Примеры сообщений об ошибках для разных реализаций tagged_value_t

gistfile1.txt

Источник: https://eao197.blogspot.com/2023/03/progc-taggedvaluet.html

Компилятор clang 14.0.6.

Объемная версия на базе SFINAE:

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$ clang++-14 -std=c++17 -pedantic -Wall -o t1_clang14 t1.cpp
t1.cpp:198:24: error: overload resolution selected deleted operator '<'
        const auto cr = (bin1 < bin2);
                         ~~~~ ^ ~~~~
t1.cpp:94:1: note: candidate function [with V = my_data, Tag = binary_tag] has been explicitly deleted
operator<( const tagged_value_t<V, Tag> & a, const tagged_value_t<V, Tag> & b ) = delete;
^
t1.cpp:83:1: note: candidate template ignored: requirement 'tagged_value_impl::has_less_then_comparison_v_fn<my_data, void>::value' was not satisfied [with V = my_data, Tag = binary_tag]
operator<( const tagged_value_t<V, Tag> & a, const tagged_value_t<V, Tag> & b )
^
t1.cpp:199:24: error: overload resolution selected deleted operator '=='
        const auto er = (bin1 == bin2);
                         ~~~~ ^  ~~~~
t1.cpp:112:1: note: candidate function [with V = my_data, Tag = binary_tag] has been explicitly deleted
operator==( const tagged_value_t<V, Tag> & a, const tagged_value_t<V, Tag> & b ) = delete;
^
t1.cpp:101:1: note: candidate template ignored: requirement 'tagged_value_impl::has_equal_to_comparison_v_fn<my_data, void>::value' was not satisfied [with V = my_data, Tag = binary_tag]
operator==( const tagged_value_t<V, Tag> & a, const tagged_value_t<V, Tag> & b )
^
2 errors generated.
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Компактная версия без SFINAE:

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$ clang++-14 -std=c++17 -pedantic -Wall -o t2_clang14 t2.cpp
t2.cpp:132:24: error: invalid operands to binary expression ('my_binaries_t' (aka 'tagged_value_t<my_data, binary_tag>') and 'my_binaries_t')
        const auto er = (bin1 == bin2);
                         ~~~~ ^  ~~~~
t2.cpp:52:1: note: candidate template ignored: substitution failure [with V = my_data, Tag = binary_tag]: invalid operands to binary expression ('const my_data' and 'const my_data')
operator==( const tagged_value_t<V, Tag> & a, const tagged_value_t<V, Tag> & b )
^
In file included from t2.cpp:1:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/iostream:39:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/ostream:38:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/ios:42:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/ios_base.h:41:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/locale_classes.h:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/string:48:
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_function.h:386:20: error: invalid operands to binary expression ('const my_data' and 'const my_data')
      { return __x < __y; }
               ~~~ ^ ~~~
t2.cpp:46:9: note: in instantiation of member function 'std::less<my_data>::operator()' requested here
        return std::less<V>{}( a.value(), b.value() );
               ^
t2.cpp:131:24: note: in instantiation of function template specialization 'operator<<my_data, binary_tag>' requested here
        const auto cr = (bin1 < bin2);
                              ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_pair.h:489:5: note: candidate template ignored: could not match 'const pair<_T1, _T2>' against 'const my_data'
    operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_iterator.h:422:5: note: candidate template ignored: could not match 'const reverse_iterator<_Iterator>' against 'const my_data'
    operator<(const reverse_iterator<_Iterator>& __x,
    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_iterator.h:461:5: note: candidate template ignored: could not match 'const reverse_iterator<_IteratorL>' against 'const my_data'
    operator<(const reverse_iterator<_IteratorL>& __x,
    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_iterator.h:1557:5: note: candidate template ignored: could not match 'const move_iterator<_IteratorL>' against 'const my_data'
    operator<(const move_iterator<_IteratorL>& __x,
    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_iterator.h:1613:5: note: candidate template ignored: could not match 'const move_iterator<_Iterator>' against 'const my_data'
    operator<(const move_iterator<_Iterator>& __x,
    ^
t2.cpp:42:1: note: candidate template ignored: could not match 'const tagged_value_t<V, Tag>' against 'const my_data'
operator<( const tagged_value_t<V, Tag> & a, const tagged_value_t<V, Tag> & b )
^
2 errors generated.
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