/*
* 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.internal.element.AuxiliaryElements;
import com.google.dart.engine.scanner.Token;
import com.google.dart.engine.scanner.TokenType;
import com.google.dart.engine.utilities.translation.DartName;
/**
* Instances of the class {@code IndexExpression} represent an index expression.
*
* <pre>
* indexExpression ::=
* {@link Expression target} '[' {@link Expression index} ']'
* </pre>
*
* @coverage dart.engine.ast
*/
public class IndexExpression extends Expression {
/**
* The expression used to compute the object being indexed, or {@code null} if this index
* expression is part of a cascade expression.
*/
private Expression target;
/**
* The period ("..") before a cascaded index expression, or {@code null} if this index expression
* is not part of a cascade expression.
*/
private Token period;
/**
* The left square bracket.
*/
private Token leftBracket;
/**
* The expression used to compute the index.
*/
private Expression index;
/**
* The right square bracket.
*/
private Token rightBracket;
/**
* The element associated with the operator based on the static type of the target, or
* {@code null} if the AST structure has not been resolved or if the operator could not be
* resolved.
*/
private MethodElement staticElement;
/**
* The element associated with the operator based on the propagated type of the target, or
* {@code null} if the AST structure has not been resolved or if the operator could not be
* resolved.
*/
private MethodElement propagatedElement;
/**
* If this expression is both in a getter and setter context, the {@link AuxiliaryElements} will
* be set to hold onto the static and propagated information. The auxiliary element will hold onto
* the elements from the getter context.
*/
private AuxiliaryElements auxiliaryElements = null;
/**
* Initialize a newly created index expression.
*
* @param target the expression used to compute the object being indexed
* @param leftBracket the left square bracket
* @param index the expression used to compute the index
* @param rightBracket the right square bracket
*/
@DartName("forTarget")
public IndexExpression(Expression target, Token leftBracket, Expression index, Token rightBracket) {
this.target = becomeParentOf(target);
this.leftBracket = leftBracket;
this.index = becomeParentOf(index);
this.rightBracket = rightBracket;
}
/**
* Initialize a newly created index expression.
*
* @param period the period ("..") before a cascaded index expression
* @param leftBracket the left square bracket
* @param index the expression used to compute the index
* @param rightBracket the right square bracket
*/
@DartName("forCascade")
public IndexExpression(Token period, Token leftBracket, Expression index, Token rightBracket) {
this.period = period;
this.leftBracket = leftBracket;
this.index = becomeParentOf(index);
this.rightBracket = rightBracket;
}
@Override
public <R> R accept(AstVisitor<R> visitor) {
return visitor.visitIndexExpression(this);
}
/**
* Get the auxiliary elements, this will be {@code null} if the node is not in a getter and setter
* context, or if it is not yet fully resolved.
*/
public AuxiliaryElements getAuxiliaryElements() {
return auxiliaryElements;
}
@Override
public Token getBeginToken() {
if (target != null) {
return target.getBeginToken();
}
return period;
}
/**
* 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 rightBracket;
}
/**
* Return the expression used to compute the index.
*
* @return the expression used to compute the index
*/
public Expression getIndex() {
return index;
}
/**
* Return the left square bracket.
*
* @return the left square bracket
*/
public Token getLeftBracket() {
return leftBracket;
}
/**
* Return the period ("..") before a cascaded index expression, or {@code null} if this index
* expression is not part of a cascade expression.
*
* @return the period ("..") before a cascaded index expression
*/
public Token getPeriod() {
return period;
}
@Override
public int getPrecedence() {
return 15;
}
/**
* Return the element associated with the operator based on the propagated type of the target, or
* {@code null} if the AST structure has not been resolved 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
* target.
*
* @return the element associated with this operator
*/
public MethodElement getPropagatedElement() {
return propagatedElement;
}
/**
* Return the expression used to compute the object being indexed. If this index expression is not
* part of a cascade expression, then this is the same as {@link #getTarget()}. If this index
* expression is part of a cascade expression, then the target expression stored with the cascade
* expression is returned.
*
* @return the expression used to compute the object being indexed
* @see #getTarget()
*/
public Expression getRealTarget() {
if (isCascaded()) {
AstNode ancestor = getParent();
while (!(ancestor instanceof CascadeExpression)) {
if (ancestor == null) {
return target;
}
ancestor = ancestor.getParent();
}
return ((CascadeExpression) ancestor).getTarget();
}
return target;
}
/**
* Return the right square bracket.
*
* @return the right square bracket
*/
public Token getRightBracket() {
return rightBracket;
}
/**
* Return the element associated with the operator based on the static type of the target, or
* {@code null} if the AST structure has not been resolved 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
* target.
*
* @return the element associated with the operator
*/
public MethodElement getStaticElement() {
return staticElement;
}
/**
* Return the expression used to compute the object being indexed, or {@code null} if this index
* expression is part of a cascade expression.
*
* @return the expression used to compute the object being indexed
* @see #getRealTarget()
*/
public Expression getTarget() {
return target;
}
/**
* Return {@code true} if this expression is computing a right-hand value.
* <p>
* Note that {@link #inGetterContext()} and {@link #inSetterContext()} are not opposites, nor are
* they mutually exclusive. In other words, it is possible for both methods to return {@code true}
* when invoked on the same node.
*
* @return {@code true} if this expression is in a context where the operator '[]' will be invoked
*/
public boolean inGetterContext() {
AstNode parent = getParent();
if (parent instanceof AssignmentExpression) {
AssignmentExpression assignment = (AssignmentExpression) parent;
if (assignment.getLeftHandSide() == this
&& assignment.getOperator().getType() == TokenType.EQ) {
return false;
}
}
return true;
}
/**
* Return {@code true} if this expression is computing a left-hand value.
* <p>
* Note that {@link #inGetterContext()} and {@link #inSetterContext()} are not opposites, nor are
* they mutually exclusive. In other words, it is possible for both methods to return {@code true}
* when invoked on the same node.
*
* @return {@code true} if this expression is in a context where the operator '[]=' will be
* invoked
*/
public boolean inSetterContext() {
AstNode parent = getParent();
if (parent instanceof PrefixExpression) {
return ((PrefixExpression) parent).getOperator().getType().isIncrementOperator();
} else if (parent instanceof PostfixExpression) {
return true;
} else if (parent instanceof AssignmentExpression) {
return ((AssignmentExpression) parent).getLeftHandSide() == this;
}
return false;
}
@Override
public boolean isAssignable() {
return true;
}
/**
* Return {@code true} if this expression is cascaded. If it is, then the target of this
* expression is not stored locally but is stored in the nearest ancestor that is a
* {@link CascadeExpression}.
*
* @return {@code true} if this expression is cascaded
*/
public boolean isCascaded() {
return period != null;
}
/**
* Set the auxiliary elements.
*/
public void setAuxiliaryElements(AuxiliaryElements auxiliaryElements) {
this.auxiliaryElements = auxiliaryElements;
}
/**
* Set the expression used to compute the index to the given expression.
*
* @param expression the expression used to compute the index
*/
public void setIndex(Expression expression) {
index = becomeParentOf(expression);
}
/**
* Set the left square bracket to the given token.
*
* @param bracket the left square bracket
*/
public void setLeftBracket(Token bracket) {
leftBracket = bracket;
}
/**
* Set the period ("..") before a cascaded index expression to the given token.
*
* @param period the period ("..") before a cascaded index expression
*/
public void setPeriod(Token period) {
this.period = period;
}
/**
* Set the element associated with the operator based on the propagated type of the target to the
* given element.
*
* @param element the element to be associated with this operator
*/
public void setPropagatedElement(MethodElement element) {
propagatedElement = element;
}
/**
* Set the right square bracket to the given token.
*
* @param bracket the right square bracket
*/
public void setRightBracket(Token bracket) {
rightBracket = bracket;
}
/**
* Set the element associated with the operator based on the static type of the target to the
* given element.
*
* @param element the static element to be associated with the operator
*/
public void setStaticElement(MethodElement element) {
staticElement = element;
}
/**
* Set the expression used to compute the object being indexed to the given expression.
*
* @param expression the expression used to compute the object being indexed
*/
public void setTarget(Expression expression) {
target = becomeParentOf(expression);
}
@Override
public void visitChildren(AstVisitor<?> visitor) {
safelyVisitChild(target, visitor);
safelyVisitChild(index, 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 index expression 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 index
* expression will be bound
*/
protected ParameterElement getPropagatedParameterElementForIndex() {
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 index expression 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 index
* expression will be bound
*/
protected ParameterElement getStaticParameterElementForIndex() {
if (staticElement == null) {
return null;
}
ParameterElement[] parameters = staticElement.getParameters();
if (parameters.length < 1) {
return null;
}
return parameters[0];
}
}