0.9.1

• Correct an improper use of unsafeCoerce in the internals of Data.Constraint.Nat and Data.Constraint.Symbol
• Correctly identify the mismatched types when you defer an unsatisfiable equality constraint through Data.Constraint.Deferrable
• Re-export the (:~~:) defined in base from Data.Constraint.Deferred with GHC 8.2 or later
• Add several new (:=>) instances for Bits, Identity, Const, Natural, IO, and Word.
• Modernize some existing Class and (:=>) instances to reflect the fact that Applicative is now a superclass of Monad on recent versions of base.

0.9

• Changes to Data.Constraint:
  • Add strengthen1 and strengthen2
• Changes to Data.Constraint.Deferrable:
  • Add a Deferrable () instance
  • The Deferrable (a ~ b) instance now shows the TypeReps of a and b when a type mismatch error is thrown
  • Add defer_ and deferEither_, counterparts to defer and deferEither which do not require proxy arguments
  • Enable PolyKinds. This allows the Deferrable (a ~ b instance to be polykinded on all supported versions of GHC except 7.10, where the kinds must be * due to an old GHC bug
  • Introduce a heterogeneous equality type (:~~:), and use it to define a Deferrable (a ~~ b) instance on GHC 8.0 or later
• Changes to Data.Constraint.Forall:
  • Implement ForallF and ForallT in terms of Forall
  • Add ForallV and InstV (supporting a variable number of parameters)
  • Add a forall combinator
• Introduce Data.Constraint.Nat and Data.Constraint.Symbol, which contain utilities for working with KnownNat and KnownSymbol constraints, respectively. These modules are only available on GHC 8.0 or later.

0.8

• GHC 8 compatibility
• transformers 0.5 compatibility
• binary 0.8 compatibility
• Dropped support for GHC 7.6 in favor of a nicer Bottom representation.

0.7

• Found a nicer encoding of the initial object in the category of constraints using a nullary constraint.

0.6.1

• Remove the need for closed type families from the new Forall.

0.6

• Completely redesigned Data.Constraint.Forall. The old design is unsound and can be abused to define unsafeCoerce! The new design requires closed type families, so this module now requires GHC 7.8+

0.5.1

• Added Data.Constraint.Deferrable.

0.5

• Added Data.Constraint.Lifting.

0.4.1.3

• Acknowledge we actually need at least base 4.5

0.4.1.2

• Restore support for building on older GHCs

0.4.1.1

• Minor documentation fixes.

0.4.1

• Added mapDict and unmapDict.
• Added a lot of documentation.

0.4

• Typeable and Data. The Data instance for (:-) is a conservative approximation that avoids having to turn (:-) into a cartesian closed category. If it becomes a pain point for users, I know how to do that, and have done so in other libraries – see hask, but I’m hesitant to bring such heavy machinery to bear and it isn’t clear how to do it in a way that is compatible with those other libraries.

0.3.5

• Explicit role annotations

0.3.4.1

• Fixed build failures.
• Fixed an unused import warning on older GHCs.

0.3.4

• Added bottom