[GHC] #1684: impossible happened when compiling darcs with GADTs.

[GHC]

#1684: impossible happened when compiling darcs with GADTs.
--------------------------------+-------------------------------------------
  Reporter:  droundy at darcs.net  |          Owner:                
      Type:  bug                |         Status:  new           
  Priority:  normal             |      Milestone:                
 Component:  Compiler           |        Version:  6.6           
  Severity:  normal             |       Keywords:                
Difficulty:  Unknown            |             Os:  Linux         
  Testcase:                     |   Architecture:  x86_64 (amd64)
--------------------------------+-------------------------------------------
ghc -DPACKAGE_NAME=\"darcs\" -DPACKAGE_TARNAME=\"darcs\"
 -DPACKAGE_VERSION=\"1.1.0pre1\" -DPACKAGE_STRING=\"darcs\ 1.1.0pre1\"
 -DPACKAGE_BUGREPORT=\"bugs at darcs.net\" -DSTDC_HEADERS=1
 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1
 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1
 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DGADT_WITNESSES=1 -DHAVE_TERMIO_H=1
 -cpp  -package regex-compat -package QuickCheck -package mtl -package
 parsec -package html -package unix  -fglasgow-exts -Wall -Werror -I.
 -I./src -i./src -DHAVE_CURSES -DHAVE_CURL -c src/Darcs/Patch/Merge.lhs
 ghc-6.6: panic! (the 'impossible' happened)
   (GHC version 6.6 for x86_64-unknown-linux):
         splitTyConApp t_s2EA{tv} [tv] t_s2EB{tv} [tv] t_s2ED{tv} [tv]

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

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1684>
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