Error message doesn't mention necessary extension in warning

In this example(Taken from http://www.haskell.org/haskellwiki/GHC/AdvancedOverlap) with the exception of removing -fglasgow-exts), GHC gives the wrong error message and fails to mention the missing necessary extension (which turns out to be ScopedTypeVariables).

If you take the example, and remove -fglasgow-exts and try to only use the minimum required language extensions,

{-# LANGUAGE EmptyDataDecls,
             MultiParamTypeClasses,
             FunctionalDependencies,
             OverlappingInstances,
             FlexibleInstances,
             UndecidableInstances #-}

GHC fails with the error

wiki.hs:30:12:
    Could not deduce (Print' flag a)
      from the context (Print a, ShowPred a flag1, Print' flag1 a)
      arising from a use of `print'' at wiki.hs:30:12-35
    Possible fix:
      add (Print' flag a) to the context of the instance declaration
    In the expression: print' (undefined :: flag)
    In the definition of `print': print = print' (undefined :: flag)
    In the instance declaration for `Print a'
Failed, modules loaded: none.

However, it compiles fine if ScopedTypeVariables is added to the list of extensions.

Trac metadata

Trac field	Value
Version	6.10.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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