Bad error message for omitting -XExistentialQuantification flag

If I compile this program:

module Foo where

data T = forall a . MkT a

with:

ghc-6.8.1  extest.hs -c

I get the error:

extest.hs:3:9: Not a constructor: `forall'

I think it would be a better error message to suggest passing in the -XExistentialQuantification flag.

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown