patch applied (ghc-6.8/ghc): Fix nasty recompilation bug in MkIface.computeChangedOccs

[Ian Lynagh]

Thu Dec 20 08:43:07 PST 2007  simonpj at microsoft.com
  * Fix nasty recompilation bug in MkIface.computeChangedOccs
  
  	MERGE to 6.8 branch
  
  In computeChangedOccs we look up the old version of a Name.
  But a WiredIn Name doesn't have an old version, because WiredIn things
  don't appear in interface files at all.
  
  Result: ghc-6.9: panic! (the 'impossible' happened)
    (GHC version 6.9 for x86_64-unknown-linux):
  	lookupVers1 base:GHC.Prim chr#{v}
  
  This fixes the problem.  The patch should merge easily onto the branch.
  
  

    M ./compiler/iface/MkIface.lhs +2