com.google.errorprone.bugpatterns.UnusedAnonymousClass Maven / Gradle / Ivy
/*
* Copyright 2015 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.ERROR;
import com.google.common.collect.ImmutableList;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.NewClassTreeMatcher;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.NewClassTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.tree.VariableTree;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(summary = "Instance created but never used", severity = ERROR)
public class UnusedAnonymousClass extends BugChecker implements NewClassTreeMatcher {
// An anonymous class creation cannot have side-effects if:
// (1) it is of an interface type (no super-class constructor side-effects)
// (2) and has no instance initializer blocks or field initializers
@Override
public Description matchNewClass(NewClassTree newClassTree, VisitorState state) {
if (state.getPath().getParentPath().getLeaf().getKind() != Kind.EXPRESSION_STATEMENT) {
return Description.NO_MATCH;
}
if (newClassTree.getClassBody() == null) {
return Description.NO_MATCH;
}
if (!newClassTree.getArguments().isEmpty()) {
return Description.NO_MATCH;
}
for (Tree def : newClassTree.getClassBody().getMembers()) {
switch (def.getKind()) {
case VARIABLE:
{
VariableTree variableTree = (VariableTree) def;
if (variableTree.getInitializer() != null) {
return Description.NO_MATCH;
}
break;
}
case BLOCK:
return Description.NO_MATCH;
default:
break;
}
}
if (!sideEffectFreeConstructor(ASTHelpers.getType(newClassTree.getIdentifier()).tsym, state)) {
return Description.NO_MATCH;
}
return describeMatch(newClassTree);
}
private static final ImmutableList TYPES_WITH_SIDE_EFFECT_FREE_CONSTRUCTORS =
ImmutableList.of(Thread.class.getName());
private static boolean sideEffectFreeConstructor(TypeSymbol classType, VisitorState state) {
if (classType.isInterface()) {
return true;
}
for (String typeName : TYPES_WITH_SIDE_EFFECT_FREE_CONSTRUCTORS) {
if (ASTHelpers.isSameType(classType.type, state.getTypeFromString(typeName), state)) {
return true;
}
}
return false;
}
}