Hi, Am Montag, den 09.09.2013, 13:25 -0400 schrieb Richard Eisenberg:
According to the original post and the comments on #5498 (http://ghc.haskell.org/trac/ghc/ticket/5498), breaking through abstraction is another reason for keeping GND outside of Safe Haskell. I'm worried that the same concern would affect newtype coercions given the current proposal.
an easy fix would be to disallow coerce in Safe Haskell. A similarly easy fix would be to add the requirements that constructors have to be in scope when generating the instance Coercible a b => Coercible (D a) (D b) rule in Safe Haskell code. Although that might cripple the feature too much, but not more than not having the feature at all. I think the latter is a good compromise for the non-advertised release. 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