Dialyzer issues being caused in main phoenix repo

[jeremyowensboggs]

With regards to phoenixframework/phoenix#3027
I have tracked it down to shard.ex

@spec list(pid, topic) :: [presence]
  def list(server_pid, topic) do
    server_pid
    |> GenServer.call({:list, topic})
    |> State.get_by_topic(topic)
  end

The spec needs to be updated to @spec list(pid | atom, topic) :: [presence]
In addition, there are several other dialzyer issues in the shard.ex file I have fixes for.

I notice that the dialyzer package is no longer supported, could I also switch to the recommended https://github.com/Comcast/dialyzex or https://github.com/jeremyjh/dialyxir?