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VoidUsed.java
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VoidUsed.java
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/*
* Copyright 2024 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.Sets.immutableEnumSet;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.suppliers.Suppliers.JAVA_LANG_VOID_TYPE;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.isSameType;
import static javax.lang.model.element.ElementKind.FIELD;
import static javax.lang.model.element.ElementKind.LOCAL_VARIABLE;
import static javax.lang.model.element.ElementKind.PARAMETER;
import com.google.common.collect.ImmutableSet;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.IdentifierTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MemberSelectTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.AssignmentTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.Tree;
import javax.lang.model.element.ElementKind;
/** A BugPattern; see the summary. */
@BugPattern(
summary =
"Using a Void-typed variable is potentially confusing, and can be replaced with a literal"
+ " `null`.",
severity = WARNING)
public final class VoidUsed extends BugChecker
implements IdentifierTreeMatcher, MemberSelectTreeMatcher {
@Override
public Description matchIdentifier(IdentifierTree tree, VisitorState state) {
return handle(tree, state);
}
@Override
public Description matchMemberSelect(MemberSelectTree tree, VisitorState state) {
return handle(tree, state);
}
private Description handle(Tree tree, VisitorState state) {
var parent = state.getPath().getParentPath().getLeaf();
if (parent instanceof AssignmentTree && ((AssignmentTree) parent).getVariable().equals(tree)) {
return NO_MATCH;
}
var symbol = getSymbol(tree);
if (symbol == null
|| !KINDS.contains(symbol.getKind())
|| !isSameType(symbol.type, JAVA_LANG_VOID_TYPE.get(state), state)) {
return NO_MATCH;
}
return describeMatch(tree, SuggestedFix.replace(tree, "null"));
}
private static final ImmutableSet<ElementKind> KINDS =
immutableEnumSet(PARAMETER, LOCAL_VARIABLE, FIELD);
}