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Java > Open Source Codes > org > aspectj > compiler > base > ast > NullExpr


1 /* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
2  *
3  * This file is part of the compiler and core tools for the AspectJ(tm)
4  * programming language; see http://aspectj.org
5  *
6  * The contents of this file are subject to the Mozilla Public License
7  * Version 1.1 (the "License"); you may not use this file except in
8  * compliance with the License. You may obtain a copy of the License at
9  * either http://www.mozilla.org/MPL/ or http://aspectj.org/MPL/.
10  *
11  * Software distributed under the License is distributed on an "AS IS" basis,
12  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
13  * for the specific language governing rights and limitations under the
14  * License.
15  *
16  * The Original Code is AspectJ.
17  *
18  * The Initial Developer of the Original Code is Xerox Corporation. Portions
19  * created by Xerox Corporation are Copyright (C) 1999-2002 Xerox Corporation.
20  * All Rights Reserved.
21  *
22  * Contributor(s):
23  */
24
25 package org.aspectj.compiler.base.ast;
26
27 import org.aspectj.compiler.base.FlowCheckerPass;
28 import org.aspectj.compiler.base.JavaCompiler;
29 import org.aspectj.compiler.base.CodeWriter;
30 import java.io.IOException JavaDoc;
31
32 import org.aspectj.compiler.base.bcg.CodeBuilder;
33 import org.aspectj.compiler.base.bcg.Label;
34
35
36 /**
37   * @grammar null
38   */
39 public class NullExpr extends Expr {
40
41     public Type discoverType() {
42         return getTypeManager().nullType;
43     }
44
45     public void unparse(CodeWriter writer) throws IOException JavaDoc {
46         writer.write("null");
47     }
48
49     public boolean canBeCopied() {
50         return true;
51     }
52     
53     public boolean isUltimatelyLiteral() {
54         return true;
55     }
56
57     // ------------------------------
58 // bcg
59 protected void cgValue(CodeBuilder cb) {
60         cb.emitNULL();
61     }
62     protected void cgEffect(CodeBuilder cb) {}
63
64     public boolean isConstantZero() { return true; }
65     // end bcg
66
67     //BEGIN: Generated from @child and @property
68
69     public NullExpr(SourceLocation location) {
70         super(location);
71
72     }
73
74     public ASTObject copyWalk(CopyWalker walker) {
75         NullExpr ret = new NullExpr(getSourceLocation());
76         ret.preCopy(walker, this);
77
78         return ret;
79     }
80
81
82     public String JavaDoc getDefaultDisplayName() {
83         return "NullExpr()";
84     }
85
86     //END: Generated from @child and @property
87 }
88
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