[GHC] #772: checkPrecMatch

#772: checkPrecMatch
-----------------------+----------------------------------------------------
  Reporter:  guest     |          Owner:         
      Type:  bug       |         Status:  new    
  Priority:  normal    |      Milestone:  6.4.2  
 Component:  Compiler  |        Version:  6.4.2  
  Severity:  normal    |       Keywords:         
Difficulty:  Unknown   |   Architecture:  Unknown
        Os:  Windows   |  
-----------------------+----------------------------------------------------
*Research> :r
 Compiling Statistics.DescriptiveAnalysis.KeyHistoryListImpl (
 ./Statistics/Descr
 iptiveAnalysis/KeyHistoryListImpl.hs, interpreted )
 : panic! (the `impossible' happened, GHC version 6.4.2):
         checkPrecMatch

 Please report this as a compiler bug.  See:
   http://www.haskell.org/ghc/reportabug
 Research>

 This happened when i compile in GHCI:

 module Test where

 class TestInfo a where

 type Bla = String

 -- GADT Descriptors
 data Descriptor where
    BA :: String -> Descriptor
    GA :: (Show a, TestInfo a) => Either a (String, String) -> Descriptor
    SA :: String -> Descriptor
    AA :: String -> [Bla]-> Descriptor
    TA :: Bla -> Bla -> Bla -> Descriptor

 instance Eq Descriptor where
   (BA descr1) == (BA descr2) = descr1 == descr2
   (GA grpsubj) == (GA grpsubj2)  = show grpsubj == show grpsubj2  -- might
 not be correct
   (SA descr) == (SA descr2) = descr == descr2
   (AA descr keys) == (AA descr2 keys2) = (descr == descr2) && (keys ==
 keys2)
   (TA orikey key1 key2) == (TA orikeyB key1B key2B) = (orikey == orikeyB)
 && (key1 == key1B) && (key2 == key2B)
   (==) = error "Error pattern not found in (==)"

 -- the last line give the compilation error

 Peter, peteanom@xxxxxxxxx

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/772>
GHC <http://www.haskell.org/ghc/>
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