deriving-via-fail5.hs:8:1: error:
    • Couldn't match representation of type ‘a’ with that of ‘b’
        arising from a use of ‘GHC.Prim.coerce’
      ‘a’ is a rigid type variable bound by
        the instance declaration
        at deriving-via-fail5.hs:(8,1)-(9,24)
      ‘b’ is a rigid type variable bound by
        the instance declaration
        at deriving-via-fail5.hs:(8,1)-(9,24)
    • In the expression:
          GHC.Prim.coerce
            @(Int -> Identity b -> ShowS)
            @(Int -> Foo4 a -> ShowS)
            (showsPrec @(Identity b)) ::
            Int -> Foo4 a -> ShowS
      In an equation for ‘showsPrec’:
          showsPrec
            = GHC.Prim.coerce
                @(Int -> Identity b -> ShowS)
                @(Int -> Foo4 a -> ShowS)
                (showsPrec @(Identity b)) ::
                Int -> Foo4 a -> ShowS
      When typechecking the code for ‘showsPrec’
        in a derived instance for ‘Show (Foo4 a)’:
        To see the code I am typechecking, use -ddump-deriv
      In the instance declaration for ‘Show (Foo4 a)’
    • Relevant bindings include
        showsPrec :: Int -> Foo4 a -> ShowS
          (bound at deriving-via-fail5.hs:8:1)

deriving-via-fail5.hs:8:1: error:
    • Couldn't match representation of type ‘a’ with that of ‘b’
        arising from a use of ‘GHC.Prim.coerce’
      ‘a’ is a rigid type variable bound by
        the instance declaration
        at deriving-via-fail5.hs:(8,1)-(9,24)
      ‘b’ is a rigid type variable bound by
        the instance declaration
        at deriving-via-fail5.hs:(8,1)-(9,24)
    • In the expression:
          GHC.Prim.coerce
            @(Identity b -> String) @(Foo4 a -> String) (show @(Identity b)) ::
            Foo4 a -> String
      In an equation for ‘show’:
          show
            = GHC.Prim.coerce
                @(Identity b -> String) @(Foo4 a -> String) (show @(Identity b)) ::
                Foo4 a -> String
      When typechecking the code for ‘show’
        in a derived instance for ‘Show (Foo4 a)’:
        To see the code I am typechecking, use -ddump-deriv
      In the instance declaration for ‘Show (Foo4 a)’
    • Relevant bindings include
        show :: Foo4 a -> String (bound at deriving-via-fail5.hs:8:1)

deriving-via-fail5.hs:8:1: error:
    • Couldn't match representation of type ‘a’ with that of ‘b’
        arising from a use of ‘GHC.Prim.coerce’
      ‘a’ is a rigid type variable bound by
        the instance declaration
        at deriving-via-fail5.hs:(8,1)-(9,24)
      ‘b’ is a rigid type variable bound by
        the instance declaration
        at deriving-via-fail5.hs:(8,1)-(9,24)
    • In the expression:
          GHC.Prim.coerce
            @([] (Identity b) -> ShowS)
            @([] (Foo4 a) -> ShowS)
            (showList @(Identity b)) ::
            [] (Foo4 a) -> ShowS
      In an equation for ‘showList’:
          showList
            = GHC.Prim.coerce
                @([] (Identity b) -> ShowS)
                @([] (Foo4 a) -> ShowS)
                (showList @(Identity b)) ::
                [] (Foo4 a) -> ShowS
      When typechecking the code for ‘showList’
        in a derived instance for ‘Show (Foo4 a)’:
        To see the code I am typechecking, use -ddump-deriv
      In the instance declaration for ‘Show (Foo4 a)’
    • Relevant bindings include
        showList :: [Foo4 a] -> ShowS (bound at deriving-via-fail5.hs:8:1)