Fix ident collision in includemod

Changes

@@ -275,6 +275,9 @@ Working version
   rather than a basename.
   (David Allsopp, report by Fabian @copy, review by Gabriel Scherer)
 
+- #10693: Fix ident collision in includemod
+  (Leo White, review by Matthew Ryan)
+
 OCaml 4.13 maintenance branch
 -----------------------------
 

testsuite/tests/typing-modules-bugs/pr10693_bad.compilers.reference

@@ -0,0 +1,55 @@
+File "pr10693_bad.ml", line 27, characters 26-27:
+27 | module Bad (A : S') : S = A
+                               ^
+Error: Signature mismatch:
+       Modules do not match:
+         sig val x : 'a option module M : Dep -> S end
+       is not included in
+         S
+       In module M:
+       Modules do not match:
+         Dep -> S
+       is not included in
+         functor (X : Dep) ->
+           sig
+             val x : X.t option
+             module M : functor (Y : Dep) -> sig val x : X.t option end
+           end
+       In module M:
+       Modules do not match:
+         S
+       is not included in
+         sig
+           val x : X.t option
+           module M : functor (Y : Dep) -> sig val x : X.t option end
+         end
+       In module M.M:
+       Modules do not match:
+         functor (X : Dep) ->
+           sig
+             val x : X.t option
+             module M : functor (Y : Dep) -> sig val x : X.t option end
+           end
+       is not included in
+         functor (Y : Dep) -> sig val x : X.t option end
+       In module M.M:
+       Modules do not match:
+         sig
+           val x : X/2.t option
+           module M : functor (Y : Dep) -> sig val x : X/2.t option end
+         end
+       is not included in
+         sig val x : X.t option end
+       In module M.M:
+       Values do not match:
+         val x : X/1.t option
+       is not included in
+         val x : X/2.t option
+       The type X/1.t option is not compatible with the type X/2.t option
+       Type X/1.t is not compatible with type X/2.t 
+       File "_none_", line 1:
+         Definition of module X/1
+       File "_none_", line 1:
+         Definition of module X/2
+       File "pr10693_bad.ml", line 17, characters 6-24: Expected declaration
+       File "pr10693_bad.ml", line 15, characters 4-22: Actual declaration

testsuite/tests/typing-modules-bugs/pr10693_bad.ml

@@ -0,0 +1,46 @@
+(* TEST
+flags = "-no-app-funct"
+ocamlc_byte_exit_status = "2"
+* setup-ocamlc.byte-build-env
+** ocamlc.byte
+*** check-ocamlc.byte-output
+*)
+module type Dep = sig type t val x : t end
+module String = struct type t = string let x = "Forty Two" end
+module Int = struct type t = int let x = 42 end
+
+module type S = sig
+  val x : 'a option
+  module M : functor (X : Dep) -> sig
+    val x : X.t option
+    module M : functor (Y : Dep) -> sig
+      val x : X.t option
+    end
+  end
+end
+
+module type S' = sig
+  val x : 'a option
+  module M : functor (_ : Dep) -> S
+end
+
+module Bad (A : S') : S = A
+
+module M = struct
+  let x = None
+  module M (_ : Dep) = struct
+    let x = None
+    module M (X : Dep) = struct
+      let x = Some X.x
+      module M (Y : Dep) = struct
+        let x = Some X.x
+      end
+    end
+  end
+end
+
+module N = Bad(M)
+module N' = N.M(String)
+module N'' = N'.M(Int)
+
+let () = print_endline (Option.get N''.x)

typing/includemod.ml

@@ -496,7 +496,9 @@ and functor_param ~in_eq ~loc env ~mark subst param1 param2 =
             Env.add_module id1 Mp_present arg2' env,
             Subst.add_module id2 (Path.Pident id1) subst
         | None, Some id2 ->
-            Env.add_module id2 Mp_present arg2' env, subst
+            let id1 = Ident.rename id2 in
+            Env.add_module id1 Mp_present arg2' env,
+            Subst.add_module id2 (Path.Pident id1) subst
         | Some id1, None ->
             Env.add_module id1 Mp_present arg2' env, subst
         | None, None ->