Cask 'fing' is unreadable: undefined method

Fing was a program I removed from the /Applications using AppCleaner. Removing that program did not make a difference in this error that I am getting. How do I fix this?

Johns-Mac-Pro:~ jjwelch$ brew cask list
Error: Cask 'fing' is unreadable: undefined method 'hyphens_to_slashes' for "2016-09":Cask::DSL::Version

Johns-Mac-Pro:~ jjwelch$ brew doctor
Error: Cask 'fing' is unreadable: undefined method 'hyphens_to_slashes' for "2016-09":Cask::DSL::Version

Looks like removing the fing directory from

/usr/local/Caskroom/

was the answer.

As a rule of thumb, if you install an app with Homebrew, you should remove it with Homebrew. System uninstallers like AppCleaner are pretty useful (I use it a lot myself), but using it to uninstall Homebrew casks leaves behind a sizable chunk of install metadata…and a very confused Homebrew.

The hack you discovered (nuking /usr/local/Caskroom/fing) works for now, but it’s an implementation detail that can change at any time.