[libc++] Fix LLVM 22 TODOs

libcxx/include/CMakeLists.txt

@@ -316,6 +316,7 @@ set(files
   __concepts/invocable.h
   __concepts/movable.h
   __concepts/predicate.h
+  __concepts/referenceable.h
   __concepts/regular.h
   __concepts/relation.h
   __concepts/same_as.h
@@ -856,7 +857,6 @@ set(files
   __type_traits/is_primary_template.h
   __type_traits/is_reference.h
   __type_traits/is_reference_wrapper.h
-  __type_traits/is_referenceable.h
   __type_traits/is_replaceable.h
   __type_traits/is_same.h
   __type_traits/is_scalar.h

libcxx/include/__type_traits/is_referenceable.h → libcxx/include/__concepts/referenceable.h

@@ -6,29 +6,27 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP___TYPE_TRAITS_IS_REFERENCEABLE_H
-#define _LIBCPP___TYPE_TRAITS_IS_REFERENCEABLE_H
+#ifndef _LIBCPP___CONCEPTS_REFERENCEABLE_H
+#define _LIBCPP___CONCEPTS_REFERENCEABLE_H
 
 #include <__config>
-#include <__type_traits/void_t.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_STD
+#if _LIBCPP_STD_VER >= 20
 
-template <class _Tp, class = void>
-inline const bool __is_referenceable_v = false;
+_LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp>
-inline const bool __is_referenceable_v<_Tp, __void_t<_Tp&> > = true;
+using __referenceable_impl _LIBCPP_NODEBUG = _Tp&;
 
-#if _LIBCPP_STD_VER >= 20
 template <class _Tp>
-concept __referenceable = __is_referenceable_v<_Tp>;
-#endif
+concept __referenceable = requires { typename __referenceable_impl<_Tp>; };
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP___TYPE_TRAITS_IS_REFERENCEABLE_H
+#endif
+
+#endif // _LIBCPP___CONCEPTS_REFERENCEABLE_H

libcxx/include/__config

@@ -1050,11 +1050,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(_ClassName) static_assert(true, "")
 #  endif
 
-// TODO(LLVM 22): Remove the workaround
-#  if defined(__OBJC__) && (!defined(_LIBCPP_CLANG_VER) || _LIBCPP_CLANG_VER < 2001)
-#    define _LIBCPP_WORKAROUND_OBJCXX_COMPILER_INTRINSICS
-#  endif
-
 #  define _PSTL_PRAGMA(x) _Pragma(#x)
 
 // Enable SIMD for compilers that support OpenMP 4.0
@@ -1255,14 +1250,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_DIAGNOSE_NULLPTR
 #  endif
 
-// TODO(LLVM 22): Remove this macro once LLVM19 support ends. __cpp_explicit_this_parameter has been set in LLVM20.
-// Clang-18 has support for deducing this, but it does not set the FTM.
-#  if defined(__cpp_explicit_this_parameter) || (defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 1800)
-#    define _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER 1
-#  else
-#    define _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER 0
-#  endif
-
 #endif // __cplusplus
 
 #endif // _LIBCPP___CONFIG

libcxx/include/__configuration/abi.h

@@ -49,14 +49,6 @@
 // According to the Standard, `bitset::operator[] const` returns bool
 #  define _LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL
 
-// In LLVM 20, we've changed to take these ABI breaks unconditionally. These flags only exist in case someone is running
-// into the static_asserts we added to catch the ABI break and don't care that it is one.
-// TODO(LLVM 22): Remove these flags
-#  define _LIBCPP_ABI_LIST_REMOVE_NODE_POINTER_UB
-#  define _LIBCPP_ABI_TREE_REMOVE_NODE_POINTER_UB
-#  define _LIBCPP_ABI_FIX_UNORDERED_NODE_POINTER_UB
-#  define _LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB
-
 // These flags are documented in ABIGuarantees.rst
 #  define _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
 #  define _LIBCPP_ABI_DO_NOT_EXPORT_BASIC_STRING_COMMON

libcxx/include/__format/format_arg.h

@@ -149,7 +149,7 @@ _LIBCPP_HIDE_FROM_ABI decltype(auto) __visit_format_arg(_Visitor&& __vis, basic_
   __libcpp_unreachable();
 }
 
-#  if _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
+#  if _LIBCPP_STD_VER >= 26
 
 template <class _Rp, class _Visitor, class _Context>
 _LIBCPP_HIDE_FROM_ABI _Rp __visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
@@ -200,7 +200,7 @@ _LIBCPP_HIDE_FROM_ABI _Rp __visit_format_arg(_Visitor&& __vis, basic_format_arg<
   __libcpp_unreachable();
 }
 
-#  endif // _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
+#  endif // _LIBCPP_STD_VER >= 26
 
 /// Contains the values used in basic_format_arg.
 ///
@@ -285,7 +285,7 @@ class _LIBCPP_NO_SPECIALIZATIONS basic_format_arg {
 
   _LIBCPP_HIDE_FROM_ABI explicit operator bool() const noexcept { return __type_ != __format::__arg_t::__none; }
 
-#  if _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
+#  if _LIBCPP_STD_VER >= 26
 
   // This function is user facing, so it must wrap the non-standard types of
   // the "variant" in a handle to stay conforming. See __arg_t for more details.
@@ -329,7 +329,7 @@ class _LIBCPP_NO_SPECIALIZATIONS basic_format_arg {
     }
   }
 
-#  endif // _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
+#  endif // _LIBCPP_STD_VER >= 26
 
 private:
   using char_type = typename _Context::char_type;
@@ -371,11 +371,8 @@ class basic_format_arg<_Context>::handle {
 // This function is user facing, so it must wrap the non-standard types of
 // the "variant" in a handle to stay conforming. See __arg_t for more details.
 template <class _Visitor, class _Context>
-#  if _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
-_LIBCPP_DEPRECATED_IN_CXX26
-#  endif
-    _LIBCPP_HIDE_FROM_ABI decltype(auto)
-    visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
+_LIBCPP_DEPRECATED_IN_CXX26 _LIBCPP_HIDE_FROM_ABI decltype(auto)
+visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
   switch (__arg.__type_) {
 #  if _LIBCPP_HAS_INT128
   case __format::__arg_t::__i128: {
@@ -387,7 +384,7 @@ _LIBCPP_DEPRECATED_IN_CXX26
     typename __basic_format_arg_value<_Context>::__handle __h{__arg.__value_.__u128_};
     return std::invoke(std::forward<_Visitor>(__vis), typename basic_format_arg<_Context>::handle{__h});
   }
-#  endif // _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
+#  endif // _LIBCPP_HAS_INT128
   default:
     return std::__visit_format_arg(std::forward<_Visitor>(__vis), __arg);
   }

libcxx/include/__format/format_context.h

@@ -175,13 +175,13 @@ class basic_format_context<typename __format::__retarget_buffer<_CharT>::__itera
                   __format::__determine_arg_t<basic_format_context, decltype(__arg)>(),
                   __basic_format_arg_value<basic_format_context>(__arg)};
           };
-#  if _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
+#  if _LIBCPP_STD_VER >= 26
           return static_cast<_Context*>(__c)->arg(__id).visit(std::move(__visitor));
 #  else
           _LIBCPP_SUPPRESS_DEPRECATED_PUSH
           return std::visit_format_arg(std::move(__visitor), static_cast<_Context*>(__c)->arg(__id));
           _LIBCPP_SUPPRESS_DEPRECATED_POP
-#  endif // _LIBCPP_STD_VER >= 26 && _LIBCPP_HAS_EXPLICIT_THIS_PARAMETER
+#  endif // _LIBCPP_STD_VER >= 26
         }) {
   }
 

libcxx/include/__hash_table

@@ -83,18 +83,6 @@ struct __hash_node_base {
   typedef _NodePtr __node_pointer;
   typedef __node_base_pointer __next_pointer;
 
-// TODO(LLVM 22): Remove this check
-#ifndef _LIBCPP_ABI_FIX_UNORDERED_NODE_POINTER_UB
-  static_assert(sizeof(__node_base_pointer) == sizeof(__node_pointer) && _LIBCPP_ALIGNOF(__node_base_pointer) ==
-                    _LIBCPP_ALIGNOF(__node_pointer),
-                "It looks like you are using std::__hash_table (an implementation detail for the unordered containers) "
-                "with a fancy pointer type that thas a different representation depending on whether it points to a "
-                "__hash_table base pointer or a __hash_table node pointer (both of which are implementation details of "
-                "the standard library). This means that your ABI is being broken between LLVM 19 and LLVM 20. If you "
-                "don't care about your ABI being broken, define the _LIBCPP_ABI_TREE_REMOVE_NODE_POINTER_UB macro to "
-                "silence this diagnostic.");
-#endif
-
   __next_pointer __next_;
 
   _LIBCPP_HIDE_FROM_ABI __next_pointer __ptr() _NOEXCEPT {

libcxx/include/__iterator/common_iterator.h

@@ -17,6 +17,7 @@
 #include <__concepts/copyable.h>
 #include <__concepts/derived_from.h>
 #include <__concepts/equality_comparable.h>
+#include <__concepts/referenceable.h>
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__iterator/concepts.h>
@@ -28,7 +29,6 @@
 #include <__memory/addressof.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/is_pointer.h>
-#include <__type_traits/is_referenceable.h>
 #include <__utility/declval.h>
 #include <variant>
 

libcxx/include/__iterator/concepts.h

@@ -20,6 +20,7 @@
 #include <__concepts/invocable.h>
 #include <__concepts/movable.h>
 #include <__concepts/predicate.h>
+#include <__concepts/referenceable.h>
 #include <__concepts/regular.h>
 #include <__concepts/relation.h>
 #include <__concepts/same_as.h>
@@ -40,7 +41,6 @@
 #include <__type_traits/is_pointer.h>
 #include <__type_traits/is_primary_template.h>
 #include <__type_traits/is_reference.h>
-#include <__type_traits/is_referenceable.h>
 #include <__type_traits/is_valid_expansion.h>
 #include <__type_traits/remove_cv.h>
 #include <__type_traits/remove_cvref.h>
@@ -117,15 +117,12 @@ template <class _Tp>
 concept __signed_integer_like = signed_integral<_Tp>;
 
 template <class _Ip>
-concept weakly_incrementable =
-    // TODO: remove this once the clang bug is fixed (https://llvm.org/PR48173).
-    !same_as<_Ip, bool> && // Currently, clang does not handle bool correctly.
-    movable<_Ip> && requires(_Ip __i) {
-      typename iter_difference_t<_Ip>;
-      requires __signed_integer_like<iter_difference_t<_Ip>>;
-      { ++__i } -> same_as<_Ip&>; // not required to be equality-preserving
-      __i++;                      // not required to be equality-preserving
-    };
+concept weakly_incrementable = movable<_Ip> && requires(_Ip __i) {
+  typename iter_difference_t<_Ip>;
+  requires __signed_integer_like<iter_difference_t<_Ip>>;
+  { ++__i } -> same_as<_Ip&>; // not required to be equality-preserving
+  __i++;                      // not required to be equality-preserving
+};
 
 // [iterator.concept.inc]
 template <class _Ip>

libcxx/include/__iterator/iter_move.h

@@ -11,10 +11,10 @@
 #define _LIBCPP___ITERATOR_ITER_MOVE_H
 
 #include <__concepts/class_or_enum.h>
+#include <__concepts/referenceable.h>
 #include <__config>
 #include <__iterator/iterator_traits.h>
 #include <__type_traits/is_reference.h>
-#include <__type_traits/is_referenceable.h>
 #include <__type_traits/remove_cvref.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>

libcxx/include/__iterator/iterator_traits.h

@@ -15,6 +15,7 @@
 #include <__concepts/convertible_to.h>
 #include <__concepts/copyable.h>
 #include <__concepts/equality_comparable.h>
+#include <__concepts/referenceable.h>
 #include <__concepts/same_as.h>
 #include <__concepts/totally_ordered.h>
 #include <__config>
@@ -32,7 +33,6 @@
 #include <__type_traits/is_object.h>
 #include <__type_traits/is_primary_template.h>
 #include <__type_traits/is_reference.h>
-#include <__type_traits/is_referenceable.h>
 #include <__type_traits/nat.h>
 #include <__type_traits/remove_const.h>
 #include <__type_traits/remove_cv.h>

libcxx/include/__math/traits.h

@@ -25,33 +25,26 @@ namespace __math {
 
 // signbit
 
-// TODO(LLVM 22): Remove conditional once support for Clang 19 is dropped.
-#if defined(_LIBCPP_COMPILER_GCC) || __has_constexpr_builtin(__builtin_signbit)
-#  define _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_CONSTEXPR_SINCE_CXX23
-#else
-#  define _LIBCPP_SIGNBIT_CONSTEXPR
-#endif
-
 // The universal C runtime (UCRT) in the WinSDK provides floating point overloads
 // for std::signbit(). By defining our overloads as templates, we can work around
 // this issue as templates are less preferred than non-template functions.
 template <class = void>
-[[__nodiscard__]] inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(float __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool signbit(float __x) _NOEXCEPT {
   return __builtin_signbit(__x);
 }
 
 template <class = void>
-[[__nodiscard__]] inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(double __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool signbit(double __x) _NOEXCEPT {
   return __builtin_signbit(__x);
 }
 
 template <class = void>
-[[__nodiscard__]] inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(long double __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool signbit(long double __x) _NOEXCEPT {
   return __builtin_signbit(__x);
 }
 
 template <class _A1, __enable_if_t<is_integral<_A1>::value, int> = 0>
-[[__nodiscard__]] inline _LIBCPP_SIGNBIT_CONSTEXPR _LIBCPP_HIDE_FROM_ABI bool signbit(_A1 __x) _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool signbit(_A1 __x) _NOEXCEPT {
   return __x < 0;
 }
 

libcxx/include/__ranges/transform_view.h

@@ -13,10 +13,10 @@
 #include <__compare/three_way_comparable.h>
 #include <__concepts/constructible.h>
 #include <__concepts/convertible_to.h>
-#include <__concepts/copyable.h>
 #include <__concepts/derived_from.h>
 #include <__concepts/equality_comparable.h>
 #include <__concepts/invocable.h>
+#include <__concepts/referenceable.h>
 #include <__config>
 #include <__functional/bind_back.h>
 #include <__functional/invoke.h>
@@ -38,7 +38,6 @@
 #include <__type_traits/is_nothrow_constructible.h>
 #include <__type_traits/is_object.h>
 #include <__type_traits/is_reference.h>
-#include <__type_traits/is_referenceable.h>
 #include <__type_traits/maybe_const.h>
 #include <__type_traits/remove_cvref.h>
 #include <__utility/forward.h>
@@ -64,7 +63,7 @@ concept __regular_invocable_with_range_ref = regular_invocable<_Fn, range_refere
 template <class _View, class _Fn>
 concept __transform_view_constraints =
     view<_View> && is_object_v<_Fn> && regular_invocable<_Fn&, range_reference_t<_View>> &&
-    __is_referenceable_v<invoke_result_t<_Fn&, range_reference_t<_View>>>;
+    __referenceable<invoke_result_t<_Fn&, range_reference_t<_View>>>;
 
 #  if _LIBCPP_STD_VER >= 23
 template <input_range _View, move_constructible _Fn>

libcxx/include/__ranges/zip_transform_view.h

@@ -17,6 +17,7 @@
 #include <__concepts/derived_from.h>
 #include <__concepts/equality_comparable.h>
 #include <__concepts/invocable.h>
+#include <__concepts/referenceable.h>
 #include <__functional/invoke.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
@@ -33,7 +34,6 @@
 #include <__type_traits/invoke.h>
 #include <__type_traits/is_object.h>
 #include <__type_traits/is_reference.h>
-#include <__type_traits/is_referenceable.h>
 #include <__type_traits/maybe_const.h>
 #include <__type_traits/remove_cvref.h>
 #include <__utility/forward.h>

libcxx/include/__tree

@@ -823,18 +823,6 @@ public:
   using __node_allocator _LIBCPP_NODEBUG = __rebind_alloc<__alloc_traits, __node>;
   using __node_traits _LIBCPP_NODEBUG    = allocator_traits<__node_allocator>;
 
-// TODO(LLVM 22): Remove this check
-#ifndef _LIBCPP_ABI_TREE_REMOVE_NODE_POINTER_UB
-  static_assert(sizeof(__node_base_pointer) == sizeof(__end_node_pointer) && _LIBCPP_ALIGNOF(__node_base_pointer) ==
-                    _LIBCPP_ALIGNOF(__end_node_pointer),
-                "It looks like you are using std::__tree (an implementation detail for (multi)map/set) with a fancy "
-                "pointer type that thas a different representation depending on whether it points to a __tree base "
-                "pointer or a __tree node pointer (both of which are implementation details of the standard library). "
-                "This means that your ABI is being broken between LLVM 19 and LLVM 20. If you don't care about your "
-                "ABI being broken, define the _LIBCPP_ABI_TREE_REMOVE_NODE_POINTER_UB macro to silence this "
-                "diagnostic.");
-#endif
-
 private:
   // check for sane allocator pointer rebinding semantics. Rebinding the
   // allocator for a new pointer type should be exactly the same as rebinding