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] trying: TaskMonad-1.0.1 (user goal)
[__1] trying: base-4.12.0.0/installed-4.1... (dependency of TaskMonad)
[__2] next goal: X11-xft (dependency of TaskMonad)
[__2] rejecting: X11-xft-0.3.1 (conflict: pkg-config package xft-any, not
found in the pkg-config database)
[__2] rejecting: X11-xft-0.3, X11-xft-0.2 (conflict:
base==4.12.0.0/installed-4.1..., X11-xft => base<4.4)
[__2] rejecting: X11-xft-0.1 (conflict: TaskMonad => X11-xft>=0.2 && <0.4)
[__2] fail (backjumping, conflict set: TaskMonad, X11-xft, base)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: base, TaskMonad, X11-xft