Add and parse cpp_decltype_type

include/cppast/cpp_decltype_type.hpp

@@ -0,0 +1,62 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#ifndef CPPAST_CPP_DECLTYPE_TYPE_HPP_INCLUDED
+#define CPPAST_CPP_DECLTYPE_TYPE_HPP_INCLUDED
+
+#include <cppast/cpp_expression.hpp>
+#include <cppast/cpp_type.hpp>
+
+namespace cppast
+{
+    /// A [cppast::cpp_type]() that isn't given but taken from an expression.
+    class cpp_decltype_type final : public cpp_type
+    {
+    public:
+        /// \returns A newly created `decltype` type.
+        static std::unique_ptr<cpp_decltype_type> build(std::unique_ptr<cpp_expression> expr)
+        {
+            return std::unique_ptr<cpp_decltype_type>(new cpp_decltype_type(std::move(expr)));
+        }
+
+        /// \returns A reference to the expression given.
+        const cpp_expression& expression() const noexcept
+        {
+            return *expr_;
+        }
+
+    private:
+        cpp_decltype_type(std::unique_ptr<cpp_expression> expr) : expr_(std::move(expr))
+        {
+        }
+
+        cpp_type_kind do_get_kind() const noexcept override
+        {
+            return cpp_type_kind::decltype_;
+        }
+
+        std::unique_ptr<cpp_expression> expr_;
+    };
+
+    /// A [cppast::cpp_type]() that isn't given but deduced using the `decltype` rules.
+    class cpp_decltype_auto_type final : public cpp_type
+    {
+    public:
+        /// \returns A newly created `auto` type.
+        static std::unique_ptr<cpp_decltype_auto_type> build()
+        {
+            return std::unique_ptr<cpp_decltype_auto_type>(new cpp_decltype_auto_type);
+        }
+
+    private:
+        cpp_decltype_auto_type() = default;
+
+        cpp_type_kind do_get_kind() const noexcept override
+        {
+            return cpp_type_kind::decltype_auto;
+        }
+    };
+} // namespace cppast
+
+#endif // CPPAST_CPP_DECLTYPE_TYPE_HPP_INCLUDED

include/cppast/cpp_type.hpp

@@ -19,6 +19,8 @@ namespace cppast
         user_defined,
 
         auto_,
+        decltype_,
+        decltype_auto,
 
         cv_qualified,
         pointer,