Directory.doesDirectoryExist inconsistency

[Claus Reinke]

I've just been chasing a portability problem, where a largish third-party
program works fine on our suns (ghc-5.02.3), but chokes under
cygwin/windows (ghc-5.04). Comes down to an inconsistency in the
handling of (trailing?) slashes in Directory.doesDirectoryExist (see
a and b below).

Consequence: under cygwin, the program doesn't see the existing directory,
tries to create it, and fails (error message doesn't seem to include the file
name, btw).

Cheers,
Claus

$ uname -a
CYGWIN_98-4.10 VAIO 1.3.10(0.51/3/2) 2002-02-25 11:14 i686 unknown

$ ghci
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 5.04, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
Loading package haskell98 ... linking ... done.
Prelude>
Prelude> Directory.doesDirectoryExist "u" >>= print
False
Prelude> Directory.createDirectory "u"
Prelude> Directory.doesDirectoryExist "u" >>= print
True
Prelude> Directory.doesDirectoryExist "u/" >>= print                  -- (a)
note this one, compare with b
False
Prelude> Directory.doesDirectoryExist "u\\" >>= print
False
Prelude> :q
Leaving GHCi.

> uname -a
SunOS myrtle 5.8 Generic_108528-16 sun4u sparc SUNW,Ultra-4
> ghci
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 5.02.3, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package std ... linking ... done.
Prelude> Directory.doesDirectoryExist "u" >>= print
False
Prelude> Directory.createDirectory "u"
Prelude> Directory.doesDirectoryExist "u" >>= print
True
Prelude> Directory.doesDirectoryExist "u/" >>= print                -- (b) note
this one, compare with a
True
Prelude> Directory.doesDirectoryExist "u\\" >>= print
False
Prelude> :q
Leaving GHCi.