/*
* 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.errorprone.bugpatterns;
import static com.google.errorprone.BugPattern.Category.JDK;
import static com.google.errorprone.BugPattern.MaturityLevel.MATURE;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.BinaryTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.BinaryTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCExpression;
import javax.annotation.Nullable;
/**
* @author lowasser@google.com (Louis Wasserman)
*/
@BugPattern(name = "EqualsNaN",
summary = "== NaN always returns false; use the isNaN methods instead",
explanation = "As per JLS 15.21.1, == NaN comparisons always return false, even NaN == NaN. "
+ "Instead, use the isNaN methods to check for NaN.",
category = JDK, severity = ERROR, maturity = MATURE)
public class EqualsNaN extends BugChecker implements BinaryTreeMatcher {
@Override
public Description matchBinary(BinaryTree tree, VisitorState state) {
String prefix;
switch (tree.getKind()) {
case EQUAL_TO:
prefix = "";
break;
case NOT_EQUAL_TO:
prefix = "!";
break;
default:
return Description.NO_MATCH;
}
JCExpression left = (JCExpression) tree.getLeftOperand();
JCExpression right = (JCExpression) tree.getRightOperand();
String leftMatch = matchNaN(left);
if (leftMatch != null) {
return describeMatch(tree, SuggestedFix.replace(tree,
String.format("%s%s.isNaN(%s)", prefix, leftMatch, toString(right, state))));
}
String rightMatch = matchNaN(right);
if (rightMatch != null) {
return describeMatch(tree, SuggestedFix.replace(tree,
String.format("%s%s.isNaN(%s)", prefix, rightMatch, toString(left, state))));
}
return Description.NO_MATCH;
}
private CharSequence toString(JCTree tree, VisitorState state) {
CharSequence source = state.getSourceForNode(tree);
return (source == null) ? tree.toString() : source;
}
@Nullable
private String matchNaN(ExpressionTree tree) {
Symbol sym = ASTHelpers.getSymbol(tree);
if (sym != null && sym.owner != null && sym.owner.asType() != null
&& sym.getSimpleName().contentEquals("NaN")) {
if (sym.owner.getQualifiedName().contentEquals("java.lang.Double")) {
return "Double";
} else if (sym.owner.getQualifiedName().contentEquals("java.lang.Float")) {
return "Float";
}
}
return null;
}
}