Misleading error message with forgotten "do"

In the following (simplified) code, I forgot to add the do keyword, when doing some refactoring. This caused GHC to give a strange error message that said approximately "The function F is applied to two arguments, but its type T has only two"... which is odd!

import Control.Monad.RWS ( evalRWS, RWS )
import Control.Monad.Writer.Class ( tell )

main = print $ evalRWS (go 1) () ()

go :: Int -> RWS () [String] () ()
go i = --Oops, forgot a do here
    return (show i) >>= (\l -> tell [l])
    -- go $ i + 1
    go i

Strangely, replacing the "go i" line with the commented-out line above it gives a sensible error message, the "Possible cause: `\l -> tell [l]' is applied to too many arguments" message, which is correct, and would've pointed me straight to the problem.

The invalid error message, which appears to be the same using GHC 7.6.3 and 7.8.3, is:

NFA.hs:8:25:
    Couldn't match type ‘String
                         -> Control.Monad.Trans.RWS.Lazy.RWST
                              () [String] () Data.Functor.Identity.Identity ()’
                  with ‘()’
    Expected type: Int
                   -> String
                   -> Control.Monad.Trans.RWS.Lazy.RWST
                        () [String] () Data.Functor.Identity.Identity ()
      Actual type: Int -> ()
    The function ‘\ l -> tell [l]’ is applied to two arguments,
    but its type ‘(Int -> RWS () [String] () ()) -> Int -> ()’
    has only two
    In the second argument of ‘(>>=)’, namely ‘(\ l -> tell [l]) go i’
    In the expression: return (show i) >>= (\ l -> tell [l]) go i

Trac metadata

Trac field	Value
Version	7.8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture