[nem-en] usesite

[Vladimir Reshetnikov]

What does 'usesite' mean here (core.n):

 [Nemerle.MacroUsage (Nemerle.MacroPhase.WithTypedMembers,
                      Nemerle.MacroTargets.Class,
                      Inherited = false, AllowMultiple = false)]
 macro StructuralHashCode (t : TypeBuilder) {
   def flds = t.GetFields (BindingFlags.Public %| BindingFlags.NonPublic %
|
                           BindingFlags.Instance %| BindingFlags.DeclaredOnly);

   def body =
     List.FoldLeft (flds, <[ 0 ]>, fun (x : IField, acc) {
       <[ $acc %^ $(x.Name : usesite).GetHashCode () ]>
     });
   t.Define (<[ decl:
     public override GetHashCode () : int {
       $body
     }
   ]>);
 }