13.4.4 Template template arguments [temp.arg.template] C++N4910:2022 (203) p365.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.

# 13.4.4 Template template arguments [temp.arg.template] C++N4910:2022 (203) p365.cpp

## 算譜(source code)

```c++:p365.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 = "13.4.4 Template template arguments [temp.arg.template] C++N4910:2022 (203) p365.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 <typeinfo>

using namespace std;

// Example 1  
template<class T> class A { // primary template int x;
};
template<class T> class A<T*> { // partial specialization
long x; };
     template<template<class U> class V> class C {
       V<int>  y;
       V<int*> z;
};
C<A> c;
// V<int> within C<A> uses the primary template, so c.y.x has type int
// V<int*> within C<A> uses the partial specialization, so c.z.x has type long
// [Example 2:
     template<class T> class A { /* ... */ };
     template<class T, class U = T> class B { /* ... */ };
     template<class ... Types> class C { /* ... */ };
     template<auto n> class D { /* ... */ };
     template<template<class> class P> class X { /* ... */ };
     template<template<class ...> class Q> class Y { /* ... */ };
     template<template<int> class R> class Z { /* ... */ };
  X<A> xa;
  X<B> xb;
  X<C> xc;
  Y<A> ya;
  Y<B> yb;
  Y<C> yc;
  Z<D> zd;
// OK // OK // OK // OK // OK // OK // OK
// [Example 3:
template <class T> struct eval;
template <template <class, class...> class TT, class T1, class... Rest>
struct eval<TT<T1, Rest...>> { };
template <class T1> struct A;
template <class T1, class T2> struct B;
template <int N> struct C;
template <class T1, int N> struct D;
template <class T1, class T2, int N = 17> struct E;
  eval<A<int>> eA;
  eval<B<int, float>> eB;
  eval<C<17>> eC;
  eval<D<int, 17>> eD;
  eval<E<int, float>> eE;
// OK, matches partial specialization of eval
// OK, matches partial specialization of eval
// error: C does not match TT in partial specialization 
// error: D does not match TT in partial specialization 
// error: E does not match TT in partial specialization
// [Example 4:
template<typename T> concept C = requires (T t) { t.f(); };
template<typename T> concept D = C<T> && requires (T t) { t.g(); };
template<template<C> class P> struct S { };
template<C> struct X { };
template<D> struct Y { };
template<typename T> struct Z { };
  S<X> s1;
  S<Y> s2;
  S<Z> s3;
int main(){
  cout  <<  n4910 << endl;
  return EXIT_SUCCESS;
}
```

## Script

```bash:clgc.sh
#!/bin/sh
rm $1l
rm $1g
echo "$ clang++ $1.cpp -std=03 -o $1l -I. -Wall" 
clang++ $1.cpp -std=c++03 -o $1l -I. -Wall
if [  -e $1l ]; then
./$1l 
fi
rm $1l
echo "$ clang++ $1.cpp -std=2b -o $1l -I. -Wall"
clang++ $1.cpp -std=c++2b -o $1l -I. -Wall
if [  -e $1l ]; then
./$1l
fi
echo "\r"
echo "$ g++ $1.cpp -std=03 -o $1g -I. -Wall"
g++ $1.cpp -std=c++03 -o $1g -I. -Wall
if [ -e $1g ]; then
./$1g
fi
rm $1g
echo "\r"
echo "$ g++ $1.cpp -std=2b -o $1g -I. -Wall"
g++ $1.cpp -std=c++2b -o $1g -I. -Wall
if [ -e $1g ]; then
./$1g 
fi
```
## 編纂・実行結果(compile and go)

```ubuntu:bash
# ./clgc.sh p365
$ clang++ p365.cpp -std=c++03 -o p365l -I. -Wall
In file included from p365.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 \
 ^
p365.cpp:38:30: error: redefinition of 'A'
     template<class T> class A { /* ... */ };
                             ^
p365.cpp:26:25: note: previous definition is here
template<class T> class A { // primary template int x;
                        ^
p365.cpp:40:21: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
     template<class ... Types> class C { /* ... */ };
                    ^
p365.cpp:40:25: error: template parameter has a different kind in template redeclaration
     template<class ... Types> class C { /* ... */ };
                        ^
p365.cpp:30:39: note: previous template declaration is here
     template<template<class U> class V> class C {
                                      ^
p365.cpp:41:15: warning: 'auto' type specifier is a C++11 extension [-Wc++11-extensions]
     template<auto n> class D { /* ... */ };
              ^
p365.cpp:41:15: error: 'auto' not allowed in template parameter until C++17
     template<auto n> class D { /* ... */ };
              ^~~~
p365.cpp:43:30: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
     template<template<class ...> class Q> class Y { /* ... */ };
                             ^
p365.cpp:46:5: error: template template argument has different template parameters than its corresponding template template parameter
  X<B> xb;
    ^
p365.cpp:39:6: note: too many template parameters in template template argument
     template<class T, class U = T> class B { /* ... */ };
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
p365.cpp:42:15: note: previous template template parameter is here
     template<template<class> class P> class X { /* ... */ };
              ^~~~~~~~~~~~~~~
p365.cpp:47:5: error: template template argument has different template parameters than its corresponding template template parameter
  X<C> xc;
    ^
p365.cpp:30:39: note: template parameter has a different kind in template argument
     template<template<class U> class V> class C {
                                      ^
p365.cpp:42:29: note: previous template template parameter is here
     template<template<class> class P> class X { /* ... */ };
                            ^
p365.cpp:50:5: error: template template argument has different template parameters than its corresponding template template parameter
  Y<C> yc;
    ^
p365.cpp:30:39: note: template parameter has a different kind in template argument
     template<template<class U> class V> class C {
                                      ^
p365.cpp:43:33: note: previous template template parameter is here
     template<template<class ...> class Q> class Y { /* ... */ };
                                ^
p365.cpp:55:33: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
template <template <class, class...> class TT, class T1, class... Rest>
                                ^
p365.cpp:55:63: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
template <template <class, class...> class TT, class T1, class... Rest>
                                                              ^
p365.cpp:56:27: error: a space is required between consecutive right angle brackets (use '> >')
struct eval<TT<T1, Rest...>> { };
                          ^~
                          > >
p365.cpp:57:21: warning: struct template 'A' was previously declared as a class template; this is valid, but may result in linker errors under the Microsoft C++ ABI [-Wmismatched-tags]
template <class T1> struct A;
                    ^
p365.cpp:26:25: note: previous use is here
template<class T> class A { // primary template int x;
                        ^
p365.cpp:57:21: note: did you mean class here?
template <class T1> struct A;
                    ^~~~~~
                    class
p365.cpp:58:31: warning: struct template 'B' was previously declared as a class template; this is valid, but may result in linker errors under the Microsoft C++ ABI [-Wmismatched-tags]
template <class T1, class T2> struct B;
                              ^
p365.cpp:39:43: note: previous use is here
     template<class T, class U = T> class B { /* ... */ };
                                          ^
p365.cpp:58:31: note: did you mean class here?
template <class T1, class T2> struct B;
                              ^~~~~~
                              class
p365.cpp:59:15: error: template parameter has a different kind in template redeclaration
template <int N> struct C;
              ^
p365.cpp:30:39: note: previous template declaration is here
     template<template<class U> class V> class C {
                                      ^
p365.cpp:60:1: error: too many template parameters in template redeclaration
template <class T1, int N> struct D;
^~~~~~~~~~~~~~~~~~~~~~~~~~
p365.cpp:41:6: note: previous template declaration is here
     template<auto n> class D { /* ... */ };
     ^~~~~~~~~~~~~~~~
p365.cpp:62:13: error: a space is required between consecutive right angle brackets (use '> >')
  eval<A<int>> eA;
            ^~
            > >
p365.cpp:63:20: error: a space is required between consecutive right angle brackets (use '> >')
  eval<B<int, float>> eB;
                   ^~
                   > >
p365.cpp:64:12: warning: use of right-shift operator ('>>') in template argument will require parentheses in C++11 [-Wc++11-compat]
  eval<C<17>> eC;
           ^
         (      )
p365.cpp:64:15: error: use of undeclared identifier 'eC'
  eval<C<17>> eC;
              ^
p365.cpp:64:17: error: expected '>'
  eval<C<17>> eC;
                ^
p365.cpp:64:9: note: to match this '<'
  eval<C<17>> eC;
        ^
p365.cpp:64:17: error: expected a type
  eval<C<17>> eC;
                ^
p365.cpp:64:17: error: expected '>'
p365.cpp:64:7: note: to match this '<'
  eval<C<17>> eC;
      ^
p365.cpp:65:17: warning: use of right-shift operator ('>>') in template argument will require parentheses in C++11 [-Wc++11-compat]
  eval<D<int, 17>> eD;
                ^
              (      )
p365.cpp:65:20: error: use of undeclared identifier 'eD'
  eval<D<int, 17>> eD;
                   ^
p365.cpp:65:22: error: expected '>'
  eval<D<int, 17>> eD;
                     ^
p365.cpp:65:9: note: to match this '<'
  eval<D<int, 17>> eD;
        ^
p365.cpp:65:22: error: expected a type
  eval<D<int, 17>> eD;
                     ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
9 warnings and 20 errors generated.
rm: cannot remove 'p365l': No such file or directory
$ clang++ p365.cpp -std=c++2b -o p365l -I. -Wall
p365.cpp:38:30: error: redefinition of 'A'
     template<class T> class A { /* ... */ };
                             ^
p365.cpp:26:25: note: previous definition is here
template<class T> class A { // primary template int x;
                        ^
p365.cpp:40:25: error: template parameter has a different kind in template redeclaration
     template<class ... Types> class C { /* ... */ };
                        ^
p365.cpp:30:39: note: previous template declaration is here
     template<template<class U> class V> class C {
                                      ^
p365.cpp:46:5: error: template template argument has different template parameters than its corresponding template template parameter
  X<B> xb;
    ^
p365.cpp:39:6: note: too many template parameters in template template argument
     template<class T, class U = T> class B { /* ... */ };
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
p365.cpp:42:15: note: previous template template parameter is here
     template<template<class> class P> class X { /* ... */ };
              ^~~~~~~~~~~~~~~
p365.cpp:47:5: error: template template argument has different template parameters than its corresponding template template parameter
  X<C> xc;
    ^
p365.cpp:30:39: note: template parameter has a different kind in template argument
     template<template<class U> class V> class C {
                                      ^
p365.cpp:42:29: note: previous template template parameter is here
     template<template<class> class P> class X { /* ... */ };
                            ^
p365.cpp:50:5: error: template template argument has different template parameters than its corresponding template template parameter
  Y<C> yc;
    ^
p365.cpp:30:39: note: template parameter has a different kind in template argument
     template<template<class U> class V> class C {
                                      ^
p365.cpp:43:33: note: previous template template parameter is here
     template<template<class ...> class Q> class Y { /* ... */ };
                                ^
p365.cpp:57:21: warning: struct template 'A' was previously declared as a class template; this is valid, but may result in linker errors under the Microsoft C++ ABI [-Wmismatched-tags]
template <class T1> struct A;
                    ^
p365.cpp:26:25: note: previous use is here
template<class T> class A { // primary template int x;
                        ^
p365.cpp:57:21: note: did you mean class here?
template <class T1> struct A;
                    ^~~~~~
                    class
p365.cpp:58:31: warning: struct template 'B' was previously declared as a class template; this is valid, but may result in linker errors under the Microsoft C++ ABI [-Wmismatched-tags]
template <class T1, class T2> struct B;
                              ^
p365.cpp:39:43: note: previous use is here
     template<class T, class U = T> class B { /* ... */ };
                                          ^
p365.cpp:58:31: note: did you mean class here?
template <class T1, class T2> struct B;
                              ^~~~~~
                              class
p365.cpp:59:15: error: template parameter has a different kind in template redeclaration
template <int N> struct C;
              ^
p365.cpp:30:39: note: previous template declaration is here
     template<template<class U> class V> class C {
                                      ^
p365.cpp:60:1: error: too many template parameters in template redeclaration
template <class T1, int N> struct D;
^~~~~~~~~~~~~~~~~~~~~~~~~~
p365.cpp:41:6: note: previous template declaration is here
     template<auto n> class D { /* ... */ };
     ^~~~~~~~~~~~~~~~
p365.cpp:64:10: error: template argument for template template parameter must be a class template or type alias template
  eval<C<17>> eC;
         ^
p365.cpp:65:10: error: template argument for non-type template parameter must be an expression
  eval<D<int, 17>> eD;
         ^~~
p365.cpp:41:20: note: template parameter is declared here
     template<auto n> class D { /* ... */ };
                   ^
p365.cpp:66:23: error: implicit instantiation of undefined template 'eval<E<int, float, 17>>'
  eval<E<int, float>> eE;
                      ^
p365.cpp:54:27: note: template is declared here
template <class T> struct eval;
                          ^
p365.cpp:73:30: error: redefinition of 'C' as different kind of symbol
template<typename T> concept C = requires (T t) { t.f(); };
                             ^
p365.cpp:30:48: note: previous definition is here
     template<template<class U> class V> class C {
                                               ^
p365.cpp:74:34: error: reference to 'C' is ambiguous
template<typename T> concept D = C<T> && requires (T t) { t.g(); };
                                 ^
p365.cpp:30:48: note: candidate found by name lookup is 'C'
     template<template<class U> class V> class C {
                                               ^
p365.cpp:73:30: note: candidate found by name lookup is 'C'
template<typename T> concept C = requires (T t) { t.f(); };
                             ^
p365.cpp:74:36: error: template argument for template template parameter must be a class template or type alias template
template<typename T> concept D = C<T> && requires (T t) { t.g(); };
                                   ^
p365.cpp:74:39: error: expected '(' for function-style cast or type construction
template<typename T> concept D = C<T> && requires (T t) { t.g(); };
                                 ~~~~ ^
p365.cpp:75:19: error: reference to 'C' is ambiguous
template<template<C> class P> struct S { };
                  ^
p365.cpp:30:48: note: candidate found by name lookup is 'C'
     template<template<class U> class V> class C {
                                               ^
p365.cpp:73:30: note: candidate found by name lookup is 'C'
template<typename T> concept C = requires (T t) { t.f(); };
                             ^
p365.cpp:75:19: error: reference to 'C' is ambiguous
template<template<C> class P> struct S { };
                  ^
p365.cpp:30:48: note: candidate found by name lookup is 'C'
     template<template<class U> class V> class C {
                                               ^
p365.cpp:73:30: note: candidate found by name lookup is 'C'
template<typename T> concept C = requires (T t) { t.f(); };
                             ^
p365.cpp:76:10: error: reference to 'C' is ambiguous
template<C> struct X { };
         ^
p365.cpp:30:48: note: candidate found by name lookup is 'C'
     template<template<class U> class V> class C {
                                               ^
p365.cpp:73:30: note: candidate found by name lookup is 'C'
template<typename T> concept C = requires (T t) { t.f(); };
                             ^
p365.cpp:76:10: error: reference to 'C' is ambiguous
template<C> struct X { };
         ^
p365.cpp:30:48: note: candidate found by name lookup is 'C'
     template<template<class U> class V> class C {
                                               ^
p365.cpp:73:30: note: candidate found by name lookup is 'C'
template<typename T> concept C = requires (T t) { t.f(); };
                             ^
p365.cpp:76:11: error: template parameter has a different kind in template redeclaration
template<C> struct X { };
          ^
p365.cpp:42:37: note: previous template declaration is here
     template<template<class> class P> class X { /* ... */ };
                                    ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
2 warnings and 20 errors generated.

$ g++ p365.cpp -std=c++03 -o p365g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p365.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 \
      |  ^~~~~
p365.cpp:38:30: error: redefinition of 'class A<T>'
   38 |      template<class T> class A { /* ... */ };
      |                              ^
p365.cpp:26:25: note: previous definition of 'class A<T>'
   26 | template<class T> class A { // primary template int x;
      |                         ^
p365.cpp:40:21: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   40 |      template<class ... Types> class C { /* ... */ };
      |                     ^~~
p365.cpp:30:39: error: template parameter 'template<class U> class V'
   30 |      template<template<class U> class V> class C {
      |                                       ^
p365.cpp:40:15: note: redeclared here as 'class ... Types'
   40 |      template<class ... Types> class C { /* ... */ };
      |               ^~~~~
p365.cpp:41:15: warning: 'auto' changes meaning in C++11; please remove it [-Wc++11-compat]
   41 |      template<auto n> class D { /* ... */ };
      |               ^~~~
      |               ----
p365.cpp:41:20: error: 'n' does not name a type
   41 |      template<auto n> class D { /* ... */ };
      |                    ^
p365.cpp:41:15: error: storage class specified for template parameter 'parameter'
   41 |      template<auto n> class D { /* ... */ };
      |               ^~~~
p365.cpp:41:44: error: expected '>' before ';' token
   41 |      template<auto n> class D { /* ... */ };
      |                                            ^
p365.cpp:41:44: error: expected unqualified-id before ';' token
p365.cpp:43:30: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   43 |      template<template<class ...> class Q> class Y { /* ... */ };
      |                              ^~~
p365.cpp:46:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class> class P> class X'
   46 |   X<B> xb;
      |      ^
p365.cpp:46:6: note:   expected a template of type 'template<class> class P', got 'template<class T, class U> class B'
p365.cpp:47:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class> class P> class X'
   47 |   X<C> xc;
      |      ^
p365.cpp:47:6: note:   expected a template of type 'template<class> class P', got 'template<template<class U> class V> class C'
p365.cpp:50:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class ...> class Q> class Y'
   50 |   Y<C> yc;
      |      ^
p365.cpp:50:6: note:   expected a template of type 'template<class ...> class Q', got 'template<template<class U> class V> class C'
p365.cpp:51:5: error: 'D' was not declared in this scope
   51 |   Z<D> zd;
      |     ^
p365.cpp:51:6: error: template argument 1 is invalid
   51 |   Z<D> zd;
      |      ^
p365.cpp:55:33: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   55 | template <template <class, class...> class TT, class T1, class... Rest>
      |                                 ^~~
p365.cpp:55:63: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   55 | template <template <class, class...> class TT, class T1, class... Rest>
      |                                                               ^~~
p365.cpp:56:27: error: '>>' should be '> >' within a nested template argument list
   56 | struct eval<TT<T1, Rest...>> { };
      |                           ^~
      |                           > >
p365.cpp:30:39: error: template parameter 'template<class U> class V'
   30 |      template<template<class U> class V> class C {
      |                                       ^
p365.cpp:59:15: note: redeclared here as 'int N'
   59 | template <int N> struct C;
      |               ^
p365.cpp:62:13: error: '>>' should be '> >' within a nested template argument list
   62 |   eval<A<int>> eA;
      |             ^~
      |             > >
p365.cpp:63:20: error: '>>' should be '> >' within a nested template argument list
   63 |   eval<B<int, float>> eB;
      |                    ^~
      |                    > >
p365.cpp:64:12: warning: '>>' operator is treated as two right angle brackets in C++11 [-Wc++11-compat]
   64 |   eval<C<17>> eC;
      |            ^~
p365.cpp:64:12: note: suggest parentheses around '>>' expression
p365.cpp:64:15: error: 'eC' was not declared in this scope; did you mean 'eB'?
   64 |   eval<C<17>> eC;
      |               ^~
      |               eB
p365.cpp:64:15: error: template argument 1 is invalid
p365.cpp:64:8: error: template argument 1 is invalid
   64 |   eval<C<17>> eC;
      |        ^~~~~~~~~
p365.cpp:65:17: warning: '>>' operator is treated as two right angle brackets in C++11 [-Wc++11-compat]
   65 |   eval<D<int, 17>> eD;
      |                 ^~
p365.cpp:65:17: note: suggest parentheses around '>>' expression
p365.cpp:65:20: error: 'eD' was not declared in this scope; did you mean 'eB'?
   65 |   eval<D<int, 17>> eD;
      |                    ^~
      |                    eB
p365.cpp:65:20: error: template argument 2 is invalid
p365.cpp:65:8: error: template argument 1 is invalid
   65 |   eval<D<int, 17>> eD;
      |        ^~~~~~~~~~~~~~
p365.cpp:66:20: error: '>>' should be '> >' within a nested template argument list
   66 |   eval<E<int, float>> eE;
      |                    ^~
      |                    > >
p365.cpp:66:23: error: aggregate 'eval<E<int, float> > eE' has incomplete type and cannot be defined
   66 |   eval<E<int, float>> eE;
      |                       ^~
p365.cpp:73:22: error: 'concept' does not name a type; did you mean 'const'?
   73 | template<typename T> concept C = requires (T t) { t.f(); };
      |                      ^~~~~~~
      |                      const
p365.cpp:73:22: note: 'concept' only available with '-std=c++20' or '-fconcepts'
p365.cpp:74:22: error: 'concept' does not name a type; did you mean 'const'?
   74 | template<typename T> concept D = C<T> && requires (T t) { t.g(); };
      |                      ^~~~~~~
      |                      const
p365.cpp:74:22: note: 'concept' only available with '-std=c++20' or '-fconcepts'
p365.cpp:75:19: error: 'C' is not a type
   75 | template<template<C> class P> struct S { };
      |                   ^
p365.cpp:76:10: error: 'C' is not a type
   76 | template<C> struct X { };
      |          ^
p365.cpp:42:37: error: template parameter 'template<class> class P'
   42 |      template<template<class> class P> class X { /* ... */ };
      |                                     ^
p365.cpp:76:10: note: redeclared here as '<typeprefixerror><anonymous>'
   76 | template<C> struct X { };
      |          ^
p365.cpp:77:10: error: 'D' is not a type
   77 | template<D> struct Y { };
      |          ^
p365.cpp:43:41: error: template parameter 'template<class ...> class Q'
   43 |      template<template<class ...> class Q> class Y { /* ... */ };
      |                                         ^
p365.cpp:77:10: note: redeclared here as '<typeprefixerror><anonymous>'
   77 | template<D> struct Y { };
      |          ^
p365.cpp:44:35: error: template parameter 'template<int <anonymous> > class R'
   44 |      template<template<int> class R> class Z { /* ... */ };
      |                                   ^
p365.cpp:78:10: note: redeclared here as 'class T'
   78 | template<typename T> struct Z { };
      |          ^~~~~~~~
p365.cpp:79:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<<typeprefixerror><anonymous> > class P> struct S'
   79 |   S<X> s1;
      |      ^
p365.cpp:79:6: note:   expected a template of type 'template<<typeprefixerror><anonymous> > class P', got 'template<template<class> class P> class X'
p365.cpp:80:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<<typeprefixerror><anonymous> > class P> struct S'
   80 |   S<Y> s2;
      |      ^
p365.cpp:80:6: note:   expected a template of type 'template<<typeprefixerror><anonymous> > class P', got 'template<template<class ...> class Q> class Y'
p365.cpp:81:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<<typeprefixerror><anonymous> > class P> struct S'
   81 |   S<Z> s3;
      |      ^
p365.cpp:81:6: note:   expected a template of type 'template<<typeprefixerror><anonymous> > class P', got 'template<template<int <anonymous> > class R> class Z'
rm: cannot remove 'p365g': No such file or directory

$ g++ p365.cpp -std=c++2b -o p365g -I. -Wall
p365.cpp:38:30: error: redefinition of 'class A<T>'
   38 |      template<class T> class A { /* ... */ };
      |                              ^
p365.cpp:26:25: note: previous definition of 'class A<T>'
   26 | template<class T> class A { // primary template int x;
      |                         ^
p365.cpp:30:39: error: template parameter 'template<class U> class V'
   30 |      template<template<class U> class V> class C {
      |                                       ^
p365.cpp:40:15: note: redeclared here as 'class ... Types'
   40 |      template<class ... Types> class C { /* ... */ };
      |               ^~~~~
p365.cpp:47:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class> class P> class X'
   47 |   X<C> xc;
      |      ^
p365.cpp:47:6: note:   expected a template of type 'template<class> class P', got 'template<template<class U> class V> class C'
p365.cpp:50:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class ...> class Q> class Y'
   50 |   Y<C> yc;
      |      ^
p365.cpp:50:6: note:   expected a template of type 'template<class ...> class Q', got 'template<template<class U> class V> class C'
p365.cpp:30:39: error: template parameter 'template<class U> class V'
   30 |      template<template<class U> class V> class C {
      |                                       ^
p365.cpp:59:15: note: redeclared here as 'int N'
   59 | template <int N> struct C;
      |               ^
p365.cpp:60:35: error: redeclared with 2 template parameters
   60 | template <class T1, int N> struct D;
      |                                   ^
p365.cpp:41:29: note: previous declaration 'template<auto n> class D' used 1 template parameter
   41 |      template<auto n> class D { /* ... */ };
      |                             ^
p365.cpp:64:10: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class U> class V> class C'
   64 |   eval<C<17>> eC;
      |          ^~
p365.cpp:64:10: note:   expected a class template, got '17'
p365.cpp:64:12: error: template argument 1 is invalid
   64 |   eval<C<17>> eC;
      |            ^~
p365.cpp:65:15: error: wrong number of template arguments (2, should be 1)
   65 |   eval<D<int, 17>> eD;
      |               ^~
p365.cpp:41:29: note: provided for 'template<auto n> class D'
   41 |      template<auto n> class D { /* ... */ };
      |                             ^
p365.cpp:65:17: error: template argument 1 is invalid
   65 |   eval<D<int, 17>> eD;
      |                 ^~
p365.cpp:66:23: error: aggregate 'eval<E<int, float> > eE' has incomplete type and cannot be defined
   66 |   eval<E<int, float>> eE;
      |                       ^~
p365.cpp:73:30: error: conflicting declaration of template 'template<class T> concept C'
   73 | template<typename T> concept C = requires (T t) { t.f(); };
      |                              ^
p365.cpp:30:48: note: previous declaration 'template<template<class U> class V> class C'
   30 |      template<template<class U> class V> class C {
      |                                                ^
p365.cpp:74:37: error: type/value mismatch at argument 1 in template parameter list for 'template<template<class U> class V> class C'
   74 | template<typename T> concept D = C<T> && requires (T t) { t.g(); };
      |                                     ^
p365.cpp:74:37: note:   expected a class template, got 'T'
p365.cpp:74:30: error: conflicting declaration of template 'template<class T> concept D'
   74 | template<typename T> concept D = C<T> && requires (T t) { t.g(); };
      |                              ^
p365.cpp:41:29: note: previous declaration 'template<auto n> class D'
   41 |      template<auto n> class D { /* ... */ };
      |                             ^
p365.cpp:42:37: error: template parameter 'template<class> class P'
   42 |      template<template<class> class P> class X { /* ... */ };
      |                                     ^
p365.cpp:76:10: note: redeclared here as 'C<...auto...> <anonymous>'
   76 | template<C> struct X { };
      |          ^
p365.cpp:43:41: error: template parameter 'template<class ...> class Q'
   43 |      template<template<class ...> class Q> class Y { /* ... */ };
      |                                         ^
p365.cpp:77:10: note: redeclared here as 'D<...auto...> <anonymous>'
   77 | template<D> struct Y { };
      |          ^
p365.cpp:44:35: error: template parameter 'template<int <anonymous> > class R'
   44 |      template<template<int> class R> class Z { /* ... */ };
      |                                   ^
p365.cpp:78:10: note: redeclared here as 'class T'
   78 | template<typename T> struct Z { };
      |          ^~~~~~~~
p365.cpp:79:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<C<...auto...> <anonymous> > class P> struct S'
   79 |   S<X> s1;
      |      ^
p365.cpp:79:6: note:   expected a template of type 'template<C<...auto...> <anonymous> > class P', got 'template<template<class> class P> class X'
p365.cpp:80:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<C<...auto...> <anonymous> > class P> struct S'
   80 |   S<Y> s2;
      |      ^
p365.cpp:80:6: note:   expected a template of type 'template<C<...auto...> <anonymous> > class P', got 'template<template<class ...> class Q> class Y'
p365.cpp:81:6: error: type/value mismatch at argument 1 in template parameter list for 'template<template<C<...auto...> <anonymous> > class P> struct S'
   81 |   S<Z> s3;
      |      ^
p365.cpp:81:6: note:   expected a template of type 'template<C<...auto...> <anonymous> > class P', got 'template<template<int <anonymous> > class R> class Z'
```

## 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

## 自己参照(self reference)

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


 ＜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 　20220703