patch applied (ghc): Fix Trac #3950: unifying types of different kinds

[Ian Lynagh]

Mon Apr 12 08:18:45 PDT 2010  simonpj at microsoft.com
  * Fix Trac #3950: unifying types of different kinds
  
  I was assuming that the unifer only unified types of the 
  same kind, but now we can "defer" unsolved constraints that
  invariant no longer holds.  Or at least is's more complicated
  to ensure.  
  
  This patch takes the path of not assuming the invariant, which
  is simpler and more robust.  See
  Note [Mismatched type lists and application decomposition]

    M ./compiler/typecheck/TcUnify.lhs -28 +43

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=ghc;a=darcs_commitdiff;h=20100412151845-1287e-9324801606a63c410ad48972453c737d07399868.gz