Hi, Am Sonntag, den 18.08.2013, 21:54 +0200 schrieb Gabor Greif:
There is also user-supplied Typeable instances which are ignored (with a warning?).
at least no Typeabe-specific warning: Prelude> newtype Age = Age Int Prelude> instance Typeable Age Prelude> :m + Data.Typeable Prelude Data.Typeable> instance Typeable Age <interactive>:5:10: Warning: No explicit method or default declaration for `typeOf' In the instance declaration for `Typeable Age' It seems that GHC does prevent it in Safe mode, though: -- Check that if the module is compiled with -XSafe, there are no -- hand written instances of old Typeable as then unsafe casts could be -- performed. Derived instances are OK. ; when (safeLanguageOn dflags) $ mapM_ (\x -> when (typInstCheck x) (addErrAt (getSrcSpan $ iSpec x) typInstErr)) local_infos (compiler/typecheck/TcInstDcls.lhs) Greetings, Joachim -- Joachim “nomeata” Breitner mail@joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata@joachim-breitner.de • GPG-Key: 0x4743206C Debian Developer: nomeata@debian.org