Resolving dependencies... Error: cabal: Could not resolve dependencies: [__0] next goal: simplexmq (user goal) [__0] rejecting: simplexmq-1.1.0 (constraint from user target requires ==1.0.2) [__0] trying: simplexmq-1.0.2 [__1] next goal: template-haskell (dependency of simplexmq) [__1] rejecting: template-haskell-2.18.0.0/installed-2.18.0.0 (conflict: simplexmq => template-haskell>=2.16 && <2.17) [__1] skipping: template-haskell-2.19.0.0, template-haskell-2.18.0.0, template-haskell-2.17.0.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=2.16 && <2.17' from 'simplexmq') [__1] rejecting: template-haskell-2.16.0.0, template-haskell-2.15.0.0, template-haskell-2.14.0.0, template-haskell-2.13.0.0, template-haskell-2.12.0.0, template-haskell-2.11.1.0, template-haskell-2.11.0.0, template-haskell-2.10.0.0, template-haskell-2.9.0.0, template-haskell-2.8.0.0, template-haskell-2.7.0.0, template-haskell-2.6.0.0, template-haskell-2.5.0.0, template-haskell-2.4.0.1, template-haskell-2.4.0.0, template-haskell-2.3.0.1, template-haskell-2.3.0.0, template-haskell-2.2.0.0 (constraint from non-upgradeable package requires installed instance) [__1] fail (backjumping, conflict set: simplexmq, template-haskell) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: simplexmq, template-haskell