I've added hlint testing and there are quite a few hints. I'll send through a pull request for this.
$ stack test hcoord:hlint-test
...
151 hints
hcoord-1.0.0.0: Test suite hlint-test failed
Completed 2 action(s).
Test suite failure for package hcoord-1.0.0.0
hlint-test: exited with: ExitFailure 1
Logs printed to console
I've added hlint testing and there are quite a few hints. I'll send through a pull request for this.