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: parsec (user goal)
[__0] rejecting: parsec-3.1.13.0, parsec-3.1.11, parsec-3.1.10, parsec-3.1.9,
parsec-3.1.8, parsec-3.1.7, parsec-3.1.6, parsec-3.1.5, parsec-3.1.4,
parsec-3.1.3, parsec-3.1.2, parsec-3.1.1, parsec-3.1.0, parsec-3.0.1,
parsec-3.0.0, parsec-2.1.0.1, parsec-2.1.0.0 (constraint from user target
requires ==2.0.0.1)
[__0] trying: parsec-2.0.0.1
[__1] next goal: base (dependency of parsec)
[__1] rejecting: base-4.12.0.0/installed-4.1... (conflict: parsec => base>=4.3
&& <4.8)
[__1] rejecting: 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)
[__1] fail (backjumping, conflict set: base, parsec)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: base, parsec