printing of anonymous type parameters after strengthening

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13603 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

4 files changed, 23 insertions, 0 deletions

diff --git a/testsuite/tests/typing-gadts/test.ml b/testsuite/tests/typing-gadts/test.ml
index 3ba7cc8b8..dc219f421 100644
--- a/testsuite/tests/typing-gadts/test.ml
+++ b/testsuite/tests/typing-gadts/test.ml
@@ -512,3 +512,9 @@ let f : type a. a ty -> a =
 let g : type a. a ty -> a =
   let () = () in
   fun x -> match x with Int y -> y;;
+
+(* Printing of anonymous variables *)
+
+module M = struct type _ t = int end;;
+module M = struct type _ t = T : int t end;;
+module N = M;;
diff --git a/testsuite/tests/typing-gadts/test.ml.principal.reference b/testsuite/tests/typing-gadts/test.ml.principal.reference
index 0a59d045f..21f8526d2 100644
--- a/testsuite/tests/typing-gadts/test.ml.principal.reference
+++ b/testsuite/tests/typing-gadts/test.ml.principal.reference
@@ -309,4 +309,7 @@ Error: This expression has type < bar : int; foo : int; .. > as 'a
 #       type 'a ty = Int : int -> int ty
 #     val f : 'a ty -> 'a = <fun>
 #       val g : 'a ty -> 'a = <fun>
+#       module M : sig type _ t = int end
+# module M : sig type _ t = T : int t end
+# module N : sig type 'a t = 'a M.t = T : int t end
 # 
diff --git a/testsuite/tests/typing-gadts/test.ml.reference b/testsuite/tests/typing-gadts/test.ml.reference
index a226a2a49..3b84f9240 100644
--- a/testsuite/tests/typing-gadts/test.ml.reference
+++ b/testsuite/tests/typing-gadts/test.ml.reference
@@ -295,4 +295,7 @@ Error: This expression has type < bar : int; foo : int; .. > as 'a
 #       type 'a ty = Int : int -> int ty
 #     val f : 'a ty -> 'a = <fun>
 #       val g : 'a ty -> 'a = <fun>
+#       module M : sig type _ t = int end
+# module M : sig type _ t = T : int t end
+# module N : sig type 'a t = 'a M.t = T : int t end
 # 
diff --git a/typing/printtyp.ml b/typing/printtyp.ml
index fe94d8fb9..dad5a13c2 100644
--- a/typing/printtyp.ml
+++ b/typing/printtyp.ml
@@ -683,6 +683,17 @@ let rec tree_of_type_decl id decl =
 
   let params = filter_params decl.type_params in
 
+  begin match decl.type_manifest with
+  | Some ty ->
+      let vars = free_variables ty in
+      List.iter
+        (function {desc = Tvar (Some "_")} as ty ->
+            if List.memq ty vars then ty.desc <- Tvar None
+          | _ -> ())
+        params
+  | None -> ()
+  end;
+
   List.iter add_alias params;
   List.iter mark_loops params;
   List.iter check_name_of_type (List.map proxy params);