Support mtl-2.3
Starting from mtl-2.3
liftM
is no longer re-exported from Control.Monad
by Control.Monad.Writer.Strict
. A simple backward-compatible fix is to replace liftM
with fmap
.
Cf. ghc!9370 (closed), ghc#21587 (closed) and https://github.com/haskell/haddock/pull/1535
Edited by Bodigrim