Rule idea: ask to use DerivingStrategies

if

• a module have both DeriveAnyClass and GeneralizedNewtypeDeriving enabled
• and have a newtype with non-specific deriving clause

then

• request to enable DerivingStrategies if not already enabled
• and use specific deriving newtype or anyclass

an example (in this case, probably irrelevant, in general: not so much).

{-# LANGUAGE DeriveAnyClass, GeneralizedNewtypeDeriving #-}

import Data.Hashable

newtype Foo = Foo Int
  deriving (Hashable)

Start with the Haskell example in the issue and inspect how HLint rules and their tests are organized. Reproduce the case with both DeriveAnyClass and GeneralizedNewtypeDeriving enabled, then verify that the rule distinguishes non-specific deriving clauses and recognizes an existing DerivingStrategies extension. Done means the requested extension and explicit deriving strategy are suggested for the applicable newtype.