generic-deriving: Generic programming library for generalised deriving

Hackage Hackage Dependencies Haskell Programming Language BSD3 License Build

This package provides functionality for generalising the deriving mechanism in Haskell to arbitrary classes. It was first described in the paper:

The current implementation integrates with the new GHC Generics. See for more information. Template Haskell code is provided for supporting older GHCs.



  • Fix Haddock parsing issue on GHC 8.0


  • Backported MonadPlus and MonadZip instances for U1, and made the Functor, Foldable, Traversable, Alternative, and Monad instances for U1 lazier to correspond with base-4.9


  • Backported Enum, Bounded, Ix, Functor, Applicative, Monad, MonadFix, MonadPlus, MonadZip, Foldable, Traversable, and Data instances (introduced in base-4.9) for datatypes in the Generics.Deriving.Base module


  • Fix TH regression on GHC 7.0


  • Added Generics.Deriving.Semigroup
  • Added GMonoid instance for Data.Monoid.Alt
  • Fixed a bug in the GEnum instances for unsigned Integral types
  • Added Safe/Trustworthy pragmas
  • Made instances polykinded where possible


  • On GHC 8.0 and up, Generics.Deriving.TH uses the new type literal-based machinery
  • Rewrote the Template Haskell code to be robust. Among other things, this fixes a bug with deriving Generic1 instances on GHC 7.8, and makes it easier to derive Generic1 instances for datatypes that utilize GHC 8.0’s -XTypeInType extension.
  • Added deriveAll0 and makeRep0 for symmetry with deriveAll1 and makeRep1
  • AddedmakeRep0FromType and makeRep1FromType to make it easier to pass in the type instance (instead of having to pass each individual type variable, which can be error-prone)
  • Added functions with the suffix -WithKindSigs to allow generating type synonyms with explicit kind signatures in the presence of kind-polymorphic type variables. This is necessary for some datatypes that use -XTypeInType to have derived Generic(1) instances, but is not turned on by default since the TH kind inference is not perfect and would cause otherwise valid code to be rejected. Use only if you know what you are doing.
  • Fixed bug where a datatype with a single, nullary constructor would generate incorrect Generic instances
  • More sensible GEnum instances for fixed-size integral types
  • Added GCopoint, GEnum, GEq, GFoldable, GFunctor, GMonoid, GShow, and GTraversable instances for datatypes introduced in GHC 8.0
  • Backported Generic(1) instances added in GHC 8.0. Specifically, Generic instances for Complex (base-4.4 and later) ExitCode, and Version; and Generic1 instances for Complex (base-4.4 and later) and Proxy (base-4.7 and later). Added GEnum, GEq, GFoldable, GFunctor, GIx, GShow, and GTraversable instances for these datatypes where appropriate.


  • Allow deriving of Generic1 using Template Haskell
  • Allow deriving of Generic(1) for data families
  • Allow deriving of Generic(1) for constructor-less plain datatypes (but not data families, due to technical restrictions)
  • Support for unboxed representation types on GHC 7.11+
  • More GCopoint, GEnum, GEq, GFoldable, GFunctor, GIx, GMonoid, GShow, and GTraversable instances
  • The field accessors for the (:+:) type in Generics.Deriving.Base have been removed to be consistent with GHC.Generics
  • Ensure that TH generates definitions for isNewtype and packageName, if a recent-enough version of GHC is used
  • Ensure that TH-generated names are unique for a given data type’s module and package (similar in spirit to Trac #10487)
  • Allow building on stage-1 compilers