[GHC] #8503: New GeneralizedNewtypeDeriving check still isn't permissive enough

[GHC]

#8503: New GeneralizedNewtypeDeriving check still isn't permissive enough
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        Reporter:  goldfire          |            Owner:  goldfire
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by nomeata):

 > (Actually, in fact I fear that we may instead construct a recursive
 dictionary instead, which we probably do not want for newtypes, though we
 do for data types, because we'll see a constraint we have already solved.
 See ​Scrap your boilerplate with class for why we want recursive
 dictionaries.)

 JFTR: Last time I checked, we did, leading to a non-terminating Coercion
 value.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8503#comment:18>
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