Thread full descr through fun_denormalize reduce

lib/elixir/lib/module/types/descr.ex

@@ -1929,25 +1929,33 @@ defmodule Module.Types.Descr do
   # representation. The goal here is to do the opposite of fun_descr
   # and put static and dynamic parts back together to improve
   # pretty printing.
-  defp fun_denormalize(%{fun: {:union, static_repr}}, %{fun: {:union, dynamic_repr}}, opts) do
-    # Denormalize each arity
-    for {arity, static_bdd} <- static_repr,
-        {^arity, dynamic_bdd} <- dynamic_repr,
-        reduce: {static_repr, dynamic_repr, []} do
-      {statics, dynamics, acc} ->
-        with {:ok, quoted} <- fun_denormalize_arity(arity, static_bdd, dynamic_bdd, opts) do
-          {Map.delete(statics, arity), Map.delete(dynamics, arity), [quoted | acc]}
-        else
-          _ -> {statics, dynamics, acc}
-        end
-    end
+  defp fun_denormalize(
+         %{fun: {:union, static_repr}} = static,
+         %{fun: {:union, dynamic_repr}} = dynamic,
+         opts
+       ) do
+    {static_repr, dynamic_repr, acc} =
+      Enum.reduce(static_repr, {static_repr, dynamic_repr, []}, fn
+        {arity, static_bdd}, {statics, dynamics, acc} ->
+          with %{^arity => dynamic_bdd} <- dynamics,
+               {:ok, quoted} <- fun_denormalize_arity(arity, static_bdd, dynamic_bdd, opts) do
+            {Map.delete(statics, arity), Map.delete(dynamics, arity), [quoted | acc]}
+          else
+            _ -> {statics, dynamics, acc}
+          end
+      end)
+
+    {fun_replace_arities(static, static_repr), fun_replace_arities(dynamic, dynamic_repr), acc}
   end
 
   # If not unions of functions, do not try to denormalize.
-  defp fun_denormalize(static_repr, dynamic_repr, _opts) do
-    {static_repr, dynamic_repr, []}
+  defp fun_denormalize(static, dynamic, _opts) do
+    {static, dynamic, []}
   end
 
+  defp fun_replace_arities(descr, arities) when arities == %{}, do: Map.delete(descr, :fun)
+  defp fun_replace_arities(descr, arities), do: %{descr | fun: {:union, arities}}
+
   defp fun_denormalize_arity(arity, static_bdd, dynamic_bdd, opts) do
     static_pos = fun_bdd_to_pos_dnf(arity, static_bdd)
     dynamic_pos = fun_bdd_to_pos_dnf(arity, dynamic_bdd)

lib/elixir/test/elixir/module/types/descr_test.exs

@@ -3689,6 +3689,34 @@ defmodule Module.Types.DescrTest do
                """
     end
 
+    test "fun union of static and dynamic keeps non-fun components" do
+      # Denormalizing a static/dynamic fun union must not drop the other parts of
+      # the type, nor crash when an arity fails to denormalize.
+
+      # (a) must not raise when denormalization fails for an arity
+      assert opt_difference(fun([term()], atom()), fun([integer()], dynamic(atom())))
+             |> to_quoted_string() ==
+               "dynamic((term() -> atom()) and (integer() -> atom()))"
+
+      # (b) non-fun components must be preserved alongside the denormalized fun
+      assert opt_union(
+               integer(),
+               opt_union(fun([integer()], atom()), dynamic(fun([integer()], atom())))
+             )
+             |> to_quoted_string() == "(integer() -> atom()) or integer()"
+
+      # several components, with a leftover non-denormalized dynamic arity
+      assert opt_union(
+               atom([:tag]),
+               opt_union(
+                 fun([integer()], atom()),
+                 dynamic(opt_union(fun([integer()], atom()), fun([integer(), integer()], atom())))
+               )
+             )
+             |> to_quoted_string() ==
+               "dynamic((integer(), integer() -> atom())) or :tag or (integer() -> atom())"
+    end
+
     test "fun (negation)" do
       assert fun([integer()], atom()) |> opt_negation() |> to_quoted_string() ==
                "not (integer() -> atom())"