[erlang-questions] Type Server

Stavros Aronis <>
Fri Mar 2 13:18:00 CET 2012


Hi Tim,

It would be better in my opinion if you tried to rely only on the erl_types
module. erl_types:t_from_form/1 and erl_types:t_is_subtype/2 could possibly
be enough for you.

Dialyzer modules export few of their functions and these usually return the
data in a way that is useful to Dialyzer and difficult to see through. You
can however follow the code in dialyzer_contracts module,
especially dialyzer_contracts:store_tmp_contract/5
and dialyzer_contracts:process_contract_remote_types/1.
dialyzer_contracts:store_tmp_contract/5
actually calls erl_types:t_from_form/1 to convert an abstract syntax spec
into the representation used in erl_types and
after dialyzer_contracts:process_contract_remote_types/1 has done its magic
it's very easy to use erl_types:t_is_subtype/2 for the checks that you are
describing!

Cheers,
Stavros


On Fri, Mar 2, 2012 at 12:59 PM, Tim Watson <>wrote:

> After poking around in the dialyzer source code a little bit, I think what
> I'm basically after is being able to run
> dialyzer_contracts:check_contract/2 independently, without doing a full
> analysis. I don't care about processing a whole call graph, I'm really just
> looking to compare two function signatures to figure out if they're
> compatible. Possibly I'm also interesting in taking one function spec and a
> set of potentially matching specs and finding the best (most strict?)
> success typing. Is that something I can do by selectively reusing parts of
> dialyzer?
>
> I've poked around in the shell trying to do things
> like get_top_level_signatures, get_spec_info and things like that, but I
> can't quite figure out the right entry point to start with. I've even tried
> a few of the debugging functions such as dialyzer_succ_typings:doit/1 but
> to no avail.
>
> Any pointers would be gratefully received!
>
> Cheers,
>
> Tim
>
> On 1 Mar 2012, at 21:03, Stavros Aronis wrote:
>
> Hi Tim!
>
> I am not sure what you mean by a "type server", as Dialyzer does not
> really have a "component" that I could imagine being separated and labeled
> so. Dialyzer has the ability to store the specs and exported types in the
> PLT and from there use them to increase the precision of the analysis it
> performs.
>
> What do you mean by "working with types"?
>
> Regards,
> Stavros
>
> On Thursday, March 1, 2012 4:43:33 PM UTC+1, Tim Watson wrote:
>>
>> Hi all,
>>
>> Both PropEr and Dialyzer appear to have a 'type server' that provides
>> functions for working with type specs. What are the chances of this being
>> available as a separate unit? There is currently very little support for
>> working with types, as the previous post about lack of support in
>> erl_syntax pointed out. It would be nice to see type specs being better
>> supported.
>>
>> Cheers,
>>
>> Tim
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