Strictness/demand info for a Name

[Alejandro Serrano Mena]

Nice, so only I get the corresponding IdInfo, my work is “done”. But I’m
still missing how to thread everything together. Right now, what I have to
work with are:

   - The HieAst node I am searching information about, from which I can get
   the name,
   - The result of the parsing, renaming, and type checking phases.

Is there a way, with that information only, to obtain the corresponding
IdInfo? (This might be a very simple question, or just have a negative
answer, but I’m not versed at all in how all this information flows within
GHC).

Thanks in advance,
Alejandro

El 13 ene 2022 16:50:01, Sebastian Graf <sgraf1337 at gmail.com> escribió:

> Yes, every imported identifier from a module that was compiled with
> optimisations should have the proper analysis information in its IdInfo.
> So if you have `base` somewhere in one of your compiled libraries and load
> it, then the identifier of `GHC.OldList.map` will have an `idDmdSig` that
> says it's strict in the list parameter.
>
> At least that's how it works in GHC, where these IdInfos are populated
> with the information from the loaded interface files. The situation with
> HLS might be different, although I wouldn't expect that.
>
> ------ Originalnachricht ------
> Von: "Alejandro Serrano Mena" <trupill at gmail.com>
> An: "Sebastian Graf" <sgraf1337 at gmail.com>
> Cc: "GHC developers" <ghc-devs at haskell.org>; "Matthew Pickering" <
> matthewtpickering at gmail.com>
> Gesendet: 13.01.2022 16:43:50
> Betreff: Re: Re[2]: Strictness/demand info for a Name
>
> Thanks for the pointers! :)
>
> Knowing this, let me maybe rephrase my question: is it possible to get
> demand information of identifiers *without* running the analysis itself?
>
> Alejandro
>
> El 13 ene 2022 15:45:29, Sebastian Graf <sgraf1337 at gmail.com> escribió:
>
>> Yes, Matt is right.
>>
>> `dmdSigInfo` describes the how a function Id uses its arguments and free
>> variables, whereas
>> `demandInfo` describes how a (local, mostly) Id is used.
>>
>> Note that if you wanted to go beyond type-checking, you could probably
>> run the analysis on the desugaring of the current module quite easily.
>> But the results would be misleading, as prior optimisations (that you
>> probably don't want to run) may arrange the program in a way that demand
>> analysis has an easier time.
>>
>> ------ Originalnachricht ------
>> Von: "Matthew Pickering" <matthewtpickering at gmail.com>
>> An: "Alejandro Serrano Mena" <trupill at gmail.com>
>> Cc: "GHC developers" <ghc-devs at haskell.org>
>> Gesendet: 13.01.2022 15:38:29
>> Betreff: Re: Strictness/demand info for a Name
>>
>> You look at `dmdSigInfo` in `IdInfo`.
>>
>>
>> Matt
>>
>>
>> On Thu, Jan 13, 2022 at 2:20 PM Alejandro Serrano Mena
>>
>> <trupill at gmail.com> wrote:
>>
>> >
>>
>> >  Dear all,
>>
>> >
>>
>> >  I’m trying to bring the information about demand and strictness to the
>> Haskell Language Server, but I cannot find a way to do so. I was wondering
>> whether you could help me :)
>>
>> >
>>
>> >  Here’s my understanding; please correct me if I’m wrong:
>>
>> >
>>
>> >  The analysis runs on Core, so getting this information for the current
>> file would require to run the compiler further than type checking, which is
>> quite expensive,
>>
>> >  However, this analysis should somehow use known information about
>> imported functions, which should be readily available somewhere,
>>
>> >  If the above is true, what is the simplest way to get the information
>> for imported things? As I mentioned above, I would prefer not to run the
>> compiler further than the type checking phase, since otherwise it gets too
>> expensive for IDE usage. Right now HLS uses the information from the .hie
>> files.
>>
>> >
>>
>> >
>>
>> >  In fact, this goes into the more general question of how to show
>> information from different analyses within the IDE; I guess solving the
>> case for strictness/analysis may open the door to more (maybe everything
>> recorded inside a `Id`?)
>>
>> >
>>
>> >  Regards,
>>
>> >  Alejandro
>>
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>>
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