Coding style: Using StandaloneKindSignatures in GHC

[Oleg Grenrus]

To clarify, are you suggesting guidelines for GHC **and** base-library?

I'm puzzled about ownership of base. Who have a final word about it?
ghc-devs, libraries at haskell.org, CLC, chessai alone, whoever is first?

- Oleg

On 21.5.2021 23.21, Richard Eisenberg wrote:
> I agree with Chris here.
>
> Let me expand upon my counter-proposal:
>
> * A datatype declaration gets a standalone kind signature whenever at
> least one of its type arguments has a kind other than Type.
> * A class declaration gets a standalone kind signature whenever at
> least one of its type arguments has a kind other than Type.(*)
> * A closed type family always gets a standalone kind signature.
> * A type synonym gets a standalone kind signature whenever either at
> least one of its arguments has a kind other than Type or its result
> has a kind other than Type.
>
> (*) The class rule has an exception: if a class has a superclass
> constraint using Monad, Functor, Applicative, Foldable, or Traversable
> (or some other class whose name textually includes one of those names,
> such as MonadIO), we understand that the constrained variable must
> have kind Type -> Type. If that type variable is the only one without
> kind Type -> Type, then the standalone kind signature is optional.
>
> In cases other than those covered above, the standalone kind signature
> is optional, at the discretion of the programmer.
>
> This suggests that Dict gets a signature, Eq does not, Fix does, and
> Either does not.
>
> Richard
>
>> On May 21, 2021, at 12:37 PM, Chris Smith <cdsmith at gmail.com
>> <mailto:cdsmith at gmail.com>> wrote:
>>
>> On Fri, May 21, 2021 at 2:11 AM Baldur Blöndal <baldurpet at gmail.com
>> <mailto:baldurpet at gmail.com>> wrote:
>>
>>     > encouraging the use of a standalone signature for type
>>     declarations where at least one parameter of the datatype does
>>     not have kind Type.
>>
>>     So Dict, Eq both get a sig but Fix and Either do not?
>>
>>       type Dict :: Constraint -> Type
>>       type Eq   :: Type -> Constraint
>>       type Fix  :: (Type -> Type) -> Type
>>
>>
>>  That's not how I understand Richard's criteria.  Dict and Fix have
>> non-Type parameters (Dict has a Constraint parameter, and Fix has a
>> (Type -> Type) parameter.  On the other hand, Eq and Either have only
>> Types as parameters.  This seems to match my intuition about when a
>> kind signature might be helpful, as well as yours as far as I can
>> tell from what you wrote.
>>
>> That's not to say I am advocating any kind of rule.  As I'm not
>> really involved in GHC development, I refrain from having any
>> opinion.  I just think you may have misread Richard's suggestion.
>
>
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