Playground for DerivingVia language extension of GHC 8.6

• Talk Slides (in Japanese): Speaker Deck, PDF, Keynote
• English version: Speaker Deck, PDF, Keynote

Explanation

• example.hs
  User-site example of DerivingVia, including isomorphic instance derivation exmaples.
• Data.Aeson.Generic.DerivingVia
  Detailed implementation for the type-driven derivation interface for JSON (de)serialisation with DerivingVia and type-level hacks.
• Data.DerivingIso
  Derivation between isomorphic types with DerivingVia, as described in the original paper.
• Data.Foldable.Monoid
  Expository module which describes the connection between Foldable (and Traversable) and free monoid constructions. This also utilizes the QuantifiedConstraints extension to express the freeness as a type-class constraint, which is also introduced in GHC 8.6.