[ghc-steering-committee] #380 GHC2021: Current status

[Alejandro Serrano Mena]

 Joachim, I love your statistics :) And I think I’m less sad that you made
it look: I think that NullaryTypeClasses is implied by
MultiParamTypeClasses, and that MonadFailDesugaring is already (or is going
to be) the default in GHC! :P

To get some more discussion, I would be very happy to hear reasons for and
against:

- GADTs:
  - Stable and well documented,
  - Adding indices to types is one of the main reasons one would like to
have MultiParamTypeClasses and TypeFamilies on,
  - I find the GADT syntax much nicer (but this is an extremely personal
choice.)

- RankNTypes:
  - I originally voted “no”, because I find it to be part of “advanced
Haskell”, and because using it may be complicated without
ImpredicativeTypes on,
  - On the other hand, it’s also been in GHC for ages.

On 3 Dec 2020 at 10:31:18, Joachim Breitner <mail at joachim-breitner.de>
wrote:

> Dear Committee,
>
>
> we have 9 votes in. Dear Cale and Eric, can we have your votes please?
>
> As always, the table
>
> https://github.com/ghc-proposals/ghc-proposals/blob/ghc2021/proposals/0000-ghc2021.rst#data
> has the current data.
>
> We had the most discussion so far about:
>
> * The innnocence of PostfixOperators
> * The effect of UnicodeSyntax on error messages
> * Whether InstanceSigs is a good design
> * Whether OverloadedString is harmless enough.
>
> I see that three is less clear signal on odd extensions that are
> obsolete, on by default, implied by others etc. That’s probably fine
> and no need to worry; some of them will be resolved by virtue of being
> implied by others. We can also sanity-check the final result, and
> include all implied ones in the final design.
>
> So where do we stand?
>
> Applying the actual quota of ⅔ out of 11, i.e. 8 votes, these would go
> in no matter how Cale and Eric vote:
>
>   BangPatterns, BinaryLiterals, ConstraintKinds, DeriveDataTypeable,
>   DeriveFoldable, DeriveFunctor, DeriveGeneric, DeriveLift,
>   DeriveTraversable, EmptyCase, EmptyDataDecls, EmptyDataDeriving,
>   ExplicitForAll, FlexibleContexts, FlexibleInstances, GADTSyntax,
>   HexFloatLiterals, ImportQualifiedPost, KindSignatures,
>   MultiParamTypeClasses, NamedFieldPuns, NumericUnderscores,
>   StandaloneDeriving, ViewPatterns
>
> The following have 6 or 7 votes, i.e. they’d go in if we extrapolate
> from the current votes:
>
>   ConstrainedClassMethods, DerivingStrategies,
>   ExistentialQuantification, GeneralisedNewtypeDeriving, InstanceSigs,
>   NegativeLiterals, PostfixOperators, RankNTypes, RecordWildCards,
>   ScopedTypeVariables, TupleSections, TypeApplications, TypeFamilies,
>   TypeOperators, TypeSynonymInstances
>
>   These extensions are short one vote:
>
>   DataKinds, DerivingVia, GADTs, LambdaCase, PolyKinds
>
>
>
>   So how sad would we all be? This is the sadness report for each
>   committee member, showing the symmetric difference between their ballot
>   and the (extrapolated) result.
>
>
>   alejandro
>   would miss:
>   DataKinds, DerivingVia, GADTs, LambdaCase, MonadFailDesugaring,
>   NamedWildCards, NoMonomorphismRestriction, NullaryTypeClasses,
>   NumDecimals, OverloadedLists, OverloadedStrings, PolyKinds,
>   StandaloneKindSignatures
>   doesn’t want:
>   RankNTypes
>
>   arnaud
>   would miss:
>   Arrows, ExplicitNamespaces, ForeignFunctionInterface,
>   FunctionalDependencies, GADTs, MonadFailDesugaring, MonoLocalBinds,
>   PartialTypeSignatures, StarIsType, TypeFamilyDependencies
>   doesn’t want:
>   ExistentialQuantification, ImportQualifiedPost, InstanceSigs,
>   NamedFieldPuns, RankNTypes, RecordWildCards, ScopedTypeVariables,
>   TupleSections, TypeSynonymInstances
>
>   iavor
>   would miss:
>   BlockArguments, MultiWayIf, NoMonomorphismRestriction,
>   NullaryTypeClasses, OverloadedStrings, ParallelListComp, RecursiveDo
>   doesn’t want:
>   ConstrainedClassMethods, ConstraintKinds, DeriveFoldable,
>   DeriveFunctor, DeriveTraversable, DerivingStrategies, EmptyCase,
>   GADTSyntax, GeneralisedNewtypeDeriving, InstanceSigs, KindSignatures,
>   NegativeLiterals, PostfixOperators, TupleSections, TypeApplications,
>   TypeFamilies, TypeOperators
>
>   joachim
>   would miss:
>   DataKinds, DerivingVia, ForeignFunctionInterface, GADTs, LambdaCase,
>   MonoLocalBinds, NamedWildCards, NondecreasingIndentation,
>   RoleAnnotations, StarIsType, UnicodeSyntax, UnliftedFFITypes,
>   UnliftedNewtypes
>   doesn’t want:
>   ConstrainedClassMethods, ScopedTypeVariables, TypeSynonymInstances
>
>   richard
>   would miss:
>   BlockArguments, DefaultSignatures, DerivingVia,
>   DisambiguateRecordFields, ExplicitNamespaces, LexicalNegation,
>   NamedWildCards, NumDecimals, ParallelListComp, PolyKinds,
>   RoleAnnotations, StandaloneKindSignatures, TemplateHaskellQuotes,
>   UnicodeSyntax, UnliftedNewtypes
>   doesn’t want:
>   NegativeLiterals, RecordWildCards, ScopedTypeVariables, TypeFamilies
>
>   simonm
>   would miss:
>   DataKinds, DefaultSignatures, ForeignFunctionInterface, GADTs,
>   LambdaCase, LiberalTypeSynonyms, MonoLocalBinds, MultiWayIf,
>   NoMonomorphismRestriction, NondecreasingIndentation, NumDecimals,
>   OverloadedStrings, PatternSynonyms, PolyKinds, UnicodeSyntax
>   doesn’t want:
>   DeriveLift, DerivingStrategies, NumericUnderscores, TypeApplications,
>   TypeOperators, ViewPatterns
>
>   spj
>   would miss:
>   MonoLocalBinds, NoMonomorphismRestriction, NullaryTypeClasses,
>   OverloadedLists, OverloadedStrings, ParallelListComp, PolyKinds,
>   RecursiveDo, RoleAnnotations, StandaloneKindSignatures, StarIsType
>   doesn’t want:
>   DerivingStrategies, GeneralisedNewtypeDeriving, NegativeLiterals,
>   RecordWildCards, TupleSections, TypeFamilies
>
>   tom
>   would miss:
>   BlockArguments, DataKinds, DefaultSignatures, DerivingVia,
>   DisambiguateRecordFields, DuplicateRecordFields, ExplicitNamespaces,
>   FunctionalDependencies, LambdaCase, LexicalNegation,
>   LiberalTypeSynonyms, MagicHash, MultiWayIf, NamedWildCards,
>   NullaryTypeClasses, NumDecimals, PackageImports, ParallelListComp,
>   PolyKinds, QuasiQuotes, RoleAnnotations, StandaloneKindSignatures,
>   TemplateHaskell, TemplateHaskellQuotes, TypeFamilyDependencies,
>   UnboxedSums, UnboxedTuples, UnicodeSyntax, UnliftedNewtypes
>   doesn’t want:
>   none!
>
>   vitaly
>   would miss:
>   DataKinds, DerivingVia, GADTs, LambdaCase, MonadFailDesugaring,
>   StarIsType
>   doesn’t want:
>   ConstrainedClassMethods, ExistentialQuantification, PostfixOperators
>
>
>   --
>   Joachim Breitner
>  mail at joachim-breitner.de
>  http://www.joachim-breitner.de/
>
>
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