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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;
/**
* Base class for all statements nodes in the AST.
*/
public abstract class Statement extends ASTNode {
/**
* Executes the statement in the specified build environment, which may be
* modified.
*
* @throws EvalException if execution of the statement could not be completed.
* @throws InterruptedException may be thrown in a sub class.
*/
final void exec(Environment env) throws EvalException, InterruptedException {
try {
doExec(env);
} catch (EvalException ex) {
throw maybeTransformException(ex);
}
}
/**
* Executes the statement.
*
* <p>This method is only invoked by the super class {@link Statement} when calling {@link
* #exec(Environment)}.
*
* @throws EvalException if execution of the statement could not be completed.
* @throws InterruptedException may be thrown in a sub class.
*/
abstract void doExec(Environment env) throws EvalException, InterruptedException;
/**
* Checks the semantics of the Statement using the Environment according to
* the rules of the Skylark language. The Environment can be used e.g. to check
* variable type collision, read only variables, detecting recursion, existence of
* built-in variables, functions, etc.
*
* <p>The semantical check should be performed after the Skylark extension is loaded
* (i.e. is syntactically correct) and before is executed. The point of the semantical check
* is to make sure (as much as possible) that no error can occur during execution (Skylark
* programmers get a "compile time" error). It should also check execution branches (e.g. in
* if statements) that otherwise might never get executed.
*
* @throws EvalException if the Statement has a semantical error.
*/
abstract void validate(ValidationEnvironment env) throws EvalException;
}
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