Author
anonymous
about 4 years ago
Language
C++
Compiler
clang HEAD 13.0.0 (https://github.com/llvm/llvm-project.git 6f3d322f250d2381370b256e648cbb76c6de0135)
Options
Warnings
Boost 1.73.0
C++2b(GNU)
no pedantic
Author
anonymous
about 4 years ago
$ clang++ prog.cc -Wall -Wextra -I/opt/wandbox/boost-1.73.0/clang-head/include -std=gnu++2b prog.cc:13:39: error: no viable conversion from 'reference_wrapper<int>' to 'reference_wrapper<const int>'
std::reference_wrapper<const int> constRef = ref;
^ ~~~
/opt/wandbox/clang-head/include/c++/v1/__functional_base:374:28: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'std::reference_wrapper<int>' to 'const std::reference_wrapper<const int> &' for 1st argument
class _LIBCPP_TEMPLATE_VIS reference_wrapper
^
/opt/wandbox/clang-head/include/c++/v1/__functional_base:374:28: note: candidate constructor (the implicit move constructor) not viable: no known conversion from 'std::reference_wrapper<int>' to 'std::reference_wrapper<const int> &&' for 1st argument
/opt/wandbox/clang-head/include/c++/v1/__functional_base:386:5: note: candidate constructor not viable: no known conversion from 'std::reference_wrapper<int>' to 'std::reference_wrapper<const int>::type &' (aka 'const int &') for 1st argument
reference_wrapper(type& __f) _NOEXCEPT
^
/opt/wandbox/clang-head/include/c++/v1/__functional_base:389:14: note: candidate constructor not viable: no known conversion from 'std::reference_wrapper<int>' to 'std::reference_wrapper<const int>::type &&' (aka 'const int &&') for 1st argument
private: reference_wrapper(type&&); public: // = delete; // do not bind to temps
^
/opt/wandbox/clang-head/include/c++/v1/__functional_base:394:5: note: candidate function
operator type&() const _NOEXCEPT {return *__f_;}
^
prog.cc:16:54: error: no viable conversion from 'optional<reference_wrapper<int>>' to 'optional<reference_wrapper<const int>>'
std::optional<std::reference_wrapper<const int>> optConstRef = optRef;
^ ~~~~~~
/opt/wandbox/clang-head/include/c++/v1/optional:689:41: note: candidate constructor not viable: no known conversion from 'std::optional<std::reference_wrapper<int>>' to 'const std::optional<std::reference_wrapper<const int>> &' for 1st argument
_LIBCPP_INLINE_VISIBILITY constexpr optional(const optional&) = default;
^
/opt/wandbox/clang-head/include/c++/v1/optional:690:41: note: candidate constructor not viable: no known conversion from 'std::optional<std::reference_wrapper<int>>' to 'std::optional<std::reference_wrapper<const int>> &&' for 1st argument
_LIBCPP_INLINE_VISIBILITY constexpr optional(optional&&) = default;
^
/opt/wandbox/clang-head/include/c++/v1/optional:691:41: note: candidate constructor not viable: no known conversion from 'std::optional<std::reference_wrapper<int>>' to 'std::nullopt_t' for 1st argument
_LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
^
/opt/wandbox/clang-head/include/c++/v1/optional:715:15: note: candidate template ignored: substitution failure [with _Up = std::optional<std::reference_wrapper<int>> &]: no member named '_EnableIfImpl' in 'std::_MetaBase<false>'
constexpr optional(_Up&& __v)
^
/opt/wandbox/clang-head/include/c++/v1/optional:730:5: note: candidate template ignored: substitution failure [with _Up = std::reference_wrapper<int>]: no member named '_EnableIfImpl' in 'std::_MetaBase<false>'
optional(const optional<_Up>& __v)
^
/opt/wandbox/clang-head/include/c++/v1/optional:748:5: note: candidate template ignored: substitution failure [with _Up = std::reference_wrapper<int>]: no member named '_EnableIfImpl' in 'std::_MetaBase<false>'
optional(optional<_Up>&& __v)
^
/opt/wandbox/clang-head/include/c++/v1/optional:701:24: note: explicit constructor is not a candidate
constexpr explicit optional(_InPlaceT, _Args&&... __args)
^
/opt/wandbox/clang-head/include/c++/v1/optional:722:24: note: explicit constructor is not a candidate
constexpr explicit optional(_Up&& __v)
^
/opt/wandbox/clang-head/include/c++/v1/optional:738:14: note: explicit constructor is not a candidate
explicit optional(const optional<_Up>& __v)
^
/opt/wandbox/clang-head/include/c++/v1/optional:756:14: note: explicit constructor is not a candidate
explicit optional(optional<_Up>&& __v)
^
2 errors generated.
Exit Code:
1