On 8/3/06, Jacques Garrigue <garrigue@math.nagoya-u.ac.jp> wrote:
> type 'a bar_t = Bar of <bar: ('a -> unit) -> unit> ;;
> let create_bar () = Bar (object method bar (_: 'a) = () end);;
> let b = create_bar ();;
> let Bar b = b;;

Okay, that got the types to work out correctly.

> If you still want to use Obj.magic, remember to put complete type
> annotions on both its input and output, as the lack of type
> information may break the compiler.

Surprisingly putting a type annotation on its output caused it to
infer a monomorphic type - I was relying on the type in the module's
signature since the type there is abstract.