Resolving dependencies... cabal: Could not resolve dependencies: [__0] next goal: cabal2ghci (user goal) [__0] rejecting: cabal2ghci-0.0.1.1 (constraint from user target requires ==0.0.1.0) [__0] trying: cabal2ghci-0.0.1.0 [__1] next goal: base (dependency of cabal2ghci) [__1] rejecting: base-4.12.0.0/installed-4.12.0.0 (conflict: cabal2ghci => base==4.5.*) [__1] skipping: base-4.14.0.0, base-4.12.0.0, base-4.11.1.0, base-4.11.0.0, base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '==4.5.*' from 'cabal2ghci') [__1] rejecting: base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) [__1] fail (backjumping, conflict set: base, cabal2ghci) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: base, cabal2ghci