Hi,

I started contributing to a project where the CI checks for Dialyzer warnings. There is this code where I inverted the condition and branches of an if/else statement to make it a tiny bit easier to read.

The code in question:

  def create_friend_request(from_user_id, to_user_id) do
    {allowed, reason} = can_send_friend_request_with_reason?(from_user_id, to_user_id)

    if allowed do
      (...)
    else
      (...)
    end
  end

Previously, it was if not allowed do and Dialyzer was fine with it. Now, Dialyzer emits this warning for the line if allowed do: The guard clause can never succeed.

This is how can_send_friend_request_with_reason? is defined:

  @spec can_send_friend_request_with_reason?(T.userid(), T.userid()) ::
          {true, :ok} | {false, String.t()}
  defdelegate can_send_friend_request_with_reason?(from_id, to_id), to: FriendRequestLib

I don’t have much experience with Dialyzer, so I wonder if I am missing something obvious?

In case you need more context than this, this is all happening in this PR. Thank you