Hmm... Seems to work even for the more obscure cases:

typeof(class{});

(4) Result: function( : object(is HilfeInput()->__class_65709_0_line_1))

typeof(Stdio.Stat());

(5) Result: object(is _static_modules.files()->Stat)

Note that it will fall back to the old syntax if it fails to look up the program id:

_typeof(compile_string(""));

(6) Result: function( : object(is 65723))

mixed x = compile_string(""); _typeof(x);

(7) Result: function( : object(is -))