[GHC] #12007: Pattern families regression

[GHC]

#12007: Pattern families regression
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        Reporter:  MikeIzbicki       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by mpickering):

 * cc: goldfire (added)


Comment:

 So I could trigger the same panic with the example here
 https://ghc.haskell.org/trac/ghc/ticket/11549#comment:1 with rc-3

 but it is fixed in HEAD.

 Here is the core which I think is causing the panic. Maybe Richard can
 look and see if he thinks anything dodgy is going on?
 Maybe there is some improper use of runtime rep polymorphism.

 {{{
 -- RHS size: {terms: 18, types: 21, coercions: 0}
 T12007.$mB
   :: forall r_a19o t_a19m.
      Foo t_a19m
      -> (t_a19m -> t_a19m -> r_a19o)
      -> (GHC.Prim.Void# -> r_a19o)
      -> r_a19o
 [GblId, Arity=3, Caf=NoCafRefs]
 T12007.$mB =
   \ (@ (rep_a19n :: GHC.Types.RuntimeRep))
     (@ (r_a19o :: TYPE rep_a19n))
     (@ t_a19m)
     (scrut_a19q :: Foo t_a19m)
     (cont_a19r :: t_a19m -> t_a19m -> r_a19o)
     (fail_a19s :: GHC.Prim.Void# -> r_a19o) ->
     let {
       cont1_a19h :: t_a19m -> t_a19m -> r_a19o
       [LclId, Arity=2]
       cont1_a19h =
         \ (a1_a18K :: t_a19m) (a2_a18L :: t_a19m) ->
           cont_a19r a1_a18K a2_a18L } in
     case scrut_a19q of { Foo a1_a18I a2_a18J ->
     cont_a19r a1_a18I a2_a18J
     }

 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12007#comment:4>
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