add missing expand call on union #421

Job	Run time
static analysis (Elixir 1.15.x \| Erlang/OTP 26.x)	53s
mix test windows (Elixir 1.12.x \| Erlang/OTP 22.x)	1m 1s
mix test (Elixir 1.12.x \| Erlang/OTP 22.x)	32s
mix test windows (Elixir 1.12.x \| Erlang/OTP 23.x)	1m 8s
mix test (Elixir 1.12.x \| Erlang/OTP 23.x)	21s
mix test windows (Elixir 1.12.x \| Erlang/OTP 24.x)	1m 12s
mix test (Elixir 1.12.x \| Erlang/OTP 24.x)	22s
mix test windows (Elixir 1.13.x \| Erlang/OTP 22.x)	58s
mix test (Elixir 1.13.x \| Erlang/OTP 22.x)	18s
mix test windows (Elixir 1.13.x \| Erlang/OTP 23.x)	1m 12s
mix test (Elixir 1.13.x \| Erlang/OTP 23.x)	31s
mix test windows (Elixir 1.13.x \| Erlang/OTP 24.x)	1m 8s
mix test (Elixir 1.13.x \| Erlang/OTP 24.x)	25s
mix test windows (Elixir 1.13.x \| Erlang/OTP 25.x)	1m 20s
mix test (Elixir 1.13.x \| Erlang/OTP 25.x)	27s
mix test windows (Elixir 1.14.x \| Erlang/OTP 23.x)	1m 34s
mix test (Elixir 1.14.x \| Erlang/OTP 23.x)	1m 7s
mix test (Elixir 1.14.x \| Erlang/OTP 24.x)	41s
mix test windows (Elixir 1.14.x \| Erlang/OTP 24.x)	1m 50s
mix test (Elixir 1.14.x \| Erlang/OTP 25.x)	59s
mix test windows (Elixir 1.14.x \| Erlang/OTP 25.x)	1m 27s
mix test (Elixir 1.14.x \| Erlang/OTP 26.x)	39s
mix test windows (Elixir 1.14.x \| Erlang/OTP 26.x)	1m 41s
mix test (Elixir 1.15.x \| Erlang/OTP 24.x)	1m 9s
mix test windows (Elixir 1.15.x \| Erlang/OTP 24.x)	1m 47s
mix test (Elixir 1.15.x \| Erlang/OTP 25.x)	39s
mix test windows (Elixir 1.15.x \| Erlang/OTP 25.x)	1m 45s
mix test (Elixir 1.15.x \| Erlang/OTP 26.x)	40s
mix test windows (Elixir 1.15.x \| Erlang/OTP 26.x)	2m 2s
	29m 48s

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