ObjectEqualsNullInspection.java

/*
 * Copyright 2003-2007 Dave Griffith, Bas Leijdekkers
 *
 * 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.siyeh.ig.bugs;

import com.intellij.psi.PsiExpression;
import com.intellij.psi.PsiExpressionList;
import com.intellij.psi.PsiMethodCallExpression;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.psiutils.ExpressionUtils;
import com.siyeh.ig.psiutils.MethodCallUtils;
import org.jetbrains.annotations.NotNull;

public class ObjectEqualsNullInspection extends BaseInspection {

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message(
      "object.equals.null.display.name");
  }

  @Override
  @NotNull
  public String buildErrorString(Object... infos) {
    return InspectionGadgetsBundle.message(
      "object.equals.null.problem.descriptor");
  }

  @Override
  public boolean isEnabledByDefault() {
    return true;
  }

  @Override
  public BaseInspectionVisitor buildVisitor() {
    return new ObjectEqualsNullVisitor();
  }

  private static class ObjectEqualsNullVisitor extends BaseInspectionVisitor {

    @Override
    public void visitMethodCallExpression(
      @NotNull PsiMethodCallExpression call) {
      super.visitMethodCallExpression(call);
      if (!MethodCallUtils.isEqualsCall(call)) {
        return;
      }
      final PsiExpressionList argumentList = call.getArgumentList();
      final PsiExpression[] args = argumentList.getExpressions();
      if (args.length == 0 || !ExpressionUtils.isNullLiteral(args[0])) {
        return;
      }
      registerError(args[0]);
    }
  }
}