22.7.5 Non-member functions [any.nonmembers] C++N4910:2022 (584) p715a.cpp

# はじめに(Introduction)

N4910  Working Draft, Standard for Programming Language C++

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/n4910.pdf

n4910は、ISO/IEC JTC1 SC22 WG21の作業原案(Working Draft)です。
公式のISO/IEC 14882原本ではありません。
ISO/IEC JTC1 SC22 WG21では、可能な限り作業文書を公開し、幅広い意見を求めています。
一連の記事はコード断片をコンパイルできる形にする方法を検討してコンパイル、リンク、実行して、規格案の原文と処理系(g++, Clang++)との違いを確認し、技術内容を検討し、ISO/IEC JTC1 SC22 WG21にフィードバックするために用います。
また、CERT C++, MISRA C++等のコーディング標準のコード断片をコンパイルする際の参考にさせていただこうと考えています。CERT C++, MISRA C++が標準化の動きとの時間的なずれがあれば確認できれば幸いです。また、boostライブラリとの関連、Linux OS, TOPPERSカーネル、g++(GCC), clang++(LLVM）との関係も調査中です。
何か、抜け漏れ、耳より情報がありましたらおしらせくださると幸いです。

 <この項は書きかけです。順次追記します。>

## 背景(back ground)
C/C++でコンパイルエラーが出ると、途方にくれることがしばしばあります。
何回かに１回は、該当するエラーが検索できます。
ただ、条件が違っていて、そこでの修正方法では目的を達成しないこともしばしばです。いろいろな条件のコンパイルエラーとその対応方法について、広く記録することによって、いつか同じエラーに遭遇した時にやくに立つことを目指しています。

この半年の間で、三度、自分のネットでの記録に助けられたことがあります。
また過去に解決できなかった記録を１０種類以上、最近になって解決できたことがあります。それは、主に次の３つの情報に基づいています。

https://stackoverflow.com
https://cpprefjp.github.io
http://ja.cppreference.com/

また
https://researchmap.jp/joub9b3my-1797580/#_1797580
に記載したサイトのお世話になっています。

## 作業方針(sequence)
Clang++では-std=c++03, C++2bの2種類
g++では-std=c++03, c++2bの２種類
でコンパイルし、

１）コンパイルエラーを収集する。
２）コンパイルエラーをなくす方法を検討する。
コンパイルエラーになる例を示すだけが目的のコードは、コンパイルエラーをなくすのではなく、コンパイルエラーの種類を収集するだけにする。
文法を示すのが目的のコード場合に、コンパイルエラーをなくすのに手間がかかる場合は、順次作業します。
３）リンクエラーをなくす方法を検討する。
文法を示すのが目的のコード場合に、リンクエラーをなくすのに手間がかかる場合は、順次作業します。
４）意味のある出力を作る。
コンパイル、リンクが通っても、意味のある出力を示そうとすると、コンパイル・リンクエラーが出て収拾できそうにない場合がある。順次作業します。

１）だけのものから４）まで進んだものと色々ある状態です。一歩でも前に進むご助言をお待ちしています。「検討事項」の欄に現状を記録するようにしています。

### C++N4910:2022 Standard Working Draft on ISO/IEC 14882(0) sample code compile list  

https://qiita.com/kaizen_nagoya/items/fc957ddddd402004bb91

### C++N4741, 2018 Standard Working Draft on ISO/IEC 14882 sample code compile list
https://qiita.com/kaizen_nagoya/items/3294c014044550896010

### C++N4606, 2016符号断片編纂一覧(example code compile list)
C++N4606, 2016 Working Draft 2016, ISO/IEC 14882, C++ standard(1) Example code compile list
https://qiita.com/kaizen_nagoya/items/df5d62c35bd6ed1c3d43/

### C++N3242, 2011 sample code compile list on clang++ and g++
https://qiita.com/kaizen_nagoya/items/685b5c1a2c17c1bf1318

## 編纂器(Compiler)
### clang++ --version
> Debian clang version 14.0.5-++20220610033153+c12386ae247c-1~exp1~20220610153237.151
Target: x86_64-pc-linux-gnu, Thread model: posix, InstalledDir: /usr/bin

### g++- --version
> g++ (GCC) 12.1.0  Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

#  22.7.5 Non-member functions [any.nonmembers] C++N4910:2022 (584) p715a.cpp

## 算譜(source code)

```c++:p15a.cpp
// C++N4910 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/n4910.pdf
const char * n4910 = " 22.7.5 Non-member functions [any.nonmembers] C++N4910:2022 (584) p715a.cpp";
// Debian clang version 14.0.5-++20220610033153+c12386ae247c-
// g++ (GCC) 12.1.0 Copyright (C) 2022 Free Software Foundation, Inc.
// Edited by Dr. OGAWA Kiyoshi. Compile procedure and results record.
// C++N4910:2022 Standard Working Draft on ISO/IEC 14882(0) sample code compile list
// https://qiita.com/kaizen_nagoya/items/fc957ddddd402004bb91

#include <iostream>
#include <cstdio>
#include <cstdlib> 
#include <cstring>
#include <cassert>
#include <coroutine>
#include <vector>
#include <complex>
#include <map>
#include <atomic>
#include <unordered_map>
#include <optional>
#include <memory>
#include <variant>
#include <any>
#include <typeinfo>

using namespace std;

// 
void swap(any& x, any& y) noexcept;
// Effects: Equivalent to x.swap(y). template<class T, class... Args>
  any make_any(Args&&... args);
// Effects: Equivalent to: return any(in_place_type<T>, std::forward<Args>(args)...); template<class T, class U, class... Args>
any make_any(initializer_list<U> il, Args&&... args);
// Effects: Equivalent to: return any(in_place_type<T>, il, std::forward<Args>(args)...);
template<class T>
  T any_cast(const any& operand);
template<class T>
  T any_cast(any& operand);
template<class T>
  T any_cast(any&& operand);
// Let U be the type remove_cvref_t<T>.
// Mandates: For the first overload, is_constructible_v<T, const U&> is true. For the second overload,
is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
third overload, static_cast<T>(std::move(*any_cast<U>(&operand))). Throws: bad_any_cast if operand.type() != typeid(remove_reference_t<T>). 
// [Example 1:
any x(5);
assert(any_cast<int>(x) == 5);
any_cast<int&>(x) = 10;
assert(any_cast<int>(x) == 10);
x = "Meow";
assert(strcmp(any_cast<const char*>(x), "Meow") == 0);
any_cast<const char*&>(x) = "Harry";
assert(strcmp(any_cast<const char*>(x), "Harry") == 0);
x = string("Meow");
string s, s2("Jane");
s = move(any_cast<string&>(x));
assert(s == "Meow");
any_cast<string&>(x) = move(s2);
assert(any_cast<const string&>(x) == "Jane");
// x holds int
// cast to value
// cast to reference
// x holds string // move from any // move to any
// x holds const char*
// Returns: If operand != nullptr && operand->type() == typeid(T), a pointer to the object con- tained by operand; otherwise, nullptr.
       string cat("Meow");
       const any y(cat);
       assert(any_cast<const string&>(y) == cat);
       any_cast<string&>(y);
template<class T>
  const T* any_cast(const any* operand) noexcept;
template<class T>
  T* any_cast(any* operand) noexcept;
// const y holds string
// error: cannot any_cast away const
// [Example 2:
       bool is_string(const any& operand) {
         return any_cast<string>(&operand) != nullptr;
}
int main(){
  cout  <<  n4910 << endl;
  return EXIT_SUCCESS;
}
```

## 編纂・実行結果(compile and go)

```ubuntu:bash
$ clang++ p715a.cpp -std=03 -o p715al -I. -Wall
In file included from p715a.cpp:19:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/atomic:38:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/c++0x_warning.h:32:2: error: This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
#error This file requires compiler and library support \
 ^
p715a.cpp:30:11: error: unknown type name 'any'
void swap(any& x, any& y) noexcept;
          ^
p715a.cpp:30:19: error: unknown type name 'any'
void swap(any& x, any& y) noexcept;
                  ^
p715a.cpp:30:27: error: expected function body after function declarator
void swap(any& x, any& y) noexcept;
                          ^
p715a.cpp:32:3: error: unknown type name 'any'
  any make_any(Args&&... args);
  ^
p715a.cpp:32:16: error: unknown type name 'Args'
  any make_any(Args&&... args);
               ^
p715a.cpp:32:20: warning: rvalue references are a C++11 extension [-Wc++11-extensions]
  any make_any(Args&&... args);
                   ^
p715a.cpp:32:22: error: type 'int &&' of function parameter pack does not contain any unexpanded parameter packs
  any make_any(Args&&... args);
               ~~~~~~^~~~~~~~
p715a.cpp:34:1: error: unknown type name 'any'
any make_any(initializer_list<U> il, Args&&... args);
^
p715a.cpp:34:31: error: use of undeclared identifier 'U'
any make_any(initializer_list<U> il, Args&&... args);
                              ^
p715a.cpp:34:38: error: unknown type name 'Args'
any make_any(initializer_list<U> il, Args&&... args);
                                     ^
p715a.cpp:34:42: warning: rvalue references are a C++11 extension [-Wc++11-extensions]
any make_any(initializer_list<U> il, Args&&... args);
                                         ^
p715a.cpp:34:44: error: type 'int &&' of function parameter pack does not contain any unexpanded parameter packs
any make_any(initializer_list<U> il, Args&&... args);
                                     ~~~~~~^~~~~~~~
p715a.cpp:37:20: error: unknown type name 'any'
  T any_cast(const any& operand);
                   ^
p715a.cpp:39:14: error: unknown type name 'any'
  T any_cast(any& operand);
             ^
p715a.cpp:41:14: error: unknown type name 'any'
  T any_cast(any&& operand);
             ^
p715a.cpp:41:17: warning: rvalue references are a C++11 extension [-Wc++11-extensions]
  T any_cast(any&& operand);
                ^
p715a.cpp:44:20: error: use of undeclared identifier 'T'
is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
                   ^
p715a.cpp:44:29: error: expected ';' after top level declarator
is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
                            ^
                            ;
p715a.cpp:48:1: error: expected unqualified-id
assert(any_cast<int>(x) == 5);
^
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:48:1: error: expected ')'
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:48:1: note: to match this '('
/usr/include/assert.h:93:6: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
     ^
p715a.cpp:49:16: error: unknown type name 'x'
any_cast<int&>(x) = 10;
               ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
3 warnings and 20 errors generated.
$ clang++ p715a.cpp -std=2b -o p715al -I. -Wall
p715a.cpp:32:16: error: unknown type name 'Args'
  any make_any(Args&&... args);
               ^
p715a.cpp:32:22: error: type 'int &&' of function parameter pack does not contain any unexpanded parameter packs
  any make_any(Args&&... args);
               ~~~~~~^~~~~~~~
p715a.cpp:34:31: error: use of undeclared identifier 'U'
any make_any(initializer_list<U> il, Args&&... args);
                              ^
p715a.cpp:34:38: error: unknown type name 'Args'
any make_any(initializer_list<U> il, Args&&... args);
                                     ^
p715a.cpp:34:44: error: type 'int &&' of function parameter pack does not contain any unexpanded parameter packs
any make_any(initializer_list<U> il, Args&&... args);
                                     ~~~~~~^~~~~~~~
p715a.cpp:44:20: error: use of undeclared identifier 'T'
is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
                   ^
p715a.cpp:48:1: error: expected unqualified-id
assert(any_cast<int>(x) == 5);
^
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:48:1: error: expected ')'
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:48:1: note: to match this '('
/usr/include/assert.h:93:6: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
     ^
p715a.cpp:49:16: error: unknown type name 'x'
any_cast<int&>(x) = 10;
               ^
p715a.cpp:49:1: error: C++ requires a type specifier for all declarations
any_cast<int&>(x) = 10;
^
p715a.cpp:49:1: error: template specialization requires 'template<>'
any_cast<int&>(x) = 10;
^       ~~~~~~
template<> 
p715a.cpp:50:1: error: expected unqualified-id
assert(any_cast<int>(x) == 10);
^
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:50:1: error: expected ')'
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:50:1: note: to match this '('
/usr/include/assert.h:93:6: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
     ^
p715a.cpp:51:1: error: C++ requires a type specifier for all declarations
x = "Meow";
^
p715a.cpp:52:1: error: expected unqualified-id
assert(strcmp(any_cast<const char*>(x), "Meow") == 0);
^
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:52:1: error: expected ')'
/usr/include/assert.h:93:7: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
      ^
p715a.cpp:52:1: note: to match this '('
/usr/include/assert.h:93:6: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
     ^
p715a.cpp:53:24: error: unknown type name 'x'
any_cast<const char*&>(x) = "Harry";
                       ^
p715a.cpp:53:1: error: C++ requires a type specifier for all declarations
any_cast<const char*&>(x) = "Harry";
^
p715a.cpp:53:1: error: template specialization requires 'template<>'
any_cast<const char*&>(x) = "Harry";
^       ~~~~~~~~~~~~~~
template<> 
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

$ g++ p715a.cpp -std=03 -o p715ag -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p715a.cpp:19:
/usr/local/include/c++/12.1.0/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
   32 | #error This file requires compiler and library support \
      |  ^~~~~
p715a.cpp:30:27: warning: identifier 'noexcept' is a keyword in C++11 [-Wc++11-compat]
   30 | void swap(any& x, any& y) noexcept;
      |                           ^~~~~~~~
p715a.cpp:79:47: warning: identifier 'nullptr' is a keyword in C++11 [-Wc++11-compat]
   79 |          return any_cast<string>(&operand) != nullptr;
      |                                               ^~~~~~~
p715a.cpp:30:6: error: variable or field 'swap' declared void
   30 | void swap(any& x, any& y) noexcept;
      |      ^~~~
p715a.cpp:30:11: error: 'any' was not declared in this scope
   30 | void swap(any& x, any& y) noexcept;
      |           ^~~
p715a.cpp:30:11: note: 'std::any' is only available from C++17 onwards
p715a.cpp:30:16: error: 'x' was not declared in this scope
   30 | void swap(any& x, any& y) noexcept;
      |                ^
p715a.cpp:30:19: error: 'any' was not declared in this scope
   30 | void swap(any& x, any& y) noexcept;
      |                   ^~~
p715a.cpp:30:19: note: 'std::any' is only available from C++17 onwards
p715a.cpp:30:24: error: 'y' was not declared in this scope; did you mean 'yn'?
   30 | void swap(any& x, any& y) noexcept;
      |                        ^
      |                        yn
p715a.cpp:32:3: error: 'any' does not name a type
   32 |   any make_any(Args&&... args);
      |   ^~~
p715a.cpp:34:1: error: 'any' does not name a type
   34 | any make_any(initializer_list<U> il, Args&&... args);
      | ^~~
p715a.cpp:37:20: error: 'any' does not name a type
   37 |   T any_cast(const any& operand);
      |                    ^~~
p715a.cpp:39:14: error: 'template<class T> T any_cast' conflicts with a previous declaration
   39 |   T any_cast(any& operand);
      |              ^~~
p715a.cpp:37:5: note: previous declaration 'T any_cast(const int&)'
   37 |   T any_cast(const any& operand);
      |     ^~~~~~~~
p715a.cpp:39:14: error: 'any' was not declared in this scope
   39 |   T any_cast(any& operand);
      |              ^~~
p715a.cpp:39:14: note: 'std::any' is only available from C++17 onwards
p715a.cpp:39:19: error: 'operand' was not declared in this scope; did you mean 'srand'?
   39 |   T any_cast(any& operand);
      |                   ^~~~~~~
      |                   srand
p715a.cpp:39:5: warning: variable templates only available with '-std=c++14' or '-std=gnu++14' [-Wc++14-extensions]
   39 |   T any_cast(any& operand);
      |     ^~~~~~~~
p715a.cpp:41:14: error: 'template<class T> T any_cast' conflicts with a previous declaration
   41 |   T any_cast(any&& operand);
      |              ^~~
p715a.cpp:37:5: note: previous declaration 'T any_cast(const int&)'
   37 |   T any_cast(const any& operand);
      |     ^~~~~~~~
p715a.cpp:41:14: error: 'any' was not declared in this scope
   41 |   T any_cast(any&& operand);
      |              ^~~
p715a.cpp:41:14: note: 'std::any' is only available from C++17 onwards
p715a.cpp:41:20: error: 'operand' was not declared in this scope; did you mean 'srand'?
   41 |   T any_cast(any&& operand);
      |                    ^~~~~~~
      |                    srand
p715a.cpp:41:5: warning: variable templates only available with '-std=c++14' or '-std=gnu++14' [-Wc++14-extensions]
   41 |   T any_cast(any&& operand);
      |     ^~~~~~~~
p715a.cpp:44:1: error: 'is_constructible_v' does not name a type
   44 | is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
      | ^~~~~~~~~~~~~~~~~~
In file included from /usr/local/include/c++/12.1.0/cassert:44,
                 from p715a.cpp:14:
p715a.cpp:48:1: error: expected unqualified-id before 'static_cast'
   48 | assert(any_cast<int>(x) == 5);
      | ^~~~~~
p715a.cpp:48:1: error: expected ')' before 'static_cast'
   48 | assert(any_cast<int>(x) == 5);
      | ^~~~~~
p715a.cpp:49:1: error: specializing member '::any_cast<int&>' requires 'template<>' syntax
   49 | any_cast<int&>(x) = 10;
      | ^~~~~~~~~~~~~~
p715a.cpp:50:1: error: expected unqualified-id before 'static_cast'
   50 | assert(any_cast<int>(x) == 10);
      | ^~~~~~
p715a.cpp:50:1: error: expected ')' before 'static_cast'
   50 | assert(any_cast<int>(x) == 10);
      | ^~~~~~
p715a.cpp:51:1: error: 'x' does not name a type
   51 | x = "Meow";
      | ^
p715a.cpp:52:1: error: expected unqualified-id before 'static_cast'
   52 | assert(strcmp(any_cast<const char*>(x), "Meow") == 0);
      | ^~~~~~
p715a.cpp:52:1: error: expected ')' before 'static_cast'
   52 | assert(strcmp(any_cast<const char*>(x), "Meow") == 0);
      | ^~~~~~
p715a.cpp:53:1: error: specializing member '::any_cast<const char*&>' requires 'template<>' syntax
   53 | any_cast<const char*&>(x) = "Harry";
      | ^~~~~~~~~~~~~~~~~~~~~~
p715a.cpp:54:1: error: expected unqualified-id before 'static_cast'
   54 | assert(strcmp(any_cast<const char*>(x), "Harry") == 0);
      | ^~~~~~
p715a.cpp:54:1: error: expected ')' before 'static_cast'
   54 | assert(strcmp(any_cast<const char*>(x), "Harry") == 0);
      | ^~~~~~
p715a.cpp:55:1: error: 'x' does not name a type
   55 | x = string("Meow");
      | ^
p715a.cpp:57:1: error: 's' does not name a type
   57 | s = move(any_cast<string&>(x));
      | ^
p715a.cpp:58:1: error: expected unqualified-id before 'static_cast'
   58 | assert(s == "Meow");
      | ^~~~~~
p715a.cpp:58:1: error: expected ')' before 'static_cast'
   58 | assert(s == "Meow");
      | ^~~~~~
p715a.cpp:59:1: error: specializing member '::any_cast<std::string&>' requires 'template<>' syntax
   59 | any_cast<string&>(x) = move(s2);
      | ^~~~~~~~~~~~~~~~~
p715a.cpp:60:1: error: expected unqualified-id before 'static_cast'
   60 | assert(any_cast<const string&>(x) == "Jane");
      | ^~~~~~
p715a.cpp:60:1: error: expected ')' before 'static_cast'
   60 | assert(any_cast<const string&>(x) == "Jane");
      | ^~~~~~
p715a.cpp:68:14: error: 'any' does not name a type
   68 |        const any y(cat);
      |              ^~~
p715a.cpp:69:8: error: expected unqualified-id before 'static_cast'
   69 |        assert(any_cast<const string&>(y) == cat);
      |        ^~~~~~
p715a.cpp:69:8: error: expected ')' before 'static_cast'
   69 |        assert(any_cast<const string&>(y) == cat);
      |        ^~~~~~
p715a.cpp:70:8: error: specializing member '::any_cast<std::string&>' requires 'template<>' syntax
   70 |        any_cast<string&>(y);
      |        ^~~~~~~~~~~~~~~~~
p715a.cpp:72:27: error: 'any' does not name a type
   72 |   const T* any_cast(const any* operand) noexcept;
      |                           ^~~
p715a.cpp:72:41: error: expected initializer before 'noexcept'
   72 |   const T* any_cast(const any* operand) noexcept;
      |                                         ^~~~~~~~
p715a.cpp:74:15: error: 'template<class T> T* any_cast' conflicts with a previous declaration
   74 |   T* any_cast(any* operand) noexcept;
      |               ^~~
p715a.cpp:37:5: note: previous declaration 'T any_cast(const int&)'
   37 |   T any_cast(const any& operand);
      |     ^~~~~~~~
p715a.cpp:74:15: error: 'any' was not declared in this scope
   74 |   T* any_cast(any* operand) noexcept;
      |               ^~~
p715a.cpp:74:15: note: 'std::any' is only available from C++17 onwards
p715a.cpp:74:20: error: 'operand' was not declared in this scope; did you mean 'srand'?
   74 |   T* any_cast(any* operand) noexcept;
      |                    ^~~~~~~
      |                    srand
p715a.cpp:74:6: warning: variable templates only available with '-std=c++14' or '-std=gnu++14' [-Wc++14-extensions]
   74 |   T* any_cast(any* operand) noexcept;
      |      ^~~~~~~~
p715a.cpp:74:28: error: expected ';' before 'noexcept'
   74 |   T* any_cast(any* operand) noexcept;
      |                            ^~~~~~~~~
      |                            ;
p715a.cpp:78:29: error: 'any' does not name a type
   78 |        bool is_string(const any& operand) {
      |                             ^~~
p715a.cpp: In function 'bool is_string(const int&)':
p715a.cpp:79:34: error: invalid conversion from 'const int*' to 'int' [-fpermissive]
   79 |          return any_cast<string>(&operand) != nullptr;
      |                                  ^~~~~~~~
      |                                  |
      |                                  const int*
p715a.cpp:37:25: note:   initializing argument 1 of 'T any_cast(const int&) [with T = std::__cxx11::basic_string<char>]'
   37 |   T any_cast(const any& operand);
      |              ~~~~~~~~~~~^~~~~~~
p715a.cpp:79:47: error: 'nullptr' was not declared in this scope
   79 |          return any_cast<string>(&operand) != nullptr;
      |                                               ^~~~~~~

$ g++ p715a.cpp -std=2b -o p715ag -I. -Wall
p715a.cpp:32:16: error: 'Args' was not declared in this scope
   32 |   any make_any(Args&&... args);
      |                ^~~~
p715a.cpp:34:31: error: 'U' was not declared in this scope
   34 | any make_any(initializer_list<U> il, Args&&... args);
      |                               ^
p715a.cpp:34:32: error: template argument 1 is invalid
   34 | any make_any(initializer_list<U> il, Args&&... args);
      |                                ^
p715a.cpp:34:38: error: 'Args' has not been declared
   34 | any make_any(initializer_list<U> il, Args&&... args);
      |                                      ^~~~
p715a.cpp:34:48: error: expansion pattern 'int&&' contains no parameter packs
   34 | any make_any(initializer_list<U> il, Args&&... args);
      |                                                ^~~~
p715a.cpp:34:52: error: 'std::any make_any(...)' redeclared as different kind of entity
   34 | any make_any(initializer_list<U> il, Args&&... args);
      |                                                    ^
p715a.cpp:32:7: note: previous declaration 'std::any make_any'
   32 |   any make_any(Args&&... args);
      |       ^~~~~~~~
p715a.cpp:44:20: error: 'T' was not declared in this scope
   44 | is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
      |                    ^
p715a.cpp:44:23: error: 'U' was not declared in this scope
   44 | is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
      |                       ^
p715a.cpp:44:1: error: parse error in template argument list
   44 | is_constructible_v<T, U&> is true. For the third overload, is_constructible_v<T, U> is true. Returns: For the first and second overload, static_cast<T>(*any_cast<U>(&operand)). For the
      | ^~~~~~~~~~~~~~~~~~~~~~~~~
p715a.cpp:44:1: error: 'is_constructible_v<<expression error>, <expression error> >' does not name a type
In file included from /usr/local/include/c++/12.1.0/cassert:44,
                 from p715a.cpp:14:
p715a.cpp:48:1: error: expected unqualified-id before 'static_cast'
   48 | assert(any_cast<int>(x) == 5);
      | ^~~~~~
p715a.cpp:48:1: error: expected ')' before 'static_cast'
   48 | assert(any_cast<int>(x) == 5);
      | ^~~~~~
p715a.cpp:49:1: error: specializing member '::any_cast<int&>' requires 'template<>' syntax
   49 | any_cast<int&>(x) = 10;
      | ^~~~~~~~~~~~~~
p715a.cpp:50:1: error: expected unqualified-id before 'static_cast'
   50 | assert(any_cast<int>(x) == 10);
      | ^~~~~~
p715a.cpp:50:1: error: expected ')' before 'static_cast'
   50 | assert(any_cast<int>(x) == 10);
      | ^~~~~~
p715a.cpp:51:1: error: 'x' does not name a type
   51 | x = "Meow";
      | ^
p715a.cpp:52:1: error: expected unqualified-id before 'static_cast'
   52 | assert(strcmp(any_cast<const char*>(x), "Meow") == 0);
      | ^~~~~~
p715a.cpp:52:1: error: expected ')' before 'static_cast'
   52 | assert(strcmp(any_cast<const char*>(x), "Meow") == 0);
      | ^~~~~~
p715a.cpp:53:1: error: specializing member '::any_cast<const char*&>' requires 'template<>' syntax
   53 | any_cast<const char*&>(x) = "Harry";
      | ^~~~~~~~~~~~~~~~~~~~~~
p715a.cpp:54:1: error: expected unqualified-id before 'static_cast'
   54 | assert(strcmp(any_cast<const char*>(x), "Harry") == 0);
      | ^~~~~~
p715a.cpp:54:1: error: expected ')' before 'static_cast'
   54 | assert(strcmp(any_cast<const char*>(x), "Harry") == 0);
      | ^~~~~~
p715a.cpp:55:1: error: 'x' does not name a type
   55 | x = string("Meow");
      | ^
p715a.cpp:57:1: error: 's' does not name a type
   57 | s = move(any_cast<string&>(x));
      | ^
p715a.cpp:58:1: error: expected unqualified-id before 'static_cast'
   58 | assert(s == "Meow");
      | ^~~~~~
p715a.cpp:58:1: error: expected ')' before 'static_cast'
   58 | assert(s == "Meow");
      | ^~~~~~
p715a.cpp:59:1: error: specializing member '::any_cast<std::string&>' requires 'template<>' syntax
   59 | any_cast<string&>(x) = move(s2);
      | ^~~~~~~~~~~~~~~~~
p715a.cpp:60:1: error: expected unqualified-id before 'static_cast'
   60 | assert(any_cast<const string&>(x) == "Jane");
      | ^~~~~~
p715a.cpp:60:1: error: expected ')' before 'static_cast'
   60 | assert(any_cast<const string&>(x) == "Jane");
      | ^~~~~~
p715a.cpp:69:8: error: expected unqualified-id before 'static_cast'
   69 |        assert(any_cast<const string&>(y) == cat);
      |        ^~~~~~
p715a.cpp:69:8: error: expected ')' before 'static_cast'
   69 |        assert(any_cast<const string&>(y) == cat);
      |        ^~~~~~
p715a.cpp:70:8: error: specializing member '::any_cast<std::string&>' requires 'template<>' syntax
   70 |        any_cast<string&>(y);
      |        ^~~~~~~~~~~~~~~~~
p715a.cpp: In function 'bool is_string(const std::any&)':
p715a.cpp:79:33: error: call of overloaded 'any_cast<std::string>(const std::any*)' is ambiguous
   79 |          return any_cast<string>(&operand) != nullptr;
      |                 ~~~~~~~~~~~~~~~~^~~~~~~~~~
p715a.cpp:37:5: note: candidate: 'T any_cast(const std::any&) [with T = std::__cxx11::basic_string<char>]'
   37 |   T any_cast(const any& operand);
      |     ^~~~~~~~
p715a.cpp:41:5: note: candidate: 'T any_cast(std::any&&) [with T = std::__cxx11::basic_string<char>]'
   41 |   T any_cast(any&& operand);
      |     ^~~~~~~~
p715a.cpp:72:12: note: candidate: 'const T* any_cast(const std::any*) [with T = std::__cxx11::basic_string<char>]'
   72 |   const T* any_cast(const any* operand) noexcept;
      |            ^~~~~~~~
In file included from p715a.cpp:24:
/usr/local/include/c++/12.1.0/any:461:23: note: candidate: '_ValueType std::any_cast(const any&) [with _ValueType = __cxx11::basic_string<char>]'
  461 |     inline _ValueType any_cast(const any& __any)
      |                       ^~~~~~~~
/usr/local/include/c++/12.1.0/any:501:23: note: candidate: '_ValueType std::any_cast(any&&) [with _ValueType = __cxx11::basic_string<char>]'
  501 |     inline _ValueType any_cast(any&& __any)
      |                       ^~~~~~~~
/usr/local/include/c++/12.1.0/any:554:30: note: candidate: 'const _ValueType* std::any_cast(const any*) [with _ValueType = __cxx11::basic_string<char>]'
  554 |     inline const _ValueType* any_cast(const any* __any) noexcept
      |                              ^~~~~~~~
```

## 検討事項(agenda)
コンパイルエラーを取るか、コンパイルエラーの理由を解説する。

<!-- リンクエラーの解説をする。clang++とg++の比較。意味のある出力。
コンパイルエラーを取るか、コンパイルエラーの理由を解説する。-->

# 参考資料(reference)

cpprefjp - C++日本語リファレンス

https://cpprefjp.github.io/

コンパイラの実装状況

https://cpprefjp.github.io/implementation-status.html


typedef は C++11 ではオワコン

https://qiita.com/Linda_pp/items/44a67c64c14cba00eef1

C99からC++14を駆け抜けるC++講座

https://qiita.com/yumetodo/items/e49a673afd9a3ecb81a8


@kazuo_reve 私が効果を確認した「小川メソッド」

https://qiita.com/kazuo_reve/items/a3ea1d9171deeccc04da

## 自己参照(self reference)

ockerにclang

https://qiita.com/kaizen_nagoya/items/8829ffeee397eda50e80

docker gnu(gcc/g++) and llvm(clang/clang++)

https://qiita.com/drafts/059874ea39c4de64c0f7

コンパイル用shell script C版(clangとgcc)とC++版(clang++とg++)

https://qiita.com/kaizen_nagoya/items/74220c0577a512c2d7da

C++N4910:2022 tag follower 200人超えました。ありがとうございます。

https://qiita.com/kaizen_nagoya/items/a63fb96d351ac5c16ff7

C++N4910:2022 tag follower 200人超えました。ありがとうございます。

https://qiita.com/kaizen_nagoya/items/a63fb96d351ac5c16ff7

コピペコンパイルエラーあるある

https://qiita.com/kaizen_nagoya/items/29c832de9d762aed2761

C++ Error Message Collection(1)does not name a type, 11 articles

https://qiita.com/kaizen_nagoya/items/acb9f1a9b5aad6df06bd

dockerにclang

https://qiita.com/kaizen_nagoya/items/8829ffeee397eda50e80

docker gnu(gcc/g++) and llvm(clang/clang++)

https://qiita.com/drafts/059874ea39c4de64c0f7

コンパイル用shell script C版(clangとgcc)とC++版(clang++とg++)

https://qiita.com/kaizen_nagoya/items/74220c0577a512c2d7da

Compare the contents of C++N4910:2022, C++N4741:2018 and C++N4606:2015

https://qiita.com/kaizen_nagoya/items/483246d40f98abff7ded

C++ sample list

https://qiita.com/kaizen_nagoya/items/54ad75b73825b7c04f86

clang++, g++コンパイルエラー方針の違いの例

https://qiita.com/kaizen_nagoya/items/ea6e5009fe126d270a82

astyle 使ってみた

https://qiita.com/kaizen_nagoya/items/3c9a87a781d53a1a23f3

C++N4606 Working Draft 2016, ISO/IEC 14882, C++ standardのコード断片をコンパイルするためにしていること
https://qiita.com/kaizen_nagoya/items/a8d7ee2f2e29e76c19c1

コンパイル用shell script C版(clangとgcc)とC++版(clang++とg++)
https://qiita.com/kaizen_nagoya/items/74220c0577a512c2d7da

Clang/Clang++(LLVM) gcc/g++(GNU) コンパイラ警告等比較
https://qiita.com/kaizen_nagoya/items/9a82b958cc3aeef0403f

C++2003とC++2017でコンパイルエラーになるならない事例集
https://qiita.com/kaizen_nagoya/items/a13ea3823441c430edff

Qiitaに投稿するCのStyle例(暫定)
https://qiita.com/kaizen_nagoya/items/946df1528a6a1ef2bc0d

cpprefjpのdecltypeをコンパイル試験
https://qiita.com/kaizen_nagoya/items/090909af702f0d5d8a67

MISRA C++ 5-0-16
https://qiita.com/kaizen_nagoya/items/7df2d4e05db724752a74

C++ Templates Part1 BASICS Chapter 3. Class Templates 3.2 Use of Class Template Stack stack1test.cpp
https://qiita.com/kaizen_nagoya/items/cd5fc49106fad5a4e9ed

ISO/IEC TS 17961:2013 C Secure Coding Rules(1) All list(to be confirmed)
https://qiita.com/kaizen_nagoya/items/54e056195c4f11b850a1

C言語（C++)に対する誤解、曲解、無理解、爽快。
https://qiita.com/kaizen_nagoya/items/3f3992c9722c1cee2e3a

C Puzzle Bookの有り難み5つ、C言語規格及びCコンパイラの特性を認識
https://qiita.com/kaizen_nagoya/items/d89a48c1536a02ecdec9

'wchar.h' file not found で困った clang++ macOS
https://qiita.com/kaizen_nagoya/items/de15cd46d657517fac11

Open POSIX Test Suiteの使い方を調べはじめました
https://qiita.com/kaizen_nagoya/items/644d5e407f5faf96e6dc

MISRA-C 2012 Referenceに掲載している文献の入手可能性を確認
https://qiita.com/kaizen_nagoya/items/96dc8b125e462d5575bb

どうやって MISRA Example Suiteをコンパイルするか
https://qiita.com/kaizen_nagoya/items/fbdbff5ff696e2ca7f00

MISRA C まとめ #include <misra_c.h>
https://qiita.com/kaizen_nagoya/items/f1a79a7cbd281607c7c9

「C++完全理解ガイド」の同意できること上位10
https://qiita.com/kaizen_nagoya/items/aa5744e0c4a8618c7671

DoCAP（ドゥーキャップ）って何ですか？

https://qiita.com/kaizen_nagoya/items/47e0e6509ab792c43327

小川メソッド　覚え（書きかけ）

https://qiita.com/kaizen_nagoya/items/3593d72eca551742df68


 ＜この記事は個人の過去の経験に基づく個人の感想です。現在所属する組織、業務とは関係がありません。＞

# 文書履歴(document history)
ver. 0.01 初稿 　20220727