ghc panic during parsing

For the following piece of code

class Bla (forall x . x) where

the ghc parser yields the appropriate error

Forall type not allowed as type parameter

However, if you change the code to this

class Bla (forall x . x :: *) where

Then ghc does this:

ghc: panic! (the 'impossible' happened)
  (GHC version 6.10.1 for i386-apple-darwin):
	parser/RdrHsSyn.lhs:(525,4)-(548,64): Non-exhaustive patterns in function collect

This is reproducible on ghc-6.8.3 and ghc-6.10.1.

I have only tried it on Mac OS X, x86.

Trac metadata

Trac field	Value
Version	6.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Parser)
Test case
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