Backport new instances introduced in GHC 8.0 #32

Historically, several new instances that were introduced in later versions of GHC weren't well publicized, causing me to have to hunt them down myself later, a very tedious process. The GHC devs have been much better about this recently, but just in case, I'll document what needs to be backported once GHC 8.0.1-rc1 is released.

I created this initial list based off of the base changelog here, so this may not be comprehensive. If there's something missing, please tell me so that I can get them all in one go (hopefully)!

New instances

• Applicative instances
  • Data.Complex (base-4.4 and later only)
    • Complex
  • Data.Monoid
    • Dual
    • Product
    • Sum
• Bounded instances
  • Control.Applicative
    • Const
  • Data.Functor.Identity (base-4.8 only)
    • Identity
• Data instances
  • Data.Monoid
    • All
    • Alt
    • Any
    • Dual
    • First
    • Last
    • Product
    • Sum
• Enum instances
  • Control.Applicative
    • Const
  • Data.Functor.Identity (base-4.8 only)
    • Identity
• Foldable instances
  • Control.Applicative
    • ZipList
  • Data.Complex (base-4.4 and later only)
    • Complex
  • Data.Monoid
    • Dual
    • First
    • Last
    • Product
    • Sum
• Functor instances
  • Data.Complex (base-4.4 and later only)
    • Complex
  • Data.Monoid
    • Dual
    • Product
    • Sum
• Generic instances (Done)
  • Data.Complex (base-4.4 and later only)
    • Complex
  • Data.Version
    • Version
  • System.Exit
    • ExitCode
• Generic1 instances (Done)
  • Data.Complex (base-4.4 and later only)
    • Complex
  • Data.Proxy (base-4.7 and later only)
    • Proxy
• Ix instances
  • Control.Applicative
    • Const
  • Data.Functor.Identity (base-4.8 only)
    • Identity
• Monad instances
  • Data.Complex (base-4.4 and later only)
    • Complex
  • Data.Monoid
    • Dual
    • Product
    • Sum
  • Data.Tuple
    • (,)
• MonadFix instances
  • Data.Monoid
    • Alt
    • Dual
    • First
    • Last
    • Product
    • Sum
• MonadZip instances
  • Data.Maybe
    • Maybe
  • Data.Monoid
    • Alt
    • Dual
    • First
    • Last
    • Product
    • Sum
• Monoid instances
  • Data.Functor.Identity
    • Identity
  • System.IO
    • IO
• Storable instances
  • Control.Applicative
    • Const
  • Data.Functor.Identity (base-4.8 only)
    • Identity
  • Data.Tuple
    • ()
• Traversable instances
  • Control.Applicative
    • ZipList
  • Data.Complex (base-4.4 and later only)
    • Complex
  • Data.Monoid
    • Dual
    • First
    • Last
    • Product
    • Sum

Other TODOs

• The Monoid instance for Identity needs to be backported to transformers Done.
• The Semigroup instance for Identity needs to be backported to transformers Done
• We should not add the upcoming MonadPlus IO and Alternative IO instances to base-orphans, as they are provided via Control.Monad.Trans.Error in transformers because of unfortunate historical reasons. We should add a note in the README about this.
• The new Functor instances readily admit Distributive, Representable, and Adjunction instances.
• Note in the README that semigroups and transformers backport some things added in GHC 8.0