[GHC] #2685: Panic in harpy with GHC 6.10 RC

[GHC]

#2685: Panic in harpy with GHC 6.10 RC
------------------------------+---------------------------------------------
 Reporter:  dons              |          Owner:                  
     Type:  bug               |         Status:  new             
 Priority:  high              |      Milestone:  6.10.1          
Component:  Compiler          |        Version:  6.9             
 Severity:  normal            |     Resolution:                  
 Keywords:                    |     Difficulty:  Unknown         
 Testcase:                    |   Architecture:  Unknown/Multiple
       Os:  Unknown/Multiple  |  
------------------------------+---------------------------------------------
Changes (by igloo):

  * priority:  normal => high
  * difficulty:  => Unknown
  * milestone:  => 6.10.1

Comment:

 Here's a minimal testcase:
 {{{
 module TH (th) where

 import Language.Haskell.TH

 newtype NT = C (() -> ())

 th :: Q [Dec]
 th = [d| foo = C undefined |]
 }}}

 {{{
 module Use where

 import TH

 $( th )
 }}}

 {{{
 $ ghc --make -O -XTemplateHaskell Use
 [1 of 2] Compiling TH               ( TH.hs, TH.o )
 [2 of 2] Compiling Use              ( Use.hs, Use.o )
 Loading package ghc-prim ... linking ... done.
 Loading package integer ... linking ... done.
 Loading package base ... linking ... done.
 Loading package syb ... linking ... done.
 Loading package array-0.2.0.0 ... linking ... done.
 Loading package packedstring-0.1.0.1 ... linking ... done.
 Loading package containers-0.2.0.0 ... linking ... done.
 Loading package pretty-1.0.1.0 ... linking ... done.
 Loading package template-haskell ... linking ... done.
 ghc: panic! (the 'impossible' happened)
   (GHC version 6.10.0.20081011 for x86_64-unknown-linux):
         mkUsage
     main:TH C{d} [(rz, base:GHC.Err.undefined{v rz}),
                   (rhB, main:TH.C{d rhB}), (rhD, main:TH.th{v rhD})]

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

 $
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2685#comment:1>
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