Merlin reports incorrect module type (confused with module signature)

[ddickstein]

Tested on 9fc6355

module type Empty = sig end

module Foo = struct
  module type S = Empty

  let x = ()
end

module type Foo = Foo.S

module S : sig
  val f : (module Foo) -> unit
end = struct
  let f (module M : Foo) = ignore M.x
end

This of course does not work - M.x is not available. However, if you try to get the type of Foo on either the val f or let f line, you will see a signature with x, suggesting that it should be available.