Resolving dependencies... cabal: Could not resolve dependencies: next goal: Bang (user goal) rejecting: Bang-0.1.1.1, 0.1.1.0, 0.1.0.6, 0.1.0.4, 0.1.0.3 (global constraint requires ==0.1.0.2) trying: Bang-0.1.0.2 next goal: bifunctors (dependency of Bang-0.1.0.2) rejecting: bifunctors-5.1, 5 (conflict: Bang => bifunctors>=4 && <5) trying: bifunctors-4.2.1 next goal: semigroupoids (dependency of bifunctors-4.2.1) rejecting: semigroupoids-5.0.0.4, 5.0.0.3, 5.0.0.2, 5.0.0.1, 5 (conflict: bifunctors => semigroupoids==4.*) trying: semigroupoids-4.3 trying: transformers-compat-0.4.0.4 (dependency of semigroupoids-4.3) trying: transformers-compat-0.4.0.4:-two trying: transformers-compat-0.4.0.4:-three next goal: transformers (dependency of Bang-0.1.0.2) rejecting: transformers-0.4.2.0/installed-21d..., 0.4.3.0, 0.4.2.0, 0.4.1.0 (conflict: Bang => transformers>=0.3 && <0.4) rejecting: transformers-0.3.0.0 (conflict: transformers-compat-0.4.0.4:three => transformers>=0.4.1 && <0.5) rejecting: transformers-0.2.2.1, 0.2.2.0, 0.2.1.0, 0.2.0.0, 0.1.4.0, 0.1.3.0, 0.1.1.0, 0.1.0.1, 0.1.0.0, 0.0.1.0, 0.0.0.0, 0.4.0.0 (conflict: Bang => transformers>=0.3 && <0.4) Dependency tree exhaustively searched.