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GHC 8.6 checklist #324

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6 tasks done
RyanGlScott opened this issue Apr 22, 2018 · 4 comments
Closed
6 tasks done

GHC 8.6 checklist #324

RyanGlScott opened this issue Apr 22, 2018 · 4 comments
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@RyanGlScott
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RyanGlScott commented Apr 22, 2018 •
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This issue serves as a reminder to do certain things before we ship a new major release that supports GHC 8.6:

  • In 6eb2133 and ddd353a, I added some CPP to temporarily support both GHC 8.4 and HEAD. We should remove this CPP once we drop support for GHC 8.4.

In addition, there are some other things that we could do if some new language extensions make it in to GHC 8.6:

  • Template Haskell changes. In particular:

  • If QuantifiedConstraints lands in 8.6, then we can completely do away with the ShowSing class. We can take code like this:

    instance (ShowSing a, ShowSing b) => ShowSing (Either a b) where showsSingPrec = ...
instance (ShowSing a, ShowSing b) => Show (Sing (e :: Either a b)) where showsPrec = showsSingPrec

    And replace it with a much more concise equivalent:

    type ShowSing k = (forall (z :: k). Show (Sing z) :: Constraint)
deriving instance (ShowSing a, ShowSing b) => Show (Sing (e :: Either a b))

    See the quantified-constraints branch for a WIP implementation of this.

  • Now that GHC is smarter about kind inference in CUSKs, we may be able to remove some superfluous kind signatures on k -> Type-kinded things (e.g., in Functor or Const).

  • Mention in the README that you'll likely need to enable NoStarIsType in order to profitably use PNum(type (*)).
RyanGlScott added a commit that referenced this issue Jun 30, 2018
@RyanGlScott
PNum(type (*)) requires NoStarIsType
ddd353a 
This requires adding some CPP to temporarily support two versions of
GHC (8.4 and HEAD). I'll amend #324 as a reminder to remove this
CPP once we drop support for GHC 8.4.
RyanGlScott added a commit that referenced this issue Jul 10, 2018
@RyanGlScott
WIP: Require GHC 8.6
5eca50d 
Don't merge yet.

This checks off all boxes in #324 except the third one (involving
`ShowSing`, which I'll tackle separately). Specifically, this:

* Removes some CPP needed for GHC 8.4.
* Bumps the `th-desugar` submodule.
* Singling `DerivingVia` does nothing (but emits a warning).
* Promoting or singling a quantified constraint results in an error.
* Now that GHC is smarter about kind inference in CUSKs, we can
  remove some superfluous kind signatures on certain class methods
  in `Applicative`, `Monad`, etc., as well as on definitions
  involving `Const`.
* Puts a mention in the `README` of how `NoStarIsType` is needed to
  use `PNum(type (*))`.
RyanGlScott added a commit that referenced this issue Jul 10, 2018
@RyanGlScott
WIP: Require GHC 8.6
4926234 
Don't merge yet.

This checks off all boxes in #324 except the third one (involving
`ShowSing`, which I'll tackle separately). Specifically, this:

* Removes some CPP needed for GHC 8.4.
* Bumps the `th-desugar` submodule.
* Singling `DerivingVia` does nothing (but emits a warning).
* Promoting or singling a quantified constraint results in an error.
* Now that GHC is smarter about kind inference in CUSKs, we can
  remove some superfluous kind signatures on certain class methods
  in `Applicative`, `Monad`, etc., as well as on definitions
  involving `Const`.
* Puts a mention in the `README` of how `NoStarIsType` is needed to
  use `PNum(type (*))`.
RyanGlScott added a commit that referenced this issue Jul 10, 2018
@RyanGlScott
WIP: Require GHC 8.6
9635d20 
Don't merge yet.

This checks off all boxes in #324 except the third one (involving
`ShowSing`, which I'll tackle separately). Specifically, this:

* Removes some CPP needed for GHC 8.4.
* Bumps the `th-desugar` submodule.
* Singling `DerivingVia` does nothing (but emits a warning).
* Promoting or singling a quantified constraint results in an error.
* Now that GHC is smarter about kind inference in CUSKs, we can
  remove some superfluous kind signatures on certain class methods
  in `Applicative`, `Monad`, etc., as well as on definitions
  involving `Const`.
* Puts a mention in the `README` of how `NoStarIsType` is needed to
  use `PNum(type (*))`.
@RyanGlScott RyanGlScott mentioned this issue Jul 10, 2018
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@RyanGlScott
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#351 and #352 implement these.

RyanGlScott added a commit that referenced this issue Jul 18, 2018
@RyanGlScott
Require GHC 8.6
5eadead 
This checks off all boxes in #324 except the third one (involving
`ShowSing`, which I'll tackle separately in #352).
Specifically, this:

* Removes some CPP needed for GHC 8.4.
* Bumps the `th-desugar` submodule.
* Singling `DerivingVia` does nothing (but emits a warning).
* Promoting or singling a quantified constraint results in an error.
* Now that GHC is smarter about kind inference in CUSKs, we can
  remove some superfluous kind signatures on certain class methods
  in `Applicative`, `Monad`, etc., as well as on definitions
  involving `Const`.
* Puts a mention in the `README` of how `NoStarIsType` is needed to
  use `PNum(type (*))`.
RyanGlScott added a commit that referenced this issue Jul 18, 2018
@RyanGlScott
Require GHC 8.6 (#351)
8342397 
* Require GHC 8.6

This checks off all boxes in #324 except the third one (involving
`ShowSing`, which I'll tackle separately in #352).
Specifically, this:

* Removes some CPP needed for GHC 8.4.
* Bumps the `th-desugar` submodule.
* Singling `DerivingVia` does nothing (but emits a warning).
* Promoting or singling a quantified constraint results in an error.
* Now that GHC is smarter about kind inference in CUSKs, we can
  remove some superfluous kind signatures on certain class methods
  in `Applicative`, `Monad`, etc., as well as on definitions
  involving `Const`.
* Puts a mention in the `README` of how `NoStarIsType` is needed to
  use `PNum(type (*))`.

* Work around haskell/cabal#5423
@RyanGlScott
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At this point, GHC 8.6 is due to be released Real Soon Now, and I don't expect any further changes that would affect the expected test results (74176fa should be the last of them, I think). Are we ready to release th-desugar-1.9 and singletons-2.5 to Hackage?

@goldfirere
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Go for it. :)

@RyanGlScott
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th-desugar-1.9 and singletons-2.5 have been released to Hackage.

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