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...
cabal: Could not resolve dependencies:
[__0] next goal: ghc-lib (user goal)
[__0] rejecting: ghc-lib-0.20190523.1 (constraint from user target requires
==0.20190523)
[__0] trying: ghc-lib-0.20190523
[__1] next goal: ghc-lib-parser (dependency of ghc-lib)
[__1] rejecting: ghc-lib-parser-0.20190523, ghc-lib-parser-0.20190516,
ghc-lib-parser-0.20190423, ghc-lib-parser-0.20190402 (conflict: ghc-lib =>
ghc-lib-parser==0.20190523.1)
[__1] fail (backjumping, conflict set: ghc-lib, ghc-lib-parser)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: ghc-lib, ghc-lib-parser