public void AddUsing(UsingClause un)
{
if (DeclarationFound){
Compiler.Report.Error (1529, un.Location, "A using clause must precede all other namespace elements except extern alias declarations");
}
if (clauses == null)
clauses = new List<UsingClause> ();
clauses.Add (un);
}
void Warning_DuplicateEntry(UsingClause entry)
{
Compiler.Report.Warning (105, 3, entry.Location,
"The using directive for `{0}' appeared previously in this namespace",
entry.ResolvedExpression.GetSignatureForError ());
}