[Haskell-cafe] view patterns

let has [] = False; has _ = True -- this one is ok let empty list = case has list of True -> False; False -> True -- the following is problematic let emp (has -> True) = False; emp (has -> False) = True <interactive>:1:4: Warning: Pattern match(es) are overlapped In the definition of `emp': emp ((has -> True)) = ... emp ((has -> False)) = ... Why do I get this error in ghc or when I try to compile a file with view patterns? (using -fglasgow-exts and -XViewPatterns, ghc 6.10.1)