gistfile1.txt

% cabal install optparse-applicative --lib
Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: base-4.12.0.0/installed-4.12.0.0 (user goal)
[__1] trying: containers-0.6.2.1 (user goal)
[__2] next goal: ghc (user goal)
[__2] rejecting: ghc-8.6.5/installed-8.6.5 (conflict: containers==0.6.2.1, ghc
=> containers==0.6.0.1/installed-0.6.0.1)
[__2] trying: ghc-8.6.5
[__3] rejecting: ghc:-buildable (conflict: base==4.12.0.0/installed-4.12.0.0,
ghc -buildable => base<0)
[__3] rejecting: ghc:+buildable (manual flag can only be changed explicitly)
[__3] fail (backjumping, conflict set: base, ghc, ghc:buildable)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: containers, base, ghc, ghc:buildable
Try running with --minimize-conflict-set to improve the error message.