And this is the case in Idris, where `cast` is a member of the `Cast` interface, and there's an implementation of `Cast String Integer`. `cast` is a function `

And this is the case in Idris, where `cast` is a member of the `Cast` interface, and there's an implementation of `Cast String Integer`. `cast` is a function `String -> Integer`, instead of the (more sensible) `String -> Either Integer CastError`.