com.google.errorprone.bugpatterns.FunctionalInterfaceMethodChanged Maven / Gradle / Ivy
/*
* Copyright 2016 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.common.collect.ImmutableSet.toImmutableSet;
import static com.google.errorprone.suppliers.Suppliers.JAVA_LANG_VOID_TYPE;
import com.google.common.collect.Iterables;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.SeverityLevel;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
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.BlockTree;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.ExpressionStatementTree;
import com.sun.source.tree.LiteralTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.ReturnTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.TreeVisitor;
import com.sun.source.util.SimpleTreeVisitor;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.Types;
import java.util.Collections;
import java.util.Set;
import javax.lang.model.element.Modifier;
/** @author Louis Wasserman */
@BugPattern(
name = "FunctionalInterfaceMethodChanged",
summary =
"Casting a lambda to this @FunctionalInterface can cause a behavior change from casting to"
+ " a functional superinterface, which is surprising to users. Prefer decorator"
+ " methods to this surprising behavior.",
severity = SeverityLevel.ERROR)
public class FunctionalInterfaceMethodChanged extends BugChecker implements MethodTreeMatcher {
private static final Matcher IS_FUNCTIONAL_INTERFACE =
Matchers.symbolHasAnnotation(FunctionalInterface.class);
@Override
public Description matchMethod(MethodTree tree, VisitorState state) {
ClassTree enclosingClazz = ASTHelpers.findEnclosingNode(state.getPath(), ClassTree.class);
if (tree.getModifiers().getFlags().contains(Modifier.DEFAULT)
&& IS_FUNCTIONAL_INTERFACE.matches(enclosingClazz, state)) {
Types types = state.getTypes();
Set functionalSuperInterfaceSams =
enclosingClazz.getImplementsClause().stream()
.filter(t -> IS_FUNCTIONAL_INTERFACE.matches(t, state))
.map(ASTHelpers::getSymbol)
.map(TypeSymbol.class::cast)
.map(types::findDescriptorSymbol) // TypeSymbol to single abstract method of the type
.collect(toImmutableSet());
// We designate an override of a superinterface SAM "behavior preserving" if it just
// calls the SAM of this interface.
Symbol thisInterfaceSam = types.findDescriptorSymbol(ASTHelpers.getSymbol(enclosingClazz));
// relatively crude: doesn't verify that the same args are passed in the same order
// so it can get false positives for behavior-preservingness (false negatives for the check)
TreeVisitor behaviorPreserving =
new BehaviorPreservingChecker(thisInterfaceSam);
if (!Collections.disjoint(
ASTHelpers.findSuperMethods(ASTHelpers.getSymbol(tree), types),
functionalSuperInterfaceSams)
&& !tree.accept(behaviorPreserving, state)) {
return describeMatch(tree);
}
}
return Description.NO_MATCH;
}
private static class BehaviorPreservingChecker extends SimpleTreeVisitor {
private boolean inBoxedVoidReturningMethod = false;
private final Symbol methodToCall;
public BehaviorPreservingChecker(Symbol methodToCall) {
super(false);
this.methodToCall = methodToCall;
}
@Override
public Boolean visitMethod(MethodTree node, VisitorState state) {
boolean prevInBoxedVoidReturningMethod = inBoxedVoidReturningMethod;
Type returnType = ASTHelpers.getType(node.getReturnType());
Type boxedVoidType = JAVA_LANG_VOID_TYPE.get(state);
if (ASTHelpers.isSameType(returnType, boxedVoidType, state)) {
inBoxedVoidReturningMethod = true;
}
boolean result = node.getBody() != null && node.getBody().accept(this, state);
inBoxedVoidReturningMethod = prevInBoxedVoidReturningMethod;
return result;
}
@Override
public Boolean visitBlock(BlockTree node, VisitorState state) {
if (inBoxedVoidReturningMethod) {
// Must have exactly 2 statements
if (node.getStatements().size() != 2) {
return false;
}
// Where the first one is a call to the methodToCall
if (!node.getStatements().get(0).accept(this, state)) {
return false;
}
// And the second one is "return null;"
if (node.getStatements().get(1) instanceof ReturnTree) {
ReturnTree returnTree = (ReturnTree) node.getStatements().get(1);
if (returnTree.getExpression() instanceof LiteralTree) {
Object returnValue = ((LiteralTree) returnTree.getExpression()).getValue();
return returnValue == null;
}
}
return false;
} else {
return node.getStatements().size() == 1
&& Iterables.getOnlyElement(node.getStatements()).accept(this, state);
}
}
@Override
public Boolean visitExpressionStatement(ExpressionStatementTree node, VisitorState state) {
return node.getExpression().accept(this, state);
}
@Override
public Boolean visitReturn(ReturnTree node, VisitorState state) {
return node.getExpression().accept(this, state);
}
@Override
public Boolean visitMethodInvocation(MethodInvocationTree node, VisitorState state) {
return ASTHelpers.getSymbol(node) == methodToCall;
}
}
}