[libc++][format] Finish P0645 Text Formatting.

This adjust the version macro and sets it as completed. All parts of the paper
have been implemented, except for the parts replaced by later papers and
LWG-issues.

Adjusted the synopsis to match the synopsis in the Standard. Not yet
implemented parts of P2216 and P2418 still use the P0645 wording.

Completes:
- P0645 Text Formatting

Depends on D115991

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D115999

libcxx/docs/ReleaseNotes.rst

@@ -38,10 +38,13 @@ What's New in Libc++ 14.0.0?
 New Features
 ------------
 
-- There's initial support for the C++20 header ``<format>``. The implementation
-  is incomplete. Some functions are known to be inefficient; both in memory
-  usage and performance. The implementation is considered experimental and isn't
-  considered ABI stable.
+- There's support for the C++20 header ``<format>``. Some parts are still
+  missing, most notably the compile-time format string validation. Some
+  functions are known to be inefficient, both in memory usage and performance.
+  The implementation isn't API- or ABI-stable and therefore considered
+  experimental. (Some not-yet-implemented papers require an API-break.)
+  Vendors can still disable this header by turning the CMake option
+  `LIBCXX_ENABLE_INCOMPLETE_FEATURES` off.
 
 - There's a new CMake option ``LIBCXX_ENABLE_UNICODE`` to disable Unicode
   support in the ``<format>`` header. This only affects the estimation of the

libcxx/docs/Status/Cxx20.rst

@@ -41,6 +41,7 @@ Paper Status
 .. note::
 
    .. [#note-P0600] P0600: The missing bits in P0600 are in |sect|\ [mem.res.class] and |sect|\ [mem.poly.allocator.class].
+   .. [#note-P0645] P0645: The paper is implemented but still marked as an incomplete feature. Not yet implemented LWG-issues will cause API and ABI breakage.
    .. [#note-P0966] P0966: It was previously erroneously marked as complete in version 8.0. See `bug 45368 <https://llvm.org/PR45368>`__.
    .. [#note-P0619] P0619: Only sections D.8, D.9, D.10 and D.13 are implemented. Sections D.4, D.7, D.11, D.12, and D.14 remain undone.
    .. [#note-P0883] P0883: shared_ptr and floating-point changes weren't applied as they themselves aren't implemented yet.

libcxx/docs/Status/Cxx20Papers.csv

@@ -103,7 +103,7 @@
 "`P0466R5 <https://wg21.link/P0466R5>`__","LWG","Layout-compatibility and Pointer-interconvertibility Traits","Cologne","",""
 "`P0553R4 <https://wg21.link/P0553R4>`__","LWG","Bit operations","Cologne","|Complete|","9.0"
 "`P0631R8 <https://wg21.link/P0631R8>`__","LWG","Math Constants","Cologne","|Complete|","11.0"
-"`P0645R10 <https://wg21.link/P0645R10>`__","LWG","Text Formatting","Cologne","|In Progress|",""
+"`P0645R10 <https://wg21.link/P0645R10>`__","LWG","Text Formatting","Cologne","|Complete| [#note-P0645]_","14.0"
 "`P0660R10 <https://wg21.link/P0660R10>`__","LWG","Stop Token and Joining Thread, Rev 10","Cologne","",""
 "`P0784R7 <https://wg21.link/P0784R7>`__","CWG","More constexpr containers","Cologne","|Complete|","12.0"
 "`P0980R1 <https://wg21.link/P0980R1>`__","LWG","Making std::string constexpr","Cologne","",""

libcxx/docs/Status/FormatIssues.csv

@@ -1,5 +1,5 @@
 Number,Name,Assignee,Patch,Status,First released version
-`P0645 <https://wg21.link/P0645>`_,"Text Formatting",Mark de Wever,,|Partial|,
+`P0645 <https://wg21.link/P0645>`_,"Text Formatting",Mark de Wever,,|Complete|,Clang 14
 `P1652 <https://wg21.link/P1652>`_,"Printf corner cases in std::format",Mark de Wever,"`D103433 <https://reviews.llvm.org/D103433>`__, `D114001 <https://reviews.llvm.org/D114001>`__",|Review|,
 `P1892 <https://wg21.link/P1892>`_,"Extended locale-specific presentation specifiers for std::format",Mark de Wever,`D103368 <https://reviews.llvm.org/D103368>`__,|Complete|,Clang 14
 `P1868 <https://wg21.link/P1868>`_,"width: clarifying units of width and precision in std::format (Implements the unicode support.)",Mark de Wever,"`D103413 <https://reviews.llvm.org/D103413>`__ `D103425 <https://reviews.llvm.org/D103425>`__ `D103670 <https://reviews.llvm.org/D103670>`__",|Complete|,Clang 14

libcxx/include/format

@@ -14,43 +14,15 @@
 
 namespace std {
   // [format.context], class template basic_format_context
-  template<class Out, class charT>
-  class basic_format_context {
-    basic_format_args<basic_format_context> args_;      // exposition only
-    Out out_;                                           // exposition only
-
-  public:
-    using iterator = Out;
-    using char_type = charT;
-    template<class T> using formatter_type = formatter<T, charT>;
-
-    basic_format_arg<basic_format_context> arg(size_t id) const;
-    std::locale locale();
-
-    iterator out();
-    void advance_to(iterator it);
-  };
+  template<class Out, class charT> class basic_format_context;
   using format_context = basic_format_context<unspecified, char>;
   using wformat_context = basic_format_context<unspecified, wchar_t>;
 
   // [format.args], class template basic_format_args
-  template<class Context>
-  class basic_format_args {
-    size_t size_;                               // exposition only
-    const basic_format_arg<Context>* data_;     // exposition only
-
-  public:
-    basic_format_args() noexcept;
-
-    template<class... Args>
-      basic_format_args(const format-arg-store<Context, Args...>& store) noexcept;
-
-    basic_format_arg<Context> get(size_t i) const noexcept;
-  };
+  template<class Context> class basic_format_args;
   using format_args = basic_format_args<format_context>;
   using wformat_args = basic_format_args<wformat_context>;
 
-
   // [format.functions], formatting functions
   template<class... Args>
     string format(string_view fmt, const Args&... args);
@@ -90,8 +62,7 @@ namespace std {
     Out out;
     iter_difference_t<Out> size;
   };
-
- template<class Out, class... Args>
+  template<class Out, class... Args>
     format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
                                         string_view fmt, const Args&... args);
   template<class Out, class... Args>
@@ -116,99 +87,22 @@ namespace std {
     size_t formatted_size(const locale& loc, wstring_view fmt, const Args&... args);
 
   // [format.formatter], formatter
-  template<> struct formatter<char, char>;
-  template<> struct formatter<char, wchar_t>;
-  template<> struct formatter<wchar_t, wchar_t>;
-
-  template<> struct formatter<charT*, charT>;
-  template<> struct formatter<const charT*, charT>;
-  template<size_t N> struct formatter<const charT[N], charT>;
-  template<class traits, class Allocator>
-    struct formatter<basic_string<charT, traits, Allocator>, charT>;
-  template<class traits>
-    struct formatter<basic_string_view<charT, traits>, charT>;
+  template<class T, class charT = char> struct formatter;
 
   // [format.parse.ctx], class template basic_format_parse_context
-  template<class charT>
-  class basic_format_parse_context {
-  public:
-    using char_type = charT;
-    using const_iterator = typename basic_string_view<charT>::const_iterator;
-    using iterator = const_iterator;
-
-  private:
-    iterator begin_;                                    // exposition only
-    iterator end_;                                      // exposition only
-    enum indexing { unknown, manual, automatic };       // exposition only
-    indexing indexing_;                                 // exposition only
-    size_t next_arg_id_;                                // exposition only
-    size_t num_args_;                                   // exposition only
-
-  public:
-    constexpr explicit basic_format_parse_context(basic_string_view<charT> fmt,
-                                                  size_t num_args = 0) noexcept;
-    basic_format_parse_context(const basic_format_parse_context&) = delete;
-    basic_format_parse_context& operator=(const basic_format_parse_context&) = delete;
-
-    constexpr const_iterator begin() const noexcept;
-    constexpr const_iterator end() const noexcept;
-    constexpr void advance_to(const_iterator it);
-
-    constexpr size_t next_arg_id();
-    constexpr void check_arg_id(size_t id);
-  };
+  template<class charT> class basic_format_parse_context;
   using format_parse_context = basic_format_parse_context<char>;
   using wformat_parse_context = basic_format_parse_context<wchar_t>;
 
   // [format.arguments], arguments
   // [format.arg], class template basic_format_arg
-  template<class Context>
-  class basic_format_arg {
-  public:
-    class handle;
-
-  private:
-    using char_type = typename Context::char_type;                              // exposition only
-
-    variant<monostate, bool, char_type,
-            int, unsigned int, long long int, unsigned long long int,
-            float, double, long double,
-            const char_type*, basic_string_view<char_type>,
-            const void*, handle> value;                                         // exposition only
-
-    template<class T> explicit basic_format_arg(const T& v) noexcept;           // exposition only
-    explicit basic_format_arg(float n) noexcept;                                // exposition only
-    explicit basic_format_arg(double n) noexcept;                               // exposition only
-    explicit basic_format_arg(long double n) noexcept;                          // exposition only
-    explicit basic_format_arg(const char_type* s);                              // exposition only
-
-    template<class traits>
-      explicit basic_format_arg(
-        basic_string_view<char_type, traits> s) noexcept;                       // exposition only
-
-    template<class traits, class Allocator>
-      explicit basic_format_arg(
-        const basic_string<char_type, traits, Allocator>& s) noexcept;          // exposition only
-
-    explicit basic_format_arg(nullptr_t) noexcept;                              // exposition only
-
-    template<class T>
-      explicit basic_format_arg(const T* p) noexcept;                           // exposition only
-
-  public:
-    basic_format_arg() noexcept;
-
-    explicit operator bool() const noexcept;
-  };
+  template<class Context> class basic_format_arg;
 
   template<class Visitor, class Context>
     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
-    array<basic_format_arg<Context>, sizeof...(Args)> args;
-  };
+  template<class Context, class... Args> struct format-arg-store;      // exposition only
 
   template<class Context = format_context, class... Args>
     format-arg-store<Context, Args...>
@@ -218,43 +112,7 @@ namespace std {
       make_wformat_args(const Args&... args);
 
   // [format.error], class format_error
-  class format_error : public runtime_error {
-  public:
-    explicit format_error(const string& what_arg);
-    explicit format_error(const char* what_arg);
-  };
-
-  // [format.parse.ctx], class template basic_format_parse_context
-  template<class charT>
-  class basic_format_parse_context {
-  public:
-    using char_type = charT;
-    using const_iterator = typename basic_string_view<charT>::const_iterator;
-    using iterator = const_iterator;
-
-  private:
-    iterator begin_;                                    // exposition only
-    iterator end_;                                      // exposition only
-    enum indexing { unknown, manual, automatic };       // exposition only
-    indexing indexing_;                                 // exposition only
-    size_t next_arg_id_;                                // exposition only
-    size_t num_args_;                                   // exposition only
-
-  public:
-    constexpr explicit basic_format_parse_context(basic_string_view<charT> fmt,
-                                                  size_t num_args = 0) noexcept;
-    basic_format_parse_context(const basic_format_parse_context&) = delete;
-    basic_format_parse_context& operator=(const basic_format_parse_context&) = delete;
-
-    constexpr const_iterator begin() const noexcept;
-    constexpr const_iterator end() const noexcept;
-    constexpr void advance_to(const_iterator it);
-
-    constexpr size_t next_arg_id();
-    constexpr void check_arg_id(size_t id);
-  };
-  using format_parse_context = basic_format_parse_context<char>;
-  using wformat_parse_context = basic_format_parse_context<wchar_t>;
+  class format_error;
 }
 
 */