Panic in typechecker when checking rules

GHC will panic when given either of the following modules. The error messages are somewhat different for the two different rules.

module GHCBug1 where

foo :: (forall a . a -> f a) -> f Int
foo f = f undefined

{-# RULES
    "bug1"
    forall (g :: a -> f a) .
    head (foo g) = undefined
 #-}

module GHCBug2 where

foo :: (forall a . a -> f a) -> f Int
foo f = f undefined

{-# RULES
    "bug2"
    forall (g :: forall a . a -> f a) .
    head (foo g) = undefined
 #-}

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
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Architecture