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/*******************************************************************************
* Copyright (c) 2000, 2019 IBM Corporation and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jdt.core.dom;
/**
* Abstract base class of AST nodes that represent expressions.
* There are several kinds of expressions.
* <p>
* <pre>
* Expression:
* {@link Annotation},
* {@link ArrayAccess},
* {@link ArrayCreation},
* {@link ArrayInitializer},
* {@link Assignment},
* {@link BooleanLiteral},
* {@link CastExpression},
* {@link CharacterLiteral},
* {@link ClassInstanceCreation},
* {@link ConditionalExpression},
* {@link CreationReference},
* {@link ExpressionMethodReference},
* {@link FieldAccess},
* {@link InfixExpression},
* {@link InstanceofExpression},
* {@link LambdaExpression},
* {@link MethodInvocation},
* {@link MethodReference},
* {@link Name},
* {@link NullLiteral},
* {@link NumberLiteral},
* {@link ParenthesizedExpression},
* {@link PostfixExpression},
* {@link PrefixExpression},
* {@link StringLiteral},
* {@link SuperFieldAccess},
* {@link SuperMethodInvocation},
* {@link SuperMethodReference},
* {@link SwitchExpression},
* {@link ThisExpression},
* {@link TypeLiteral},
* {@link TypeMethodReference},
* {@link VariableDeclarationExpression}
* </pre>
* </p>
*
* @since 2.0
*/
public abstract class Expression extends ASTNode {
/**
* Creates a new AST node for an expression owned by the given AST.
* <p>
* N.B. This constructor is package-private.
* </p>
*
* @param ast the AST that is to own this node
*/
Expression(AST ast) {
super(ast);
}
/**
* Resolves and returns the compile-time constant expression value as
* specified in JLS2 15.28, if this expression has one. Constant expression
* values are unavailable unless bindings are requested when the AST is
* being built. If the type of the value is a primitive type, the result
* is the boxed equivalent (i.e., int returned as an <code>Integer</code>);
* if the type of the value is <code>String</code>, the result is the string
* itself. If the expression does not have a compile-time constant expression
* value, the result is <code>null</code>.
* <p>
* Resolving constant expressions takes into account the value of simple
* and qualified names that refer to constant variables (JLS2 4.12.4).
* </p>
* <p>
* Note 1: enum constants are not considered constant expressions.
* The result is always <code>null</code> for these.
* </p>
* <p>
* Note 2: Compile-time constant expressions cannot denote <code>null</code>.
* So technically {@link NullLiteral} nodes are not constant expressions.
* The result is <code>null</code> for these nonetheless.
* </p>
*
* @return the constant expression value, or <code>null</code> if this
* expression has no constant expression value or if bindings were not
* requested when the AST was created
* @since 3.1
*/
public final Object resolveConstantExpressionValue() {
return this.ast.getBindingResolver().resolveConstantExpressionValue(this);
}
/**
* Resolves and returns the binding for the type of this expression.
* <p>
* Note that bindings are generally unavailable unless requested when the
* AST is being built.
* </p>
*
* @return the binding for the type of this expression, or
* <code>null</code> if the type cannot be resolved
*/
public final ITypeBinding resolveTypeBinding() {
return this.ast.getBindingResolver().resolveExpressionType(this);
}
/**
* Returns whether this expression node is the site of a boxing
* conversion (JLS3 5.1.7). This information is available only
* when bindings are requested when the AST is being built.
*
* @return <code>true</code> if this expression is the site of a
* boxing conversion, or <code>false</code> if either no boxing conversion
* is involved or if bindings were not requested when the AST was created
* @since 3.1
*/
public final boolean resolveBoxing() {
return this.ast.getBindingResolver().resolveBoxing(this);
}
/**
* Returns whether this expression node is the site of an unboxing
* conversion (JLS3 5.1.8). This information is available only
* when bindings are requested when the AST is being built.
*
* @return <code>true</code> if this expression is the site of an
* unboxing conversion, or <code>false</code> if either no unboxing
* conversion is involved or if bindings were not requested when the
* AST was created
* @since 3.1
*/
public final boolean resolveUnboxing() {
return this.ast.getBindingResolver().resolveUnboxing(this);
}
}
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