Merge 2023-06 LWG Motion 21

P2637R3 Member visit

Author: tkoeppe

source/future.tex

@@ -2064,6 +2064,34 @@
 \end{note}
 \end{itemdescr}
 
+\rSec1[depr.format]{Deprecated formatting}
+
+\rSec2[depr.format.syn]{Header \tcode{<format>} synopsis}
+
+\pnum
+The header \libheaderref{format}{format.syn} has the following additions:
+
+\begin{codeblock}
+namespace std {
+  template<class Visitor, class Context>
+    decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
+}
+\end{codeblock}
+
+\rSec2[depr.format.arg]{Formatting arguments}
+
+\indexlibraryglobal{visit_format_arg}%
+\begin{itemdecl}
+template<class Visitor, class Context>
+  decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return visit(std::forward<Visitor>(vis), arg.value);}
+\end{itemdescr}
+
 \rSec1[depr.locale.stdcvt]{Deprecated standard code conversion facets}
 
 \rSec2[depr.locale.stdcvt.general]{General}

source/support.tex

@@ -628,7 +628,7 @@
 #define @\defnlibxname{cpp_lib_filesystem}@                        201703L // also in \libheader{filesystem}
 #define @\defnlibxname{cpp_lib_flat_map}@                          202207L // also in \libheader{flat_map}
 #define @\defnlibxname{cpp_lib_flat_set}@                          202207L // also in \libheader{flat_set}
-#define @\defnlibxname{cpp_lib_format}@                            202305L // also in \libheader{format}
+#define @\defnlibxname{cpp_lib_format}@                            202306L // also in \libheader{format}
 #define @\defnlibxname{cpp_lib_format_ranges}@                     202207L // also in \libheader{format}
 #define @\defnlibxname{cpp_lib_formatters}@                        202302L // also in \libheader{stacktrace}, \libheader{thread}
 #define @\defnlibxname{cpp_lib_forward_like}@                      202207L // freestanding, also in \libheader{utility}
@@ -779,7 +779,7 @@
 #define @\defnlibxname{cpp_lib_unordered_map_try_emplace}@         201411L // also in \libheader{unordered_map}
 #define @\defnlibxname{cpp_lib_unreachable}@                       202202L // freestanding, also in \libheader{utility}
 #define @\defnlibxname{cpp_lib_unwrap_ref}@                        201811L // freestanding, also in \libheader{type_traits}
-#define @\defnlibxname{cpp_lib_variant}@                           202106L // also in \libheader{variant}
+#define @\defnlibxname{cpp_lib_variant}@                           202306L // also in \libheader{variant}
 #define @\defnlibxname{cpp_lib_void_t}@                            201411L // freestanding, also in \libheader{type_traits}
 \end{codeblock}
 

source/utilities.tex

@@ -5022,6 +5022,12 @@
 
     // \ref{variant.swap}, swap
     constexpr void swap(variant&) noexcept(@\seebelow@);
+
+    // \ref{variant.visit}, visitation
+    template<class Self, class Visitor>
+      constexpr decltype(auto) visit(this Self&&, Visitor&&);
+    template<class R, class Self, class Visitor>
+      constexpr R visit(this Self&&, Visitor&&);
   };
 }
 \end{codeblock}
@@ -6140,6 +6146,44 @@
 no complexity requirements.
 \end{itemdescr}
 
+\indexlibrarymember{visit}{variant}%
+\begin{itemdecl}
+template<class Self, class Visitor>
+  constexpr decltype(auto) visit(this Self&& self, Visitor&& vis);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+Let \tcode{V} be
+\tcode{\exposid{OVERRIDE_REF}(Self\&\&, \exposid{COPY_CONST}(remove_reference_t<Self>, variant))}\iref{forward}.
+
+\pnum
+\constraints
+The call to \tcode{visit} does not use
+an explicit \grammarterm{template-argument-list} that
+begins with a type \grammarterm{template-argument}.
+
+\pnum
+\effects
+Equivalent to: \tcode{return std::visit(std::forward<Visitor>(vis), (V)self);}
+\end{itemdescr}
+
+\indexlibrarymember{visit}{variant}%
+\begin{itemdecl}
+template<class R, class Self, class Visitor>
+  constexpr R visit(this Self&& self, Visitor&& vis);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+Let \tcode{V} be
+\tcode{\exposid{OVERRIDE_REF}(Self\&\&, \exposid{COPY_CONST}(remove_reference_t<Self>, variant))}\iref{forward}.
+
+\pnum
+\effects
+Equivalent to: \tcode{return std::visit<R>(std::forward<Visitor>(vis), (V)self);}
+\end{itemdescr}
+
 \rSec2[variant.monostate]{Class \tcode{monostate}}%
 \indexlibraryglobal{monostate}%
 
@@ -15022,9 +15066,6 @@
   // \ref{format.arg}, class template \tcode{basic_format_arg}
   template<class Context> class basic_format_arg;
 
-  template<class Visitor, class Context>
-    decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
-
   // \ref{format.arg.store}, class template \exposid{format-arg-store}
   template<class Context, class... Args> class @\exposidnc{format-arg-store}@;        // \expos
 
@@ -16884,14 +16925,14 @@
 
   // Formats an \tcode{S} with width given by the argument \tcode{width_arg_id}.
   auto format(S s, format_context& ctx) const {
-    int width = visit_format_arg([](auto value) -> int {
+    int width = ctx.arg(width_arg_id).visit([](auto value) -> int {
       if constexpr (!is_integral_v<decltype(value)>)
         throw format_error("width is not integral");
       else if (value < 0 || value > numeric_limits<int>::max())
         throw format_error("invalid width");
       else
         return value;
-      }, ctx.arg(width_arg_id));
+      });
     return format_to(ctx.out(), "{0:x<{1}}", s.value, width);
   }
 };
@@ -17513,6 +17554,11 @@
     basic_format_arg() noexcept;
 
     explicit operator bool() const noexcept;
+
+    template<class Visitor>
+      decltype(auto) visit(this basic_format_arg arg, Visitor&& vis);
+    template<class R, class Visitor>
+      R visit(this basic_format_arg arg, Visitor&& vis);
   };
 }
 \end{codeblock}
@@ -17618,6 +17664,30 @@
 \tcode{!holds_alternative<monostate>(value)}.
 \end{itemdescr}
 
+\indexlibrarymember{visit}{basic_format_arg}%
+\begin{itemdecl}
+template<class Visitor>
+  decltype(auto) visit(this basic_format_arg arg, Visitor&& vis);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return arg.value.visit(std::forward<Visitor>(vis));}
+\end{itemdescr}
+
+\indexlibrarymember{visit}{basic_format_arg}%
+\begin{itemdecl}
+template<class R, class Visitor>
+  R visit(this basic_format_arg arg, Visitor&& vis);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return arg.value.visit<R>(std::forward<Visitor>(vis));}
+\end{itemdescr}
+
 \pnum
 The class \tcode{handle} allows formatting an object of a user-defined type.
 
@@ -17689,18 +17759,6 @@
 Equivalent to: \tcode{format_(parse_ctx, format_ctx, ptr_);}
 \end{itemdescr}
 
-\indexlibraryglobal{visit_format_arg}%
-\begin{itemdecl}
-template<class Visitor, class Context>
-  decltype(auto) visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg);
-\end{itemdecl}
-
-\begin{itemdescr}
-\pnum
-\effects
-Equivalent to: \tcode{return visit(std::forward<Visitor>(vis), arg.value);}
-\end{itemdescr}
-
 \rSec3[format.arg.store]{Class template \exposid{format-arg-store}}
 
 \begin{codeblock}