[GHC] #9574: GHC Panic: No Skolem Info

[GHC]

#9574: GHC Panic: No Skolem Info
-------------------------------------+-------------------------------------
              Reporter:  ian_mi      |            Owner:
                  Type:  bug         |           Status:  closed
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.9
            Resolution:  fixed       |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
  polykinds/T9574                    |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
Changes (by simonpj):

 * status:  new => closed
 * testcase:   => polykinds/T9574
 * resolution:   => fixed


Comment:

 Thank you for reducing the test case so well.  The problem is that the
 instance
 {{{
 instance Funct ('KProxy :: KProxy o) where
     type Codomain 'KProxy = NatTr (Proxy :: o -> *)
 }}}
 should bind 'o' on the LHS of the type instance:
 {{{
 instance Funct ('KProxy :: KProxy o) where
     type Codomain ('KProxy :: KProxy o) = NatTr (Proxy :: o -> *)
 }}}
 Otherwise there is nothing to connect the lhs and rhs.  I've added this
 check.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9574#comment:8>
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