Excessive heap usage

With Main.hs:

module Main (main) where

import InputOutput

main :: IO ()
main = do
          let content1 = concat (replicate 1000000 "1x") ++ "0"
          let i1 = fst $ input content1
          view i1

          let content2 = concat (replicate 1000001 "1y") ++ "0"
          let i2 = fst $ input content2
          view i2

view :: [Char] -> IO ()
view [] = return ()
view (i : is) = i `seq` view is

and InputOutput.hs:

module InputOutput (input) where

class InputOutput a where
    input :: String -> (a, String)

instance InputOutput Char where
    input (x : bs) = (x, bs)

instance InputOutput a => InputOutput [a] where
    input ('0':bs) = ([], bs)
    input ('1':bs) = case input bs of
                     (x, bs') ->
                         case input bs' of
                         ~(xs, bs'') -> (x : xs, bs'')

according to

ghc -O -prof -auto-all --make Main.hs -fforce-recomp
./Main +RTS -h

heap usage goes up to about 20M with the HEAD, but only about 200 bytes with 6.8.2.

This is with 6.11.20081108, but I started investigating with the HEAD when I saw similar problems with more-or-less 6.10.1.

Trac metadata

Trac field	Value
Version	6.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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