A rule that disallows comparison to booleans.
For example, these are considered invalid:
foo == true true != bar false === baz
This is because these expressions evaluate to
false, so you
could get the same result by using either the variable directly, or negating
Additionally, with a duck typed language such as Elixir, we should be more
interested in whether something is “truthy” or “falsey” than if they are