*  @param name          The class name.
     *  @param s             The enclosing scope.
     */
    boolean checkUniqueClassName(DiagnosticPosition pos, Name name, Scope s) {
        for (Scope.Entry e = s.lookup(name); e.scope == s; e = e.next()) {
            if (e.sym.kind == TYP && e.sym.name != names.error) {
                duplicateError(pos, e.sym);
                return false;
            }
        }
        for (Symbol sym = s.owner; sym != null; sym = sym.owner) {
            if (sym.kind == TYP && sym.name == name && sym.name != names.error) {
                duplicateError(pos, sym);
                return true;
            }
        }
        return true;
    }