Type from local module would escape its scope?

[Bruno De Fraine <Bruno.De.Fraine@vub.ac.be>]

Hello list,

I don't quite understand this behavior regarding local modules (in  
OCaml 3.09.2):

The following is accepted:

module type FOO =
sig
   type t
   val value : t
end ;;

let foo () =
   let module Foo : FOO =
   struct
     type t = int
     let value = 1
   end in
   ignore Foo.value
;;

While the following is rejected:

let foo (ignore: 'a -> unit) =
   let module Foo : FOO =
   struct
     type t = int
     let value = 1
   end in
   ignore Foo.value
;;

With an error on the expression "Foo.value" stating that "The type  
constructor Foo.t would escape its scope". Reading about the typical  
case for this error message in http://caml.inria.fr/pub/ml-archives/ 
caml-list/2002/10/0cf087feab3ef8dc5ccba5a8592472fb.en.html didn't  
really help me. Why does it make a difference whether ignore is an  
argument?

Thanks,
Bruno