Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[__0] next goal: witness (user goal)
[__0] rejecting: witness-0.7 (conflict: requires unknown extension
TypeAbstractions; did you mean TypeApplications?)
[__0] rejecting: witness-0.6.2, witness-0.6.1, witness-0.6, witness-0.5,
witness-0.4, witness-0.3.0.1, witness-0.3, witness-0.2, witness-0.1
(constraint from user target requires ==0.7)
[__0] fail (backjumping, conflict set: witness)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: witness