Have you tried doing this? If so, `coerce` is the least of our problems: `unsafeCoerce#` is much worse! When I just tried, GHC told me that I couldn't import GHC.Prim into a module with -XSafe enabled.
So, this seems to be a documentation bug (the Haddock description of GHC.Prim indeed says "Safe Inferred"), but not a "real" bug. Let me know if you see otherwise! Thanks, Richard On Aug 16, 2014, at 6:06 PM, Wolfgang Jeltsch <g9ks1...@acme.softbase.org> wrote: > Hi, > > thank you for these links. > > Still, it is interesting that also in GHC 7.8 you can have a coerce that > is considered “Safe”, although the discussions on Trac concluded that > this should not be the case. You can just import coerce via GHC.Prim, > which is “Safe-Inferred”. > > All the best, > Wolfgang > > Am Freitag, den 15.08.2014, 19:40 -0400 schrieb Richard Eisenberg: >> See https://ghc.haskell.org/trac/ghc/ticket/8745 and >> https://ghc.haskell.org/trac/ghc/ticket/8827 which discuss this problem at >> length. >> >> The short answer: It's conceivable that a role-unaware library author would >> have abstraction expectations that are defeated through the use of `coerce`. >> >> I would strongly welcome a proposal for how to make `coerce`, and hence >> GeneralizedNewtypeDeriving, to be considered Safe for 7.10. >> >> Richard >> >> On Aug 15, 2014, at 4:04 PM, Wolfgang Jeltsch <g9ks1...@acme.softbase.org> >> wrote: >> >>> Hi, >>> >>> I would expect the function >>> >>> coerce :: Coercible a b => a -> b >>> >>> to be safe in the sense of Safe Haskell. However, the Data.Coerce module >>> is marked “Unsafe”. The coerce function is also available via GHC.Exts >>> and GHC.Prim. The former module is marked “Unsafe”, but the latter is >>> (surprisingly) marked “Safe-Inferred”. >>> >>> What are the reasons behind this? >>> >>> All the best, >>> Wolfgang >>> >>> _______________________________________________ >>> Glasgow-haskell-users mailing list >>> Glasgow-haskell-users@haskell.org >>> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users >>> >> > > > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users@haskell.org > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users > _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
