[GHC] #13318: ghc-7.10.1 panics when compiling singletons-1.1.2.1

[GHC]

#13318: ghc-7.10.1 panics when compiling singletons-1.1.2.1
-------------------------------------+-------------------------------------
           Reporter:  WrenThornton   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Not sure if this has been fixed in newer versions or not, but:

 {{{
 [39 of 45] Compiling Data.Singletons.Prelude.List (
 src/Data/Singletons/Prelude/List.hs,
 dist/build/Data/Singletons/Prelude/List.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.1 for x86_64-apple-darwin):
         Template variable unbound in rewrite rule
   n_X2iZh
   [a_a2gBn, t_a2gBo, n_a2iB7, ipv_s2szc, ipv_s2szd, sc_s2tXD,
    sc_s2tXF, sc_s2tXG, sg_s2tXH]
   [a_X2gZv, t_X2gZx, n_X2iZh, ipv_X2sXn, ipv_X2sXp, sc_X2ulQ,
    sc_X2ulT, sc_X2ulV, sg_X2ulX]
   [TYPE a_a2gBn, TYPE t_a2gBo,
    TYPE Let1627878522XsSym4 t_a2gBo n_a2iB7 ipv_s2szc ipv_s2szd,
    sc_s2tXD,
    (SCons
       @ a_a2gBn
       @ (ipv_s2szc : ipv_s2szd)
       @ ipv_s2szc
       @ ipv_s2szd
       @~ <ipv_s2szc : ipv_s2szd>_N
       sc_s2tXF
       sc_s2tXG)
    `cast` (sg_s2tXH
            :: R:Sing[]z (ipv_s2szc : ipv_s2szd)
               ~R# Sing (Apply (Apply (:$) ipv_s2szc) ipv_s2szd))]
   [TYPE a_a2gBn, TYPE t_a2gBo,
    TYPE Let1627878522XsSym4 t_a2gBo ipv_s2szc ipv_X2sQZ ipv_X2sR1,
    sc_s2tXD,
    (SCons
       @ a_a2gBn
       @ (ipv_X2sQZ : ipv_X2sR1)
       @ ipv_X2sQZ
       @ ipv_X2sR1
       @~ <ipv_X2sQZ : ipv_X2sR1>_N
       ipv_s2szf
       ipv_s2szg)
    `cast` (Sub (Sym (TFCo:R:Sing[]z[0] <a_a2gBn>_N)) (Sym
 (TFCo:R:Apply[][]:$$l0[0]
                                                            <a_a2gBn>_N
 <ipv_X2sR1>_N <ipv_X2sQZ>_N)
                                                       ; (Apply
                                                            (Sym
 (TFCo:R:Apply(->)k:$l0[0]
 <a_a2gBn>_N <ipv_X2sQZ>_N))
 <ipv_X2sR1>_N)_N)
            :: R:Sing[]z (ipv_X2sQZ :$$$ ipv_X2sR1)
               ~R# Sing (Apply (Apply (:$) ipv_X2sQZ) ipv_X2sR1))]

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13318>
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