Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[__0] next goal: union (user goal)
[__0] rejecting: union-0.1.3 (conflict: requires unknown language GHC2024; did
you mean GHC2021?)
[__0] rejecting: union-0.1.2, union-0.1.1.2, union-0.1.1.1, union-0.1.1.0,
union-0.1.0.0 (constraint from user target requires ==0.1.3)
[__0] fail (backjumping, conflict set: union)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: union