Hello,

I just had some fun and went through the list of GHC extensions in the manual, thinking of which ones might make a reasonable subset for a potential GHC2020.  Below is the list I came up with.  My reasoning was, roughy:

   * I wouldn't mind if these were on all the time

   * It is unlikely that turning on the extension will break something dramatically

   * It is unlikely that using the extension might lead to errors

   * The extensions are somewhat coherent

   * I explicitly included extensions that I personally don't use much, but I've heard that others like

I wonder what others think of this list?  What would you add/remove?

-Iavor

BlockArguments
EmptyCase
EmptyDatadecls
ExplicitNamespaces
ImportQualifiedPost
LambdaCase
MultiWayIf
StandaloneDeriving

BinaryLiterals
HexFloatLiterals
NumericUnderscores

NamedFieldPuns
RecordWildCards
TupleSections

ApplicativeDo
RecursiveDo
ParallelListComp

BangPatterns
PatternSynonyms
ViewPatterns
PatternGuards

ForeignFunctionInterface
CApiFFI

RankNTypes
ExistentialQuantification
ScopedTypeVariables
TypeSynonymInstances
ConstraintKinds

StandaloneKindSignatures
KindSignatures
TypeOperators