[GHC] #8827: Inferring Safe mode with GeneralizedNewtypeDeriving is wrong

[GHC]

#8827: Inferring Safe mode with GeneralizedNewtypeDeriving is wrong
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        Reporter:  goldfire          |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:  7.8.1
       Component:  Compiler          |          Version:  7.8.1-rc2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:  8226, 8745
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Comment (by simonpj):

 I don't have a strong opinion; (C) is fine with me if library authors are
 happy.  Maybe they will be; after all, they didn't have lifted coercions
 before, and (by default) they still won't.

 Note that (C) is not related to the visiblity or otherwise of a recursive
 set of data constructors; it's simply a question of what the default roles
 for an un-annotated data type are.

 Does anyone else care?

 It's a tremendous pity that all this is happening just as 7.8 is on the
 verge of release (indeed, I thought it had already happened).  I am
 reluctant to delay it while we debate this issue further.  (I am not
 optimistic about a rapid consensus.)

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8827#comment:19>
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