@hackage trivial-constraint0.4.0.0

Constraints that any type, resp. no type fulfills

Since GHC 7.4, constraints are first-class: we have the constraint kind, and thus type-classes have a kind such as * -> Constraint.

These can be used as parameters to data types. They also can be combined quite nicely,

type NewConstraint a = (Constraint1 a, Constraint2 a)

however you always need to start with a plain old type class when building constraints.

This library provides a type class that is not really a constraint at all, so you can "start from zero" with building up a custom constraint. Also its opposite (a constraint that no type can ever fulfill).