diff --git a/data/Default.hs b/data/Default.hs
--- a/data/Default.hs
+++ b/data/Default.hs
@@ -147,8 +147,8 @@
 
 error = (\x -> x) ==> id
 error = (\x y -> x) ==> const
-error = (\(_,y) -> y) ==> snd
-error = (\(x,_) -> x) ==> fst
+error = (\(x,y) -> y) ==> snd where _ = notIn x y
+error = (\(x,y) -> x) ==> fst where _ = notIn y x
 warn "Use curry" = (\x y-> f (x,y)) ==> curry f where _ = notIn [x,y] f
 warn "Use uncurry" = (\(x,y) -> f x y) ==> uncurry f where _ = notIn [x,y] f
 error "Redundant $" = (($) . f) ==> f
@@ -506,6 +506,7 @@
 foo = evaluate [12] -- return [12]
 test = \ a -> f a >>= \ b -> return (a, b)
 fooer input = catMaybes . map Just $ input -- mapMaybe Just
+main = print $ map (\_->5) [2,3,5] -- const 5
 
 import Prelude \
 yes = flip mapM -- Control.Monad.forM
diff --git a/hlint.cabal b/hlint.cabal
--- a/hlint.cabal
+++ b/hlint.cabal
@@ -1,7 +1,7 @@
 cabal-version:      >= 1.6
 build-type:         Simple
 name:               hlint
-version:            1.8.37
+version:            1.8.39
 license:            BSD3
 license-file:       LICENSE
 category:           Development
diff --git a/src/Hint/Match.hs b/src/Hint/Match.hs
--- a/src/Hint/Match.hs
+++ b/src/Hint/Match.hs
@@ -131,7 +131,7 @@
 
 unifyPat :: NameMatch -> Pat_ -> Pat_ -> Maybe [(String,Exp_)]
 unifyPat nm (PVar _ x) (PVar _ y) = Just [(fromNamed x, toNamed $ fromNamed y)]
-unifyPat nm PWildCard{} PVar{} = Just []
+unifyPat nm (PVar _ x) PWildCard{} = Just [(fromNamed x, toNamed $ "_" ++ fromNamed x)]
 unifyPat nm x y = unifyDef nm x y 
 
 
diff --git a/src/Hint/Naming.hs b/src/Hint/Naming.hs
--- a/src/Hint/Naming.hs
+++ b/src/Hint/Naming.hs
@@ -3,7 +3,7 @@
     Suggest the use of camelCase
 
     Only permit:
-    _*[A-Za-z]*_*'*
+    _*[A-Za-z]*_*#*'*
 
     Apply this to things that would get exported by default only
     Also allow prop_ as it's a standard QuickCheck idiom
@@ -24,6 +24,7 @@
 data Yes = FOO_A | Foo_B -- data Yes = FOO_A | FooB
 case_foo = 1
 cast_foo = 1 -- castFoo = ...
+runMutator# = 1
 </TEST>
 -}
 
@@ -80,7 +81,7 @@
 suggestName :: String -> Maybe String
 suggestName x = listToMaybe [f x | not $ isSym x || good || not (any isLower x) || "prop_" `isPrefixOf` x || "case_" `isPrefixOf` x]
     where
-        good = all isAlphaNum $ drp '_' $ drp '\'' $ reverse $ drp '_' x
+        good = all isAlphaNum $ drp '_' $ drp '#' $ drp '\'' $ reverse $ drp '_' x
         drp x = dropWhile (== x)
 
         f xs = us ++ g ys