typespec allows for async response from request functions

[jeffrom]

currently this fails dialyzer checks:

def get do
  HTTPoison.get!(url, [], stream_to: self())
  |> read_response()
end

def read_response(%HTTPoison.AsyncResponse{}) do
end

dialyzer output:

The call 'Elixir.CoolModule':do_response(#{'__struct__':='Elixir.HTTPoison.Response', 'body':=_, 'headers':=[any()], 'request_url':=binary() |
 [binary() | maybe_improper_list(any(),binary() | []) | char()] | {'hackney_url',atom(),atom(),binary(),'undefined' | binary(),'nil' | 'undefined' | binary(),binary(),binary(),[any(
)],'undefined' | integer(),binary(),binary()}, 'status_code':=integer()}) will never return since it differs in the 1st argument from the success typing arguments: (#{'__struct__':=
'Elixir.HTTPoison.AsyncResponse', 'id':=_, _=>_})

and

The pattern #{'id':=_id@1, '__struct__':='Elixir.HTTPoison.AsyncResponse'} can never match the type #{'__struct__':='Elixir.HTTPoison.Response', 'body':
=_, 'headers':=[any()], 'request_url':=binary() | [binary() | maybe_improper_list(any(),binary() | []) | char()] | {'hackney_url',atom(),atom(),binary(),'undefined' | binary(),'nil'
 | 'undefined' | binary(),binary(),binary(),[any()],'undefined' | integer(),binary(),binary()}, 'status_code':=integer()}

Thanks for the great work!

[edgurgel]

Thanks!