Use unsnocNE for HLint

src/Swarm/Language/Pretty.hs

@@ -9,15 +9,13 @@
 -- Pretty-printing for the Swarm language.
 module Swarm.Language.Pretty where
 
-import Control.Lens (unsnoc)
 import Control.Lens.Combinators (pattern Empty)
 import Control.Unification
 import Control.Unification.IntVar
 import Data.Bool (bool)
 import Data.Functor.Fixedpoint (Fix, unFix)
 import Data.List.NonEmpty qualified as NE
 import Data.Map.Strict qualified as M
-import Data.Maybe (fromJust)
 import Data.Set (Set)
 import Data.Set qualified as S
 import Data.String (fromString)
@@ -32,7 +30,7 @@ import Swarm.Language.Parse (getLocRange)
 import Swarm.Language.Syntax
 import Swarm.Language.Typecheck
 import Swarm.Language.Types
-import Swarm.Util (showEnum, showLowT)
+import Swarm.Util (showEnum, showLowT, unsnocNE)
 import Witch
 
 ------------------------------------------------------------
@@ -160,7 +158,7 @@ instance ((UnchainableFun t), (PrettyPrec t)) => PrettyPrec (TypeF t) where
   prettyPrec p (TyCmdF ty) = pparens (p > 9) $ "cmd" <+> prettyPrec 10 ty
   prettyPrec _ (TyDelayF ty) = braces $ ppr ty
   prettyPrec p (TyFunF ty1 ty2) =
-    let (iniF, lastF) = fromJust . unsnoc $ ty1 : unchainFun ty2
+    let (iniF, lastF) = unsnocNE $ ty1 NE.:| unchainFun ty2
         funs = (prettyPrec 1 <$> iniF) <> [ppr lastF]
         inLine l r = l <+> "->" <+> r
         multiLine l r = l <+> "->" <> hardline <> r

src/Swarm/Util.hs

@@ -27,6 +27,7 @@ module Swarm.Util (
   surfaceEmpty,
   applyWhen,
   hoistMaybe,
+  unsnocNE,
 
   -- * Directory utilities
   readFileMay,
@@ -239,6 +240,23 @@ applyWhen False _ x = x
 hoistMaybe :: (Applicative m) => Maybe b -> MaybeT m b
 hoistMaybe = MaybeT . pure
 
+-- | Like 'unsnoc', but for 'NonEmpty' so without the 'Maybe'
+--
+-- Taken from Cabal-syntax Distribution.Utils.Generic.
+--
+-- Example:
+--
+-- >>> unsnocNE (1 :| [2, 3])
+-- ([1,2],3)
+--
+-- >>> unsnocNE (1 :| [])
+-- ([],1)
+unsnocNE :: NonEmpty a -> ([a], a)
+unsnocNE (x :| xs) = go x xs
+ where
+  go y [] = ([], y)
+  go y (z : zs) = let ~(ws, w) = go z zs in (y : ws, w)
+
 ------------------------------------------------------------
 -- Directory stuff