/*
* Copyright 2012, the Dart project authors.
*
* Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
*
* 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.dart.engine.ast;
import com.google.dart.engine.element.MethodElement;
import com.google.dart.engine.element.ParameterElement;
import com.google.dart.engine.scanner.Token;
/**
* Instances of the class {@code BinaryExpression} represent a binary (infix) expression.
*
* <pre>
* binaryExpression ::=
* {@link Expression leftOperand} {@link Token operator} {@link Expression rightOperand}
* </pre>
*
* @coverage dart.engine.ast
*/
public class BinaryExpression extends Expression {
/**
* The expression used to compute the left operand.
*/
private Expression leftOperand;
/**
* The binary operator being applied.
*/
private Token operator;
/**
* The expression used to compute the right operand.
*/
private Expression rightOperand;
/**
* The element associated with the operator based on the static type of the left operand, or
* {@code null} if the AST structure has not been resolved, if the operator is not user definable,
* or if the operator could not be resolved.
*/
private MethodElement staticElement;
/**
* The element associated with the operator based on the propagated type of the left operand, or
* {@code null} if the AST structure has not been resolved, if the operator is not user definable,
* or if the operator could not be resolved.
*/
private MethodElement propagatedElement;
/**
* Initialize a newly created binary expression.
*
* @param leftOperand the expression used to compute the left operand
* @param operator the binary operator being applied
* @param rightOperand the expression used to compute the right operand
*/
public BinaryExpression(Expression leftOperand, Token operator, Expression rightOperand) {
this.leftOperand = becomeParentOf(leftOperand);
this.operator = operator;
this.rightOperand = becomeParentOf(rightOperand);
}
@Override
public <R> R accept(AstVisitor<R> visitor) {
return visitor.visitBinaryExpression(this);
}
@Override
public Token getBeginToken() {
return leftOperand.getBeginToken();
}
/**
* Return the best element available for this operator. If resolution was able to find a better
* element based on type propagation, that element will be returned. Otherwise, the element found
* using the result of static analysis will be returned. If resolution has not been performed,
* then {@code null} will be returned.
*
* @return the best element available for this operator
*/
public MethodElement getBestElement() {
MethodElement element = getPropagatedElement();
if (element == null) {
element = getStaticElement();
}
return element;
}
@Override
public Token getEndToken() {
return rightOperand.getEndToken();
}
/**
* Return the expression used to compute the left operand.
*
* @return the expression used to compute the left operand
*/
public Expression getLeftOperand() {
return leftOperand;
}
/**
* Return the binary operator being applied.
*
* @return the binary operator being applied
*/
public Token getOperator() {
return operator;
}
@Override
public int getPrecedence() {
return operator.getType().getPrecedence();
}
/**
* Return the element associated with the operator based on the propagated type of the left
* operand, or {@code null} if the AST structure has not been resolved, if the operator is not
* user definable, or if the operator could not be resolved. One example of the latter case is an
* operator that is not defined for the type of the left-hand operand.
*
* @return the element associated with the operator
*/
public MethodElement getPropagatedElement() {
return propagatedElement;
}
/**
* Return the expression used to compute the right operand.
*
* @return the expression used to compute the right operand
*/
public Expression getRightOperand() {
return rightOperand;
}
/**
* Return the element associated with the operator based on the static type of the left operand,
* or {@code null} if the AST structure has not been resolved, if the operator is not user
* definable, or if the operator could not be resolved. One example of the latter case is an
* operator that is not defined for the type of the left operand.
*
* @return the element associated with the operator
*/
public MethodElement getStaticElement() {
return staticElement;
}
/**
* Set the expression used to compute the left operand to the given expression.
*
* @param expression the expression used to compute the left operand
*/
public void setLeftOperand(Expression expression) {
leftOperand = becomeParentOf(expression);
}
/**
* Set the binary operator being applied to the given operator.
*
* @return the binary operator being applied
*/
public void setOperator(Token operator) {
this.operator = operator;
}
/**
* Set the element associated with the operator based on the propagated type of the left operand
* to the given element.
*
* @param element the element to be associated with the operator
*/
public void setPropagatedElement(MethodElement element) {
propagatedElement = element;
}
/**
* Set the expression used to compute the right operand to the given expression.
*
* @param expression the expression used to compute the right operand
*/
public void setRightOperand(Expression expression) {
rightOperand = becomeParentOf(expression);
}
/**
* Set the element associated with the operator based on the static type of the left operand to
* the given element.
*
* @param element the static element to be associated with the operator
*/
public void setStaticElement(MethodElement element) {
staticElement = element;
}
@Override
public void visitChildren(AstVisitor<?> visitor) {
safelyVisitChild(leftOperand, visitor);
safelyVisitChild(rightOperand, visitor);
}
/**
* If the AST structure has been resolved, and the function being invoked is known based on
* propagated type information, then return the parameter element representing the parameter to
* which the value of the right operand will be bound. Otherwise, return {@code null}.
* <p>
* This method is only intended to be used by {@link Expression#getPropagatedParameterElement()}.
*
* @return the parameter element representing the parameter to which the value of the right
* operand will be bound
*/
protected ParameterElement getPropagatedParameterElementForRightOperand() {
if (propagatedElement == null) {
return null;
}
ParameterElement[] parameters = propagatedElement.getParameters();
if (parameters.length < 1) {
return null;
}
return parameters[0];
}
/**
* If the AST structure has been resolved, and the function being invoked is known based on static
* type information, then return the parameter element representing the parameter to which the
* value of the right operand will be bound. Otherwise, return {@code null}.
* <p>
* This method is only intended to be used by {@link Expression#getStaticParameterElement()}.
*
* @return the parameter element representing the parameter to which the value of the right
* operand will be bound
*/
protected ParameterElement getStaticParameterElementForRightOperand() {
if (staticElement == null) {
return null;
}
ParameterElement[] parameters = staticElement.getParameters();
if (parameters.length < 1) {
return null;
}
return parameters[0];
}
}