Fix potential bug with caused by delaying the addition of aliases

Author: lthls

middle_end/flambda/types/env/typing_env.rec.ml

@@ -43,16 +43,16 @@ module Cached : sig
     -> Type_grammar.t
     -> Binding_time.t
     -> Name_mode.t
-    -> new_aliases:Aliases.t
     -> t
 
   val replace_variable_binding
      : t
     -> Variable.t
     -> Type_grammar.t
-    -> new_aliases:Aliases.t
     -> t
 
+  val with_aliases : t -> aliases:Aliases.t -> t
+
   val add_symbol_projection : t -> Variable.t -> Symbol_projection.t -> t
 
   val find_symbol_projection : t -> Variable.t -> Symbol_projection.t option
@@ -131,27 +131,30 @@ end = struct
      (used to be add-or-replace), the [names_to_types] map addition was a
      major source of allocation. *)
 
-  let add_or_replace_binding t (name : Name.t) ty binding_time name_mode ~new_aliases =
+  let add_or_replace_binding t (name : Name.t) ty binding_time name_mode =
     let names_to_types =
       Name.Map.add name (ty, binding_time, name_mode) t.names_to_types
     in
     { names_to_types;
-      aliases = new_aliases;
+      aliases = t.aliases;
       symbol_projections = t.symbol_projections;
     }
 
-  let replace_variable_binding t var ty ~new_aliases =
+  let replace_variable_binding t var ty =
     let names_to_types =
       Name.Map.replace (Name.var var)
         (function (_old_ty, binding_time, name_mode) ->
           ty, binding_time, name_mode)
         t.names_to_types
     in
     { names_to_types;
-      aliases = new_aliases;
+      aliases = t.aliases;
       symbol_projections = t.symbol_projections;
     }
 
+  let with_aliases t ~aliases =
+    { t with aliases; }
+
   let add_symbol_projection t var proj =
     let symbol_projections = Variable.Map.add var proj t.symbol_projections in
     { t with symbol_projections; }
@@ -260,6 +263,12 @@ module One_level = struct
   let level t = t.level
   let just_after_level t = t.just_after_level
 
+  let with_aliases t ~aliases =
+    let just_after_level =
+      Cached.with_aliases t.just_after_level ~aliases
+    in
+    { t with just_after_level; }
+
   let is_empty t = Typing_env_level.is_empty t.level
 
 (*
@@ -781,6 +790,12 @@ let with_current_level_and_next_binding_time t ~current_level
   invariant t;
   t
 
+let with_aliases t ~aliases =
+  let current_level =
+    One_level.with_aliases t.current_level ~aliases
+  in
+  with_current_level t ~current_level
+
 let cached t = One_level.just_after_level t.current_level
 
 let add_variable_definition t var kind name_mode =
@@ -810,7 +825,6 @@ let add_variable_definition t var kind name_mode =
     Cached.add_or_replace_binding (cached t)
       name (Type_grammar.unknown kind)
       t.next_binding_time name_mode
-      ~new_aliases:(aliases t)
   in
   let current_level =
     One_level.create (current_scope t) level ~just_after_level
@@ -911,7 +925,7 @@ let invariant_for_new_equation t aliases name ty =
     end
   end
 
-let rec add_equation0 t aliases name ty =
+let rec add_equation0 t name ty =
   if !Clflags.Flambda.Debug.concrete_types_only_on_canonicals then begin
     let is_concrete =
       match Type_grammar.get_alias_exn ty with
@@ -946,20 +960,18 @@ let rec add_equation0 t aliases name ty =
           then
             Cached.replace_variable_binding
               (One_level.just_after_level t.current_level)
-              var ty ~new_aliases:aliases
+              var ty
           else
             Cached.add_or_replace_binding
               (One_level.just_after_level t.current_level)
               name ty Binding_time.imported_variables Name_mode.in_types
-              ~new_aliases:aliases
         in
         just_after_level)
       ~symbol:(fun _ ->
         let just_after_level =
           Cached.add_or_replace_binding
             (One_level.just_after_level t.current_level)
             name ty Binding_time.symbols Name_mode.normal
-            ~new_aliases:aliases
         in
         just_after_level)
   in
@@ -1014,15 +1026,15 @@ and add_equation t name ty =
           end)
         ~const:(fun _ -> ())
   end;
-  let aliases, simple, t, ty =
+  let simple, t, ty =
     let aliases = aliases t in
     match Type_grammar.get_alias_exn ty with
     | exception Not_found ->
       (* Equations giving concrete types may only be added to the canonical
          element as known by the alias tracker (the actual canonical, ignoring
          any name modes). *)
       let canonical = Aliases.get_canonical_ignoring_name_mode aliases name in
-      aliases, canonical, t, ty
+      canonical, t, ty
     | alias_of ->
       let alias_of = Simple.without_coercion alias_of in
       (* Forget where [name] and [alias_of] came from---our job is now to
@@ -1048,12 +1060,13 @@ and add_equation t name ty =
           ~element2:alias_of
           ~binding_time_and_mode2:binding_time_and_mode_alias_of
       in
+      let t = with_aliases t ~aliases in
       (* We need to change the demoted alias's type to point to the new
          canonical element. *)
       let ty =
         Type_grammar.alias_type_of kind canonical_element
       in
-      aliases, alias_of_demoted_element, t, ty
+      alias_of, t, ty
   in
   (* Beware: if we're about to add the equation on a name which is different
      from the one that the caller passed in, then we need to make sure that the