deferred type error with rankNTypes

{-# LANGUAGE RankNTypes #-}

type A a = forall b. (a -> b) -> b

doA :: (a -> b) -> A a -> b
doA f l = l f

-- f :: A a -> [a] -> [a]   -- correct type
f :: A a -> a               -- wrong type
f = doA (:)

main = return ()

compiled with wrong type and -fdefer-type-errors gives ghc panic

-- F.hs:10:5: Warning:
--     Occurs check: cannot construct the infinite type: a0 = [a0] -> [a0]
--     Expected type: A a -> a
--       Actual type: A a0 -> a
--     In the return type of a call of `doA'
--     In the expression: doA (:)
--     In an equation for `f': f = doA (:)
-- 
-- F.hs:10:9: Warning:
--     Couldn't match type `a' with `[a0] -> [a0]'
--       `a' is a rigid type variable bound by
--           the type signature for f :: A a -> a at F.hs:9:6
--     Expected type: a0 -> a
--       Actual type: a0 -> [a0] -> [a0]
--     In the first argument of `doA', namely `(:)'
--     In the expression: doA (:)
--     In an equation for `f': f = doA (:)
-- ghc: panic! (the 'impossible' happened)
--   (GHC version 7.6.2 for x86_64-unknown-linux):
-- 	evTermCoercion
--     error @ghc-prim:GHC.Prim.Any{(w) tc 31N}
--              ghc-prim:GHC.Prim.*{(w) tc 34d}
--            ghc-prim:GHC.Types.~{(w) tc 31Q} ([ghc-prim:GHC.Prim.Any{(w) tc 31N}
--                                                 ghc-prim:GHC.Prim.*{(w) tc 34d}]
--                                              -> [ghc-prim:GHC.Prim.Any{(w) tc 31N}
--                                                    ghc-prim:GHC.Prim.*{(w) tc 34d}])
--           F.hs:10:5:
--     Occurs check: cannot construct the infinite type: a0 = [a0] -> [a0]
--     Expected type: A a -> a
--       Actual type: A a0 -> a
--     In the return type of a call of `doA'
--     In the expression: doA (:)
--     In an equation for `f': f = doA (:)
-- (deferred type error)