forall not recognized in RULES

{-# LANGUAGE GADTs, TypeFamilies, TypeOperators
  -- , ScopedTypeVariables
   #-}
{-# OPTIONS_GHC -Wall -frewrite-rules #-}

-- ScopedTypeVariables works around a 6.10 bug.  The forall keyword is
-- supposed to be recognized in a RULES pragma, but it's not.
-- 
-- This bug was introduced between ghc 6.9.20080622 and 6.10.0.20081007.

-- | Mapping from all elements of @a@ to the results of some function
class HasTrie a where
    -- | Representation of trie with domain type @a@
    data (:->:) a :: * -> *
    -- Create the trie for the entire domain of a function
    trie   :: (a  ->  b) -> (a :->: b)
    -- | Convert a trie to a function, i.e., access a field of the trie
    untrie :: (a :->: b) -> (a  ->  b)

{-# RULES
"trie/untrie"   forall t. trie (untrie t) = t
"untrie/trie"   forall f. untrie (trie f) = f
 #-}

Trac metadata

Trac field	Value
Version	6.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	conal
Operating system
Architecture