Tp, _Indices...>> : public integral_constant<size_t, sizeof...(_Indices)> {};
+
+template <size_t _Ip, typename _Tp, _Tp... _Indices>
+struct tuple_element<_Ip, integer_sequence<_Tp, _Indices...>> {
+  static_assert(_Ip < sizeof...(_Indices), "Index out of bounds in std::tuple_element<> (std::integer_sequence)");
+  using type _LIBCPP_NODEBUG = _Tp;
+};
+
+template <size_t _Ip, typename _Tp, _Tp... _Indices>
+struct tuple_element<_Ip, const integer_sequence<_Tp, _Indices...>> {
+  static_assert(_Ip < sizeof...(_Indices), "Index out of bounds in std::tuple_element<> (const std::integer_sequence)");
+  using type _LIBCPP_NODEBUG = _Tp;
+};
+
+template <size_t _Ip, typename _Tp, _Tp... _Indices>
+_LIBCPP_HIDE_FROM_ABI constexpr _Tp get(integer_sequence<_Tp, _Indices...>) _NOEXCEPT {
+  static_assert(_Ip < sizeof...(_Indices), "Index out of bounds in std::get<> (std::integer_sequence)");
+  return _Indices...[_Ip];
+}
+#    endif // _LIBCPP_STD_VER >= 20
----------------
localspook wrote:

```suggestion
#    endif // _LIBCPP_STD_VER >= 26
```

https://github.com/llvm/llvm-project/pull/167184