Rework optional<T>

1 files changed, 76 insertions, 3 deletions

diff --git a/toolsrc/include/vcpkg_optional.h b/toolsrc/include/vcpkg_optional.h
index 7b935bea9..745377a82 100644
--- a/toolsrc/include/vcpkg_optional.h
+++ b/toolsrc/include/vcpkg_optional.h
@@ -1,5 +1,78 @@
 #pragma once
-#include <memory>
+#include "LineInfo.h"
+#include "vcpkg_Checks.h"
 
-template<class T>
-using optional = std::unique_ptr<T>;
+namespace vcpkg
+{
+    struct nullopt_t
+    {
+        explicit constexpr nullopt_t(int) {}
+    };
+
+    const static constexpr nullopt_t nullopt{ 0 };
+
+    template <class T>
+    class optional
+    {
+    public:
+        // Constructors are intentionally implicit
+        constexpr optional(nullopt_t) : m_is_present(false), m_t() { }
+
+        optional(const T& t) : m_is_present(true), m_t(t) { }
+
+        optional(T&& t) : m_is_present(true), m_t(std::move(t)) { }
+
+        T&& get_or_exit(const LineInfo& line_info) &&
+        {
+            this->exit_if_null(line_info);
+            return std::move(this->m_t);
+        }
+
+        const T& get_or_exit(const LineInfo& line_info) const &
+        {
+            this->exit_if_null(line_info);
+            return this->m_t;
+        }
+
+        constexpr explicit operator bool() const
+        {
+            return this->m_is_present;
+        }
+
+        constexpr bool has_value() const
+        {
+            return m_is_present;
+        }
+
+        template <class U>
+        T value_or(U&& default_value) const &
+        {
+            return bool(*this) ? this->m_t : static_cast<T>(std::forward<U>(default_value));
+        }
+
+        template <class U>
+        T value_or(U&& default_value) &&
+        {
+            return bool(*this) ? std::move(this->m_t) : static_cast<T>(std::forward<U>(default_value));
+        }
+
+        const T* get() const
+        {
+            return bool(*this) ? &this->m_t : nullptr;
+        }
+
+        T* get()
+        {
+            return bool(*this) ? &this->m_t : nullptr;
+        }
+
+    private:
+        void exit_if_null(const LineInfo& line_info) const
+        {
+            Checks::check_exit(line_info, this->m_is_present, "Value was null");
+        }
+
+        bool m_is_present;
+        T m_t;
+    };
+}