/* CheckNullOperator Copyright (C) 1999-2002 Jochen Hoenicke.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; see the file COPYING.LESSER.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id: CheckNullOperator.java.in,v 4.1.2.1 2002/05/28 17:34:06 hoenicke Exp $
 */

package alterrs.jode.expr;

import java.util.Collection;

import alterrs.jode.decompiler.LocalInfo;
import alterrs.jode.decompiler.TabbedPrintWriter;
import alterrs.jode.type.Type;

/**
 * This is a pseudo operator, which represents the check against null that jikes
 * and javac generates for inner classes:
 * <p/>
 * 
 * <pre>
 * outer.new Inner()
 * </pre>
 * 
 * is translated by javac to
 * 
 * <pre>
 * new Outer$Inner(outer((void) DUP.getClass()));
 * </pre>
 * 
 * and by jikes to
 * 
 * <pre>
 *   new Outer$Inner(outer (DUP == null ? throw null));
 * </pre>
 */

public class CheckNullOperator extends Operator {
	LocalInfo local;

	public CheckNullOperator(Type type, LocalInfo li) {
		super(type, 0);
		local = li;
		initOperands(1);
	}

	public int getPriority() {
		return 200;
	}

	public void updateSubTypes() {
		local.setType(type);
		subExpressions[0].setType(Type.tSubType(type));
	}

	public void updateType() {
		Type newType = Type.tSuperType(subExpressions[0].getType())
				.intersection(type);
		local.setType(newType);
		updateParentType(newType);
	}

	public void removeLocal() {
		local.remove();
	}

	public void fillInGenSet(Collection in, Collection gen) {
		if (gen != null)
			gen.add(local);
		super.fillInGenSet(in, gen);
	}

	public void fillDeclarables(Collection used) {
		used.add(local);
		super.fillDeclarables(used);
	}

	public void dumpExpression(TabbedPrintWriter writer)
			throws java.io.IOException {
		writer.print("(" + local.getName() + " = ");
		subExpressions[0].dumpExpression(writer, 0);
		writer.print(").getClass() != null ? " + local.getName() + " : null");
	}

	public boolean opEquals(Operator o) {
		return o instanceof CheckNullOperator;
	}
}
