[libcxx-commits] [libcxx] [libc++] P3168R2 Give std::optional Range Support (PR #146491)

[Yanzuo Liu via libcxx-commits]

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@@ -578,6 +600,64 @@ struct __is_std_optional : false_type {};
 template <class _Tp>
 struct __is_std_optional<optional<_Tp>> : true_type {};
 
+#    if _LIBCPP_STD_VER >= 26
+
+template <class _T>
+constexpr bool ranges::enable_view<optional<_T>> = true;
+
+template <class _T>
+constexpr auto format_kind<optional<_T>> = range_format::disabled;
+
+template <typename _Tp>
+class __optional_iterator {
+public:
+  using value_type        = _Tp;
+  using difference_type   = std::ptrdiff_t;
+  using pointer           = _Tp*;
+  using reference         = _Tp&;
+  using iterator_category = random_access_iterator_tag;
+  using iterator_concept  = contiguous_iterator_tag;
+
+private:
+  pointer __ptr_;
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit __optional_iterator(pointer __ptr) : __ptr_(__ptr) {}
+  _LIBCPP_HIDE_FROM_ABI friend class optional<std::remove_const_t<_Tp>>;
+  _LIBCPP_HIDE_FROM_ABI friend class optional<const _Tp>;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI constexpr __optional_iterator() : __ptr_(nullptr) {}
+
+  _LIBCPP_HIDE_FROM_ABI constexpr __optional_iterator(const __optional_iterator&)            = default;
+  _LIBCPP_HIDE_FROM_ABI constexpr __optional_iterator& operator=(const __optional_iterator&) = default;
+
+  _LIBCPP_HIDE_FROM_ABI constexpr reference operator*() const { return *__ptr_; }
+  _LIBCPP_HIDE_FROM_ABI constexpr pointer operator->() const { return *__ptr_; }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr __optional_iterator& operator++() {
+    __ptr_ = nullptr;
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zwuis wrote:

This doesn't meet the _Cpp17RandomAccessIterator_ requirements.

https://github.com/llvm/llvm-project/pull/146491