patch applied (ghc): Fix a bug in MatchCon, and clarify what dataConInstOrigArgTys does

[Simon Peyton Jones]

Thu Jun  7 14:38:37 PDT 2007  Lemmih <lemmih at gmail.com>
  * Fix a bug in MatchCon, and clarify what dataConInstOrigArgTys does
  
  There was an outright bug in MatchCon.matchOneCon, in the construction
  of arg_tys.  Easily fixed.  It never showed up becuase the arg_tys are
  only used in WildPats, and they in turn seldom have their types looked
  (except by hsPatType).  So I can't make a test case for htis.
  
  While I was investigating, I added a bit of clarifation and
  invariant-checking to dataConInstOrigArgTys and dataConInstArgTys
  

    M ./compiler/basicTypes/DataCon.lhs -18 +21
    M ./compiler/deSugar/MatchCon.lhs -8 +12
    M ./compiler/ghci/RtClosureInspect.hs -1 +1
    M ./compiler/hsSyn/HsPat.lhs +3
    M ./compiler/iface/BuildTyCl.lhs +2
    M ./compiler/typecheck/TcDeriv.lhs -1 +2