From 75c67ab5cd6bc0faeede6198943a7bdc02a7deed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonathan=20M=C3=BCller?= <git@foonathan.net>
Date: Sat, 21 Jan 2017 13:15:13 +0100
Subject: [PATCH] Add cpp_namespace_alias

---
 include/cppast/cpp_entity_type.hpp | 15 ++++++++
 include/cppast/cpp_namespace.hpp   | 56 ++++++++++++++++++++++++++++++
 src/cpp_entity_type.cpp            |  1 +
 src/cpp_namespace.cpp              | 11 ++++++
 4 files changed, 83 insertions(+)

diff --git a/include/cppast/cpp_entity_type.hpp b/include/cppast/cpp_entity_type.hpp
index 838624c..34f673f 100644
--- a/include/cppast/cpp_entity_type.hpp
+++ b/include/cppast/cpp_entity_type.hpp
@@ -5,6 +5,8 @@
 #ifndef CPPAST_CPP_ENTITY_TYPE_HPP_INCLUDED
 #define CPPAST_CPP_ENTITY_TYPE_HPP_INCLUDED
 
+#include <cppast/detail/assert.hpp>
+
 namespace cppast
 {
     /// All possible types of C++ entities.
@@ -13,10 +15,23 @@ namespace cppast
         file_t,
 
         namespace_t,
+        namespace_alias_t,
     };
 
     /// \returns Whether or not a given entity type is one derived from [cppast::cpp_scope]().
     bool is_scope(cpp_entity_type type) noexcept;
+
+    /// \exclude
+    namespace detail
+    {
+        template <typename T, typename Org>
+        T downcast_entity(Org& org, cpp_entity_type dest_type) noexcept
+        {
+            DEBUG_ASSERT(org.type() == dest_type, detail::precondition_error_handler{},
+                         "invalid downcast");
+            return static_cast<T>(org);
+        }
+    } // namespace detail
 } // namespace cppast
 
 #endif // CPPAST_CPP_ENTITY_TYPE_HPP_INCLUDED
diff --git a/include/cppast/cpp_namespace.hpp b/include/cppast/cpp_namespace.hpp
index b6e4ba5..af0286b 100644
--- a/include/cppast/cpp_namespace.hpp
+++ b/include/cppast/cpp_namespace.hpp
@@ -60,6 +60,62 @@ namespace cppast
 
         bool inline_;
     };
+
+    /// A reference to a [cppast::cpp_namespace]().
+    class cpp_namespace_ref
+    {
+    public:
+        /// \effects Creates it giving it the target id and name.
+        /// \requires A [cppast::cpp_namespace]() must register in the [cppast::cpp_entity_index]() with that id.
+        cpp_namespace_ref(cpp_entity_id target_id, std::string target_name)
+        : target_(std::move(target_id)), name_(std::move(target_name))
+        {
+        }
+
+        /// \returns The name of the reference, as spelled in the source code.
+        const std::string& name() const noexcept
+        {
+            return name_;
+        }
+
+        /// \returns The [cppast::cpp_namespace]() it refers to.
+        const cpp_namespace& get(const cpp_entity_index& idx) const noexcept;
+
+    private:
+        cpp_entity_id target_;
+        std::string   name_;
+    };
+
+    /// A [cppast::cpp_entity]() modelling a namespace alias.
+    class cpp_namespace_alias final : public cpp_entity
+    {
+    public:
+        static std::unique_ptr<cpp_namespace_alias> build(const cpp_entity_index& idx,
+                                                          cpp_entity_id id, std::string name,
+                                                          cpp_namespace_ref target)
+        {
+            auto ptr = std::unique_ptr<cpp_namespace_alias>(
+                new cpp_namespace_alias(std::move(name), std::move(target)));
+            idx.register_entity(std::move(id), type_safe::ref(*ptr));
+            return ptr;
+        }
+
+        /// \returns The [cppast::cpp_namespace_ref]() to the aliased namespace.
+        const cpp_namespace_ref& target() const noexcept
+        {
+            return target_;
+        }
+
+    private:
+        cpp_namespace_alias(std::string name, cpp_namespace_ref target)
+        : cpp_entity(std::move(name)), target_(std::move(target))
+        {
+        }
+
+        cpp_entity_type do_get_entity_type() const noexcept override;
+
+        cpp_namespace_ref target_;
+    };
 } // namespace cppast
 
 #endif // CPPAST_CPP_NAMESPACE_HPP_INCLUDED
diff --git a/src/cpp_entity_type.cpp b/src/cpp_entity_type.cpp
index b602ad3..b0bef71 100644
--- a/src/cpp_entity_type.cpp
+++ b/src/cpp_entity_type.cpp
@@ -14,6 +14,7 @@ bool cppast::is_scope(cpp_entity_type type) noexcept
         return true;
 
     case cpp_entity_type::file_t:
+    case cpp_entity_type::namespace_alias_t:
         break;
     }
 
diff --git a/src/cpp_namespace.cpp b/src/cpp_namespace.cpp
index bb8e706..0667433 100644
--- a/src/cpp_namespace.cpp
+++ b/src/cpp_namespace.cpp
@@ -12,3 +12,14 @@ cpp_entity_type cpp_namespace::do_get_entity_type() const noexcept
 {
     return cpp_entity_type::namespace_t;
 }
+
+const cpp_namespace& cpp_namespace_ref::get(const cpp_entity_index& idx) const noexcept
+{
+    return detail::downcast_entity<const cpp_namespace&>(idx.lookup(target_).value(),
+                                                         cpp_entity_type::namespace_t);
+}
+
+cpp_entity_type cpp_namespace_alias::do_get_entity_type() const noexcept
+{
+    return cpp_entity_type::namespace_alias_t;
+}