/*
 * Copyright 1999-2009 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

//todo: one might eliminate uninits.andSets when monotonic

package com.sun.tools.javac.comp;

import com.sun.tools.javac.code.Symtab;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.Types;
import com.sun.tools.javac.tree.TreeScanner;
import com.sun.tools.javac.tree.JCTree.JCBlock;
import com.sun.tools.javac.tree.JCTree.JCReturn;
import com.sun.tools.javac.util.Context;

public class LambdaFlow extends TreeScanner {
    protected static final Context.Key<LambdaFlow> lambdaFlowKey =
        new Context.Key<LambdaFlow>();

    private final Types types;
    private final Symtab syms;
    private Type lub;
    
    public static LambdaFlow instance(Context context) {
        LambdaFlow instance = context.get(lambdaFlowKey);
        if (instance == null)
            instance = new LambdaFlow(context);
        return instance;
    }

    protected LambdaFlow(Context context) {
        context.put(lambdaFlowKey, this);
        types = Types.instance(context);
        syms = Symtab.instance(context);
    }

    public Type inferReturnType(JCBlock lambdaBody) {
        lub = null;
        try {
            scan(lambdaBody);
            return (lub == null)?syms.voidType:lub;
        } finally {
            lub = null;
        }
    }
    
    @Override
    public void visitReturn(JCReturn tree) {
        Type type = tree.type;
        if (lub == null)
          lub = type;
        else
          lub = types.lub(lub, type);
    }
}