22 General utilities library [utilities]

22.8 Expected objects [expected]

22.8.4 Class template bad_expected_access [expected.bad]

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namespace std { template<class E> class bad_expected_access : public bad_expected_access<void> { public: constexpr explicit bad_expected_access(E); constexpr const char* what() const noexcept override; constexpr E& error() & noexcept; constexpr const E& error() const & noexcept; constexpr E&& error() && noexcept; constexpr const E&& error() const && noexcept; private: E unex; // exposition only }; }
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The class template bad_expected_access defines the type of objects thrown as exceptions to report the situation where an attempt is made to access the value of an expected<T, E> object for which has_value() is false.
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constexpr explicit bad_expected_access(E e);
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Effects: Initializes unex with std​::​move(e).
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constexpr const E& error() const & noexcept; constexpr E& error() & noexcept;
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Returns: unex.
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constexpr E&& error() && noexcept; constexpr const E&& error() const && noexcept;
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Returns: std​::​move(unex).
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constexpr const char* what() const noexcept override;
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Returns: An implementation-defined ntbs, which during constant evaluation is encoded with the ordinary literal encoding ([lex.ccon]).