/*
* Copyright 2015 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.ERROR;
import static com.google.errorprone.matchers.Matchers.argument;
import static com.google.errorprone.matchers.Matchers.instanceMethod;
import com.google.auto.value.AutoValue;
import com.google.common.collect.Iterables;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.matchers.Matchers;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.tree.JCTree;
/** @author cushon@google.com (Liam Miller-Cushon) */
@BugPattern(
name = "IsInstanceOfClass",
summary = "The argument to Class#isInstance(Object) should not be a Class",
category = JDK,
severity = ERROR
)
public class IsInstanceOfClass extends BugChecker implements MethodInvocationTreeMatcher {
private static final Matcher<MethodInvocationTree> INSTANCE_OF_CLASS =
Matchers.allOf(
instanceMethod().onExactClass("java.lang.Class").named("isInstance"),
argument(
0,
// Class is final so we could just use isSameType, but we want to
// test for the same _erased_ type.
Matchers.<ExpressionTree>isSubtypeOf("java.lang.Class")));
/**
* Suggests removing getClass() or changing to Class.class.
*/
@Override
public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
if (!INSTANCE_OF_CLASS.matches(tree, state)) {
return Description.NO_MATCH;
}
return describeMatch(tree, SuggestedFix.replace(tree, buildReplacement(tree, state)));
}
static String buildReplacement(MethodInvocationTree tree, VisitorState state) {
Operand lhs = classify((JCTree) ASTHelpers.getReceiver(tree.getMethodSelect()), state);
Operand rhs = classify((JCTree) Iterables.getOnlyElement(tree.getArguments()), state);
// expr.getClass().isInstance(Bar.class) -> expr instanceof Bar
if (lhs.kind() == Kind.GET_CLASS && rhs.kind() == Kind.LITERAL) {
return String.format("%s instanceof %s", lhs.value(), rhs.value());
}
// expr1.getClass().isInstance(expr2.getClass()) -> expr2.getClass().isInstance(expr1)
if (lhs.kind() == Kind.GET_CLASS && rhs.kind() == Kind.GET_CLASS) {
return String.format("%s.getClass().isInstance(%s)", rhs.value(), lhs.value());
}
// Foo.class.isInstance(Bar.class) -> Bar.class == Class.class
if (lhs.kind() == Kind.LITERAL && rhs.kind() == Kind.LITERAL) {
return String.format("%s.class == Class.class", rhs.value()); // !!
}
// Foo.class.isInstance(expr.getClass()) -> expr instanceof Foo
if (lhs.kind() == Kind.LITERAL && rhs.kind() == Kind.GET_CLASS) {
return String.format("%s instanceof %s", rhs.value(), lhs.value());
}
// clazz.isInstance(expr.getClass()) -> clazz.isInstance(expr)
if (rhs.kind() == Kind.GET_CLASS) {
return String.format("%s.isInstance(%s)", lhs.source(), rhs.value());
}
// expr.getClass().isInstance(clazz) -> clazz.isInstance(expr)
if (lhs.kind() == Kind.GET_CLASS) {
return String.format("%s.isInstance(%s)", rhs.source(), lhs.value());
}
// clazz1.isInstance(clazz2) -> clazz2.isAssignableFrom(clazz1)
// clazz.isInstance(Bar.class) -> Bar.class.isAssignableFrom(clazz)
// Foo.class.isInstance(clazz) -> clazz.isAssignableFrom(Foo.class)
return String.format("%s.isAssignableFrom(%s)", rhs.source(), lhs.source());
}
enum Kind {
LITERAL,
GET_CLASS,
EXPR
}
@AutoValue
abstract static class Operand {
abstract Kind kind();
abstract CharSequence value();
abstract CharSequence source();
static Operand create(Kind kind, CharSequence value, CharSequence source) {
return new AutoValue_IsInstanceOfClass_Operand(kind, value, source);
}
}
static Operand classify(JCTree tree, VisitorState state) {
CharSequence source = state.getSourceForNode(tree);
if (tree instanceof MethodInvocationTree) {
// expr.getClass() -> "expr"
MethodInvocationTree receiverInvocation = (MethodInvocationTree) tree;
MethodSymbol sym = ASTHelpers.getSymbol(receiverInvocation);
if (sym != null) {
if (sym.getSimpleName().contentEquals("getClass") && sym.params().isEmpty()) {
if (receiverInvocation.getMethodSelect() instanceof IdentifierTree) {
// unqualified `getClass()`
return Operand.create(Kind.EXPR, state.getSourceForNode(tree), source);
}
return Operand.create(
Kind.GET_CLASS,
state.getSourceForNode((JCTree) ASTHelpers.getReceiver(receiverInvocation)),
source);
}
}
} else if (tree instanceof MemberSelectTree) {
// Foo.class -> "Foo"
MemberSelectTree select = (MemberSelectTree) tree;
if (select.getIdentifier().contentEquals("class")) {
return Operand.create(
Kind.LITERAL, state.getSourceForNode((JCTree) select.getExpression()), source);
}
}
return Operand.create(Kind.EXPR, source, source);
}
}