[Haskell-cafe] Bundle patterns with type aliases

[David Feuer]

Here's an example:

pattern State :: (s -> (a, s)) -> State s a
pattern State f <- (coerce . runStateT -> f) where
  State = state

This would be very nice to bundle with the State type synonym.

On Thu, Sep 16, 2021, 2:22 PM Carter Schonwald <carter.schonwald at gmail.com>
wrote:

> These are great ideas! Could you please create a ghc tracker ticket with a
> tiny examples or two?
>
> There may be specific technical reasons we might not be able to do so for
> type synonyms in ghc, but I don’t see any obvious barriers in the case of
> David’s excellent idea, I’ve def seen lots of great code out there where
> you’d really want either associated pattern synonyms or to bundle pattern
> synonyms with the exported public interface for a type class.
>
> I’m sure there’s some devil in the details but these sound lovely.  Step
> -1 is making up 1-2 toy examples and explaining what and why you want it on
> a ghc ticket!
>
> On Wed, Sep 8, 2021 at 1:25 PM David Feuer <david.feuer at gmail.com> wrote:
>
>> I would like that, along with the ability to bundle patterns with classes.
>>
>> On Wed, Sep 8, 2021, 1:13 PM Keith <keith.wygant at gmail.com> wrote:
>>
>>> Is there currently a way to 'bundle' a pattern with a type alias? And if
>>> not, could that capability be added to the PatternSynonyms GHC extension?
>>> (Is this the right place to ask, or should I be asking a GHC list?)
>>>
>>> --Keith
>>> Sent from my phone with K-9 Mail.
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