Ticket #3888 (closed bug: fixed)
Suggest -XGeneralizedNewtypeDeriving for newtypes
newtype A = A Int deriving Enum
Can't make a derived instance of `Enum A'
(`A' has non-nullary constructors)
In the newtype declaration for `A'
But perhaps -XGeneralizedNewtypeDeriving should be suggested (ideally only if the wrapped type actually had such an instance)?