split storage from value

also, quit inheritance in storage class

toml/storage.hpp

@@ -0,0 +1,42 @@
+#ifndef TOML11_STORAGE_HPP
+#define TOML11_STORAGE_HPP
+#include "utility.hpp"
+
+namespace toml
+{
+namespace detail
+{
+
+// this contains pointer and deep-copy the content if copied.
+// to avoid recursive pointer.
+template<typename T>
+struct storage
+{
+    using value_type = T;
+
+    storage(value_type const& v): ptr(toml::make_unique<T>(v)) {}
+    storage(value_type&&      v): ptr(toml::make_unique<T>(std::move(v))) {}
+    ~storage() = default;
+
+    storage(const storage& rhs): ptr(toml::make_unique<T>(*rhs.ptr)) {}
+    storage& operator=(const storage& rhs)
+    {
+        this->ptr = toml::make_unique<T>(*rhs.ptr);
+        return *this;
+    }
+    storage(storage&&) = default;
+    storage& operator=(storage&&) = default;
+
+    bool is_ok() const noexcept {return static_cast<bool>(ptr);}
+
+    value_type&       value() &      noexcept {return *ptr;}
+    value_type const& value() const& noexcept {return *ptr;}
+    value_type&&      value() &&     noexcept {return std::move(*ptr);}
+
+  private:
+    std::unique_ptr<value_type> ptr;
+};
+
+} // detail
+} // toml
+#endif// TOML11_STORAGE_HPP

toml/value.hpp

@@ -3,6 +3,8 @@
 #include "traits.hpp"
 #include "utility.hpp"
 #include "exception.hpp"
+#include "storage.hpp"
+#include "region.hpp"
 #include "types.hpp"
 #include <vector>
 #include <tuple>
@@ -13,38 +15,6 @@
 namespace toml
 {
 
-namespace detail
-{
-struct storage_base
-{
-    storage_base(): type(toml::value_t::Empty){}
-    storage_base(toml::value_t t): type(t){}
-    virtual ~storage_base() = default;
-    toml::value_t type;
-};
-
-template<typename T>
-struct storage : public storage_base
-{
-    static_assert(std::is_same<T, toml::Array>::value ||
-                  std::is_same<T, toml::Table>::value,
-                  "toml::detail::storage is for toml::Array or toml::Table!");
-    typedef T value_type;
-
-    storage() = default;
-    ~storage() noexcept override = default;
-    storage(storage const&) = default;
-    storage(storage&&)      = default;
-    storage& operator=(storage const&) = default;
-    storage& operator=(storage&&)      = default;
-
-    storage(value_type const& v) : value(v){}
-    storage(value_type&& v) : value(std::move(v)){}
-
-    value_type value;
-};
-} // detail
-
 template<typename T>
 struct value_traits
 {