Expression.java

/*******************************************************************************
 * Copyright (c) 2000, 2011 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.che.ide.ext.java.jdt.core.dom;

/**
 * Abstract base class of AST nodes that represent expressions. There are several kinds of expressions.
 * <p>
 * <p/>
 * <pre>
 * Expression:
 *    {@link Annotation},
 *    {@link ArrayAccess},
 *    {@link ArrayCreation},
 *    {@link ArrayInitializer},
 *    {@link Assignment},
 *    {@link BooleanLiteral},
 *    {@link CastExpression},
 *    {@link CharacterLiteral},
 *    {@link ClassInstanceCreation},
 *    {@link ConditionalExpression},
 *    {@link FieldAccess},
 *    {@link InfixExpression},
 *    {@link InstanceofExpression},
 *    {@link MethodInvocation},
 *    {@link Name},
 *    {@link NullLiteral},
 *    {@link NumberLiteral},
 *    {@link ParenthesizedExpression},
 *    {@link PostfixExpression},
 *    {@link PrefixExpression},
 *    {@link StringLiteral},
 *    {@link SuperFieldAccess},
 *    {@link SuperMethodInvocation},
 *    {@link ThisExpression},
 *    {@link TypeLiteral},
 *    {@link VariableDeclarationExpression}
 * </pre>
 * <p/>
 * </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);
    }
}