diff options
Diffstat (limited to 'nihil.error/error.ccm')
| -rw-r--r-- | nihil.error/error.ccm | 150 |
1 files changed, 85 insertions, 65 deletions
diff --git a/nihil.error/error.ccm b/nihil.error/error.ccm index 7ed9d5c..b821e0a 100644 --- a/nihil.error/error.ccm +++ b/nihil.error/error.ccm @@ -32,87 +32,107 @@ namespace nihil { // Things which can be errors. using error_t = std::variant<std::monostate, std::string, std::error_code, std::error_condition>; -export struct error : std::exception +// A proxy class used when constructing errors. This has implicit constructors from various types, +// which means we don't have to handle every possible combination of types in error itself. +export struct error_proxy { - // Create an empty error, representing success. - error() = default; - - // Destroy an error. - ~error() override = default; + // Construct from... - // Create an error from a freeform string. - explicit error(std::string_view what) + // ... a string_view + error_proxy(std::string_view const what) // NOLINT : m_error(std::string(what)) { } - // Create an error from a freeform string and a cause. - error(std::string_view what, error cause) - : m_error(std::string(what)) - , m_cause(std::make_shared<error>(std::move(cause))) + // ... an std::string; so we can move the string into place if it's an rvalue. + error_proxy(auto &&what) // NOLINT + requires (std::same_as<std::remove_cvref_t<decltype(what)>, std::string>) + : m_error(std::forward<decltype(what)>(what)) { } - // Create an error from a freeform string and an error code enum cause. - template <typename Cause> - requires(std::is_error_code_enum<Cause>::value || - std::is_error_condition_enum<Cause>::value) - error(std::string_view what, Cause &&cause) - : error(what, error(std::forward<Cause>(cause))) + // ... a C string + error_proxy(char const *what) // NOLINT + : m_error(std::string(what)) { } - // Create an error from an std::error_condition. - explicit error(std::error_condition what) + // ... an std::error_code + error_proxy(std::error_code const what) // NOLINT : m_error(what) { } - // Create an error from an std::error_condition and a cause. - error(std::error_condition what, error cause) + // ... an std::error_condition + error_proxy(std::error_condition const what) // NOLINT : m_error(what) - , m_cause(std::make_shared<error>(std::move(cause))) { } - // Create an error from an std::error_code. - explicit error(std::error_code what) - : m_error(what) + // ... an error code enum + template <typename T> + requires(std::is_error_code_enum<T>::value) + error_proxy(T what) // NOLINT + : m_error(make_error_code(what)) { } - // Create an error from an std::error_code and a cause. - error(std::error_code what, error cause) - : m_error(what) - , m_cause(std::make_shared<error>(std::move(cause))) + // ... an error condition enum + template <typename T> + requires(std::is_error_condition_enum<T>::value) + error_proxy(T what) // NOLINT + : m_error(make_error_condition(what)) { } - // Create an error from an std::error_code enum. - explicit error(auto errc) - requires(std::is_error_code_enum<decltype(errc)>::value) - : error(make_error_code(errc)) + // Not copyable. + error_proxy(error_proxy const &) = delete; + auto operator=(error_proxy const &) -> error_proxy & = delete; + + // Not movable. + error_proxy(error_proxy &&) = delete; + auto operator=(error_proxy &&) -> error_proxy & = delete; + + ~error_proxy() = default; + + // Let error extract the error_t. + [[nodiscard]] auto error() && -> error_t && { + return std::move(m_error); } - // Create an error from an std::error_code enum and a cause/ - error(auto errc, error cause) - requires(std::is_error_code_enum<decltype(errc)>::value) - : error(make_error_code(errc), std::move(cause)) +private: + // The error. + error_t m_error; +}; + +// The error class. +export struct error : std::exception +{ + // Create an empty error, representing success. + error() = default; + + // Destroy an error. + ~error() override = default; + + // Create an error from an error proxy. + explicit error(error_proxy &&proxy) + : m_error(std::move(std::move(proxy).error())) { } - // Create an error from an std::error_condition enum. - explicit error(auto errc) - requires(std::is_error_condition_enum<decltype(errc)>::value) - : error(make_error_condition(errc)) + // Create an error from an error proxy and an error cause. + error(error_proxy &&proxy, error cause) + : m_error(std::move(std::move(proxy).error())) + , m_cause(std::make_shared<error>(std::move(cause))) { } - // Create an error from an std::error_condition enum and a cause. - error(auto errc, error cause) - requires(std::is_error_condition_enum<decltype(errc)>::value) - : error(make_error_condition(errc), std::move(cause)) + // Create an error from an error proxy and an error_proxy cause. + // For example, error("cannot open file", std::errc::permission_denied). + error(error_proxy &&proxy, error_proxy &&cause) + : m_error(std::move(std::move(proxy).error())) + , m_cause(std::make_shared<error>(std::move(cause))) { } @@ -178,7 +198,7 @@ export struct error : std::exception [[nodiscard]] auto code(this error const &self) -> std::optional<std::error_code> { auto const *code = std::get_if<std::error_code>(&self.m_error); - if (code) + if (code != nullptr) return {*code}; return {}; } @@ -187,7 +207,7 @@ export struct error : std::exception [[nodiscard]] auto condition(this error const &self) -> std::optional<std::error_condition> { auto const *condition = std::get_if<std::error_condition>(&self.m_error); - if (condition) + if (condition != nullptr) return {*condition}; return {}; } @@ -202,7 +222,7 @@ export struct error : std::exception return m_what->c_str(); } - // Allow error to be implicitly converted to std::expectde and std::unexpected, to make using it + // Allow error to be implicitly converted to std::expected and std::unexpected, to make using it // with std::expected easier. template<typename T> @@ -228,6 +248,16 @@ export struct error : std::exception } private: + // This error. + error_t m_error = make_error_code(std::errc()); + + // The cause of this error, if any. + std::shared_ptr<error> m_cause; + + // For std::exception::what(), we need to keep the string valid + // until we're destroyed. + mutable std::optional<std::string> m_what; + // Equality comparison. [[nodiscard]] friend auto operator==(error const &lhs, error const &rhs) -> bool { @@ -251,22 +281,6 @@ private: return lhs.condition() == rhs; } - // Print an error to a stream. - friend auto operator<<(std::ostream &strm, error const &e) -> std::ostream & - { - return strm << e.full_str(); - } - - // This error. - error_t m_error = make_error_code(std::errc()); - - // The cause of this error, if any. - std::shared_ptr<error> m_cause; - - // For std::exception::what(), we need to keep the string valid - // until we're destroyed. - mutable std::optional<std::string> m_what; - // Compare an error to an std::error_code enum. [[nodiscard]] friend auto operator==(error const &lhs, auto rhs) -> bool requires(std::is_error_code_enum<decltype(rhs)>::value) @@ -280,6 +294,12 @@ private: { return lhs.condition() == rhs; } + + // Print an error to a stream. + friend auto operator<<(std::ostream &strm, error const &e) -> std::ostream & + { + return strm << e.full_str(); + } }; } // namespace nihil |