Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: Shpadoinkle-router-0.3.0.1 (user goal) [__1] next goal: servant-server (dependency of Shpadoinkle-router) [__1] rejecting: servant-server-0.18.2 (conflict: Shpadoinkle-router => servant-server>=0.16 && <0.18) [__1] skipping: servant-server-0.18.1, servant-server-0.18 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=0.16 && <0.18' from 'Shpadoinkle-router') [__1] trying: servant-server-0.17 [__2] next goal: base (dependency of Shpadoinkle-router) [__2] rejecting: base-4.14.1.0/installed-4.14.1.0 (conflict: servant-server => base>=4.9 && <4.14) [__2] skipping: base-4.15.0.0, base-4.14.1.0, base-4.14.0.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=4.9 && <4.14' from 'servant-server') [__2] rejecting: base-4.13.0.0, 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, 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: Shpadoinkle-router, base, servant-server) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: base, servant-server, Shpadoinkle-router