Resolving dependencies... Error: cabal: Could not resolve dependencies: [__0] trying: proto3-suite-0.6.0 (user goal) [__1] trying: proto3-suite:+swagger [__2] next goal: swagger2 (dependency of proto3-suite +swagger) [__2] rejecting: swagger2-2.8.7, swagger2-2.8.6, swagger2-2.8.5, swagger2-2.8.4, swagger2-2.8.3, swagger2-2.8.2, swagger2-2.8.1, swagger2-2.8 (conflict: proto3-suite +swagger => swagger2>=2.1.6 && <2.8) [__2] trying: swagger2-2.7 [__3] next goal: base (dependency of proto3-suite) [__3] rejecting: base-4.16.3.0/installed-4.16.3.0 (conflict: swagger2 => base>=4.9 && <4.16) [__3] skipping: base-4.18.0.0, base-4.17.1.0, base-4.17.0.0, base-4.16.4.0, base-4.16.3.0, base-4.16.2.0, base-4.16.1.0, base-4.16.0.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=4.9 && <4.16' from 'swagger2') [__3] rejecting: base-4.15.1.0, base-4.15.0.0, base-4.14.3.0, base-4.14.2.0, base-4.14.1.0, base-4.14.0.0, 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) [__3] fail (backjumping, conflict set: base, proto3-suite, swagger2) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: base, swagger2, proto3-suite, proto3-suite:swagger Try running with --minimize-conflict-set to improve the error message.