GeneralizedNewtypeDeriving should fail with data families

Here is an example:

{-# LANGUAGE GeneralizedNewtypeDeriving, TypeFamilies #-}
module Foo where

data family T a
data instance T Int = T_Int Int

class C a where
  foo :: a -> T a

instance C Int where
  foo = T_Int

newtype Foo = Foo Int deriving(C)

The deriving(C) clause on Foo should fail but instead it derives an instance which can't possible be correct since there is no corresponding data instance T Foo. This is closely related to #2721 (closed) (where newtype deriving was disabled in the presence of associated types) but much more difficult to test for. Probably also related to #1496 (closed).

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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