com.google.errorprone.bugpatterns.EqualsUnsafeCast Maven / Gradle / Ivy
/*
* Copyright 2018 The Error Prone Authors.
*
* 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.errorprone.bugpatterns;
import static com.google.common.collect.Iterables.getOnlyElement;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.equalsMethodDeclaration;
import static com.google.errorprone.util.ASTHelpers.findEnclosingNode;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.isSubtype;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.InstanceOfTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.StatementTree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.tree.TypeCastTree;
import com.sun.source.util.TreePathScanner;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Type;
import java.util.ArrayList;
import java.util.List;
/**
* Checks for {@code equals} implementations making unsafe casts.
*
* @author [email protected] (Graeme Morgan)
*/
@BugPattern(
name = "EqualsUnsafeCast",
summary =
"The contract of #equals states that it should return false for incompatible types, "
+ "while this implementation may throw ClassCastException.",
severity = WARNING)
public final class EqualsUnsafeCast extends BugChecker implements MethodTreeMatcher {
private static final String INSTANCEOF_CHECK = "if (!(%s instanceof %s)) { return false; }";
@Override
public Description matchMethod(MethodTree tree, VisitorState state) {
if (!equalsMethodDeclaration().matches(tree, state)) {
return NO_MATCH;
}
Symbol parameter = getSymbol(getOnlyElement(tree.getParameters()));
new TreePathScanner() {
private boolean methodInvoked = false;
private final List checkedTypes = new ArrayList<>();
@Override
public Void visitInstanceOf(InstanceOfTree node, Void unused) {
checkedTypes.add(getType(node.getType()));
return super.visitInstanceOf(node, null);
}
@Override
public Void visitMethodInvocation(MethodInvocationTree node, Void unused) {
// Some equals implementations rely on super#equals for their class check. To avoid false
// positives there, consider any method invocation to imply that this might be safe.
// This also matches for any class comparisons with getClass.
methodInvoked = true;
return null;
}
@Override
public Void visitTypeCast(TypeCastTree node, Void unused) {
ExpressionTree expression = node.getExpression();
if (!methodInvoked
&& expression.getKind() == Kind.IDENTIFIER
&& parameter.equals(getSymbol(expression))
&& checkedTypes.stream().noneMatch(t -> isSubtype(t, getType(node.getType()), state))) {
StatementTree enclosingStatement =
findEnclosingNode(getCurrentPath(), StatementTree.class);
state.reportMatch(
describeMatch(
node,
SuggestedFix.prefixWith(
enclosingStatement,
String.format(
INSTANCEOF_CHECK,
state.getSourceForNode(expression),
state.getSourceForNode(node.getType())))));
}
return super.visitTypeCast(node, null);
}
}.scan(state.getPath(), null);
return NO_MATCH;
}
}