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Telegram/lib_base/base/required.h

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+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#pragma once
+
+namespace base {
+
+template <typename T>
+struct required {
+	template <
+		typename U,
+		typename = std::enable_if_t<std::is_constructible_v<T, U&&>>>
+	constexpr required(U &&value) noexcept : _value(std::forward<U>(value)) {
+	}
+	template <
+		typename U,
+		typename = std::enable_if_t<std::is_assignable_v<T, U&&>>>
+	constexpr required &operator=(U &&value) noexcept {
+		_value = std::forward<U>(value);
+		return *this;
+	}
+	constexpr required(required &&) = default;
+	constexpr required(const required &) = default;
+	constexpr required &operator=(required &&) = default;
+	constexpr required &operator=(const required &) = default;
+
+	[[nodiscard]] constexpr T &operator*() noexcept {
+		return _value;
+	}
+	[[nodiscard]] constexpr const T &operator*() const noexcept {
+		return _value;
+	}
+	[[nodiscard]] constexpr T &value() noexcept {
+		return _value;
+	}
+	[[nodiscard]] constexpr const T &value() const noexcept {
+		return _value;
+	}
+	[[nodiscard]] constexpr T *operator->() noexcept {
+		return &_value;
+	}
+	[[nodiscard]] constexpr const T *operator->() const noexcept {
+		return &_value;
+	}
+	[[nodiscard]] constexpr T *get() noexcept {
+		return &_value;
+	}
+	[[nodiscard]] constexpr const T *get() const noexcept {
+		return &_value;
+	}
+	[[nodiscard]] operator T&() noexcept {
+		return _value;
+	}
+	[[nodiscard]] operator const T&() const noexcept {
+		return _value;
+	}
+
+private:
+	T _value;
+
+};
+
+} // namespace base