Confusing error message with PolyKinds

Consider the following example code:

import Control.Arrow

foo :: a b (m b)
foo = arr return

if we typecheck this we rightly get two errors about missing instances (Arrow a, Monad m). However, if we enable PolyKinds we get the following error message:

T.hs:4:7:
    Kind incompatibility when matching types:
      a0 :: * -> * -> *
      a :: k1 -> k -> *
    Expected type: a b (m b)
      Actual type: a0 b0 (m0 b0)
    Relevant bindings include foo :: a b (m b) (bound at T.hs:4:1)
    In the expression: arr return
    In an equation for ‘foo’: foo = arr return

I can sort of see where this is coming from if I think really hard :), so perhaps it's not a bug per se, but it's definitely confusing; and it's a pity that a type error (forgotten type qualifier) is reported as a kind error.

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture