checking for module Control.Monad.Error... no; and neither in package mtl
configure: error: Cannot find Control.Monad.Error; try installing package mtl?
mtl is installed and of course it provides Control.Monad.Error. However I also
have mtl-tf installed and it provides Control.Monad.Error too. This trips up
the configure test. (unregistering mtl-tf makes the test go through) |