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     cabal-doctest-1.0.6
Starting     fail-4.9.0.0
Starting     parallel-3.2.2.0
Starting     primitive-0.6.4.0
Building     fail-4.9.0.0
Building     cabal-doctest-1.0.6
Building     parallel-3.2.2.0
Building     primitive-0.6.4.0
Completed    fail-4.9.0.0
Completed    cabal-doctest-1.0.6
Completed    parallel-3.2.2.0
Completed    primitive-0.6.4.0
Starting     atomic-primops-0.8.3
Building     atomic-primops-0.8.3
Completed    atomic-primops-0.8.3
Downloading  rcu-0.2.4
Downloaded   rcu-0.2.4
Starting     rcu-0.2.4
Building     rcu-0.2.4
Completed    rcu-0.2.4