orin% ocaml
        OCaml version 4.06.0

# module type FOO = sig type foo val foo : foo end;;
module type FOO = sig type foo val foo : foo end
# module Foo : FOO = struct type foo = int let foo = 0 end;;
module Foo : FOO
# Foo.foo = 0;;
Characters 10-11:
  Foo.foo = 0;;
            ^
Error: This expression has type int but an expression was expected of type
         Foo.foo
#