fix package requires order

Signed-off-by: ArthurW <arthur@tarides.com>

Author: art-w

src/dune_rules/lib.ml

@@ -1285,9 +1285,12 @@ end = struct
                "expected Virtual or Parameter"
                [ "implements", to_dyn impl ])
       in
-      List.concat [ requires_implements; requires_params; requires ]
-      |> Set.of_list
-      |> Set.to_list
+      let requires = List.concat [ requires_implements; requires_params; requires ] in
+      let _, requires =
+        List.fold_left requires ~init:(Set.empty, []) ~f:(fun (seen, lst) lib ->
+          if Set.mem seen lib then seen, lst else Set.add seen lib, lib :: lst)
+      in
+      List.rev requires
     in
     let resolve_impl impl_name =
       let open Resolve.Memo.O in

test/blackbox-tests/test-cases/oxcaml/instantiate-parameterised.t

@@ -658,7 +658,7 @@ The `dune-package` should list the different instantiations in the dependencies:
    (archives (byte lib_ab/lib_ab.cma) (native lib_ab/lib_ab.cmxa))
    (plugins (byte lib_ab/lib_ab.cma) (native lib_ab/lib_ab.cmxs))
    (native_archives lib_ab/lib_ab.a)
-   (requires project.a (project.a_of_b) project.b)
+   (requires project.a project.b (project.a_of_b))
    (parameters project.a project.b)
    (main_module_name Lib_ab)
    (modes byte native)
@@ -674,12 +674,12 @@ The `dune-package` should list the different instantiations in the dependencies:
    (plugins (byte lib_apply/lib_apply.cma) (native lib_apply/lib_apply.cmxs))
    (native_archives lib_apply/lib_apply.a)
    (requires
-    project.a_impl
-    (project.a_of_b)
     project.b
-    project.b_impl
+    project.a_impl
     (project.lib_ab project.a_impl)
+    project.b_impl
     (project.lib_ab project.a_impl project.b_impl)
+    (project.a_of_b)
     (project.lib_ab project.a_of_b)
     (project.lib_ab project.a_of_b project.b_impl))
    (parameters project.b)