add a known-bug test for buggy 'rec' (non)use in the #show command

testsuite/tests/tool-toplevel/known-bugs/broken_rec_in_show.ml

@@ -0,0 +1,47 @@
+(* TEST
+   * expect
+*)
+
+(* This is a known-bug file for use of 'rec' by the '#show' command,
+   to record known regressions from #7453 and #9094 *)
+
+type t = T of t;;
+[%%expect{|
+type t = T of t
+|}]
+#show t;;
+(* this output is CORRECT, it does not use nonrec *)
+[%%expect{|
+type t = T of t
+|}];;
+
+type nonrec t = Foo of t;;
+[%%expect{|
+type nonrec t = Foo of t
+|}];;
+#show t;;
+(* this output in INCORRECT, it should use nonrec *)
+[%%expect{|
+type t = Foo of t
+|}];;
+
+
+
+module M : sig type t val x : t end = struct type t = int let x = 0 end;;
+[%%expect{|
+module M : sig type t val x : t end
+|}];;
+(* this output is CORRECT, it does not use 'rec' *)
+[%%expect{|
+|}];;
+
+module rec M : sig type t val x : M.t end = struct type t = int let x = 0 end;;
+(* this output is strange, it is surprising to use M/2 here. *)
+[%%expect{|
+module rec M : sig type t val x : M/2.t end
+|}];;
+#show_module M;;
+(* this output is INCORRECT, it should use 'rec' *)
+[%%expect{|
+module M : sig type t val x : M.t end
+|}];;