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// Copyright 2014 The Bazel Authors. 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.devtools.build.lib.syntax.DictionaryLiteral.DictionaryEntryLiteral;
import com.google.devtools.build.lib.syntax.IfStatement.ConditionalStatements;
import java.util.List;
/**
* A visitor for visiting the nodes in the syntax tree left to right, top to
* bottom.
*/
public class SyntaxTreeVisitor {
public void visit(ASTNode node) {
// dispatch to the node specific method
node.accept(this);
}
// methods dealing with sequences of nodes
public void visitAll(List<? extends ASTNode> nodes) {
for (ASTNode node : nodes) {
visit(node);
}
}
/**
* Visit a sequence ("block") of statements (e.g. an if branch, for block, function block etc.)
*
* This method allows subclasses to handle statement blocks more easily, like doing an action
* after every statement in a block without having to override visit(...) for all statements.
*
* @param statements list of statements in the block
*/
public void visitBlock(List<Statement> statements) {
visitAll(statements);
}
// node specific visit methods
public void visit(Argument.Passed node) {
visit(node.getValue());
}
public void visit(Parameter<Expression, Expression> node) {
if (node.getDefaultValue() != null) {
visit(node.getDefaultValue());
}
}
public void visit(BuildFileAST node) {
visitBlock(node.getStatements());
visitAll(node.getComments());
}
public void visit(BinaryOperatorExpression node) {
visit(node.getLhs());
visit(node.getRhs());
}
public void visit(FuncallExpression node) {
visit(node.getFunction());
visitAll(node.getArguments());
}
public void visit(@SuppressWarnings("unused") Identifier node) {}
public void visit(AbstractComprehension node) {
for (ListComprehension.Clause clause : node.getClauses()) {
visit(clause.getExpression());
if (clause.getLValue() != null) {
visit(clause.getLValue());
}
}
visitAll(node.getOutputExpressions());
}
public void visit(ForStatement node) {
visit(node.getCollection());
visit(node.getVariable());
visitBlock(node.getBlock());
}
public void visit(LoadStatement node) {
visitAll(node.getSymbols());
}
public void visit(ListLiteral node) {
visitAll(node.getElements());
}
public void visit(@SuppressWarnings("unused") IntegerLiteral node) {}
public void visit(@SuppressWarnings("unused") StringLiteral node) {}
public void visit(LValue node) {
visit(node.getExpression());
}
public void visit(AssignmentStatement node) {
visit(node.getExpression());
visit(node.getLValue());
}
public void visit(AugmentedAssignmentStatement node) {
visit(node.getExpression());
visit(node.getLValue());
}
public void visit(ExpressionStatement node) {
visit(node.getExpression());
}
public void visit(IfStatement node) {
visitAll(node.getThenBlocks());
visitBlock(node.getElseBlock());
}
public void visit(ConditionalStatements node) {
visit(node.getCondition());
visitBlock(node.getStatements());
}
public void visit(FunctionDefStatement node) {
visit(node.getIdentifier());
// Do not use visitAll for the parameters, because we would lose the type information.
// Inside the AST, we know that Parameters are using Expressions.
for (Parameter<Expression, Expression> param : node.getParameters()) {
visit(param);
}
visitBlock(node.getStatements());
}
public void visit(PassStatement node) {}
public void visit(ReturnStatement node) {
if (node.getReturnExpression() != null) {
visit(node.getReturnExpression());
}
}
public void visit(FlowStatement node) {
}
public void visit(DictionaryLiteral node) {
visitAll(node.getEntries());
}
public void visit(DictionaryEntryLiteral node) {
visit(node.getKey());
visit(node.getValue());
}
public void visit(UnaryOperatorExpression node) {
visit(node.getOperand());
}
public void visit(DotExpression node) {
visit(node.getObject());
visit(node.getField());
}
public void visit(IndexExpression node) {
visit(node.getObject());
visit(node.getKey());
}
public void visit(SliceExpression node) {
visit(node.getObject());
if (node.getStart() != null) {
visit(node.getStart());
}
if (node.getEnd() != null) {
visit(node.getEnd());
}
if (node.getStep() != null) {
visit(node.getStep());
}
}
public void visit(@SuppressWarnings("unused") Comment node) {}
public void visit(ConditionalExpression node) {
visit(node.getCondition());
visit(node.getThenCase());
if (node.getElseCase() != null) {
visit(node.getElseCase());
}
}
}
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