[GHC] #14220: GeneralizedNewtypeDeriving and polymorphic arguments don't play nicely together

[GHC]

#14220: GeneralizedNewtypeDeriving and polymorphic arguments don't play nicely
together
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        Reporter:  ivanm         |                Owner:  (none)
            Type:  bug           |               Status:  new
        Priority:  normal        |            Milestone:
       Component:  Compiler      |              Version:  8.0.2
      Resolution:                |             Keywords:
Operating System:  MacOS X       |         Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown  |            Test Case:
      Blocked By:                |             Blocking:
 Related Tickets:                |  Differential Rev(s):
       Wiki Page:                |
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Comment (by Iceland_jack):

 Doesn't panic for 8.0.1

 {{{
 $ ghci -ignore-dot-ghci /tmp/a.hs
 GHCi, version 7.8.4: http://www.haskell.org/ghc/  :? for help
 Loading package ghc-prim ... linking ... done.
 Loading package integer-gmp ... linking ... done.
 Loading package base ... linking ... done.
 [1 of 1] Compiling Main             ( /tmp/a.hs, interpreted )

 /tmp/a.hs:10:13:
     Could not coerce from ‘proxy Int’ to ‘proxy MyInt’
       because ‘proxy Int’ and ‘proxy MyInt’ are different types.
       arising from the coercion of the method ‘nameOf’ from type
                    ‘forall (proxy :: * -> *). proxy Int -> String’ to type
                    ‘forall (proxy :: * -> *). proxy MyInt -> String’
     Possible fix:
       use a standalone 'deriving instance' declaration,
         so you can specify the instance context yourself
     When deriving the instance for (NameOf MyInt)
 Failed, modules loaded: none.
 Prelude>
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14220#comment:1>
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