Consider enabling additional warnings

To ensure code quality, consider enabling additional warnings (if there are no false positives):

```
$  scalac -X |& grep warn
  -Xfatal-warnings               Fail the compilation if there are any warnings.
  -Xlint                         Enable recommended additional warnings.
$ scalac -Y |& grep warn
  -Yinline-warnings                   Emit inlining warnings. (Normally surpressed due to high volume)
  -Ywarn-adapted-args                 Warn if an argument list is modified to match the receiver.
  -Ywarn-all                          Enable all -Y warnings.
  -Ywarn-dead-code                    Warn when dead code is identified.
  -Ywarn-inaccessible                 Warn about inaccessible types in method signatures.
  -Ywarn-nullary-override             Warn when non-nullary overrides nullary, e.g. `def foo()` over `def foo`.
  -Ywarn-nullary-unit                 Warn when nullary methods return Unit.
  -Ywarn-numeric-widen                Warn when numerics are widened.
  -Ywarn-value-discard                Warn when non-Unit expression results are unused.
```