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,,,