[libc++] Implement P3168R2: Give optional range support

libcxx/docs/FeatureTestMacroTable.rst

@@ -480,7 +480,7 @@ Status
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_not_fn``                                       ``202306L``
     ---------------------------------------------------------- -----------------
-    ``__cpp_lib_optional_range_support``                       *unimplemented*
+    ``__cpp_lib_optional_range_support``                       ``202406L``
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_out_ptr``                                      ``202311L``
     ---------------------------------------------------------- -----------------

libcxx/docs/ReleaseNotes/22.rst

@@ -36,6 +36,9 @@ What's New in Libc++ 22.0.0?
 ==============================
 
 Implemented Papers
+
+- P3168R2: Give ``std::optional`` Range Support (`Github <https://github.com/llvm/llvm-project/issues/105430>`__)
+
 ------------------
 
 

libcxx/docs/Status/Cxx2cPapers.csv

@@ -66,7 +66,7 @@
 "`P2747R2 <https://wg21.link/P2747R2>`__","``constexpr`` placement new","2024-06 (St. Louis)","|Complete|","20",""
 "`P2997R1 <https://wg21.link/P2997R1>`__","Removing the common reference requirement from the indirectly invocable concepts","2024-06 (St. Louis)","|Complete|","19","Implemented as a DR against C++20. (MSVC STL and libstdc++ will do the same.)"
 "`P2389R2 <https://wg21.link/P2389R2>`__","``dextents`` Index Type Parameter","2024-06 (St. Louis)","|Complete|","19",""
-"`P3168R2 <https://wg21.link/P3168R2>`__","Give ``std::optional`` Range Support","2024-06 (St. Louis)","","",""
+"`P3168R2 <https://wg21.link/P3168R2>`__","Give ``std::optional`` Range Support","2024-06 (St. Louis)","|Complete|","22",""
 "`P3217R0 <https://wg21.link/P3217R0>`__","Adjoints to 'Enabling list-initialization for algorithms': find_last","2024-06 (St. Louis)","","",""
 "`P2985R0 <https://wg21.link/P2985R0>`__","A type trait for detecting virtual base classes","2024-06 (St. Louis)","|Complete|","20",""
 "`P0843R14 <https://wg21.link/P0843R14>`__","``inplace_vector``","2024-06 (St. Louis)","","",""

libcxx/include/__iterator/wrap_iter.h

@@ -117,6 +117,8 @@ class __wrap_iter {
   friend class span;
   template <class _Tp, size_t _Size>
   friend struct array;
+  template <class _Tp>
+  friend class optional;
 };
 
 template <class _Iter1>

libcxx/include/optional

@@ -20,6 +20,11 @@ namespace std {
   template <class T>
     class optional;
 
+  template<class T>
+   constexpr bool ranges::enable_view<optional<T>> = true;
+  template<class T>
+   constexpr auto format_kind<optional<T>> = range_format::disabled;
+
   template<class T>
     concept is-derived-from-optional = requires(const T& t) {       // exposition only
       []<class U>(const optional<U>&){ }(t);
@@ -102,6 +107,8 @@ namespace std {
   class optional {
   public:
     using value_type = T;
+    using iterator               = implementation-defined; // see [optional.iterators]
+    using const_iterator         = implementation-defined; // see [optional.iterators]
 
     // [optional.ctor], constructors
     constexpr optional() noexcept;
@@ -135,6 +142,12 @@ namespace std {
     // [optional.swap], swap
     void swap(optional &) noexcept(see below ); // constexpr in C++20
 
+    // [optional.iterators], iterator support
+    constexpr iterator begin() noexcept;
+    constexpr const_iterator begin() const noexcept;
+    constexpr iterator end() noexcept;
+    constexpr const_iterator end() const noexcept;
+
     // [optional.observe], observers
     constexpr T const *operator->() const noexcept;
     constexpr T *operator->() noexcept;
@@ -186,13 +199,16 @@ namespace std {
 #  include <__compare/three_way_comparable.h>
 #  include <__concepts/invocable.h>
 #  include <__config>
+#  include <__cstddef/ptrdiff_t.h>
 #  include <__exception/exception.h>
 #  include <__functional/hash.h>
 #  include <__functional/invoke.h>
 #  include <__functional/unary_function.h>
 #  include <__fwd/functional.h>
+#  include <__iterator/wrap_iter.h>
 #  include <__memory/addressof.h>
 #  include <__memory/construct_at.h>
+#  include <__ranges/enable_view.h>
 #  include <__tuple/sfinae_helpers.h>
 #  include <__type_traits/add_pointer.h>
 #  include <__type_traits/conditional.h>
@@ -233,6 +249,10 @@ namespace std {
 #  include <initializer_list>
 #  include <version>
 
+#  if _LIBCPP_STD_VER >= 26
+#    include <__format/range_format.h>
+#  endif
+
 // standard-mandated includes
 
 // [optional.syn]
@@ -567,6 +587,14 @@ using __optional_sfinae_assign_base_t _LIBCPP_NODEBUG =
 template <class _Tp>
 class optional;
 
+#    if _LIBCPP_STD_VER >= 26
+template <class _Tp>
+constexpr bool ranges::enable_view<optional<_Tp>> = true;
+
+template <class _Tp>
+constexpr range_format format_kind<optional<_Tp>> = range_format::disabled;
+#    endif
+
 #    if _LIBCPP_STD_VER >= 20
 
 template <class _Tp>
@@ -586,8 +614,17 @@ class _LIBCPP_DECLSPEC_EMPTY_BASES optional
       private __optional_sfinae_assign_base_t<_Tp> {
   using __base _LIBCPP_NODEBUG = __optional_move_assign_base<_Tp>;
 
+#    if _LIBCPP_STD_VER >= 26
+  using pointer       = std::add_pointer_t<std::remove_cvref_t<_Tp>>;
+  using const_pointer = std::add_pointer_t<const std::remove_cvref_t<_Tp>>;
+#    endif
+
 public:
   using value_type = _Tp;
+#    if _LIBCPP_STD_VER >= 26
+  using iterator       = __wrap_iter<pointer>;
+  using const_iterator = __wrap_iter<const_pointer>;
+#    endif
 
   using __trivially_relocatable _LIBCPP_NODEBUG =
       conditional_t<__libcpp_is_trivially_relocatable<_Tp>::value, optional, void>;
@@ -792,6 +829,18 @@ public:
     }
   }
 
+#    if _LIBCPP_STD_VER >= 26
+  // [optional.iterators], iterator support
+  _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() noexcept { return iterator(std::addressof(this->__get())); }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
+    return const_iterator(std::addressof(this->__get()));
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr iterator end() noexcept { return begin() + this->has_value(); }
+  _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept { return begin() + this->has_value(); }
+#    endif
+
   _LIBCPP_HIDE_FROM_ABI constexpr add_pointer_t<value_type const> operator->() const noexcept {
     _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(this->has_value(), "optional operator-> called on a disengaged value");
     return std::addressof(this->__get());

libcxx/include/version

@@ -585,7 +585,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # define __cpp_lib_mdspan                               202406L
 # undef  __cpp_lib_not_fn
 # define __cpp_lib_not_fn                               202306L
-// # define __cpp_lib_optional_range_support               202406L
+# define __cpp_lib_optional_range_support               202406L
 # undef  __cpp_lib_out_ptr
 # define __cpp_lib_out_ptr                              202311L
 // # define __cpp_lib_philox_engine                        202406L

libcxx/modules/std/optional.inc

@@ -10,14 +10,23 @@
 export namespace std {
   // [optional.optional], class template optional
   using std::optional;
-
+#if _LIBCPP_STD_VER >= 26
+  // [optional.iterators], iterator support
+  namespace ranges {
+    using std::ranges::enable_view;
+  }
+#endif
   // [optional.nullopt], no-value state indicator
   using std::nullopt;
   using std::nullopt_t;
 
   // [optional.bad.access], class bad_optional_access
   using std::bad_optional_access;
 
+#if _LIBCPP_STD_VER >= 26
+  using std::format_kind;
+#endif
+
   // [optional.relops], relational operators
   using std::operator==;
   using std::operator!=;

libcxx/test/libcxx/transitive_includes/cxx26.csv

@@ -2,6 +2,7 @@ algorithm cctype
 algorithm climits
 algorithm compare
 algorithm cstdint
+algorithm cstdio
 algorithm cstring
 algorithm ctime
 algorithm cwchar
@@ -11,6 +12,8 @@ algorithm iosfwd
 algorithm limits
 algorithm optional
 algorithm ratio
+algorithm stdexcept
+algorithm string_view
 algorithm tuple
 algorithm version
 any cstdint
@@ -330,26 +333,32 @@ flat_map cctype
 flat_map climits
 flat_map compare
 flat_map cstdint
+flat_map cstdio
 flat_map cstring
 flat_map cwchar
 flat_map cwctype
 flat_map initializer_list
+flat_map iosfwd
 flat_map limits
 flat_map optional
 flat_map stdexcept
+flat_map string_view
 flat_map tuple
 flat_map version
 flat_set cctype
 flat_set climits
 flat_set compare
 flat_set cstdint
+flat_set cstdio
 flat_set cstring
 flat_set cwchar
 flat_set cwctype
 flat_set initializer_list
+flat_set iosfwd
 flat_set limits
 flat_set optional
 flat_set stdexcept
+flat_set string_view
 flat_set tuple
 flat_set version
 format array
@@ -417,13 +426,16 @@ functional array
 functional cctype
 functional compare
 functional cstdint
+functional cstdio
 functional cstring
 functional cwchar
 functional cwctype
 functional initializer_list
+functional iosfwd
 functional limits
 functional optional
 functional stdexcept
+functional string_view
 functional tuple
 functional typeinfo
 functional unordered_map
@@ -623,13 +635,16 @@ locale version
 map cctype
 map compare
 map cstdint
+map cstdio
 map cstring
 map cwchar
 map cwctype
 map initializer_list
+map iosfwd
 map limits
 map optional
 map stdexcept
+map string_view
 map tuple
 map version
 mdspan array
@@ -673,22 +688,36 @@ mutex typeinfo
 mutex version
 new version
 numbers version
+numeric cctype
 numeric climits
 numeric compare
 numeric cstdint
+numeric cstdio
 numeric cstring
 numeric ctime
+numeric cwchar
+numeric cwctype
 numeric initializer_list
+numeric iosfwd
 numeric limits
 numeric optional
 numeric ratio
+numeric stdexcept 
+numeric string_view
 numeric tuple
 numeric version
+optional cctype
 optional compare
 optional cstdint
+optional cstdio
 optional cstring
+optional cwchar
+optional cwctype
 optional initializer_list
+optional iosfwd
 optional limits
+optional stdexcept
+optional string_view
 optional version
 ostream array
 ostream bitset
@@ -806,6 +835,7 @@ ranges limits
 ranges optional
 ranges span
 ranges stdexcept
+ranges string_view
 ranges tuple
 ranges variant
 ranges version
@@ -851,12 +881,16 @@ semaphore version
 set cctype
 set compare
 set cstdint
+set cstdio
 set cstring
 set cwchar
 set cwctype
 set initializer_list
+set iosfwd
 set limits
 set optional
+set stdexcept 
+set string_view
 set tuple
 set version
 shared_mutex cerrno
@@ -1091,21 +1125,34 @@ typeindex typeinfo
 typeindex version
 typeinfo cstdint
 typeinfo version
+unordered_map cctype
 unordered_map compare
 unordered_map cstdint
+unordered_map cstdio
 unordered_map cstring
+unordered_map cwchar
+unordered_map cwctype
 unordered_map initializer_list
+unordered_map iosfwd
 unordered_map limits
 unordered_map optional
 unordered_map stdexcept
+unordered_map string_view
 unordered_map tuple
 unordered_map version
+unordered_set cctype
 unordered_set compare
 unordered_set cstdint
+unordered_set cstdio
 unordered_set cstring
+unordered_set cwchar
+unordered_set cwctype
 unordered_set initializer_list
+unordered_set iosfwd
 unordered_set limits
 unordered_set optional
+unordered_set stdexcept 
+unordered_set string_view
 unordered_set tuple
 unordered_set version
 utility compare

libcxx/test/std/language.support/support.limits/support.limits.general/optional.version.compile.pass.cpp

@@ -152,17 +152,11 @@
 #    error "__cpp_lib_optional should have the value 202110L in c++26"
 #  endif
 
-#  if !defined(_LIBCPP_VERSION)
-#    ifndef __cpp_lib_optional_range_support
-#      error "__cpp_lib_optional_range_support should be defined in c++26"
-#    endif
-#    if __cpp_lib_optional_range_support != 202406L
-#      error "__cpp_lib_optional_range_support should have the value 202406L in c++26"
-#    endif
-#  else
-#    ifdef __cpp_lib_optional_range_support
-#      error "__cpp_lib_optional_range_support should not be defined because it is unimplemented in libc++!"
-#    endif
+#  ifndef __cpp_lib_optional_range_support
+#    error "__cpp_lib_optional_range_support should be defined in c++26"
+#  endif
+#  if __cpp_lib_optional_range_support != 202406L
+#    error "__cpp_lib_optional_range_support should have the value 202406L in c++26"
 #  endif
 
 #endif // TEST_STD_VER > 23