fails:Array#compact does not return self
fails:Array#compact does not return subclass instance for Array subclasses
fails:Array#compact does not keep tainted status even if all elements are removed
fails:Array#compact does not keep untrusted status even if all elements are removed
fails:Array#compact! removes all nil elements
fails:Array#compact! returns self if some nil elements are removed
fails:Array#compact! returns nil if there are no nil elements to remove
fails:Array#compact! keeps tainted status even if all elements are removed
fails:Array#compact! keeps untrusted status even if all elements are removed
fails:Array#compact! raises a RuntimeError on a frozen array
