replace boost optional with mapbox optional

2 files changed, 74 insertions, 15 deletions

diff --git a/include/mbgl/util/optional.hpp b/include/mbgl/util/optional.hpp
new file mode 100644
index 0000000000..133e2c8f97
--- /dev/null
+++ b/include/mbgl/util/optional.hpp
@@ -0,0 +1,69 @@
+#ifndef MAPBOX_UTIL_OPTIONAL_HPP
+#define MAPBOX_UTIL_OPTIONAL_HPP
+
+#include <type_traits>
+
+#include "variant.hpp"
+
+namespace mapbox
+{
+namespace util
+{
+
+template <typename T> class optional
+{
+    static_assert(!std::is_reference<T>::value, "optional doesn't support references");
+
+    struct none_type
+    {
+    };
+
+    variant<none_type, T> variant_;
+
+  public:
+    optional() = default;
+
+    optional(optional const &rhs)
+    {
+        if (this != &rhs)
+        { // protect against invalid self-assignment
+            variant_ = rhs.variant_;
+        }
+    }
+
+    optional(T const &v) { variant_ = v; }
+
+    explicit operator bool() const noexcept { return variant_.template is<T>(); }
+
+    T const &get() const { return variant_.template get<T>(); }
+    T &get() { return variant_.template get<T>(); }
+
+    T const &operator*() const { return this->get(); }
+    T operator*() { return this->get(); }
+
+    optional &operator=(T const &v)
+    {
+        variant_ = v;
+        return *this;
+    }
+
+    optional &operator=(optional const &rhs)
+    {
+        if (this != &rhs)
+        {
+            variant_ = rhs.variant_;
+        }
+        return *this;
+    }
+
+    template <typename... Args> void emplace(Args &&... args)
+    {
+        variant_ = T{std::forward<Args>(args)...};
+    }
+
+    void reset() { variant_ = none_type{}; }
+};
+}
+}
+
+#endif
diff --git a/include/mbgl/util/variant.hpp b/include/mbgl/util/variant.hpp
index 1eca5160c7..3b5659425a 100644
--- a/include/mbgl/util/variant.hpp
+++ b/include/mbgl/util/variant.hpp
@@ -4,7 +4,6 @@
 #include <utility>
 #include <typeinfo>
 #include <type_traits>
-#include <algorithm> // std::move/swap
 #include <stdexcept> // runtime_error
 #include <new> // operator new
 #include <cstddef> // size_t
@@ -515,22 +514,13 @@ public:
     VARIANT_INLINE variant(no_init)
         : type_index(detail::invalid_value) {}
 
+    // http://isocpp.org/blog/2012/11/universal-references-in-c11-scott-meyers
     template <typename T, class = typename std::enable_if<
-                         detail::is_valid_type<T, Types...>::value>::type>
-    VARIANT_INLINE explicit variant(T const& val) noexcept
-        : type_index(detail::value_traits<T, Types...>::index)
-    {
-        constexpr std::size_t index = sizeof...(Types) - detail::value_traits<T, Types...>::index - 1;
-        using target_type = typename detail::select_type<index, Types...>::type;
-        new (&data) target_type(val);
-    }
-
-    template <typename T, class = typename std::enable_if<
-                          detail::is_valid_type<T, Types...>::value>::type>
+                          detail::is_valid_type<typename std::remove_reference<T>::type, Types...>::value>::type>
     VARIANT_INLINE variant(T && val) noexcept
-        : type_index(detail::value_traits<T, Types...>::index)
+        : type_index(detail::value_traits<typename std::remove_reference<T>::type, Types...>::index)
     {
-        constexpr std::size_t index = sizeof...(Types) - detail::value_traits<T, Types...>::index - 1;
+        constexpr std::size_t index = sizeof...(Types) - detail::value_traits<typename std::remove_reference<T>::type, Types...>::index - 1;
         using target_type = typename detail::select_type<index, Types...>::type;
         new (&data) target_type(std::forward<T>(val)); // nothrow
     }
@@ -565,7 +555,7 @@ public:
     template <typename T>
     VARIANT_INLINE variant<Types...>& operator=(T && rhs) noexcept
     {
-        variant<Types...> temp(std::move(rhs));
+        variant<Types...> temp(std::forward<T>(rhs));
         swap(*this, temp);
         return *this;
     }