patch applied (ghc): Implement a smart constructor mkUnsafeCoercion, and use it

[Simon Peyton Jones]

Mon Mar  1 03:17:44 PST 2010  simonpj at microsoft.com
  * Implement a smart constructor mkUnsafeCoercion, and use it
  
  This just ensures that an unsafe coercion is as localised as possible.
  For example, instead of
      UnsafeCo (Int -> t1) (Int -> t2)
  use 
      Int -> UnsafeCo t1 t2

    M ./compiler/types/Coercion.lhs -1 +10
    M ./compiler/types/OptCoercion.lhs -7 +10

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20100301111744-1287e-0bd18b859d4bb47ceaa09d1f6cdf73c01aeaa1b7.gz