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/*
* Copyright 2020 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.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.anyOf;
import static com.google.errorprone.matchers.Matchers.instanceMethod;
import static com.google.errorprone.matchers.Matchers.isBoxedPrimitiveType;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.stripParentheses;
import com.google.common.collect.ImmutableList;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.SeverityLevel;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.SynchronizedTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.suppliers.Suppliers;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.SynchronizedTree;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.TreeScanner;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.VarSymbol;
import javax.lang.model.element.ElementKind;
/** Detects locks on boxed primitives. */
@BugPattern(
name = "LockOnBoxedPrimitive",
summary =
"It is dangerous to use a boxed primitive as a lock as it can unintentionally lead to"
+ " sharing a lock with another piece of code.",
severity = SeverityLevel.WARNING)
public class LockOnBoxedPrimitive extends BugChecker
implements SynchronizedTreeMatcher, MethodInvocationTreeMatcher {
private static final Matcher LOCKING_METHOD =
anyOf(
instanceMethod()
.anyClass()
.named("wait")
.withParametersOfType(ImmutableList.of(Suppliers.LONG_TYPE)),
instanceMethod()
.anyClass()
.named("wait")
.withParametersOfType(ImmutableList.of(Suppliers.LONG_TYPE, Suppliers.INT_TYPE)),
instanceMethod().anyClass().namedAnyOf("wait", "notify", "notifyAll").withNoParameters());
private static final Matcher BOXED_PRIMITIVE = isBoxedPrimitiveType();
@Override
public Description matchSynchronized(SynchronizedTree tree, VisitorState state) {
ExpressionTree locked = stripParentheses(tree.getExpression());
if (!isDefinitelyBoxedPrimitive(locked, state)) {
return NO_MATCH;
}
return describeMatch(tree, createFix(locked, state));
}
private SuggestedFix createFix(ExpressionTree locked, VisitorState state) {
Symbol lock = getSymbol(locked);
if (lock == null) {
return SuggestedFix.emptyFix();
}
if (!lock.getKind().equals(ElementKind.FIELD)) {
return SuggestedFix.emptyFix();
}
SuggestedFix.Builder fix = SuggestedFix.builder();
String lockName = lock.getSimpleName() + "Lock";
new TreeScanner() {
@Override
public Void visitVariable(VariableTree node, Void unused) {
VarSymbol sym = getSymbol(node);
if (lock.equals(sym)) {
String unboxedType =
SuggestedFixes.qualifyType(state, fix, state.getTypes().unboxedType(getType(node)));
fix.prefixWith(
node,
String.format(
"private final Object %s = new Object();\n@GuardedBy(\"%s\")",
lockName, lockName))
.replace(node.getType(), unboxedType)
.addImport("com.google.errorprone.annotations.concurrent.GuardedBy");
}
return super.visitVariable(node, null);
}
@Override
public Void visitSynchronized(SynchronizedTree node, Void aVoid) {
ExpressionTree expression = stripParentheses(node.getExpression());
if (lock.equals(getSymbol(expression))) {
fix.replace(expression, lockName);
}
return super.visitSynchronized(node, aVoid);
}
}.scan(state.getPath().getCompilationUnit(), null);
return fix.build();
}
@Override
public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
if (LOCKING_METHOD.matches(tree, state)
&& isDefinitelyBoxedPrimitive(ASTHelpers.getReceiver(tree), state)) {
return describeMatch(tree.getMethodSelect());
}
return NO_MATCH;
}
/** Returns true if the expression tree is definitely referring to a boxed primitive. */
private static boolean isDefinitelyBoxedPrimitive(ExpressionTree tree, VisitorState state) {
return BOXED_PRIMITIVE.matches(tree, state);
}
}