Switch getLiteralStringExt to Identity where it can never be Nothing

src/ShellCheck/Analytics.hs

@@ -1066,9 +1066,7 @@ checkNumberComparisons params (TC_Binary id typ op lhs rhs) = do
       checkStrings =
         mapM_ stringError . take 1 . filter isNonNum
 
-      isNonNum t = fromMaybe False $ do
-        s <- getLiteralStringExt (const $ return "") t
-        return . not . all numChar $ s
+      isNonNum t = not . all numChar . runIdentity $ getLiteralStringExt (const $ return "") t
       numChar x = isDigit x || x `elem` "+-. "
 
       stringError t = err (getId t) 2170 $
@@ -2595,7 +2593,7 @@ checkTildeInPath _ (T_SimpleCommand _ vars _) =
             warn id 2147 "Literal tilde in PATH works poorly across programs."
     checkVar _ = return ()
 
-    hasTilde t = fromMaybe False (liftM2 elem (return '~') (getLiteralStringExt (const $ return "") t))
+    hasTilde t = '~' `elem` runIdentity (getLiteralStringExt (const $ return "") t)
     isQuoted T_DoubleQuoted {} = True
     isQuoted T_SingleQuoted {} = True
     isQuoted _ = False

src/ShellCheck/Checks/Commands.hs

@@ -249,13 +249,12 @@ prop_checkGrepRe23= verifyNot checkGrepRe "grep '.*' file"
 checkGrepRe = CommandCheck (Basename "grep") check where
     check cmd = f cmd (arguments cmd)
     -- --regex=*(extglob) doesn't work. Fixme?
-    skippable (Just s) = not ("--regex=" `isPrefixOf` s) && "-" `isPrefixOf` s
-    skippable _ = False
+    skippable s = not ("--regex=" `isPrefixOf` s) && "-" `isPrefixOf` s
     f _ [] = return ()
     f cmd (x:r) =
-        let str = getLiteralStringExt (const $ return "_") x
+        let str = runIdentity $ getLiteralStringExt (const $ return "_") x
         in
-            if str `elem` [Just "--", Just "-e", Just "--regex"]
+            if str `elem` ["--", "-e", "--regex"]
             then checkRE cmd r -- Regex is *after* this
             else
                 if skippable str
@@ -366,7 +365,7 @@ checkFindExecWithSingleArgument = CommandCheck (Basename "find") (f . arguments)
     check (exec:arg:term:_) = do
         execS <- getLiteralString exec
         termS <- getLiteralString term
-        cmdS <- getLiteralStringExt (const $ return " ") arg
+        let cmdS = runIdentity $ getLiteralStringExt (const $ return " ") arg
 
         guard $ execS `elem` ["-exec", "-execdir"] && termS `elem` [";", "+"]
         guard $ cmdS `matches` commandRegex