/*
* Copyright 2007 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.dev.js;
import com.google.gwt.dev.js.ast.JsArrayAccess;
import com.google.gwt.dev.js.ast.JsArrayLiteral;
import com.google.gwt.dev.js.ast.JsBinaryOperation;
import com.google.gwt.dev.js.ast.JsConditional;
import com.google.gwt.dev.js.ast.JsContext;
import com.google.gwt.dev.js.ast.JsExprStmt;
import com.google.gwt.dev.js.ast.JsExpression;
import com.google.gwt.dev.js.ast.JsFunction;
import com.google.gwt.dev.js.ast.JsInvocation;
import com.google.gwt.dev.js.ast.JsNameRef;
import com.google.gwt.dev.js.ast.JsNew;
import com.google.gwt.dev.js.ast.JsObjectLiteral;
import com.google.gwt.dev.js.ast.JsPostfixOperation;
import com.google.gwt.dev.js.ast.JsPrefixOperation;
import com.google.gwt.dev.js.ast.JsRegExp;
import com.google.gwt.dev.js.ast.JsVisitor;
/**
* Determines if an expression statement needs to be surrounded by parentheses.
*
* The statement or the left-most expression needs to be surrounded by
* parentheses if the left-most expression is an object literal or a function
* object. Function declarations do not need parentheses.
*
* For example the following require parentheses:<br>
* <ul>
* <li>{ key : 'value'}</li>
* <li>{ key : 'value'}.key</li>
* <li>function () {return 1;}()</li>
* <li>function () {return 1;}.prototype</li>
* </ul>
*
* The following do not require parentheses:<br>
* <ul>
* <li>var x = { key : 'value'}</li>
* <li>"string" + { key : 'value'}.key</li>
* <li>function func() {}</li>
* <li>function() {}</li>
* </ul>
*/
public class JsFirstExpressionVisitor extends JsVisitor {
public static boolean exec(JsExprStmt statement) {
JsFirstExpressionVisitor visitor = new JsFirstExpressionVisitor();
JsExpression expression = statement.getExpression();
// Pure function declarations do not need parentheses
if (expression instanceof JsFunction) {
return false;
}
visitor.accept(statement.getExpression());
return visitor.needsParentheses;
}
private boolean needsParentheses = false;
private JsFirstExpressionVisitor() {
}
public boolean visit(JsArrayAccess x, JsContext<JsExpression> ctx) {
accept(x.getArrayExpr());
return false;
}
public boolean visit(JsArrayLiteral x, JsContext<JsExpression> ctx) {
return false;
}
public boolean visit(JsBinaryOperation x, JsContext<JsExpression> ctx) {
accept(x.getArg1());
return false;
}
public boolean visit(JsConditional x, JsContext<JsExpression> ctx) {
accept(x.getTestExpression());
return false;
}
public boolean visit(JsFunction x, JsContext<JsExpression> ctx) {
needsParentheses = true;
return false;
}
public boolean visit(JsInvocation x, JsContext<JsExpression> ctx) {
accept(x.getQualifier());
return false;
}
public boolean visit(JsNameRef x, JsContext<JsExpression> ctx) {
if (!x.isLeaf()) {
accept(x.getQualifier());
}
return false;
}
public boolean visit(JsNew x, JsContext<JsExpression> ctx) {
return false;
}
public boolean visit(JsObjectLiteral x, JsContext<JsExpression> ctx) {
needsParentheses = true;
return false;
}
public boolean visit(JsPostfixOperation x, JsContext<JsExpression> ctx) {
accept(x.getArg());
return false;
}
public boolean visit(JsPrefixOperation x, JsContext<JsExpression> ctx) {
return false;
}
public boolean visit(JsRegExp x, JsContext<JsExpression> ctx) {
return false;
}
}