The expression "01" fails to typecheck with this error:
Error: (line 2 column 2): Type Error during an application. Caused by: Type clash: type Cal.Core.Prelude.Num a => a -> b is not a member of type class Cal.Core.Prelude.Num.
Error: (line 2 column 1): Ambiguous type signature in inferred type Cal.Core.Prelude.Num a => a.