generalize_expansive: test that we treat missing types as abstract types

testsuite/tests/typing-missing-cmi-2/bar.mli

@@ -0,0 +1 @@
+val foo : unit -> 'a Foo.t

testsuite/tests/typing-missing-cmi-2/baz.ml

@@ -0,0 +1 @@
+let x = Bar.foo ()

testsuite/tests/typing-missing-cmi-2/foo.mli

@@ -0,0 +1 @@
+type 'a t

testsuite/tests/typing-missing-cmi-2/ocamltests

@@ -0,0 +1 @@
+test.ml

testsuite/tests/typing-missing-cmi-2/test.compilers.reference

@@ -0,0 +1 @@
+val x : '_weak1 Foo.t

testsuite/tests/typing-missing-cmi-2/test.ml

@@ -0,0 +1,15 @@
+(* TEST
+files = "foo.mli bar.mli baz.ml"
+* setup-ocamlc.byte-build-env
+** ocamlc.byte
+module = "foo.mli"
+*** ocamlc.byte
+module = "bar.mli"
+**** script
+script = "rm foo.cmi"
+***** ocamlc.byte
+flags = "-c -i"
+module = "baz.ml"
+ocamlc_byte_exit_status = "0"
+****** check-ocamlc.byte-output
+*)

typing/ctype.ml

@@ -795,7 +795,10 @@ let rec generalize_expansive env var_level visited ty =
       Tconstr (path, tyl, abbrev) ->
         let variance =
           try (Env.find_type path env).type_variance
-          with Not_found -> List.map (fun _ -> Variance.may_inv) tyl in
+          with Not_found ->
+            (* See testsuite/tests/typing-missing-cmi-2 for an example *)
+            List.map (fun _ -> Variance.may_inv) tyl
+        in
         abbrev := Mnil;
         List.iter2
           (fun v t ->