Fix tuple_insert_static crash on non-normalized empty type

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

@@ -5366,27 +5366,32 @@ defmodule Module.Types.Descr do
     end
   end
 
-  defp tuple_insert_static(descr, _, _) when descr == @none, do: none()
-
-  defp tuple_insert_static(descr, index, type) do
-    Map.update!(descr, :tuple, fn bdd ->
-      bdd_map(bdd, fn bdd_leaf(tag, elements) ->
-        # If the tuple is open, then we want List.insert_at to put the new element at the correct
-        # index, which requires filling the tuple with `term()` values first.
-        # Closed tuples of an incorrect size will be ignored (they are cancelled by the earlier
-        # intersection with `tuple_of_size_at_least`).
-        elements =
-          if tag == :open and length(elements) < index do
-            tuple_fill(elements, index)
-          else
-            elements
-          end
+  defp tuple_insert_static(%{tuple: bdd} = descr, index, type) do
+    %{
+      descr
+      | tuple:
+          bdd_map(bdd, fn bdd_leaf(tag, elements) ->
+            # If the tuple is open, then we want List.insert_at to put the new element at the correct
+            # index, which requires filling the tuple with `term()` values first.
+            # Closed tuples of an incorrect size will be ignored (they are cancelled by the earlier
+            # intersection with `tuple_of_size_at_least`).
+            elements =
+              if tag == :open and length(elements) < index do
+                tuple_fill(elements, index)
+              else
+                elements
+              end
 
-        bdd_leaf_new(tag, List.insert_at(elements, index, type))
-      end)
-    end)
+            bdd_leaf_new(tag, List.insert_at(elements, index, type))
+          end)
+    }
   end
 
+  # No tuple component: either none() or a semantically-empty static part whose
+  # non-normalized non-tuple components (e.g. an empty list literal) survive
+  # syntactically. There is nothing to insert into, so the result is empty.
+  defp tuple_insert_static(_descr, _index, _type), do: none()
+
   @doc """
   Replace an element in the tuple at the given (0-based) index.
 

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

@@ -2087,6 +2087,20 @@ defmodule Module.Types.DescrTest do
       # Errors must propagate even when the inserted value is dynamic
       assert tuple_insert_at(integer(), 0, dynamic()) == :badtuple
       assert tuple_insert_at(tuple([atom([:ok])]), 2, dynamic()) == :badindex
+
+      # Must not crash when a gradual descr's static part is a non-normalized
+      # empty (semantically empty but syntactically present) non-tuple component.
+      a1 = opt_union(dynamic(), non_empty_list(integer(), none()))
+      assert equal?(a1, dynamic())
+
+      assert tuple_insert_at(a1, 1, atom([:x]))
+             |> equal?(tuple_insert_at(dynamic(), 1, atom([:x])))
+
+      a2 = opt_union(tuple([dynamic()]), non_empty_list(none()))
+      assert equal?(a2, tuple([dynamic()]))
+
+      assert tuple_insert_at(a2, 1, atom([:x]))
+             |> equal?(tuple_insert_at(tuple([dynamic()]), 1, atom([:x])))
     end
 
     test "tuple_replace_at" do