break018 skips a step

[igloo]

The break018 test is failing:

@@ -1,13 +1,11 @@
 Stopped at ../mdo.hs:(29,0)-(31,26)
-_result :: IO (N a) = _
-Stopped at ../mdo.hs:(29,15)-(31,26)
-_result :: IO (N Char) = _
-x :: Char = 'h'
-xs :: [Char] = _
+_result :: (# GHC.Prim.State# GHC.Prim.RealWorld, N a #) = _
 Stopped at ../mdo.hs:29:29-41
 _result :: IO (N Char) = _
 f :: N Char = _
 l :: N Char = _
 x :: Char = 'h'
 Stopped at ../mdo.hs:(7,0)-(8,41)
-_result :: IO (N a) = _
+_result :: (# GHC.Prim.State# GHC.Prim.RealWorld, N a #) = _
+Stopped at ../mdo.hs:7:25-38
+_result :: IO (IORef Bool) = _
*** unexpected failure for break018(ghci)

What's happening here is that as we :st through the evaluation we aren't stopping at the mdo expression any more; we go straight from the entire l2dll to the newNode expression:

l2dll :: [a] -> IO (N a)
l2dll (x:xs) = mdo c      <- newNode l x f
                   (f, l) <- l2dll' c xs
                   return c

[simonmar]

Fixed:

Mon Apr 20 07:25:25 PDT 2009  Simon Marlow <marlowsd@gmail.com>
 * FIX #2845: Allow breakpoints on expressions with unlifted type