Add cpp_using_directive

include/cppast/cpp_entity_type.hpp

@@ -16,6 +16,7 @@ namespace cppast
 
         namespace_t,
         namespace_alias_t,
+        using_directive_t,
     };
 
     /// \returns Whether or not a given entity type is one derived from [cppast::cpp_scope]().

include/cppast/cpp_namespace.hpp

@@ -78,6 +78,12 @@ namespace cppast
             return name_;
         }
 
+        /// \returns The [cppast::cpp_entity_id]() of the namespace it refers to.
+        const cpp_entity_id& id() const noexcept
+        {
+            return target_;
+        }
+
         /// \returns The [cppast::cpp_namespace]() it refers to.
         const cpp_namespace& get(const cpp_entity_index& idx) const noexcept;
 
@@ -90,6 +96,7 @@ namespace cppast
     class cpp_namespace_alias final : public cpp_entity
     {
     public:
+        /// \returns A newly created and registered namespace alias.
         static std::unique_ptr<cpp_namespace_alias> build(const cpp_entity_index& idx,
                                                           cpp_entity_id id, std::string name,
                                                           cpp_namespace_ref target)
@@ -116,6 +123,38 @@ namespace cppast
 
         cpp_namespace_ref target_;
     };
+
+    /// A [cppast::cpp_entity]() modelling a using directive.
+    ///
+    /// A using directive is `using namespace std`, for example.
+    class cpp_using_directive final : public cpp_entity
+    {
+    public:
+        /// \returns A newly created using directive.
+        /// \notes It is not meant to be registered at the [cppast::cpp_entity_index](),
+        /// as nothing can refer to it.
+        static std::unique_ptr<cpp_using_directive> build(const cpp_namespace_ref& target)
+        {
+            return std::unique_ptr<cpp_using_directive>(new cpp_using_directive(target));
+        }
+
+        /// \returns The [cppast::cpp_namespace_ref]() that is exposed.
+        /// \notes The name of the reference is the same as the name of this entity.
+        cpp_namespace_ref target() const
+        {
+            return {target_, name()};
+        }
+
+    private:
+        cpp_using_directive(const cpp_namespace_ref& target)
+        : cpp_entity(target.name()), target_(target.id())
+        {
+        }
+
+        cpp_entity_type do_get_entity_type() const noexcept override;
+
+        cpp_entity_id target_;
+    };
 } // namespace cppast
 
 #endif // CPPAST_CPP_NAMESPACE_HPP_INCLUDED

src/cpp_entity_type.cpp

@@ -15,6 +15,7 @@ bool cppast::is_scope(cpp_entity_type type) noexcept
 
     case cpp_entity_type::file_t:
     case cpp_entity_type::namespace_alias_t:
+    case cpp_entity_type::using_directive_t:
         break;
     }
 

src/cpp_namespace.cpp

@@ -23,3 +23,8 @@ cpp_entity_type cpp_namespace_alias::do_get_entity_type() const noexcept
 {
     return cpp_entity_type::namespace_alias_t;
 }
+
+cpp_entity_type cpp_using_directive::do_get_entity_type() const noexcept
+{
+    return cpp_entity_type::using_directive_t;
+}