I am not a Haskeller, but you can use "!h searchterm" on Duck Duck Go.
Re:The Haskell user experience
by ddellacosta on Thursday August 06, 2015 @12:11AM
(#10014484)
OMG thank you, this was the thing that got me to finally permanently set my toolbar search in FF to Duck Duck Go...
https://www.haskell.org/hoogle/?hoogle=a+-%3E+[b]
It's as useful as you might hope!