Fix #9695: no error when opening an alias to a missing module

Changes

@@ -712,6 +712,9 @@ OCaml 4.11
   (Gabriel Scherer, review by Jacques Garrigue and Leo White,
    report by Hugo Heuzard)
 
+- #9695: no error when opening an alias to a missing module
+  (Jacques Garrigue, report by Gabriel Scherer)
+
 OCaml 4.10 maintenance branch
 -----------------------------
 

testsuite/tests/typing-modules-bugs/pr9695_bad.compilers.reference

@@ -0,0 +1,4 @@
+File "pr9695_bad.ml", line 10, characters 18-19:
+10 | let () = let open A in x
+                       ^
+Error: This is an alias for module MissingModule, which is missing

testsuite/tests/typing-modules-bugs/pr9695_bad.ml

@@ -0,0 +1,10 @@
+(* TEST
+flags = " -w a -no-alias-deps"
+ocamlc_byte_exit_status = "2"
+* setup-ocamlc.byte-build-env
+** ocamlc.byte
+*** check-ocamlc.byte-output
+*)
+
+module A = MissingModule
+let () = let open A in x

typing/env.ml

@@ -2002,9 +2002,10 @@ let add_components slot root env0 comps =
   }
 
 let open_signature slot root env0 =
-  match get_components (find_module_components root env0) with
-  | Functor_comps _ -> None
-  | Structure_comps comps ->
+  match get_components_res (find_module_components root env0) with
+  | Error _
+  | Ok (Functor_comps _) -> None
+  | Ok (Structure_comps comps) ->
     Some (add_components slot root env0 comps)