patch applied (ghc): Default the kind of unconstrained meta-type variables before tcSimplifyTop

[Simon Peyton Jones]

Wed Nov  1 09:33:25 PST 2006  simonpj at microsoft.com
  * Default the kind of unconstrained meta-type variables before tcSimplifyTop
  
  This patch fixes a long standing bug, Trac #179, 
  and a recently reported one, Trac #963.
  
  The problem in both cases was an unconstrained type variable 'a', of kind
  argTypeKind (printed "??") or openTypeKind ("?").  At top level we now default
  the kind of such variables to liftedTypeKind ("*").  This is important because
  then instance declarations can match it. The defaulting function is called
  TcMType.zonkTopTyVar, and is commented.  (Most of the extra lines in the
  patch are comments!)
  

    M ./compiler/typecheck/TcMType.lhs -1 +25
    M ./compiler/typecheck/TcSimplify.lhs +3