I’m having an issue getting my Dialyzer to agree with my output, and can’t seem to figure it out. Essentially, the response is {:error, %Mint.HTTP2{}, %Mint.HTTPError{}} instead of just {:error, _} and I can’t get the spec to reflect that.

This is the issue I’m facing, I keep getting an error from my Mint transport service (which is a whole separate issue) but I keep getting alerts that my handle_response isn’t able to match the type. After looking into it more the error tuple has two arguments in the shape of: {:error, %Mint.HTTP2{}, %Mint.HTTPError{}}.

Here is my handle_response:

  @spec handle_response(
          {:ok, [map()] | function()}
          | {:error, String.t()}
          | {:error, %Mint.HTTP2{}, %Mint.HTTPError{}},
          Keyword.t()
        ) ::
          {:ok, [map()] | function()} | {:error, term()}
  defp handle_response(resp, opts)

  defp handle_response({:ok, stream} = resp, stream: true) when is_function(stream), do: resp

  defp handle_response({:ok, resp}, opts) when is_binary(resp),
    do: handle_response({:ok, Jason.decode!(resp)}, opts)

  defp handle_response({:ok, resp}, _), do: {:ok, Map.get(resp, "choices", [])}

  defp handle_response({:error, _} = err, _), do: err

  defp handle_response({:error, http, http_error}, _)
       when is_map(http) and is_map(http_error),
       do: {:error, http_error}

But I keep getting an error from my dialyzer here:

lib/broadcast.ex:129:pattern_match
The pattern can never match the type.

Pattern:
{:error, _http, _http_error}, _

Type:
{:error, _} | {:ok, _}, [{:stream, _}, ...]

I’m not sure why, I’m pretty sure the spec should be correct. Can anyone see what would be incorrect about this or does this seem reasonable?