Desugar a type to test whether it is primitive or not.

src/AST/TypeExtensions.cs

@@ -10,7 +10,7 @@
 
         public static bool IsPrimitiveType(this Type t, out PrimitiveType primitive)
         {
-            var builtin = t as BuiltinType;
+            var builtin = t.Desugar() as BuiltinType;
             if (builtin != null)
             {
                 primitive = builtin.Type;

tests/Basic/Basic.h

@@ -303,9 +303,12 @@ struct EmptyNamedNestedEnum
     enum { Value = 10 };
 };
 
-
+typedef unsigned long foo_t;
 typedef struct SomeStruct
 {
+	const foo_t& operator[](int i) const { return p[i]; }
+	foo_t& operator[](int i) { return p[i]; }
+	foo_t* p;
 }
 SomeStruct;