T5095.hs:9:9: error:
    • Overlapping instances for Eq a arising from a use of ‘==’
      Matching instances:
        instance [overlappable] Show a => Eq a -- Defined at T5095.hs:5:31
        instance (Eq a, Eq b) => Eq (Either a b)
          -- Defined in ‘Data.Either’
        instance Eq Ordering -- Defined in ‘GHC.Classes’
        ...plus 24 others
        ...plus 14 instance involving out-of-scope typess
        (use -fprint-potential-instances to see them all)
      (The choice depends on the instantiation of ‘a’
       To pick the first instance above, use IncoherentInstances
       when compiling the other instance declarations)
    • In the expression: x == y
      In an equation for ‘f’: f x y = x == y