Use find instead of listToMaybe and filter

src/ShellCheck/Analytics.hs

@@ -1234,10 +1234,10 @@ checkLiteralBreakingTest _ t = potentially $
         return ()
 
     comparisonWarning list = do
-        token <- listToMaybe $ filter hasEquals list
+        token <- find hasEquals list
         return $ err (getId token) 2077 "You need spaces around the comparison operator."
     tautologyWarning t s = do
-        token <- listToMaybe $ filter isNonEmpty $ getWordParts t
+        token <- find isNonEmpty $ getWordParts t
         return $ err (getId token) 2157 s
 
 prop_checkConstantNullary = verify checkConstantNullary "[[ '$(foo)' ]]"
@@ -2910,7 +2910,7 @@ checkLoopVariableReassignment params token =
   where
     check = do
         str <- loopVariable token
-        next <- listToMaybe $ filter (\x -> loopVariable x == Just str) path
+        next <- find (\x -> loopVariable x == Just str) path
         return $ do
             warn (getId token) 2165 "This nested loop overrides the index variable of its parent."
             warn (getId next)  2167 "This parent loop has its index variable overridden."

src/ShellCheck/Checks/ShellSupport.hs

@@ -340,8 +340,8 @@ checkBashisms = ForShell [Sh, Dash] $ \t -> do
             potentially $ do
                 allowed' <- Map.lookup name allowedFlags
                 allowed <- allowed'
-                (word, flag) <- listToMaybe $
+                (word, flag) <- find
-                    filter (\x -> (not . null . snd $ x) && snd x `notElem` allowed) flags
+                    (\x -> (not . null . snd $ x) && snd x `notElem` allowed) flags
                 return . warnMsg (getId word) $ name ++ " -" ++ flag ++ " is"
 
             when (name == "source") $ warnMsg id "'source' in place of '.' is"

src/ShellCheck/Parser.hs

@@ -34,7 +34,7 @@ import Control.Monad.Identity
 import Control.Monad.Trans
 import Data.Char
 import Data.Functor
-import Data.List (isPrefixOf, isInfixOf, isSuffixOf, partition, sortBy, intercalate, nub)
+import Data.List (isPrefixOf, isInfixOf, isSuffixOf, partition, sortBy, intercalate, nub, find)
 import Data.Maybe
 import Data.Monoid
 import Debug.Trace
@@ -589,7 +589,7 @@ readConditionContents single =
 
     checkTrailingOp x = fromMaybe (return ()) $ do
         (T_Literal id str) <- getTrailingUnquotedLiteral x
-        trailingOp <- listToMaybe (filter (`isSuffixOf` str) binaryTestOps)
+        trailingOp <- find (`isSuffixOf` str) binaryTestOps
         return $ parseProblemAtId id ErrorC 1108 $
             "You need a space before and after the " ++ trailingOp ++ " ."