Use a phantom type instead of undefined in L.LayoutBuilderP
Use a phantom type instead of undefined in L.LayoutBuilderP

Ignore-this: f9009c339ac20245ca0b1dc8154b673f

This better expresses the idea that the argument to alwaysTrue is just there to
select an instance. Another option could be to do use a fundep, which seems to
be compatible with the two instances so far.

class Predicate p w | p -> w

darcs-hash:20110609051858-1499c-ea3f8f433a510fea3c6fcc79b77098d14afe163f

kmels/xmonad-launcher,kmels/xmonad-launcher