patch applied (ghc): Make record selection look cheap

[Simon Peyton Jones]

Wed Sep  6 04:52:42 PDT 2006  simonpj at microsoft.com
  * Make record selection look cheap
  
  exprIsCheap was already making record selection look cheap, esp for
  dictionary selection; e.g.
     (==) dEq
  
  The idea is to allow those record selections to migrate inside a
  lambda, because on the whole it's more expensive to share than 
  repeat them.
  
  But sometimes dictionary selection is nested; e.g.
     (==) ($p1Num dNum)
  
  This turned out to make a (fragile) rewrite rule fire a little
  more robustly, but it seems like a good idea in any case.
  
  This patch makes nested record selections also look cheap.
  

    M ./compiler/coreSyn/CoreUtils.lhs -1 +1