Add and parse cpp_auto_type

include/cppast/cpp_type.hpp

@@ -18,6 +18,8 @@ namespace cppast
         builtin,
         user_defined,
 
+        auto_,
+
         cv_qualified,
         pointer,
         reference,
@@ -176,6 +178,25 @@ namespace cppast
         cpp_type_ref entity_;
     };
 
+    /// A [cppast::cpp_type]() that isn't given but deduced by `auto`.
+    class cpp_auto_type final : public cpp_type
+    {
+    public:
+        /// \returns A newly created `auto` type.
+        static std::unique_ptr<cpp_auto_type> build()
+        {
+            return std::unique_ptr<cpp_auto_type>(new cpp_auto_type);
+        }
+
+    private:
+        cpp_auto_type() = default;
+
+        cpp_type_kind do_get_kind() const noexcept override
+        {
+            return cpp_type_kind::auto_;
+        }
+    };
+
     class cpp_template_parameter_type;
     class cpp_template_instantiation_type;
 

src/cpp_type.cpp

@@ -122,6 +122,7 @@ bool cppast::is_valid(const cpp_type& type) noexcept
 
     case cpp_type_kind::builtin:
     case cpp_type_kind::user_defined:
+    case cpp_type_kind::auto_:
     case cpp_type_kind::template_parameter:
     case cpp_type_kind::template_instantiation:
     case cpp_type_kind::unexposed:

src/libclang/type_parser.cpp

@@ -544,9 +544,8 @@ namespace
         case CXType_MemberPointer:
             return cpp_pointer_type::build(parse_member_pointee_type(context, cur, type));
 
-        // TODO: auto/decltype
         case CXType_Auto:
-            break;
+            return make_leave_type(type, [](std::string&&) { return cpp_auto_type::build(); });
         }
 
         DEBUG_UNREACHABLE(detail::assert_handler{});

test/cpp_type_alias.cpp

@@ -31,6 +31,9 @@ bool equal_types(const cpp_entity_index& idx, const cpp_type& parsed, const cpp_
         return equal_ref(idx, user_parsed.entity(), user_synthesized.entity());
     }
 
+    case cpp_type_kind::auto_:
+        return true;
+
     case cpp_type_kind::cv_qualified:
     {
         auto& cv_a = static_cast<const cpp_cv_qualified_type&>(parsed);

test/cpp_variable.cpp

@@ -30,6 +30,10 @@ struct foo {} i;
 const struct bar {} j = bar();
 struct baz {} k{};
 static struct {} l;
+
+// auto
+auto m = 128;
+const auto& n = m;
 )";
 
     cpp_entity_index idx;
@@ -122,10 +126,25 @@ static struct {} l;
         else if (var.name() == "l")
             check_variable(var, *cpp_user_defined_type::build(cpp_type_ref(cpp_entity_id(""), "")),
                            nullptr, cpp_storage_class_static, false, false);
+        else if (var.name() == "m")
+            check_variable(var, *cpp_auto_type::build(),
+                           type_safe::ref(
+                               *cpp_literal_expression::build(cpp_builtin_type::build("int"),
+                                                              "128")),
+                           cpp_storage_class_none, false, false);
+        else if (var.name() == "n")
+            check_variable(var, *cpp_reference_type::
+                                    build(cpp_cv_qualified_type::build(cpp_auto_type::build(),
+                                                                       cpp_cv_const),
+                                          cpp_ref_lvalue),
+                           type_safe::ref(
+                               *cpp_unexposed_expression::build(cpp_builtin_type::build("int"),
+                                                                "m")),
+                           cpp_storage_class_none, false, false);
         else
             REQUIRE(false);
     });
-    REQUIRE(count == 12u);
+    REQUIRE(count == 14u);
 }
 
 TEST_CASE("static cpp_variable")