/*
* 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.AnalysisEngine;
import com.google.dart.engine.element.Element;
import com.google.dart.engine.element.ExecutableElement;
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 AssignmentExpression} represent an assignment expression.
*
* <pre>
* assignmentExpression ::=
* {@link Expression leftHandSide} {@link Token operator} {@link Expression rightHandSide}
* </pre>
*
* @coverage dart.engine.ast
*/
public class AssignmentExpression extends Expression {
/**
* The expression used to compute the left hand side.
*/
private Expression leftHandSide;
/**
* The assignment operator being applied.
*/
private Token operator;
/**
* The expression used to compute the right hand side.
*/
private Expression rightHandSide;
/**
* The element associated with the operator based on the static type of the left-hand-side, or
* {@code null} if the AST structure has not been resolved, if the operator is not a compound
* operator, 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-hand-side, or
* {@code null} if the AST structure has not been resolved, if the operator is not a compound
* operator, or if the operator could not be resolved.
*/
private MethodElement propagatedElement;
/**
* Initialize a newly created assignment expression.
*
* @param leftHandSide the expression used to compute the left hand side
* @param operator the assignment operator being applied
* @param rightHandSide the expression used to compute the right hand side
*/
public AssignmentExpression(Expression leftHandSide, Token operator, Expression rightHandSide) {
if (leftHandSide == null || rightHandSide == null) {
String message;
if (leftHandSide == null) {
if (rightHandSide == null) {
message = "Both the left-hand and right-hand sides are null";
} else {
message = "The left-hand size is null";
}
} else {
message = "The right-hand size is null";
}
AnalysisEngine.getInstance().getLogger().logError(message, new Exception(message));
}
this.leftHandSide = becomeParentOf(leftHandSide);
this.operator = operator;
this.rightHandSide = becomeParentOf(rightHandSide);
}
@Override
public <R> R accept(AstVisitor<R> visitor) {
return visitor.visitAssignmentExpression(this);
}
@Override
public Token getBeginToken() {
return leftHandSide.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 rightHandSide.getEndToken();
}
/**
* Set the expression used to compute the left hand side to the given expression.
*
* @return the expression used to compute the left hand side
*/
public Expression getLeftHandSide() {
return leftHandSide;
}
/**
* Return the assignment operator being applied.
*
* @return the assignment operator being applied
*/
public Token getOperator() {
return operator;
}
@Override
public int getPrecedence() {
return 1;
}
/**
* Return the element associated with the operator based on the propagated type of the
* left-hand-side, or {@code null} if the AST structure has not been resolved, if the operator is
* not a compound operator, 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 hand side.
*
* @return the expression used to compute the right hand side
*/
public Expression getRightHandSide() {
return rightHandSide;
}
/**
* Return the element associated with the operator based on the static type of the left-hand-side,
* or {@code null} if the AST structure has not been resolved, if the operator is not a compound
* operator, 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 getStaticElement() {
return staticElement;
}
/**
* Return the expression used to compute the left hand side.
*
* @param expression the expression used to compute the left hand side
*/
public void setLeftHandSide(Expression expression) {
leftHandSide = becomeParentOf(expression);
}
/**
* Set the assignment operator being applied to the given operator.
*
* @param operator the assignment 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-hand-side
* 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 left hand side to the given expression.
*
* @param expression the expression used to compute the left hand side
*/
public void setRightHandSide(Expression expression) {
rightHandSide = becomeParentOf(expression);
}
/**
* Set the element associated with the operator based on the static type of the left-hand-side 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(leftHandSide, visitor);
safelyVisitChild(rightHandSide, 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 getPropagatedParameterElementForRightHandSide() {
ExecutableElement executableElement = null;
if (propagatedElement != null) {
executableElement = propagatedElement;
} else {
if (leftHandSide instanceof Identifier) {
Identifier identifier = (Identifier) leftHandSide;
Element leftElement = identifier.getPropagatedElement();
if (leftElement instanceof ExecutableElement) {
executableElement = (ExecutableElement) leftElement;
}
}
if (leftHandSide instanceof PropertyAccess) {
SimpleIdentifier identifier = ((PropertyAccess) leftHandSide).getPropertyName();
Element leftElement = identifier.getPropagatedElement();
if (leftElement instanceof ExecutableElement) {
executableElement = (ExecutableElement) leftElement;
}
}
}
if (executableElement == null) {
return null;
}
ParameterElement[] parameters = executableElement.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 getStaticParameterElementForRightHandSide() {
ExecutableElement executableElement = null;
if (staticElement != null) {
executableElement = staticElement;
} else {
if (leftHandSide instanceof Identifier) {
Element leftElement = ((Identifier) leftHandSide).getStaticElement();
if (leftElement instanceof ExecutableElement) {
executableElement = (ExecutableElement) leftElement;
}
}
if (leftHandSide instanceof PropertyAccess) {
Element leftElement = ((PropertyAccess) leftHandSide).getPropertyName().getStaticElement();
if (leftElement instanceof ExecutableElement) {
executableElement = (ExecutableElement) leftElement;
}
}
}
if (executableElement == null) {
return null;
}
ParameterElement[] parameters = executableElement.getParameters();
if (parameters.length < 1) {
return null;
}
return parameters[0];
}
}