@hackage unsatisfiable0

This package provides a

class Unsatisfiable (msg :: TypeError)

and

unsatisfiable :: forall msg a. Unsatisfiable msg => a

combinator.

There is also a plugin which

• Pretty-prints msgs of wanted Unsatisfiable, and

• Solves all other constraints if there is given Unsatisfiable

The plugin also works with -fdefer-type-errors.