Convert maps to list before traversing in descr

Author: josevalim

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

@@ -3525,7 +3525,7 @@ defmodule Module.Types.Descr do
 
   defp map_materialize_negated_set(set, bdd) do
     all_fields = bdd_reduce(bdd, %{}, fn {_, fields}, acc -> Map.merge(fields, acc) end)
-    for {atom, _} <- all_fields, not :sets.is_element(atom, set), do: atom
+    for {atom, _} <- :maps.to_list(all_fields), not :sets.is_element(atom, set), do: atom
   end
 
   # Compute which keys are optional, which ones are required, as well as domain keys

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

@@ -1895,6 +1895,11 @@ defmodule Module.Types.DescrTest do
 
       assert map_get(closed_map([{domain_key(:atom), integer()}]), atom([:a, :b])) ==
                {true, integer()}
+
+      # Have one of the keys be a __struct__
+      map = closed_map([{:a, atom([:a])}, {:__struct__, term()}, {domain_key(:atom), pid()}])
+      {true, term} = map_get(map, atom() |> difference(atom([:a])))
+      assert equal?(term, term())
     end
 
     test "with lists" do