21 Metaprogramming library [meta]

21.4 Reflection [meta.reflection]

21.4.4 Class exception [meta.reflection.exception]

namespace std::meta { class exception : public std::exception { private: optional<string> what_; // exposition only u8string u8what_; // exposition only info from_; // exposition only source_location where_; // exposition only public: consteval exception(u8string_view what, info from, source_location where = source_location::current()) noexcept; consteval exception(string_view what, info from, source_location where = source_location::current()) noexcept; exception(const exception&) = default; exception(exception&&) = default; exception& operator=(const exception&) = default; exception& operator=(exception&&) = default; constexpr const char* what() const noexcept override; consteval u8string_view u8what() const noexcept; consteval info from() const noexcept; consteval source_location where() const noexcept; }; }

Reflection functions throw exceptions of type meta::exception to signal an error.

meta::exception is a consteval-only type.

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consteval exception(u8string_view what, info from,
                    source_location where = source_location::current()) noexcept;

Effects: Initializes u8what_ with what, from_ with from, and where_ with where.

If what can be represented in the ordinary literal encoding, initializes what_ with what, transcoded from UTF-8 to the ordinary literal encoding.

Otherwise, what_ is value-initialized.

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consteval exception(string_view what, info from,
                    source_location where = source_location::current()) noexcept;

Constant When: what designates a sequence of characters that can be encoded in UTF-8.

Effects: Initializes what_ with what, u8what_ with what transcoded from the ordinary literal encoding to UTF-8, from_ with from and where_ with where.

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constexpr const char* what() const noexcept override;

Constant When: what_.has_value() is true.

Returns: what_->c_str().

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consteval u8string_view what() const noexcept;

Returns: u8what_.

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consteval info from() const noexcept;

Returns: from_.

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consteval source_location where() const noexcept;

Returns: where_.