com.google.errorprone.bugpatterns.BadInstanceof 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.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.isNonNullUsingDataflow;
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.InstanceOfTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.InstanceOfTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
/**
* Matches instanceof checks where the expression is a subtype of the checked type.
*
* @author [email protected] (Graeme Morgan)
*/
@BugPattern(
summary = "instanceof used in a way that is equivalent to a null check.",
severity = WARNING,
tags = SIMPLIFICATION)
public final class BadInstanceof extends BugChecker implements InstanceOfTreeMatcher {
@Override
public Description matchInstanceOf(InstanceOfTree tree, VisitorState state) {
if (!isSubtype(getType(tree.getExpression()), getType(tree.getType()), state)) {
return NO_MATCH;
}
String subType = SuggestedFixes.prettyType(getType(tree.getExpression()), state);
String expression = state.getSourceForNode(tree.getExpression());
String superType = state.getSourceForNode(tree.getType());
if (isNonNullUsingDataflow().matches(tree.getExpression(), state)) {
return buildDescription(tree)
.setMessage(
String.format(
"`%s` is a non-null instance of %s which is a subtype of %s, so this check is"
+ " always true.",
expression, subType, superType))
.build();
}
return buildDescription(tree)
.setMessage(
String.format(
"`%s` is an instance of %s which is a subtype of %s, so this is equivalent to a"
+ " null check.",
expression, subType, superType))
.addFix(getFix(tree, state))
.build();
}
private static SuggestedFix getFix(InstanceOfTree tree, VisitorState state) {
Tree parent = state.getPath().getParentPath().getLeaf();
Tree grandParent = state.getPath().getParentPath().getParentPath().getLeaf();
if (parent.getKind() == Kind.PARENTHESIZED
&& grandParent.getKind() == Kind.LOGICAL_COMPLEMENT) {
return SuggestedFix.replace(
grandParent, state.getSourceForNode(tree.getExpression()) + " == null");
}
return SuggestedFix.replace(tree, state.getSourceForNode(tree.getExpression()) + " != null");
}
}