code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.checks.modifier;
  
  import com.puppycrawl.tools.checkstyle.StatelessCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.Scope;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
  
  /**
   * <p>
   * Checks for implicit modifiers on nested types in classes and records.
   * </p>
   * <p>
   * This check is effectively the opposite of
   * <a href="https://checkstyle.org/checks/modifier/redundantmodifier.html#RedundantModifier">
   * RedundantModifier</a>.
   * It checks the modifiers on nested types in classes and records, ensuring that certain modifiers
   * are explicitly specified even though they are actually redundant.
   * </p>
   * <p>
   * Nested enums, interfaces, and records within a class are always {@code static} and as such the
   * compiler does not require the {@code static} modifier. This check provides the ability to enforce
   * that the {@code static} modifier is explicitly coded and not implicitly added by the compiler.
   * </p>
   * <pre>
   * public final class Person {
   *   enum Age {  // violation
   *     CHILD, ADULT
   *   }
   * }
   * </pre>
   * <p>
   * Rationale for this check: Nested enums, interfaces, and records are treated differently from
   * nested classes as they are only allowed to be {@code static}. Developers should not need to
   * remember this rule, and this check provides the means to enforce that the modifier is coded
   * explicitly.
   * </p>
   * <ul>
   * <li>
   * Property {@code violateImpliedStaticOnNestedEnum} - Control whether to enforce that
   * {@code static} is explicitly coded on nested enums in classes and records.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedStaticOnNestedInterface} - Control whether to enforce that
   * {@code static} is explicitly coded on nested interfaces in classes and records.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * <li>
   * Property {@code violateImpliedStaticOnNestedRecord} - Control whether to enforce that
   * {@code static} is explicitly coded on nested records in classes and records.
   * Type is {@code boolean}.
   * Default value is {@code true}.
   * </li>
   * </ul>
   * <p>
   * To configure the check so that it checks that all implicit modifiers on nested interfaces, enums,
   * and records are explicitly specified in classes and records.
   * </p>
   * <p>
   * Configuration:
   * </p>
   * <pre>
   * &lt;module name="ClassMemberImpliedModifier" /&gt;
   * </pre>
   * <p>
   * Code:
   * </p>
   * <pre>
   * public final class Person {
   *   static interface Address1 {  // valid
   *   }
   *
   *   interface Address2 {  // violation
   *   }
   *
   *   static enum Age1 {  // valid
   *     CHILD, ADULT
   *   }
   *
   *   enum Age2 {  // violation
   *     CHILD, ADULT
   *   }
   *
   *   public static record GoodRecord() {} // valid
   *   public record BadRecord() {} // violation
   *
   *   public static record OuterRecord() {
   *     static record InnerRecord1(){} // valid
   *     record InnerRecord2(){} // violation
   *   }
   * }
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code class.implied.modifier}
   * </li>
   * </ul>
   *
   * @since 8.16
   */
  @StatelessCheck
  public class ClassMemberImpliedModifierCheck
      extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties" file.
       */
      public static final String MSG_KEY = "class.implied.modifier";
  
      /** Name for 'static' keyword. */
      private static final String STATIC_KEYWORD = "static";
  
      /**
       * Control whether to enforce that {@code static} is explicitly coded
       * on nested enums in classes and records.
       */
      private boolean violateImpliedStaticOnNestedEnum = true;
  
      /**
       * Control whether to enforce that {@code static} is explicitly coded
       * on nested interfaces in classes and records.
       */
      private boolean violateImpliedStaticOnNestedInterface = true;
  
      /**
       * Control whether to enforce that {@code static} is explicitly coded
       * on nested records in classes and records.
       */
      private boolean violateImpliedStaticOnNestedRecord = true;
  
      /**
       * Setter to control whether to enforce that {@code static} is explicitly coded
       * on nested enums in classes and records.
       *
       * @param violateImplied
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedStaticOnNestedEnum(boolean violateImplied) {
          violateImpliedStaticOnNestedEnum = violateImplied;
      }
  
      /**
       * Setter to control whether to enforce that {@code static} is explicitly coded
       * on nested interfaces in classes and records.
       *
       * @param violateImplied
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedStaticOnNestedInterface(boolean violateImplied) {
          violateImpliedStaticOnNestedInterface = violateImplied;
      }
  
      /**
       * Setter to control whether to enforce that {@code static} is explicitly coded
       * on nested records in classes and records.
       *
       * @param violateImplied
       *        True to perform the check, false to turn the check off.
       */
      public void setViolateImpliedStaticOnNestedRecord(boolean violateImplied) {
          violateImpliedStaticOnNestedRecord = violateImplied;
      }
  
      @Override
      public int[] getDefaultTokens() {
          return getAcceptableTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return getAcceptableTokens();
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return new int[] {
              TokenTypes.INTERFACE_DEF,
              TokenTypes.ENUM_DEF,
              TokenTypes.RECORD_DEF,
          };
      }
  
      @Override
      public void visitToken(DetailAST ast) {
          if (isInTypeBlock(ast)) {
              final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
              switch (ast.getType()) {
                  case TokenTypes.ENUM_DEF:
                      if (violateImpliedStaticOnNestedEnum
                              && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
                          log(ast, MSG_KEY, STATIC_KEYWORD);
                      }
                      break;
                  case TokenTypes.INTERFACE_DEF:
                      if (violateImpliedStaticOnNestedInterface
                              && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
                          log(ast, MSG_KEY, STATIC_KEYWORD);
                      }
                      break;
                  case TokenTypes.RECORD_DEF:
                      if (violateImpliedStaticOnNestedRecord
                              && modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
                          log(ast, MSG_KEY, STATIC_KEYWORD);
                      }
                      break;
                  default:
                      throw new IllegalStateException(ast.toString());
              }
          }
      }
  
      /**
       * Checks if ast is in a class, enum, anon class or record block.
       *
       * @param ast the current ast
       * @return true if ast is in a class, enum, anon class or record
       */
      private static boolean isInTypeBlock(DetailAST ast) {
          return ScopeUtil.isInScope(ast, Scope.ANONINNER)
                  || ScopeUtil.isInClassBlock(ast)
                  || ScopeUtil.isInEnumBlock(ast)
                  || ScopeUtil.isInRecordBlock(ast);
      }
  
  }
  