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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.base.Preconditions;
/**
* Syntax node for an assignment statement.
*/
public final class AssignmentStatement extends Statement {
private final Expression lvalue;
private final Expression expression;
/**
* Constructs an assignment: "lvalue := value".
*/
AssignmentStatement(Expression lvalue, Expression expression) {
this.lvalue = lvalue;
this.expression = expression;
}
/**
* Returns the LHS of the assignment.
*/
public Expression getLValue() {
return lvalue;
}
/**
* Returns the RHS of the assignment.
*/
public Expression getExpression() {
return expression;
}
@Override
public String toString() {
return lvalue + " = " + expression + '\n';
}
@Override
void exec(Environment env) throws EvalException, InterruptedException {
if (!(lvalue instanceof Ident)) {
throw new EvalException(getLocation(),
"can only assign to variables, not to '" + lvalue + "'");
}
Ident ident = (Ident) lvalue;
Object result = expression.eval(env);
Preconditions.checkNotNull(result, "result of %s is null", expression);
if (env.isSkylarkEnabled()) {
// The variable may have been referenced successfully if a global variable
// with the same name exists. In this case an Exception needs to be thrown.
SkylarkEnvironment skylarkEnv = (SkylarkEnvironment) env;
if (skylarkEnv.hasBeenReadGlobalVariable(ident.getName())) {
throw new EvalException(getLocation(), "Variable '" + ident.getName()
+ "' is referenced before assignment."
+ "The variable is defined in the global scope.");
}
Class<?> variableType = skylarkEnv.getVariableType(ident.getName());
Class<?> resultType = EvalUtils.getSkylarkType(result.getClass());
if (variableType != null && !variableType.equals(resultType)
&& !resultType.equals(Environment.NoneType.class)
&& !variableType.equals(Environment.NoneType.class)) {
throw new EvalException(getLocation(), String.format("Incompatible variable types, "
+ "trying to assign %s (type of %s) to variable %s which is already %s",
EvalUtils.prettyPrintValue(result),
EvalUtils.getDataTypeName(result),
ident.getName(),
EvalUtils.getDataTypeNameFromClass(variableType)));
}
}
env.update(ident.getName(), result);
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
void validate(ValidationEnvironment env) throws EvalException {
// TODO(bazel-team): Implement other validations.
if (lvalue instanceof Ident) {
Ident ident = (Ident) lvalue;
SkylarkType resultType = expression.validate(env);
env.update(ident.getName(), resultType, getLocation());
} else {
throw new EvalException(getLocation(),
"can only assign to variables, not to '" + lvalue + "'");
}
}
}
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