Add FieldAccessor alias at the namespace level

FieldAccessor alias of the base class cannot be accessed from a class
template

Author: Manu343726

include/jinja2cpp/reflected_value.h

@@ -20,10 +20,13 @@ struct TypeReflectedImpl : std::integral_constant<bool, val>
 {
 };
 
+template<typename T>
+using FieldAccessor = std::function<Value(const T&)>;
+
 template<typename T>
 struct TypeReflected : TypeReflectedImpl<T, true>
 {
-    using FieldAccessor = std::function<Value (const T& value)>;
+    using FieldAccessor = jinja2::FieldAccessor<T>;
 };