Re: [GHC] #10009: type inference regression when faking injective type families

29 Apr 2015

      #10009: type inference regression when faking injective type families
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        Reporter:  aavogt            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  high              |               Milestone:  7.10.2
       Component:  Compiler (Type    |                 Version:  7.10.1-rc1
  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:  #10226            |
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Comment (by simonpj):

 I tried to test `hlist-0.3.4.1`, but stalled on
 {{{
 Data/HList/HList.hs:55:1:
     The associated type ‘UnPrime’
     mentions none of the type or kind variables of the class ‘ConvHList a’
     In the class declaration for ‘ConvHList’
 }}}
 which is an absolutely correct error message.

 Simon

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10009#comment:25
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