[GHC] #3990: UNPACK doesn't unbox data families

[GHC]

#3990: UNPACK doesn't unbox data families
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        Reporter:  rl                |                Owner:
            Type:  bug               |               Status:  new
        Priority:  low               |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.0.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 If it possible that the fix in comment:13 has broken? I am seeing no
 evidence of unpacking in this example with `master`,
 {{{#!hs
 {-# LANGUAGE TypeFamilies #-}
 module Hi where

 data family Complex a
 data instance Complex Double = CD {-# UNPACK #-} !Double
                                   {-# UNPACK #-} !Double

 data T = T {-# UNPACK #-} !(Complex Double)

 hi :: T
 hi = T (CD 1 1)
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/3990#comment:20>
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