[GHC] #15920: Implement a flag which disables safe Haskell

[GHC]

#15920: Implement a flag which disables safe Haskell
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        Reporter:  mpickering        |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  high              |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.6.2
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D5360
       Wiki Page:                    |
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Comment (by goldfire):

 I know it's "too late", but this strikes me as something that should get
 more visibility. With the feature requested here, it is now possible to
 compile a module with `{-# LANGUAGE Safe #-}` in it but that uses
 `unsafeCoerce`. The fact that this happens might be buried in a `.cabal`
 file or even more obfuscated.

 While I certainly recognize why Matt wanted this, and I see no reasonable
 alternative, I do think that this begs the larger question of what
 guarantees we can expect from a module with `{-# LANGUAGE Safe #-}` in it.

 I think the best course would be to make a post-hoc ghc-proposal to seek
 community input on the design here. I don't advocate reverting the patch
 -- I see how you can be quite blocked without this -- but I still want to
 have a larger conversation about the design goals here.

 Do you agree?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15920#comment:5>
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