Resolving dependencies... cabal: Could not resolve dependencies: [__0] next goal: tweet-hs (user goal) [__0] rejecting: tweet-hs-1.0.2.2, tweet-hs-1.0.2.1, tweet-hs-1.0.1.43, tweet-hs-1.0.1.42, tweet-hs-1.0.1.41, tweet-hs-1.0.1.40, tweet-hs-1.0.1.39, tweet-hs-1.0.1.38 (constraint from user target requires ==1.0.1.37) [__0] trying: tweet-hs-1.0.1.37 [__1] next goal: megaparsec (dependency of tweet-hs) [__1] rejecting: megaparsec-9.0.1 (conflict: tweet-hs => megaparsec>=6.0 && <7.0) [__1] skipping: megaparsec-9.0.0, megaparsec-8.0.0, megaparsec-7.0.5, megaparsec-7.0.4, megaparsec-7.0.3, megaparsec-7.0.2, megaparsec-7.0.1, megaparsec-7.0.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=6.0 && <7.0' from 'tweet-hs') [__1] trying: megaparsec-6.5.0 [__2] next goal: base (dependency of tweet-hs) [__2] rejecting: base-4.14.1.0/installed-4.14.1.0 (conflict: megaparsec => base>=4.7 && <4.13) [__2] skipping: base-4.15.0.0, base-4.14.1.0, base-4.14.0.0, base-4.13.0.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=4.7 && <4.13' from 'megaparsec') [__2] rejecting: 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, 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) [__2] fail (backjumping, conflict set: base, megaparsec, tweet-hs) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: tweet-hs, base, megaparsec