`canonicalizePath "\\\\localhost\\C$\.."` incorrectly produces `"\\\\localhost\\"`

Lifted from https://github.com/agda/agda/issues/8116#issuecomment-3391680164: ```haskell import System.Directory import System.FilePath list :: FilePath -> IO () list dir = do putStrLn $ replicate 66 '-' putStrLn dir putStrLn $ replicate 66 '-' mapM_ (putStrLn . ("- " ++)) . take 2 =<< listDirectory dir up :: FilePath -> IO FilePath up dir = canonicalizePath (dir </> "..") upIO :: IO FilePath -> IO FilePath upIO = (up =<<) -- https://stackoverflow.com/questions/2787203/unc-path-to-a-folder-on-my-local-computer main :: IO () main = do -- let dir = "\\\\?\\C:\\Users\\admin" let dir = "\\\\localhost\\C$\\Users\\admin" let ups = take 4 $ iterate upIO (pure dir) mapM_ (list =<<) ups ``` This produces: ``` ------------------------------------------------------------------ \\localhost\C$\Users\admin ------------------------------------------------------------------ - VirtualBox VMs - Videos ------------------------------------------------------------------ \\localhost\C$\Users ------------------------------------------------------------------ - Public - desktop.ini ------------------------------------------------------------------ \\localhost\C$ ------------------------------------------------------------------ - Windows - Users ------------------------------------------------------------------ \\localhost\ ------------------------------------------------------------------ test-directory: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOExce ption: \\localhost\: getDirectoryContents:findFirstFile: does not exist (The specified path is invalid.) While handling findFirstFile: does not exist (The specified path is invalid.) ``` In contrast, `"\\\\?\\C:\\Users\\admin"` is treated correctly. Canonicalization turns this into `C:\Users\admin`. There is a suspicion that `canonicalizePath` does not work correctly on UNC pathes. The unitests for `canonicalizePath` seem to steer clear of UNC paths, except for this one: https://github.com/haskell/directory/blob/6442a3cf04f74d82cdf8c9213324313d52b23d28/tests/CanonicalizePath.hs#L164-L166