Phantom types break new polykind Typeable with either StandaloneDeriving or AutoDeriveTypeable

This test program, reduced from an attempt to bring ekmett's tagged package to HEAD,

{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE AutoDeriveTypeable #-}

newtype Tagged s b = Tagged { unTagged :: b }

results in

GHCi, version 7.7.20130218: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( typeable.hs, interpreted )

typeable.hs:5:1:
    Derived typeable instance must be of form (Typeable Tagged)
    In the stand-alone deriving instance for
      `Data.Typeable.Internal.Typeable Tagged'

This message is also emitted if I replace AutoDeriveTypeable StandaloneDeriving and deriving instance Typeable Tagged.

However, a "deriving (Typeable)" clause on the newtype definition works just fine.

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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