/*
* 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.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ClassTree;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.NestingKind;
/**
* @author alexloh@google.com (Alex Loh)
* @author cushon@google.com (Liam Miller-Cushon)
*/
@BugPattern(
name = "ClassCanBeStatic",
summary = "Inner class is non-static but does not reference enclosing class",
explanation =
"An inner class should be static unless it references members"
+ " of its enclosing class. An inner class that is made non-static unnecessarily"
+ " uses more memory and does not make the intent of the class clear.",
category = JDK,
severity = WARNING
)
public class ClassCanBeStatic extends BugChecker implements ClassTreeMatcher {
@Override
public Description matchClass(final ClassTree tree, final VisitorState state) {
final ClassSymbol currentClass = ASTHelpers.getSymbol(tree);
if (currentClass == null || !currentClass.hasOuterInstance()) {
return NO_MATCH;
}
if (currentClass.getNestingKind() != NestingKind.MEMBER) {
// local or anonymous classes can't be static
return NO_MATCH;
}
switch (currentClass.owner.enclClass().getNestingKind()) {
case TOP_LEVEL:
break;
case MEMBER:
// class is nested inside an inner class, so it can't be static
if (currentClass.owner.enclClass().hasOuterInstance()) {
return NO_MATCH;
}
break;
case LOCAL:
case ANONYMOUS:
// members of local and anonymous classes can't be static
return NO_MATCH;
}
if (tree.getExtendsClause() != null
&& ASTHelpers.getType(tree.getExtendsClause()).tsym.hasOuterInstance()) {
return NO_MATCH;
}
if (CanBeStaticAnalyzer.referencesOuter(tree, currentClass, state)) {
return NO_MATCH;
}
return describeMatch(tree, SuggestedFixes.addModifiers(tree, state, Modifier.STATIC));
}
}