• simonpj@microsoft.com's avatar
    Default the kind of unconstrained meta-type variables before tcSimplifyTop · 335bc125
    simonpj@microsoft.com authored
    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!)
    335bc125
TcSimplify.lhs 81.4 KB