Fix autocomplete crash when expanding struct with __MODULE__ (#14308)

Author: lukaszsamson

lib/iex/lib/iex/autocomplete.ex

@@ -378,16 +378,18 @@ defmodule IEx.Autocomplete do
     case Code.Fragment.container_cursor_to_quoted(code) do
       {:ok, quoted} ->
         case Macro.path(quoted, &match?({:__cursor__, _, []}, &1)) do
-          [cursor, {:%{}, _, pairs}, {:%, _, [{:__aliases__, _, aliases}, _map]} | _] ->
+          [cursor, {:%{}, _, pairs}, {:%, _, [{:__aliases__, _, aliases = [h | _]}, _map]} | _]
+          when is_atom(h) ->
             container_context_struct(cursor, pairs, aliases, shell)
 
           [
             cursor,
             pairs,
             {:|, _, _},
             {:%{}, _, _},
-            {:%, _, [{:__aliases__, _, aliases}, _map]} | _
-          ] ->
+            {:%, _, [{:__aliases__, _, aliases = [h | _]}, _map]} | _
+          ]
+          when is_atom(h) ->
             container_context_struct(cursor, pairs, aliases, shell)
 
           [cursor, pairs, {:|, _, [{variable, _, nil} | _]}, {:%{}, _, _} | _] ->

lib/iex/test/iex/autocomplete_test.exs

@@ -416,6 +416,9 @@ defmodule IEx.AutocompleteTest do
     assert {:yes, ~c"ry: ", []} = expand(~c"%URI{path: \"foo\", que")
     assert {:no, [], []} = expand(~c"%URI{path: \"foo\", unkno")
     assert {:no, [], []} = expand(~c"%Unknown{path: \"foo\", unkno")
+
+    assert {:yes, [], _} = expand(~c"%__MODULE__{")
+    assert {:yes, [], _} = expand(~c"%__MODULE__.Some{")
   end
 
   test "completion for struct keys in update syntax" do