Warning: The install command is a part of the legacy v1 style of cabal usage. Please switch to using either the new project style and the new-install command or the legacy v1-install alias as new-style projects will become the default in the next version of cabal-install. Please file a bug if you cannot replicate a working v1- use case with the new-style commands. For more information, see: https://wiki.haskell.org/Cabal/NewBuild Resolving dependencies... Starting reg-alloc-0.1.0.0 Building reg-alloc-0.1.0.0 Failed to install reg-alloc-0.1.0.0 Build log ( /home/builder/.cabal/logs/ghc-8.6.3/reg-alloc-0.1.0.0-2vX9H92MPch2uBWkh9A8Ne.log ): cabal: Entering directory '/tmp/cabal-tmp-8767/reg-alloc-0.1.0.0' Configuring reg-alloc-0.1.0.0... Preprocessing library for reg-alloc-0.1.0.0.. Building library instantiated with RegAlloc = for reg-alloc-0.1.0.0.. RegAlloc.hsig:1:1: error: File name does not match module name: Saw: ‘Main’ Expected: ‘RegAlloc’ | 1 | signautre RegAlloc where | ^ cabal: Leaving directory '/tmp/cabal-tmp-8767/reg-alloc-0.1.0.0' cabal: Error: some packages failed to install: reg-alloc-0.1.0.0-2vX9H92MPch2uBWkh9A8Ne failed during the building phase. The exception was: ExitFailure 1