Do not skip dynamic for indivisible types inside functions

Author: josevalim

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

@@ -1618,6 +1618,8 @@ defmodule Module.Types.Descr do
   end
 
   defp fun_pos_to_quoted([_ | _] = pos, opts) do
+    opts = Keyword.put(opts, :skip_dynamic_for_indivisible, false)
+
     pos
     |> Enum.sort()
     |> Enum.map(&fun_intersection_to_quoted(&1, opts))
@@ -2034,7 +2036,7 @@ defmodule Module.Types.Descr do
       term_type?(descr) ->
         [{:dynamic, [], []}]
 
-      single = indivisible_bitmap(descr) ->
+      single = indivisible_bitmap(descr, opts) ->
         [single]
 
       true ->
@@ -2045,8 +2047,9 @@ defmodule Module.Types.Descr do
     end
   end
 
-  defp indivisible_bitmap(descr) do
-    with %{bitmap: bitmap} when map_size(descr) == 1 <- descr,
+  defp indivisible_bitmap(descr, opts) do
+    with true <- Keyword.get(opts, :skip_dynamic_for_indivisible, true),
+         %{bitmap: bitmap} when map_size(descr) == 1 <- descr,
          [single] <- bitmap_to_quoted(bitmap) do
       single
     else

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

@@ -1818,6 +1818,9 @@ defmodule Module.Types.DescrTest do
     end
 
     test "function with dynamic signatures" do
+      assert fun([dynamic(integer())], float()) |> to_quoted_string() ==
+               "(dynamic(integer()) -> float())"
+
       assert fun([dynamic(atom())], float()) |> to_quoted_string() ==
                "(dynamic(atom()) -> float())"