[GHC] #9103: hackage's type-level-0.2.4 fails to compile

[GHC]

#9103: hackage's type-level-0.2.4 fails to compile
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        Reporter:  slyfox            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler (Type    |                 Version:  7.8.2
  checker)                           |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |                Blocking:
      Blocked By:                    |  Differential Revisions:
 Related Tickets:  #8634             |
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Comment (by simonpj):

 OK, so aside from the "redundant constraint" problem (now reported as
 #10100), what's left in this ticket?
  * The error message looks absolutely right to me.
 {{{
 Data/TypeLevel/Num/Ops.hs:90:10:
     Illegal instance declaration for ‘Succ' (x, x) (x, x) D0 D0 True’
       The liberal coverage condition fails in class ‘Succ'’
         for functional dependency: ‘yh yl yz -> xh xl’
       Reason: lhs types ‘D0’, ‘D0’, ‘True’
         do not jointly determine rhs types ‘(x, x)’, ‘(x, x)’
     In the instance declaration for ‘Succ' (x, x) (x, x) D0 D0 True’
 }}}

  * Yes, the user manual about "lifting the Paterson conditions" is wrong:
 see #8634, comment:14.

  * If, for some reason, this code is really really what you want, then you
 need `DysFunctionalDependencies`; for that see #8634.

 So can we close this ticket?

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9103#comment:11>
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