Revert "[libc++][format] P2637R3: Member visit (std::basic_format_arg) (#76449)"

This reverts commit 7d9b5aa since
std/utilities/format/format.arguments/format.arg/visit.return_type.pass.cpp
is failing on Windows when building with Clang-cl.

Author: petrhosek

libcxx/docs/ReleaseNotes/18.rst

@@ -79,7 +79,6 @@ Implemented Papers
 - P1759R6 - Native handles and file streams
 - P2868R3 - Remove Deprecated ``std::allocator`` Typedef From C++26
 - P2517R1 - Add a conditional ``noexcept`` specification to ``std::apply``
-- P2637R3 - Member ``visit``
 - P2447R6 - ``span`` over initializer list
 
 

libcxx/docs/Status/Cxx2cPapers.csv

@@ -17,7 +17,7 @@
 "`P0792R14 <https://wg21.link/P0792R14>`__","LWG","``function_ref``: a type-erased callable reference","Varna June 2023","","",""
 "`P2874R2 <https://wg21.link/P2874R2>`__","LWG","Mandating Annex D Require No More","Varna June 2023","","",""
 "`P2757R3 <https://wg21.link/P2757R3>`__","LWG","Type-checking format args","Varna June 2023","","","|format|"
-"`P2637R3 <https://wg21.link/P2637R3>`__","LWG","Member ``visit``","Varna June 2023","|Complete|","18.0",""
+"`P2637R3 <https://wg21.link/P2637R3>`__","LWG","Member ``visit``","Varna June 2023","|Partial|","18.0",""
 "`P2641R4 <https://wg21.link/P2641R4>`__","CWG, LWG","Checking if a ``union`` alternative is active","Varna June 2023","","",""
 "`P1759R6 <https://wg21.link/P1759R6>`__","LWG","Native handles and file streams","Varna June 2023","|Complete|","18.0",""
 "`P2697R1 <https://wg21.link/P2697R1>`__","LWG","Interfacing ``bitset`` with ``string_view``","Varna June 2023","|Complete|","18.0",""

libcxx/docs/Status/FormatIssues.csv

@@ -16,7 +16,7 @@ Number,Name,Standard,Assignee,Status,First released version
 "`P2693R1 <https://wg21.link/P2693R1>`__","Formatting ``thread::id`` and ``stacktrace``","C++23","Mark de Wever","|In Progress|"
 "`P2510R3 <https://wg21.link/P2510R3>`__","Formatting pointers","C++26","Mark de Wever","|Complete|",17.0
 "`P2757R3 <https://wg21.link/P2757R3>`__","Type-checking format args","C++26","","",
-"`P2637R3 <https://wg21.link/P2637R3>`__","Member ``visit``","C++26","Hristo Hristov","|Complete|",18.0
+"`P2637R3 <https://wg21.link/P2637R3>`__","Member ``visit``","C++26","","",
 "`P2905R2 <https://wg21.link/P2905R2>`__","Runtime format strings","C++26 DR","Mark de Wever","|Complete|",18.0
 "`P2918R2 <https://wg21.link/P2918R2>`__","Runtime format strings II","C++26","Mark de Wever","|Complete|",18.0
 "`P2909R4 <https://wg21.link/P2909R4>`__","Fix formatting of code units as integers (Dude, where’s my ``char``?)","C++26 DR","Mark de Wever","|Complete|",18.0

libcxx/include/__config

@@ -995,12 +995,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_DEPRECATED_IN_CXX23
 #  endif
 
-#  if _LIBCPP_STD_VER >= 26
-#    define _LIBCPP_DEPRECATED_IN_CXX26 _LIBCPP_DEPRECATED
-#  else
-#    define _LIBCPP_DEPRECATED_IN_CXX26
-#  endif
-
 #  if !defined(_LIBCPP_HAS_NO_CHAR8_T)
 #    define _LIBCPP_DEPRECATED_WITH_CHAR8_T _LIBCPP_DEPRECATED
 #  else

libcxx/include/__format/format_arg.h

@@ -93,7 +93,7 @@ _LIBCPP_HIDE_FROM_ABI constexpr __arg_t __get_packed_type(uint64_t __types, size
 
 } // namespace __format
 
-// This function is not user observable, so it can directly use the non-standard
+// This function is not user obervable, so it can directly use the non-standard
 // types of the "variant". See __arg_t for more details.
 template <class _Visitor, class _Context>
 _LIBCPP_HIDE_FROM_ABI decltype(auto) __visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
@@ -144,59 +144,6 @@ _LIBCPP_HIDE_FROM_ABI decltype(auto) __visit_format_arg(_Visitor&& __vis, basic_
   __libcpp_unreachable();
 }
 
-#  if _LIBCPP_STD_VER >= 26 && defined(_LIBCPP_HAS_EXPLICIT_THIS_PARAMETER)
-
-template <class _Rp, class _Visitor, class _Context>
-_LIBCPP_HIDE_FROM_ABI _Rp __visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
-  switch (__arg.__type_) {
-  case __format::__arg_t::__none:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__monostate_);
-  case __format::__arg_t::__boolean:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__boolean_);
-  case __format::__arg_t::__char_type:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__char_type_);
-  case __format::__arg_t::__int:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__int_);
-  case __format::__arg_t::__long_long:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__long_long_);
-  case __format::__arg_t::__i128:
-#    ifndef _LIBCPP_HAS_NO_INT128
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__i128_);
-#    else
-    __libcpp_unreachable();
-#    endif
-  case __format::__arg_t::__unsigned:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__unsigned_);
-  case __format::__arg_t::__unsigned_long_long:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__unsigned_long_long_);
-  case __format::__arg_t::__u128:
-#    ifndef _LIBCPP_HAS_NO_INT128
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__u128_);
-#    else
-    __libcpp_unreachable();
-#    endif
-  case __format::__arg_t::__float:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__float_);
-  case __format::__arg_t::__double:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__double_);
-  case __format::__arg_t::__long_double:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__long_double_);
-  case __format::__arg_t::__const_char_type_ptr:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__const_char_type_ptr_);
-  case __format::__arg_t::__string_view:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__string_view_);
-  case __format::__arg_t::__ptr:
-    return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), __arg.__value_.__ptr_);
-  case __format::__arg_t::__handle:
-    return std::invoke_r<_Rp>(
-        std::forward<_Visitor>(__vis), typename basic_format_arg<_Context>::handle{__arg.__value_.__handle_});
-  }
-
-  __libcpp_unreachable();
-}
-
-#  endif // _LIBCPP_STD_VER >= 26 && defined(_LIBCPP_HAS_EXPLICIT_THIS_PARAMETER)
-
 /// Contains the values used in basic_format_arg.
 ///
 /// This is a separate type so it's possible to store the values and types in
@@ -280,52 +227,6 @@ class _LIBCPP_TEMPLATE_VIS basic_format_arg {
 
   _LIBCPP_HIDE_FROM_ABI explicit operator bool() const noexcept { return __type_ != __format::__arg_t::__none; }
 
-#  if _LIBCPP_STD_VER >= 26 && defined(_LIBCPP_HAS_EXPLICIT_THIS_PARAMETER)
-
-  // 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>
-  _LIBCPP_HIDE_FROM_ABI decltype(auto) visit(this basic_format_arg __arg, _Visitor&& __vis) {
-    switch (__arg.__type_) {
-#    ifndef _LIBCPP_HAS_NO_INT128
-    case __format::__arg_t::__i128: {
-      typename __basic_format_arg_value<_Context>::__handle __h{__arg.__value_.__i128_};
-      return std::invoke(std::forward<_Visitor>(__vis), typename basic_format_arg<_Context>::handle{__h});
-    }
-
-    case __format::__arg_t::__u128: {
-      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
-    default:
-      return std::__visit_format_arg(std::forward<_Visitor>(__vis), __arg);
-    }
-  }
-
-  // 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 _Rp, class _Visitor>
-  _LIBCPP_HIDE_FROM_ABI _Rp visit(this basic_format_arg __arg, _Visitor&& __vis) {
-    switch (__arg.__type_) {
-#    ifndef _LIBCPP_HAS_NO_INT128
-    case __format::__arg_t::__i128: {
-      typename __basic_format_arg_value<_Context>::__handle __h{__arg.__value_.__i128_};
-      return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), typename basic_format_arg<_Context>::handle{__h});
-    }
-
-    case __format::__arg_t::__u128: {
-      typename __basic_format_arg_value<_Context>::__handle __h{__arg.__value_.__u128_};
-      return std::invoke_r<_Rp>(std::forward<_Visitor>(__vis), typename basic_format_arg<_Context>::handle{__h});
-    }
-#    endif
-    default:
-      return std::__visit_format_arg<_Rp>(std::forward<_Visitor>(__vis), __arg);
-    }
-  }
-
-#  endif // _LIBCPP_STD_VER >= 26 && defined(_LIBCPP_HAS_EXPLICIT_THIS_PARAMETER)
-
 private:
   using char_type = typename _Context::char_type;
 
@@ -366,11 +267,7 @@ class _LIBCPP_TEMPLATE_VIS 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 && defined(_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_HIDE_FROM_ABI decltype(auto) visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
   switch (__arg.__type_) {
 #  ifndef _LIBCPP_HAS_NO_INT128
   case __format::__arg_t::__i128: {
@@ -382,7 +279,7 @@ _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 && defined(_LIBCPP_HAS_EXPLICIT_THIS_PARAMETER)
+#  endif
   default:
     return std::__visit_format_arg(std::forward<_Visitor>(__vis), __arg);
   }

libcxx/include/__format/format_context.h

@@ -163,25 +163,20 @@ class _LIBCPP_TEMPLATE_VIS basic_format_context<typename __format::__retarget_bu
 #  endif
         __ctx_(std::addressof(__ctx)),
         __arg_([](void* __c, size_t __id) {
-          auto __visitor = [&](auto __arg) -> basic_format_arg<basic_format_context> {
-            if constexpr (same_as<decltype(__arg), monostate>)
-              return {};
-            else if constexpr (same_as<decltype(__arg), typename basic_format_arg<_Context>::handle>)
-              // At the moment it's not possible for formatting to use a re-targeted handle.
-              // TODO FMT add this when support is needed.
-              std::__throw_format_error("Re-targeting handle not supported");
-            else
-              return basic_format_arg<basic_format_context>{
-                  __format::__determine_arg_t<basic_format_context, decltype(__arg)>(),
-                  __basic_format_arg_value<basic_format_context>(__arg)};
-          };
-#  if _LIBCPP_STD_VER >= 26 && defined(_LIBCPP_HAS_EXPLICIT_THIS_PARAMETER)
-          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 && defined(_LIBCPP_HAS_EXPLICIT_THIS_PARAMETER)
+          return std::visit_format_arg(
+              [&](auto __arg) -> basic_format_arg<basic_format_context> {
+                if constexpr (same_as<decltype(__arg), monostate>)
+                  return {};
+                else if constexpr (same_as<decltype(__arg), typename basic_format_arg<_Context>::handle>)
+                  // At the moment it's not possible for formatting to use a re-targeted handle.
+                  // TODO FMT add this when support is needed.
+                  std::__throw_format_error("Re-targeting handle not supported");
+                else
+                  return basic_format_arg<basic_format_context>{
+                      __format::__determine_arg_t<basic_format_context, decltype(__arg)>(),
+                      __basic_format_arg_value<basic_format_context>(__arg)};
+              },
+              static_cast<_Context*>(__c)->arg(__id));
         }) {
   }
 

libcxx/include/format

@@ -170,7 +170,7 @@ namespace std {
   template<class Context> class basic_format_arg;
 
   template<class Visitor, class Context>
-    see below visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg); // Deprecated in C++26
+    see below visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
 
   // [format.arg.store], class template format-arg-store
   template<class Context, class... Args> struct format-arg-store;      // exposition only