id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
4136	Automatically derived Read of operator is not inverse of automatically derived Show	dsf		"This program fails as shown below using ghc 6.13 snapshot 20100519

{{{
data T = (:=:) | (:!=:) deriving (Show,Read)

main = 
  putStrLn (""show (:=:) = "" ++ show (:=:)) >>
  putStrLn (""read (show (:=:)) :: T = "" ++
            show (read (show (:=:)) :: T))
}}}
Result:
{{{
> main
show (:=:) = :=:
read (show (:=:)) :: T = *** Exception: Prelude.read: no parse
}}}"	bug	closed	normal		Compiler	6.13	fixed			Unknown/Multiple	Unknown/Multiple	Runtime crash		deriving/should_run/T4136