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// Copyright 2014 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
//
// 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.devtools.build.lib.syntax;
import com.google.common.annotations.VisibleForTesting;
import com.google.devtools.build.lib.events.Location;
import java.io.Serializable;
/**
* Root class for nodes in the Abstract Syntax Tree of the Build language.
*/
public abstract class ASTNode implements Serializable {
private Location location;
protected ASTNode() {}
/**
* Returns whether this node represents a new scope, e.g. a function call.
*/
protected boolean isNewScope() {
return false;
}
/**
* Returns an exception which should be thrown instead of the original one.
*/
protected final EvalException handleException(Exception original) {
// If there is already a non-empty stack trace, we only add this node iff it describes a
// new scope (e.g. FuncallExpression).
if (original instanceof EvalExceptionWithStackTrace) {
EvalExceptionWithStackTrace real = (EvalExceptionWithStackTrace) original;
if (isNewScope()) {
real.registerNode(this);
}
return real;
}
// Returns the original exception if it cannot be attached to a stack trace.
if (original instanceof EvalException && !((EvalException) original).canBeAddedToStackTrace()) {
return (EvalException) original;
}
return new EvalExceptionWithStackTrace(original, this);
}
@VisibleForTesting // productionVisibility = Visibility.PACKAGE_PRIVATE
public void setLocation(Location location) {
this.location = location;
}
public Location getLocation() {
return location;
}
/** @return the same node with its location set, in a slightly more fluent style */
public static <NODE extends ASTNode> NODE setLocation(Location location, NODE node) {
node.setLocation(location);
return node;
}
/**
* Print the syntax node in a form useful for debugging. The output is not
* precisely specified, and should not be used by pretty-printing routines.
*/
@Override
public abstract String toString();
@Override
public int hashCode() {
throw new UnsupportedOperationException(); // avoid nondeterminism
}
@Override
public boolean equals(Object that) {
throw new UnsupportedOperationException();
}
/**
* Implements the double dispatch by calling into the node specific
* <code>visit</code> method of the {@link SyntaxTreeVisitor}
*
* @param visitor the {@link SyntaxTreeVisitor} instance to dispatch to.
*/
public abstract void accept(SyntaxTreeVisitor visitor);
}
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