ImpredicativeTypes type checking fails depending on syntax of arguments

g1 and g2 below type check, but g1', g2', and g2'' don't even though the types are exactly the same.

{-# LANGUAGE ImpredicativeTypes, NoMonomorphismRestriction #-}
module Test where
f1 :: Maybe (forall a. [a] -> [a]) -> Maybe ([Int], [Char])
f1 (Just g) = Just (g [3], g "hello")
f1 Nothing  = Nothing

f2 :: [forall a. [a] -> [a]] -> Maybe ([Int], [Char])
f2 [g] = Just (g [3], g "hello")
f2 []  = Nothing

g1 = (f1 . Just) reverse
g1' = f1 (Just reverse)

g2 = f2 [reverse]
g2' = f2 ((:[]) reverse)
g2'' = f2 (reverse : [])

Compiling it with HEAD gives these errors:

[1 of 1] Compiling Test             ( test.hs, test.o )

test.hs:12:16:
    Couldn't match expected type ‛forall a. [a] -> [a]’
                with actual type ‛[a2] -> [a2]’
    In the first argument of ‛Just’, namely ‛reverse’
    In the first argument of ‛f1’, namely ‛(Just reverse)’

test.hs:15:17:
    Couldn't match expected type ‛forall a. [a] -> [a]’
                with actual type ‛[a0] -> [a0]’
    In the first argument of ‛: []’, namely ‛reverse’
    In the first argument of ‛f2’, namely ‛((: []) reverse)’

test.hs:16:12:
    Couldn't match expected type ‛forall a. [a] -> [a]’
                with actual type ‛[a1] -> [a1]’
    In the first argument of ‛(:)’, namely ‛reverse’
    In the first argument of ‛f2’, namely ‛(reverse : [])’

Trac metadata

Trac field	Value
Version	7.8.1-rc1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture