This seems like a thorny issue. How does the patch handle the following?

    # let rec r = (let rec x = `A r and y = fun () -> x in y);;
    val r : unit -> [> `A of 'a ] as 'a = <fun>
    # let (`A x) = r () in x ();;
    Segmentation fault

Note that in this example, the right-hand sides of each equation are more sensible, since no value is eliminated during its definition (the suspicious 'y ()' from the original test case has been removed).

(The polymorphic variant `A is used to allow recursive types, you can also try this example using plain variants and -rectypes.) 

(ocaml/ocaml#7231#c15819)