refactor(pkg): make add_impls_to_cache more private (#11270)

Signed-off-by: Rudi Grinberg <[email protected]>

src/0install-solver/solver_core.ml

@@ -168,15 +168,17 @@ module Make (Model : S.SOLVER_INPUT) = struct
     let impl_cache = ImplCache.create () in
     let conflict_classes = Conflict_classes.create sat in
     let+ () =
-      let rec add_impls_to_cache role =
-        let+ clause, impls = make_impl_clause sat ~dummy_impl role in
-        ( clause
-        , fun () ->
-            Fiber.sequential_iter impls ~f:(fun (impl_var, impl) ->
-              Conflict_classes.process conflict_classes impl_var impl;
-              Model.requires role impl |> Fiber.sequential_iter ~f:(process_dep impl_var))
-        )
-      and lookup_impl key = ImplCache.lookup impl_cache add_impls_to_cache key
+      let rec lookup_impl =
+        let add_impls_to_cache role =
+          let+ clause, impls = make_impl_clause sat ~dummy_impl role in
+          ( clause
+          , fun () ->
+              Fiber.sequential_iter impls ~f:(fun (impl_var, impl) ->
+                Conflict_classes.process conflict_classes impl_var impl;
+                Model.requires role impl
+                |> Fiber.sequential_iter ~f:(process_dep impl_var)) )
+        in
+        fun key -> ImplCache.lookup impl_cache add_impls_to_cache key
       and process_dep user_var dep : unit Fiber.t =
         (* Process a dependency of [user_var]:
            - find the candidate implementations to satisfy it