/*
* Copyright 2012 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.errorprone.bugpatterns;
import static com.google.errorprone.BugPattern.Category.JDK;
import static com.google.errorprone.BugPattern.MaturityLevel.EXPERIMENTAL;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import static com.google.errorprone.matchers.Matchers.allOf;
import static com.google.errorprone.matchers.Matchers.anyOf;
import static com.google.errorprone.matchers.Matchers.binaryTree;
import static com.google.errorprone.matchers.Matchers.isSubtypeOf;
import static com.google.errorprone.matchers.Matchers.kindIs;
import static com.google.errorprone.matchers.Matchers.not;
import static com.sun.source.tree.Tree.Kind.EQUAL_TO;
import static com.sun.source.tree.Tree.Kind.NOT_EQUAL_TO;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.BinaryTreeMatcher;
import com.google.errorprone.fixes.Fix;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.BinaryTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.Tree;
import com.sun.tools.javac.code.Flags;
import com.sun.tools.javac.code.Symbol;
/**
* @author scottjohnson@google.com (Scott Johnson)
*/
@BugPattern(name = "NumericEquality",
summary = "Numeric comparison using reference equality instead of value equality",
explanation = "Numbers are compared for reference equality/inequality using == or != "
+ "instead of for value equality using .equals()",
category = JDK, severity = ERROR, maturity = EXPERIMENTAL)
public class NumericEquality extends BugChecker implements BinaryTreeMatcher {
public static final Matcher<ExpressionTree> SUBCLASS_OF_NUMBER =
allOf(isSubtypeOf("java.lang.Number"), not(kindIs(Tree.Kind.NULL_LITERAL)));
public static final Matcher<BinaryTree> MATCHER = allOf(
anyOf(kindIs(EQUAL_TO), kindIs(NOT_EQUAL_TO)),
binaryTree(SUBCLASS_OF_NUMBER, SUBCLASS_OF_NUMBER));
@Override
public Description matchBinary(BinaryTree tree, VisitorState state) {
ExpressionTree leftOperand = tree.getLeftOperand();
ExpressionTree rightOperand = tree.getRightOperand();
Symbol left = ASTHelpers.getSymbol(leftOperand);
Symbol right = ASTHelpers.getSymbol(rightOperand);
if (left == null || right == null) {
return Description.NO_MATCH;
}
// Using a static final object as a sentinel is OK
if ((isFinal(left) && left.isStatic()) || (isFinal(right) && right.isStatic())) {
return Description.NO_MATCH;
}
// Match left and right operand to subclasses of java.lang.Number and not null
if (!MATCHER.matches(tree, state)) {
return Description.NO_MATCH;
}
StringBuilder fixedExpression = new StringBuilder();
if (tree.getKind() == Tree.Kind.NOT_EQUAL_TO) {
fixedExpression.append("!");
}
fixedExpression.append(
"Objects.equal(" + leftOperand + ", " + rightOperand + ")");
Fix fix = SuggestedFix.builder()
.replace(tree, fixedExpression.toString())
.addImport("com.google.common.base.Objects")
.build();
return describeMatch(tree, fix);
}
public static boolean isFinal(Symbol s) {
return (s.flags() & Flags.FINAL) != 0;
}
}