avoid invalid filepaths on Windows

Cabal-QuickCheck/src/Test/QuickCheck/Instances/Cabal.hs

@@ -5,8 +5,8 @@ module Test.QuickCheck.Instances.Cabal () where
 
 import Control.Applicative        (liftA2)
 import Data.Bits                  (shiftR)
-import Data.Char                  (isAlphaNum, isDigit)
-import Data.List                  (intercalate)
+import Data.Char                  (isAlphaNum, isDigit, toLower)
+import Data.List                  (intercalate, isPrefixOf, isInfixOf)
 import Data.List.NonEmpty         (NonEmpty (..))
 import Distribution.Utils.Generic (lowercase)
 import Test.QuickCheck
@@ -503,14 +503,25 @@ shortListOf1 bound gen = sized $ \n -> do
     vectorOf k gen
 
 arbitraryShortToken :: Gen String
-arbitraryShortToken = arbitraryShortStringWithout "{}[]"
+arbitraryShortToken = arbitraryShortStringWithout "{}[]" (const True)
 
 arbitraryShortPath :: Gen String
-arbitraryShortPath = arbitraryShortStringWithout "{}[],"
-
-arbitraryShortStringWithout :: String -> Gen String
-arbitraryShortStringWithout excludeChars =
-    shortListOf1 5 $ elements [c | c <- ['#' ..  '~' ], c `notElem` excludeChars ]
+arbitraryShortPath = arbitraryShortStringWithout "{}[],<>:|*?" (not . winDevice)
+    where
+        devices = ["con", "aux", "prn", "com", "lpt", "nul"]
+        winDevice :: String -> Bool
+        winDevice p = let p' = map toLower p in any (isDev p') devices
+        isDev :: String -> String -> Bool
+        isDev p s = s `isPrefixOf` p || ('\\' : s) `isInfixOf` p
+
+arbitraryShortStringWithout :: String -> (String -> Bool) -> Gen String
+arbitraryShortStringWithout excludeChars validp =
+    shortListOf1 5 $ elements (str 5)
+    where
+        str :: Int -> String
+        str 0 = error "could not generate valid string"
+        str n = let s = [c | c <- ['#' ..  '~' ], c `notElem` excludeChars ]
+                 in if validp s then s else str (n - 1)
 
 -- |
 intSqrt :: Int -> Int