The impossible happened with implicit parameters

{-# OPTIONS -XImplicitParams -XRankNTypes #-}
module Bug where

t :: forall a. ((?p :: Int) => a) -> String
t _ = "Hello"

f :: (forall a. a -> String) -> Int
f _ = 3

result :: Int
result = f t

$ ghc -c Bug.hs
ghc: panic! (the 'impossible' happened)
  (GHC version 6.10.1 for x86_64-unknown-linux):
	TcTyFuns.flattenType: unexpected PredType

Trac metadata

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