Comparing `std::optional` in `BOOST_TEST` is ambiguous until GCC 10

[Flamefire]

See https://godbolt.org/z/EEMz865o4

#include <optional>
#include <boost/test/unit_test.hpp>

BOOST_TEST_DONT_PRINT_LOG_VALUE(std::optional<int>)

void foo() {
    std::optional<int> a,b;
    BOOST_TEST(a==b);
}

Yields:

<source>:8:5: error: request for member 'evaluate' in 'std::operator==<int, boost::test_tools::assertion::value_expr<std::optional<int>&> >(boost::test_tools::assertion::seed::operator->*(T&&) const [with T = std::optional<int>&](a), b)', which is of non-class type 'std::__optional_relop_t<boost::test_tools::assertion::binary_expr<boost::test_tools::assertion::value_expr<std::optional<int>&>, int, boost::test_tools::assertion::op::EQ<std::optional<int>, int, void> > >' {aka 'bool'}
    8 |     BOOST_TEST(a==b);
      |     ^~~~~~~~~~

It works in GCC 10 and up

More of the error output

: In function 'void foo()': :8:19: warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: 8 | BOOST_TEST(a==b); | ^ In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1101:5: note: candidate 1: 'constexpr std::__optional_relop_t() == declval<_Tp>()))> std::operator==(const _Up&, const std::optional<_Tp>&) [with _Tp = int; _Up = boost::test_tools::assertion::value_expr&>; std::__optional_relop_t() == declval<_Tp>()))> = bool]' 1101 | operator==(const _Up& __lhs, const optional<_Tp>& __rhs) | ^~~~~~~~ In file included from /app/boost/include/boost/test/test_tools.hpp:53, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /app/boost/include/boost/test/tools/assertion.hpp:227:5: note: candidate 2: 'boost::test_tools::assertion::binary_expr::RhsT::type> > boost::test_tools::assertion::expression_base::operator==(T&&) [with T = std::optional&; ExprType = boost::test_tools::assertion::value_expr&>; ValType = std::optional; typename boost::test_tools::assertion::expression_base::RhsT::type = std::optional]' 227 | BOOST_TEST_FOR_EACH_CONST_OP( ADD_OP_SUPPORT ) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from /app/boost/include/boost/test/test_tools.hpp:52, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: :8:5: error: request for member 'evaluate' in 'std::operator==&> >(boost::test_tools::assertion::seed::operator->*(T&&) const [with T = std::optional&](a), b)', which is of non-class type 'std::__optional_relop_t&>, int, boost::test_tools::assertion::op::EQ, int, void> > >' {aka 'bool'} 8 | BOOST_TEST(a==b); | ^~~~~~~~~~ In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional: In instantiation of 'constexpr std::__optional_relop_t() == declval<_Tp>()))> std::operator==(const _Up&, const std::optional<_Tp>&) [with _Tp = int; _Up = boost::test_tools::assertion::value_expr&>; std::__optional_relop_t() == declval<_Tp>()))> = bool]': :8:5: required from here /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: error: no match for 'operator==' (operand types are 'const boost::test_tools::assertion::value_expr&>' and 'const int') 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /app/boost/include/boost/test/test_tools.hpp:53, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /app/boost/include/boost/test/tools/assertion.hpp:227:5: note: candidate: 'boost::test_tools::assertion::binary_expr::RhsT::type> > boost::test_tools::assertion::expression_base::operator==(T&&) [with T = const int&; ExprType = boost::test_tools::assertion::value_expr&>; ValType = std::optional; typename boost::test_tools::assertion::expression_base::RhsT::type = int]' 227 | BOOST_TEST_FOR_EACH_CONST_OP( ADD_OP_SUPPORT ) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /app/boost/include/boost/test/tools/assertion.hpp:227:5: note: passing 'const boost::test_tools::assertion::value_expr&>*' as 'this' argument discards qualifiers In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: candidate: 'operator==(int, int)' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: conversion of argument 1 would be ill-formed: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: error: invalid user-defined conversion from 'const boost::test_tools::assertion::value_expr&>' to 'int' [-fpermissive] In file included from /app/boost/include/boost/test/test_tools.hpp:53, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /app/boost/include/boost/test/tools/assertion.hpp:250:5: note: candidate is: 'boost::test_tools::assertion::expression_base::operator bool() [with ExprType = boost::test_tools::assertion::value_expr&>; ValType = std::optional]' 250 | operator bool() | ^~~~~~~~ /app/boost/include/boost/test/tools/assertion.hpp:250:5: note: passing 'const boost::test_tools::assertion::value_expr&>*' as 'this' argument discards qualifiers In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: error: passing 'const boost::test_tools::assertion::value_expr&>' as 'this' argument discards qualifiers [-fpermissive] 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /app/boost/include/boost/test/test_tools.hpp:53, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /app/boost/include/boost/test/tools/assertion.hpp:250:5: note: in call to 'boost::test_tools::assertion::expression_base::operator bool() [with ExprType = boost::test_tools::assertion::value_expr&>; ValType = std::optional]' 250 | operator bool() | ^~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/utility:70, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:36, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_pair.h:448:5: note: candidate: 'template constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)' 448 | operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_pair.h:448:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::pair<_T1, _T2>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_algobase.h:67, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/char_traits.h:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:40, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:325:5: note: candidate: 'template constexpr bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)' 325 | operator==(const reverse_iterator<_Iterator>& __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:325:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::reverse_iterator<_Iterator>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_algobase.h:67, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/char_traits.h:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:40, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:363:5: note: candidate: 'template constexpr bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)' 363 | operator==(const reverse_iterator<_IteratorL>& __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:363:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::reverse_iterator<_Iterator>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_algobase.h:67, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/char_traits.h:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:40, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:1136:5: note: candidate: 'template constexpr bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)' 1136 | operator==(const move_iterator<_IteratorL>& __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:1136:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::move_iterator<_IteratorL>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_algobase.h:67, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/char_traits.h:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:40, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:1142:5: note: candidate: 'template constexpr bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)' 1142 | operator==(const move_iterator<_Iterator>& __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/stl_iterator.h:1142:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::move_iterator<_IteratorL>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/char_traits.h:40, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:40, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/postypes.h:222:5: note: candidate: 'template bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)' 222 | operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs) | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/postypes.h:222:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::fpos<_StateT>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:41, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/allocator.h:167:5: note: candidate: 'template bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_T2>&)' 167 | operator==(const allocator<_T1>&, const allocator<_T2>&) | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/allocator.h:167:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::allocator<_CharT>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:48, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:55, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string_view:471:5: note: candidate: 'template constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::basic_string_view<_CharT, _Traits>)' 471 | operator==(basic_string_view<_CharT, _Traits> __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string_view:471:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'boost::test_tools::assertion::value_expr&>' is not derived from 'std::basic_string_view<_CharT, _Traits>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:48, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:55, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string_view:477:5: note: candidate: 'template constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::__detail::__idt >)' 477 | operator==(basic_string_view<_CharT, _Traits> __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string_view:477:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'boost::test_tools::assertion::value_expr&>' is not derived from 'std::basic_string_view<_CharT, _Traits>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:48, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:55, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string_view:483:5: note: candidate: 'template constexpr bool std::operator==(std::__detail::__idt >, std::basic_string_view<_CharT, _Traits>)' 483 | operator==(__detail::__idt> __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string_view:483:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:55, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6149:5: note: candidate: 'template bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&, const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&)' 6149 | operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6149:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:55, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6157:5: note: candidate: 'template typename __gnu_cxx::__enable_if::__value, bool>::__type std::operator==(const std::__cxx11::basic_string<_CharT>&, const std::__cxx11::basic_string<_CharT>&)' 6157 | operator==(const basic_string<_CharT>& __lhs, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6157:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::__cxx11::basic_string<_CharT>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:55, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6171:5: note: candidate: 'template bool std::operator==(const _CharT*, const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&)' 6171 | operator==(const _CharT* __lhs, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6171:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: mismatched types 'const _CharT*' and 'boost::test_tools::assertion::value_expr&>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/string:55, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/stdexcept:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:38, from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6183:5: note: candidate: 'template bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)' 6183 | operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_string.h:6183:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:983:5: note: candidate: 'template constexpr std::__optional_relop_t() == declval<_Up>()))> std::operator==(const std::optional<_Tp>&, const std::optional<_Up>&)' 983 | operator==(const optional<_Tp>& __lhs, const optional<_Up>& __rhs) | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:983:5: note: template argument deduction/substitution failed: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::optional<_Tp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1034:5: note: candidate: 'template constexpr bool std::operator==(const std::optional<_Tp>&, std::nullopt_t)' 1034 | operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1034:5: note: template argument deduction/substitution failed: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::optional<_Tp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1039:5: note: candidate: 'template constexpr bool std::operator==(std::nullopt_t, const std::optional<_Tp>&)' 1039 | operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1039:5: note: template argument deduction/substitution failed: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: mismatched types 'const std::optional<_Tp>' and 'const int' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1095:5: note: candidate: 'template constexpr std::__optional_relop_t() == declval<_Up>()))> std::operator==(const std::optional<_Tp>&, const _Up&)' 1095 | operator==(const optional<_Tp>& __lhs, const _Up& __rhs) | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1095:5: note: template argument deduction/substitution failed: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::optional<_Tp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1101:5: note: candidate: 'template constexpr std::__optional_relop_t() == declval<_Tp>()))> std::operator==(const _Up&, const std::optional<_Tp>&)' 1101 | operator==(const _Up& __lhs, const optional<_Tp>& __rhs) | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1101:5: note: template argument deduction/substitution failed: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: mismatched types 'const std::optional<_Tp>' and 'const int' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/ios_base.h:46, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/ios:42, from /app/boost/include/boost/test/tools/detail/print_helper.hpp:30, from /app/boost/include/boost/test/utils/lazy_ostream.hpp:16, from /app/boost/include/boost/test/tools/context.hpp:19, from /app/boost/include/boost/test/test_tools.hpp:42, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:292:3: note: candidate: 'bool std::operator==(const std::error_code&, const std::error_code&)' 292 | operator==(const error_code& __lhs, const error_code& __rhs) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:292:32: note: no known conversion for argument 1 from 'const boost::test_tools::assertion::value_expr&>' to 'const std::error_code&' 292 | operator==(const error_code& __lhs, const error_code& __rhs) noexcept | ~~~~~~~~~~~~~~~~~~^~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:297:3: note: candidate: 'bool std::operator==(const std::error_code&, const std::error_condition&)' 297 | operator==(const error_code& __lhs, const error_condition& __rhs) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:297:32: note: no known conversion for argument 1 from 'const boost::test_tools::assertion::value_expr&>' to 'const std::error_code&' 297 | operator==(const error_code& __lhs, const error_condition& __rhs) noexcept | ~~~~~~~~~~~~~~~~~~^~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:304:3: note: candidate: 'bool std::operator==(const std::error_condition&, const std::error_code&)' 304 | operator==(const error_condition& __lhs, const error_code& __rhs) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:304:37: note: no known conversion for argument 1 from 'const boost::test_tools::assertion::value_expr&>' to 'const std::error_condition&' 304 | operator==(const error_condition& __lhs, const error_code& __rhs) noexcept | ~~~~~~~~~~~~~~~~~~~~~~~^~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:311:3: note: candidate: 'bool std::operator==(const std::error_condition&, const std::error_condition&)' 311 | operator==(const error_condition& __lhs, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/system_error:311:37: note: no known conversion for argument 1 from 'const boost::test_tools::assertion::value_expr&>' to 'const std::error_condition&' 311 | operator==(const error_condition& __lhs, | ~~~~~~~~~~~~~~~~~~~~~~~^~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/locale_facets.h:48, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/basic_ios.h:37, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/ios:44, from /app/boost/include/boost/test/tools/detail/print_helper.hpp:30, from /app/boost/include/boost/test/utils/lazy_ostream.hpp:16, from /app/boost/include/boost/test/tools/context.hpp:19, from /app/boost/include/boost/test/test_tools.hpp:42, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/streambuf_iterator.h:208:5: note: candidate: 'template bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)' 208 | operator==(const istreambuf_iterator<_CharT, _Traits>& __a, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/streambuf_iterator.h:208:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::istreambuf_iterator<_CharT, _Traits>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/tuple:39, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:37, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:80, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/array:252:5: note: candidate: 'template bool std::operator==(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)' 252 | operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two) | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/array:252:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::array<_Tp, _Nm>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:37, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:80, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/tuple:1419:5: note: candidate: 'template constexpr bool std::operator==(const std::tuple<_Tps ...>&, const std::tuple<_Elements ...>&)' 1419 | operator==(const tuple<_TElements...>& __t, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/tuple:1419:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::tuple<_Tps ...>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:80, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:715:5: note: candidate: 'template bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)' 715 | operator==(const unique_ptr<_Tp, _Dp>& __x, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:715:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::unique_ptr<_Tp, _Dp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:80, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:721:5: note: candidate: 'template bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, std::nullptr_t)' 721 | operator==(const unique_ptr<_Tp, _Dp>& __x, nullptr_t) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:721:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::unique_ptr<_Tp, _Dp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:80, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:726:5: note: candidate: 'template bool std::operator==(std::nullptr_t, const std::unique_ptr<_Tp, _Dp>&)' 726 | operator==(nullptr_t, const unique_ptr<_Tp, _Dp>& __x) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/unique_ptr.h:726:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: mismatched types 'const std::unique_ptr<_Tp, _Dp>' and 'const int' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:52, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:81, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr_base.h:1412:5: note: candidate: 'template bool std::operator==(const std::__shared_ptr<_Tp1, _Lp>&, const std::__shared_ptr<_Tp2, _Lp>&)' 1412 | operator==(const __shared_ptr<_Tp1, _Lp>& __a, | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr_base.h:1412:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::__shared_ptr<_Tp1, _Lp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:52, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:81, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr_base.h:1418:5: note: candidate: 'template bool std::operator==(const std::__shared_ptr<_Tp, _Lp>&, std::nullptr_t)' 1418 | operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr_base.h:1418:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::__shared_ptr<_Tp, _Lp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:52, from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:81, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr_base.h:1423:5: note: candidate: 'template bool std::operator==(std::nullptr_t, const std::__shared_ptr<_Tp, _Lp>&)' 1423 | operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr_base.h:1423:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: mismatched types 'const std::__shared_ptr<_Tp, _Lp>' and 'const int' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:81, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:383:5: note: candidate: 'template bool std::operator==(const std::shared_ptr<_Tp>&, const std::shared_ptr<_Tp>&)' 383 | operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:383:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::shared_ptr<_Tp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:81, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:388:5: note: candidate: 'template bool std::operator==(const std::shared_ptr<_Tp>&, std::nullptr_t)' 388 | operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:388:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: 'const boost::test_tools::assertion::value_expr&>' is not derived from 'const std::shared_ptr<_Tp>' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~ In file included from /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/memory:81, from /app/boost/include/boost/smart_ptr/detail/sp_counted_impl.hpp:27, from /app/boost/include/boost/smart_ptr/detail/shared_count.hpp:23, from /app/boost/include/boost/smart_ptr/shared_ptr.hpp:17, from /app/boost/include/boost/shared_ptr.hpp:17, from /app/boost/include/boost/test/tools/assertion_result.hpp:21, from /app/boost/include/boost/test/tools/old/impl.hpp:20, from /app/boost/include/boost/test/test_tools.hpp:46, from /app/boost/include/boost/test/unit_test.hpp:18, from :2: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:393:5: note: candidate: 'template bool std::operator==(std::nullptr_t, const std::shared_ptr<_Tp>&)' 393 | operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept | ^~~~~~~~ /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/bits/shared_ptr.h:393:5: note: template argument deduction/substitution failed: In file included from :1: /cefs/22/22e6cdc013c8541ce3d1548e_consolidated/compilers_c++_x86_gcc_9.5.0/include/c++/9.5.0/optional:1103:29: note: mismatched types 'const std::shared_ptr<_Tp>' and 'const int' 1103 | { return __rhs && __lhs == *__rhs; } | ~~~~~~^~~~~~~~~

[mborland]

That is odd, because the only compatibility macros in the pointed to files are for C++11 support. Fortunately it can be worked around with an extra set of parenthesis.

#include <optional>
#include <boost/test/unit_test.hpp>

BOOST_TEST_DONT_PRINT_LOG_VALUE(std::optional<int>)

void foo() {
    std::optional<int> a,b;
    BOOST_TEST((a==b));
}

See: https://godbolt.org/z/oMEWevMbs

[Flamefire]

BOOST_TEST((a==b)); is like BOOST_CHECK(a==b) and looses the printing capabilities.

The interesting diagnostic from GCC:

warning: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:

What I find a bit confusing is this type: boost::test_tools::assertion::binary_expr<boost::test_tools::assertion::value_expr<std::optional<int>&>, int, boost::test_tools::assertion::op::EQ<std::optional<int>, int, void> >
Shouldn't that be EQ<optional,optional>?