[GHC] #9112: support for deriving Vector/MVector instances

[GHC]

#9112: support for deriving Vector/MVector instances
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        Reporter:  jwlato            |            Owner:
            Type:  feature request   |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.8.2
      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 simonpj):

 I can't reproduce this because I fall at an early fence:
 {{{
 bash$ cabal install hackage-server
 Resolving dependencies...
 cabal: Could not resolve dependencies:
 trying: hackage-server-0.4 (user goal)
 trying: base-4.7.0.0/installed-018... (dependency of hackage-server-0.4)
 next goal: process (dependency of hackage-server-0.4)
 rejecting: process-1.2.0.0/installed-eaf... (conflict: process =>
 unix==2.7.0.1/installed-23f..., hackage-server => unix<2.7)
 trying: process-1.2.0.0
 next goal: Cabal (dependency of hackage-server-0.4)
 rejecting: Cabal-1.18.1.3/installed-9a9..., 1.20.0.0, 1.18.1.3, 1.18.1.2,
 1.18.1.1, 1.18.1, 1.18.0 (conflict: hackage-server => Cabal>=1.16 &&
 <1.17)
 trying: Cabal-1.16.0.3
 rejecting: Cabal-1.16.0.3:+base3 (conflict: process==1.2.0.0,
 Cabal-1.16.0.3:base3 => process>=1 && <1.2)
 rejecting: Cabal-1.16.0.3:-base3 (conflict:
 base==4.7.0.0/installed-018...,
 Cabal-1.16.0.3:base3 => base<3)
 Backjump limit reached (change with --max-backjumps).

 bash$ ghc --version
 The Glorious Glasgow Haskell Compilation System, version 7.8.2
 }}}
 I have no idea what all this means.  But it looks plausible that it's the
 same issue, and is rightly rejected on the grounds that it could be
 unsound.  We have yet to figure out a way to solve this; see #9123.

 I do not know whether this is a show-stopper any particular packages, and
 if so which.  Nor do I know if there is a reasonable way to work around
 it.  Perhaps others will know more than I do.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9112#comment:7>
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