[xmonad] error when building xmobar 0.9-3

[Chengqi(Lars) Song]

i need to add xft and utf-8 support to xmobar, so i chose to install aur/xmobar;
i add two lines in PKGBUILD for that:

    runhaskell Setup configure --flags="with_utf8" || return 1
    runhaskell Setup configure --flags="with_xft" || return 1

then i tried to build aur/xmobar, but i got the following error msg:

--------------------------start of output--------------------------
Building xmobar-0.9...
[ 1 of 25] Compiling Commands         ( Commands.hs, dist/build/xmobar/xmobar-tmp/Commands.o )
[ 2 of 25] Compiling Runnable[boot]   ( Runnable.hs-boot, dist/build/xmobar/xmobar-tmp/Runnable.o-boot )
[ 3 of 25] Compiling XUtil            ( dist/build/xmobar/xmobar-tmp/XUtil.hs, dist/build/xmobar/xmobar-tmp/XUtil.o )
[ 4 of 25] Compiling Plugins          ( Plugins.hs, dist/build/xmobar/xmobar-tmp/Plugins.o )
[ 5 of 25] Compiling Plugins.StdinReader ( Plugins/StdinReader.hs, dist/build/xmobar/xmobar-tmp/Plugins/StdinReader.o )

Plugins/StdinReader.hs:29:15:
    Ambiguous type variable `e' in the constraint:
      `GHC.Exception.Exception e'
        arising from a use of `catch' at Plugins/StdinReader.hs:29:15-78
    Probable fix: add a type signature that fixes these type variable(s)
==> ERROR: Build Failed.
    Aborting...
Error: Makepkg was unable to build xmobar package.
--------------------------end   of output--------------------------

whats wrong here? it seems the community/xmobar has no utf8 and xft enabled, but it's really needed for CJK users.

thanks
lars