Strictness/demand info for a Name

Sebastian Graf sgraf1337 at
Thu Jan 13 14:45:29 UTC 2022

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>
An: "Alejandro Serrano Mena" <trupill at>
Cc: "GHC developers" <ghc-devs at>
Gesendet: 13.01.2022 15:38:29
Betreff: Re: Strictness/demand info for a Name

>You look at `dmdSigInfo` in `IdInfo`.
>On Thu, Jan 13, 2022 at 2:20 PM Alejandro Serrano Mena
><trupill at> 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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