Re: gen_statem:start_monitor dialyzer warning

Hi Raimo,

 A little help if you could please point me to some starter.

The type-spec of net:getnameinfo
<https://erlang.org/doc/man/net.html#getnameinfo-2> can be made better as
currently the type of SockAddr = term() is provided, which can be made even
more explicit. An example is in the same file in the type declaration of
ifaddrs() <https://erlang.org/doc/man/net.html#type-ifaddrs>, the field addr
:= socket:sockaddr() <https://erlang.org/doc/man/socket.html#type-sockaddr>

I wanted to change it and raise a pull request, but not sure where can I.
Can you please help me with some pointers. Rest I can follow.

Thanks and Regards
Nalin Ranjan

On Mon, Jan 25, 2021 at 5:22 PM Raimo Niskanen <
[email protected]> wrote:

> On Sun, Jan 24, 2021 at 02:31:54PM +0100, Kostis Sagonas wrote:
> > On 1/24/21 2:14 PM, Matt Kowalczyk wrote:
> > > Having a hard time understanding why the following sample code
> generates
> > > a dialyzer warning,
> >
> > Either because somebody added wrong specs to 'gen_statem' or forgot to
> > update the specs of 'gen'.
>
> There is room for improvement here.
>
> We have a few Issues reported to bugs.erlang.org regarding type exports
> from gen_server and gen_statem, and internal discussions have not completed
> on how much types that would be useful to export...
>
> Here gen does not export the right type for gen:start(_, monitor, ...).
> I am not sure that we should specify types in gen; it is an internal
> module,
> so maybe it would be better to rely on Dialyzer figuring them out
> instead...
>
> Also gen_statem exports start_ret() but not start_mon_ret().  That is not
> consistent.
>
> Cheers
> / Raimo
>
>
> >
> >
> > ===== gen_statem has these types and specs =====
> >
> > -type start_mon_ret() ::
> >          {'ok', {pid(),reference()}}
> >        | 'ignore'
> >        | {'error', term()}.
> >
> > -spec start_monitor(
> >       Module :: module(), Args :: term(), Opts :: [start_opt()]) ->
> >                  start_mon_ret().
> > start_monitor(Module, Args, Opts) ->
> >      gen:start(?MODULE, monitor, Module, Args, Opts).
> >
> >
> > ===== gen:start/5's return type is: ======
> >
> > -type start_ret()  :: {'ok', pid()} | 'ignore' | {'error', term()}.
> >
> >
> > Their intersection is: 'ignore' | {'error', term()}.
> >
> >
> > Dialyzer is never wrong (C), but wrong specs can cause confusion.
> >
> > Kostis
>
> --
>
> / Raimo Niskanen, Erlang/OTP, Ericsson AB
>