if(cast(TypeInfo_Array)typeid(char[]))
      writefln("match");
   if(cast(TypeInfo_Array)typeid(typeof("hi")))
      writefln("match");

Everything's fine so far; it prints match twice. But try this from a variadic function and it's no longer true:

   void foo(...)
   {
      int i;
      for(i = 0; i != _arguments.length; i++)
      {
         if(cast(TypeInfo_Array)_arguments[i])
            writefln("%s matches", i);
   }

   void main()
   {
      foo(42, "hello", cast(char[])"world");
   }

and it does not match. The type of _arguments[1] ends up being TypeInfo_Aa.

The only reason why (typeid(char[]) == _arguments[i]) will work is because the toString() are both "char[]" which is what == on TypeInfo compares.

Solution: typeid(char[]) should be TypeInfo_Aa, and TypeInfo_Aa should derive from TypeInfo_Array. This goes for the other array types as well.