///////////////////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
   // Copyright (C) 2001-2026 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.coding;
  
  import java.util.ArrayDeque;
  import java.util.BitSet;
  import java.util.Deque;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Queue;
  import java.util.Set;
  
  import javax.annotation.Nullable;
  
  import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
  import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
  import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
  
  /**
   * <div>
   * Checks that references to instance variables and methods of the present
   * object are explicitly of the form "this.varName" or "this.methodName(args)"
   * and that those references don't rely on the default behavior when "this." is absent.
   * </div>
   *
   * <p>Warning: the Check is very controversial if 'validateOnlyOverlapping' option is set to 'false'
   * and not that actual nowadays.</p>
   *
   * <p>Rationale:</p>
   * <ol>
   *   <li>
   *     The same notation/habit for C++ and Java (C++ have global methods, so having
   *     &quot;this.&quot; do make sense in it to distinguish call of method of class
   *     instead of global).
   *   </li>
   *   <li>
   *     Non-IDE development (ease of refactoring, some clearness to distinguish
   *     static and non-static methods).
   *   </li>
   * </ol>
   *
   * <p>
   * Notes:
   * Limitations: Nothing is currently done about static variables
   * or catch-blocks.  Static methods invoked on a class name seem to be OK;
   * both the class name and the method name have a DOT parent.
   * Non-static methods invoked on either this or a variable name seem to be
   * OK, likewise.
   * </p>
   *
   * @since 3.4
   */
  // -@cs[ClassDataAbstractionCoupling] This check requires to work with and identify many frames.
  @FileStatefulCheck
  public class RequireThisCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_METHOD = "require.this.method";
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_VARIABLE = "require.this.variable";
  
      /** Set of all declaration tokens. */
      private static final BitSet DECLARATION_TOKENS = TokenUtil.asBitSet(
          TokenTypes.VARIABLE_DEF,
          TokenTypes.CTOR_DEF,
          TokenTypes.METHOD_DEF,
          TokenTypes.CLASS_DEF,
          TokenTypes.ENUM_DEF,
          TokenTypes.ANNOTATION_DEF,
          TokenTypes.INTERFACE_DEF,
          TokenTypes.PARAMETER_DEF,
         TokenTypes.TYPE_ARGUMENT,
         TokenTypes.RECORD_DEF,
         TokenTypes.RECORD_COMPONENT_DEF,
         TokenTypes.RESOURCE
     );
     /** Set of all assign tokens. */
     private static final BitSet ASSIGN_TOKENS = TokenUtil.asBitSet(
         TokenTypes.ASSIGN,
         TokenTypes.PLUS_ASSIGN,
         TokenTypes.STAR_ASSIGN,
         TokenTypes.DIV_ASSIGN,
         TokenTypes.MOD_ASSIGN,
         TokenTypes.SR_ASSIGN,
         TokenTypes.BSR_ASSIGN,
         TokenTypes.SL_ASSIGN,
         TokenTypes.BAND_ASSIGN,
         TokenTypes.BXOR_ASSIGN
     );
     /** Set of all compound assign tokens. */
     private static final BitSet COMPOUND_ASSIGN_TOKENS = TokenUtil.asBitSet(
         TokenTypes.PLUS_ASSIGN,
         TokenTypes.STAR_ASSIGN,
         TokenTypes.DIV_ASSIGN,
         TokenTypes.MOD_ASSIGN,
         TokenTypes.SR_ASSIGN,
         TokenTypes.BSR_ASSIGN,
         TokenTypes.SL_ASSIGN,
         TokenTypes.BAND_ASSIGN,
         TokenTypes.BXOR_ASSIGN
     );
 
     /** Frame for the currently processed AST. */
     private final Deque<AbstractFrame> current = new ArrayDeque<>();
 
     /** Tree of all the parsed frames. */
     private Map<DetailAST, AbstractFrame> frames;
 
     /** Control whether to check references to fields. */
     private boolean checkFields = true;
     /** Control whether to check references to methods. */
     private boolean checkMethods = true;
     /** Control whether to check only overlapping by variables or arguments. */
     private boolean validateOnlyOverlapping = true;
 
     /**
      * Setter to control whether to check references to fields.
      *
      * @param checkFields should we check fields usage or not
      * @since 3.4
      */
     public void setCheckFields(boolean checkFields) {
         this.checkFields = checkFields;
     }
 
     /**
      * Setter to control whether to check references to methods.
      *
      * @param checkMethods should we check methods usage or not
      * @since 3.4
      */
     public void setCheckMethods(boolean checkMethods) {
         this.checkMethods = checkMethods;
     }
 
     /**
      * Setter to control whether to check only overlapping by variables or arguments.
      *
      * @param validateOnlyOverlapping should we check only overlapping by variables or arguments
      * @since 6.17
      */
     public void setValidateOnlyOverlapping(boolean validateOnlyOverlapping) {
         this.validateOnlyOverlapping = validateOnlyOverlapping;
     }
 
     @Override
     public int[] getDefaultTokens() {
         return getRequiredTokens();
     }
 
     @Override
     public int[] getRequiredTokens() {
         return new int[] {
             TokenTypes.CLASS_DEF,
             TokenTypes.INTERFACE_DEF,
             TokenTypes.ENUM_DEF,
             TokenTypes.ANNOTATION_DEF,
             TokenTypes.CTOR_DEF,
             TokenTypes.METHOD_DEF,
             TokenTypes.LITERAL_FOR,
             TokenTypes.SLIST,
             TokenTypes.IDENT,
             TokenTypes.RECORD_DEF,
             TokenTypes.COMPACT_CTOR_DEF,
             TokenTypes.LITERAL_TRY,
             TokenTypes.RESOURCE,
             TokenTypes.COMPACT_COMPILATION_UNIT,
         };
     }
 
     @Override
     public int[] getAcceptableTokens() {
         return getRequiredTokens();
     }
 
     @Override
     public void beginTree(DetailAST rootAST) {
         frames = new HashMap<>();
         current.clear();
 
         final Deque<AbstractFrame> frameStack = new ArrayDeque<>();
         DetailAST curNode = rootAST;
         while (curNode != null) {
             collectDeclarations(frameStack, curNode);
             DetailAST toVisit = curNode.getFirstChild();
             while (curNode != null && toVisit == null) {
                 endCollectingDeclarations(frameStack, curNode);
                 toVisit = curNode.getNextSibling();
                 curNode = curNode.getParent();
             }
             curNode = toVisit;
         }
     }
 
     @Override
     public void visitToken(DetailAST ast) {
         switch (ast.getType()) {
             case TokenTypes.IDENT -> processIdent(ast);
             case TokenTypes.CLASS_DEF, TokenTypes.INTERFACE_DEF, TokenTypes.ENUM_DEF,
                  TokenTypes.ANNOTATION_DEF, TokenTypes.SLIST, TokenTypes.METHOD_DEF,
                  TokenTypes.CTOR_DEF, TokenTypes.LITERAL_FOR, TokenTypes.RECORD_DEF,
                  TokenTypes.COMPACT_COMPILATION_UNIT ->
                 current.push(frames.get(ast));
             case TokenTypes.LITERAL_TRY -> {
                 if (ast.getFirstChild().getType() == TokenTypes.RESOURCE_SPECIFICATION) {
                     current.push(frames.get(ast));
                 }
             }
             default -> {
                 // Do nothing
             }
         }
     }
 
     @Override
     public void leaveToken(DetailAST ast) {
         switch (ast.getType()) {
             case TokenTypes.CLASS_DEF, TokenTypes.INTERFACE_DEF, TokenTypes.ENUM_DEF,
                  TokenTypes.ANNOTATION_DEF, TokenTypes.SLIST, TokenTypes.METHOD_DEF,
                  TokenTypes.CTOR_DEF, TokenTypes.LITERAL_FOR,
                  TokenTypes.RECORD_DEF -> current.pop();
             case TokenTypes.LITERAL_TRY -> {
                 if (current.peek().getType() == FrameType.TRY_WITH_RESOURCES_FRAME) {
                     current.pop();
                 }
             }
             default -> {
                 // Do nothing
             }
         }
     }
 
     /**
      * Checks if a given IDENT is method call or field name which
      * requires explicit {@code this} qualifier.
      *
      * @param ast IDENT to check.
      */
     private void processIdent(DetailAST ast) {
         if (!shouldSkipAnnotationContext(ast)) {
             final int parentType = ast.getParent().getType();
             if (parentType == TokenTypes.METHOD_CALL) {
                 if (checkMethods) {
                     final AbstractFrame frame = getMethodWithoutThis(ast);
                     if (frame != null) {
                         logViolation(MSG_METHOD, ast, frame);
                     }
                 }
             }
             else {
                 if (checkFields) {
                     final AbstractFrame frame = getFieldWithoutThis(ast, parentType);
                     final boolean canUseThis = !isInCompactConstructor(ast);
                     if (frame != null && canUseThis) {
                         logViolation(MSG_VARIABLE, ast, frame);
                     }
                 }
             }
         }
     }
 
     /**
      * Determines whether the given IDENT should be skipped because it is
      * in an annotation context. When {@code validateOnlyOverlapping} is
      * {@code true}, all annotation contexts are skipped. When it is
      * {@code false}, only annotation structural elements (member names,
      * type names, and annotation field defaults) are skipped, while actual
      * field reference values inside annotations are still processed.
      *
      * @param ast IDENT token
      * @return true if the IDENT should be skipped
      */
     private static boolean shouldSkipAnnotationContext(DetailAST ast) {
         return isInsideAnnotationFieldDef(ast) || isAnnotationStructuralElement(ast);
     }
 
     /**
      * Checks whether the given IDENT is inside an annotation field definition
      * (e.g., default values in {@code @interface} members).
      *
      * @param ast IDENT token
      * @return true if IDENT is inside an annotation field definition
      */
     private static boolean isInsideAnnotationFieldDef(DetailAST ast) {
         DetailAST current = ast;
         boolean insideAnnotationFieldDef = false;
         while (current != null) {
             if (current.getType() == TokenTypes.ANNOTATION_FIELD_DEF) {
                 insideAnnotationFieldDef = true;
                 break;
             }
             current = current.getParent();
         }
         return insideAnnotationFieldDef;
     }
 
     /**
      * Checks if an IDENT is an annotation structural element — either
      * an annotation type name (e.g., {@code SuppressWarnings} in
      * {@code @SuppressWarnings}) or an annotation member name (e.g.,
      * {@code value} in {@code value = "unused"}).
      *
      * @param ast IDENT token
      * @return true if the IDENT is an annotation type name or member name
      */
     private static boolean isAnnotationStructuralElement(DetailAST ast) {
         DetailAST current = ast.getParent();
         final int parentType = current.getType();
         while (current.getType() == TokenTypes.DOT) {
             current = current.getParent();
         }
         final int topType = current.getType();
         return topType == TokenTypes.ANNOTATION
                 || parentType == TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR;
     }
 
     /**
      * Helper method to log a Violation.
      *
      * @param msgKey key to locale message format.
      * @param ast a node to get line id column numbers associated with the message.
      * @param frame the class frame where the violation is found.
      */
     private void logViolation(String msgKey, DetailAST ast, AbstractFrame frame) {
         if (frame.getFrameName().equals(getNearestClassFrameName())) {
             log(ast, msgKey, ast.getText(), "");
         }
         else if (!(frame instanceof AnonymousClassFrame)
                 && !(frame instanceof CompactCompilationUnitFrame)) {
             log(ast, msgKey, ast.getText(), frame.getFrameName() + '.');
         }
     }
 
     /**
      * Returns the frame where the field is declared, if the given field is used without
      * 'this', and null otherwise.
      *
      * @param ast field definition ast token.
      * @param parentType type of the parent.
      * @return the frame where the field is declared, if the given field is used without
      *         'this' and null otherwise.
      */
     private AbstractFrame getFieldWithoutThis(DetailAST ast, int parentType) {
         final boolean importOrPackage = ScopeUtil.getSurroundingScope(ast).isEmpty();
         final boolean typeName = parentType == TokenTypes.TYPE
                 || parentType == TokenTypes.LITERAL_NEW;
         AbstractFrame frame = null;
 
         if (!importOrPackage
                 && !typeName
                 && !DECLARATION_TOKENS.get(parentType)
                 && !isLambdaParameter(ast)) {
             final AbstractFrame fieldFrame = findClassFrame(ast, false);
 
             if (fieldFrame != null && ((ClassFrame) fieldFrame).hasInstanceMember(ast)) {
                 frame = getClassFrameWhereViolationIsFound(ast);
             }
         }
         return frame;
     }
 
     /**
      * Return whether ast is in a COMPACT_CTOR_DEF.
      *
      * @param ast The token to check
      * @return true if ast is in a COMPACT_CTOR_DEF, false otherwise
      */
     private static boolean isInCompactConstructor(DetailAST ast) {
         boolean isInCompactCtor = false;
         DetailAST parent = ast;
         while (parent != null) {
             if (parent.getType() == TokenTypes.COMPACT_CTOR_DEF) {
                 isInCompactCtor = true;
                 break;
             }
             parent = parent.getParent();
         }
         return isInCompactCtor;
     }
 
     /**
      * Parses the next AST for declarations.
      *
      * @param frameStack stack containing the FrameTree being built.
      * @param ast AST to parse.
      */
     // -@cs[JavaNCSS] This method is a big switch and is too hard to remove.
     private static void collectDeclarations(Deque<AbstractFrame> frameStack, DetailAST ast) {
         final AbstractFrame frame = frameStack.peek();
 
         switch (ast.getType()) {
             case TokenTypes.VARIABLE_DEF -> collectVariableDeclarations(ast, frame);
 
             case TokenTypes.RECORD_COMPONENT_DEF -> {
                 final DetailAST componentIdent = ast.findFirstToken(TokenTypes.IDENT);
                 ((ClassFrame) frame).addInstanceMember(componentIdent);
             }
 
             case TokenTypes.PARAMETER_DEF -> {
                 if (!CheckUtil.isReceiverParameter(ast) && !isLambdaParameter(ast)) {
                     final DetailAST parameterIdent = ast.findFirstToken(TokenTypes.IDENT);
                     frame.addIdent(parameterIdent);
                 }
             }
 
             case TokenTypes.RESOURCE -> {
                 final DetailAST resourceIdent = ast.findFirstToken(TokenTypes.IDENT);
                 if (resourceIdent != null) {
                     frame.addIdent(resourceIdent);
                 }
             }
 
             case TokenTypes.CLASS_DEF, TokenTypes.INTERFACE_DEF, TokenTypes.ENUM_DEF,
                  TokenTypes.ANNOTATION_DEF, TokenTypes.RECORD_DEF -> {
                 final DetailAST classFrameNameIdent = ast.findFirstToken(TokenTypes.IDENT);
                 frameStack.addFirst(new ClassFrame(frame, classFrameNameIdent));
             }
 
             case TokenTypes.COMPACT_COMPILATION_UNIT ->
                 frameStack.addFirst(new CompactCompilationUnitFrame(frame, ast));
 
             case TokenTypes.SLIST -> frameStack.addFirst(new BlockFrame(frame, ast));
 
             case TokenTypes.METHOD_DEF -> collectMethodDeclarations(frameStack, ast, frame);
 
             case TokenTypes.CTOR_DEF, TokenTypes.COMPACT_CTOR_DEF -> {
                 final DetailAST ctorFrameNameIdent = ast.findFirstToken(TokenTypes.IDENT);
                 frameStack.addFirst(new ConstructorFrame(frame, ctorFrameNameIdent));
             }
 
             case TokenTypes.ENUM_CONSTANT_DEF -> {
                 final DetailAST ident = ast.findFirstToken(TokenTypes.IDENT);
                 ((ClassFrame) frame).addStaticMember(ident);
             }
 
             case TokenTypes.LITERAL_CATCH -> {
                 final AbstractFrame catchFrame = new CatchFrame(frame, ast);
                 frameStack.addFirst(catchFrame);
             }
 
             case TokenTypes.LITERAL_FOR -> {
                 final AbstractFrame forFrame = new ForFrame(frame, ast);
                 frameStack.addFirst(forFrame);
             }
 
             case TokenTypes.LITERAL_NEW -> {
                 final DetailAST lastChild = ast.getLastChild();
                 if (lastChild != null && lastChild.getType() == TokenTypes.OBJBLOCK) {
                     frameStack.addFirst(new AnonymousClassFrame(frame, ast.toString()));
                 }
             }
 
             case TokenTypes.LITERAL_TRY -> {
                 if (ast.getFirstChild().getType() == TokenTypes.RESOURCE_SPECIFICATION) {
                     frameStack.addFirst(new TryWithResourcesFrame(frame, ast));
                 }
             }
 
             default -> {
                 // do nothing
             }
         }
     }
 
     /**
      * Collects variable declarations.
      *
      * @param ast variable token.
      * @param frame current frame.
      */
     private static void collectVariableDeclarations(DetailAST ast, AbstractFrame frame) {
         final DetailAST ident = ast.findFirstToken(TokenTypes.IDENT);
         if (frame.getType() == FrameType.CLASS_FRAME) {
             final DetailAST mods =
                     ast.findFirstToken(TokenTypes.MODIFIERS);
             if (ScopeUtil.isInInterfaceBlock(ast)
                     || ScopeUtil.isInAnnotationBlock(ast)
                     || mods.findFirstToken(TokenTypes.LITERAL_STATIC) != null) {
                 ((ClassFrame) frame).addStaticMember(ident);
             }
             else {
                 ((ClassFrame) frame).addInstanceMember(ident);
             }
         }
         else {
             frame.addIdent(ident);
         }
     }
 
     /**
      * Collects {@code METHOD_DEF} declarations.
      *
      * @param frameStack stack containing the FrameTree being built.
      * @param ast AST to parse.
      * @param frame current frame.
      */
     private static void collectMethodDeclarations(Deque<AbstractFrame> frameStack,
                                                   DetailAST ast, AbstractFrame frame) {
         final DetailAST methodFrameNameIdent = ast.findFirstToken(TokenTypes.IDENT);
         final DetailAST mods = ast.findFirstToken(TokenTypes.MODIFIERS);
         if (mods.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
             ((ClassFrame) frame).addInstanceMethod(methodFrameNameIdent);
         }
         else {
             ((ClassFrame) frame).addStaticMethod(methodFrameNameIdent);
         }
         frameStack.addFirst(new MethodFrame(frame, methodFrameNameIdent));
     }
 
     /**
      * Ends parsing of the AST for declarations.
      *
      * @param frameStack Stack containing the FrameTree being built.
      * @param ast AST that was parsed.
      */
     private void endCollectingDeclarations(Queue<AbstractFrame> frameStack, DetailAST ast) {
         switch (ast.getType()) {
             case TokenTypes.CLASS_DEF, TokenTypes.INTERFACE_DEF, TokenTypes.ENUM_DEF,
                  TokenTypes.ANNOTATION_DEF, TokenTypes.SLIST, TokenTypes.METHOD_DEF,
                  TokenTypes.CTOR_DEF, TokenTypes.LITERAL_CATCH, TokenTypes.LITERAL_FOR,
                  TokenTypes.RECORD_DEF, TokenTypes.COMPACT_CTOR_DEF,
                  TokenTypes.COMPACT_COMPILATION_UNIT ->
                 frames.put(ast, frameStack.poll());
 
             case TokenTypes.LITERAL_NEW -> {
                 final DetailAST lastChild = ast.getLastChild();
                 if (lastChild != null && lastChild.getType() == TokenTypes.OBJBLOCK) {
                     frameStack.remove();
                 }
             }
 
             case TokenTypes.LITERAL_TRY -> {
                 if (ast.getFirstChild().getType() == TokenTypes.RESOURCE_SPECIFICATION) {
                     frames.put(ast, frameStack.poll());
                 }
             }
 
             default -> {
                 // do nothing
             }
         }
     }
 
     /**
      * Returns the class frame where violation is found (where the field is used without 'this')
      * or null otherwise.
      *
      * @param ast IDENT ast to check.
      * @return the class frame where violation is found or null otherwise.
      */
     @Nullable
     private AbstractFrame getClassFrameWhereViolationIsFound(DetailAST ast) {
         AbstractFrame frameWhereViolationIsFound = null;
         final AbstractFrame variableDeclarationFrame = findFrame(ast, false);
         final FrameType variableDeclarationFrameType = variableDeclarationFrame.getType();
 
         if (variableDeclarationFrameType == FrameType.CLASS_FRAME
                 && isViolationNoOverlapping(ast)) {
             frameWhereViolationIsFound = variableDeclarationFrame;
         }
         else if (variableDeclarationFrameType == FrameType.METHOD_FRAME) {
             frameWhereViolationIsFound = getFrameForMethod(ast, variableDeclarationFrame);
         }
         else if (variableDeclarationFrameType == FrameType.CTOR_FRAME
                && isOverlappingByArgument(ast)
                && !isUserDefinedArrangementOfThis(variableDeclarationFrame, ast)) {
             frameWhereViolationIsFound = findFrame(ast, true);
         }
         else if (variableDeclarationFrameType == FrameType.BLOCK_FRAME
                 && isViolationForBlockFrame(ast, variableDeclarationFrame)) {
             frameWhereViolationIsFound = findFrame(ast, true);
         }
         return frameWhereViolationIsFound;
     }
 
     /**
      * Checks if a violation occurred for a CLASS_FRAME when not overlapping.
      *
      * @param ast IDENT ast to check.
      * @return true if a violation occurred.
      */
     private boolean isViolationNoOverlapping(DetailAST ast) {
         final DetailAST prevSibling = ast.getPreviousSibling();
         final int parentType = ast.getParent().getType();
         return !validateOnlyOverlapping
                 && (prevSibling == null
                     || parentType != TokenTypes.DOT && parentType != TokenTypes.METHOD_REF)
                 && canBeReferencedFromStaticContext(ast);
     }
 
     /**
      * Checks if a violation occurred for a BLOCK_FRAME.
      *
      * @param ast IDENT ast to check.
      * @param variableDeclarationFrame the frame where the variable is declared.
      * @return true if a violation occurred.
      */
     private boolean isViolationForBlockFrame(DetailAST ast,
                                              AbstractFrame variableDeclarationFrame) {
         return isOverlappingByLocalVariable(ast)
                 && canAssignValueToClassField(ast)
                 && !isUserDefinedArrangementOfThis(variableDeclarationFrame, ast)
                 && !isReturnedVariable(variableDeclarationFrame, ast)
                 && canBeReferencedFromStaticContext(ast);
     }
 
     /**
      * Returns the class frame where violation is found (where the field is used without 'this')
      * or null otherwise.
      *
      * @param ast IDENT ast to check.
      * @param variableDeclarationFrame the frame where the variable is declared.
      * @return the class frame where violation is found or null otherwise.
      */
     private AbstractFrame getFrameForMethod(DetailAST ast,
                                             AbstractFrame variableDeclarationFrame) {
         AbstractFrame frameWhereViolationIsFound = null;
         if (isOverlappingByArgument(ast)) {
             if (isViolationForMethodOverlapping(ast, variableDeclarationFrame)) {
                 frameWhereViolationIsFound = findFrame(ast, true);
             }
         }
         else if (isViolationForMethodNoOverlapping(ast, variableDeclarationFrame)) {
             frameWhereViolationIsFound = findFrame(ast, true);
         }
         return frameWhereViolationIsFound;
     }
 
     /**
      * Checks if a violation occurred for a METHOD_FRAME when overlapping.
      *
      * @param ast IDENT ast to check.
      * @param variableDeclarationFrame the frame where the variable is declared.
      * @return true if a violation occurred.
      */
     private boolean isViolationForMethodOverlapping(DetailAST ast,
                                                      AbstractFrame variableDeclarationFrame) {
         return !isUserDefinedArrangementOfThis(variableDeclarationFrame, ast)
                 && !isReturnedVariable(variableDeclarationFrame, ast)
                 && canBeReferencedFromStaticContext(ast)
                 && canAssignValueToClassField(ast);
     }
 
     /**
      * Checks if a violation occurred for a METHOD_FRAME when not overlapping.
      *
      * @param ast IDENT ast to check.
      * @param variableDeclarationFrame the frame where the variable is declared.
      * @return true if a violation occurred.
      */
     private boolean isViolationForMethodNoOverlapping(DetailAST ast,
                                                        AbstractFrame variableDeclarationFrame) {
         final DetailAST prevSibling = ast.getPreviousSibling();
         return !validateOnlyOverlapping
                 && prevSibling == null
                 && ASSIGN_TOKENS.get(ast.getParent().getType())
                 && !isUserDefinedArrangementOfThis(variableDeclarationFrame, ast)
                 && canBeReferencedFromStaticContext(ast)
                 && canAssignValueToClassField(ast);
     }
 
     /**
      * Checks whether user arranges 'this' for variable in method, constructor, or block on his own.
      *
      * @param currentFrame current frame.
      * @param ident ident token.
      * @return true if user arranges 'this' for variable in method, constructor,
      *         or block on his own.
      */
     private static boolean isUserDefinedArrangementOfThis(AbstractFrame currentFrame,
                                                           DetailAST ident) {
         final DetailAST blockFrameNameIdent = currentFrame.getFrameNameIdent();
         final DetailAST definitionToken = blockFrameNameIdent.getParent();
         final DetailAST blockStartToken = definitionToken.findFirstToken(TokenTypes.SLIST);
         final DetailAST blockEndToken = getBlockEndToken(blockFrameNameIdent, blockStartToken);
 
         boolean userDefinedArrangementOfThis = false;
 
         final Set<DetailAST> variableUsagesInsideBlock =
             getAllTokensWhichAreEqualToCurrent(definitionToken, ident,
                 blockEndToken.getLineNo());
 
         for (DetailAST variableUsage : variableUsagesInsideBlock) {
             final DetailAST prevSibling = variableUsage.getPreviousSibling();
             if (prevSibling != null
                     && prevSibling.getType() == TokenTypes.LITERAL_THIS) {
                 userDefinedArrangementOfThis = true;
                 break;
             }
         }
         return userDefinedArrangementOfThis;
     }
 
     /**
      * Returns the token which ends the code block.
      *
      * @param blockNameIdent block name identifier.
      * @param blockStartToken token which starts the block.
      * @return the token which ends the code block.
      */
     private static DetailAST getBlockEndToken(DetailAST blockNameIdent, DetailAST blockStartToken) {
         DetailAST blockEndToken = null;
         final DetailAST blockNameIdentParent = blockNameIdent.getParent();
         if (blockNameIdentParent.getType() == TokenTypes.CASE_GROUP) {
             blockEndToken = blockNameIdentParent.getNextSibling();
         }
         else {
             final Set<DetailAST> rcurlyTokens = getAllTokensOfType(blockNameIdent,
                     TokenTypes.RCURLY);
             for (DetailAST currentRcurly : rcurlyTokens) {
                 final DetailAST parent = currentRcurly.getParent();
                 if (TokenUtil.areOnSameLine(blockStartToken, parent)) {
                     blockEndToken = currentRcurly;
                 }
             }
         }
         return blockEndToken;
     }
 
     /**
      * Checks whether the current variable is returned from the method.
      *
      * @param currentFrame current frame.
      * @param ident variable ident token.
      * @return true if the current variable is returned from the method.
      */
     private static boolean isReturnedVariable(AbstractFrame currentFrame, DetailAST ident) {
         final DetailAST blockFrameNameIdent = currentFrame.getFrameNameIdent();
         final DetailAST definitionToken = blockFrameNameIdent.getParent();
         final DetailAST blockStartToken = definitionToken.findFirstToken(TokenTypes.SLIST);
         final DetailAST blockEndToken = getBlockEndToken(blockFrameNameIdent, blockStartToken);
 
         final Set<DetailAST> returnsInsideBlock = getAllTokensOfType(definitionToken,
             TokenTypes.LITERAL_RETURN, blockEndToken.getLineNo());
 
         return returnsInsideBlock.stream()
             .anyMatch(returnToken -> isAstInside(returnToken, ident));
     }
 
     /**
      * Checks if the given {@code ast} is equal to the {@code tree} or a child of it.
      *
      * @param tree The tree to search.
      * @param ast The AST to look for.
      * @return {@code true} if the {@code ast} was found.
      */
     private static boolean isAstInside(DetailAST tree, DetailAST ast) {
         boolean result = false;
 
         if (isAstSimilar(tree, ast)) {
             result = true;
         }
         else {
             for (DetailAST child = tree.getFirstChild(); child != null
                     && !result; child = child.getNextSibling()) {
                 result = isAstInside(child, ast);
             }
         }
 
         return result;
     }
 
     /**
      * Checks whether a field can be referenced from a static context.
      *
      * @param ident ident token.
      * @return true if field can be referenced from a static context.
      */
     private static boolean canBeReferencedFromStaticContext(DetailAST ident) {
         boolean staticContext = false;
 
         final DetailAST codeBlockDefinition = getCodeBlockDefinitionToken(ident);
         if (codeBlockDefinition != null) {
             final DetailAST modifiers = codeBlockDefinition.getFirstChild();
             staticContext = codeBlockDefinition.getType() == TokenTypes.STATIC_INIT
                 || modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) != null;
         }
         return !staticContext;
     }
 
     /**
      * Returns code block definition token for current identifier.
      *
      * @param ident ident token.
      * @return code block definition token for current identifier or null if code block
      *         definition was not found.
      */
     private static DetailAST getCodeBlockDefinitionToken(DetailAST ident) {
         DetailAST parent = ident;
         while (parent != null
                && parent.getType() != TokenTypes.METHOD_DEF
                && parent.getType() != TokenTypes.STATIC_INIT) {
             parent = parent.getParent();
         }
         return parent;
     }
 
     /**
      * Checks whether a value can be assigned to a field.
      * A value can be assigned to a final field only in constructor block. If there is a method
      * block, value assignment can be performed only to non final field.
      *
      * @param ast an identifier token.
      * @return true if a value can be assigned to a field.
      */
     private boolean canAssignValueToClassField(DetailAST ast) {
         AbstractFrame fieldUsageFrame = findFrame(ast, false);
         while (fieldUsageFrame.getType() == FrameType.BLOCK_FRAME) {
             fieldUsageFrame = fieldUsageFrame.getParent();
         }
         final boolean fieldUsageInConstructor =
             fieldUsageFrame.getType() == FrameType.CTOR_FRAME;
 
         final AbstractFrame declarationFrame = findFrame(ast, true);
         final boolean finalField = ((ClassFrame) declarationFrame).hasFinalField(ast);
 
         return fieldUsageInConstructor || !finalField;
     }
 
     /**
      * Checks whether an overlapping by method or constructor argument takes place.
      *
      * @param ast an identifier.
      * @return true if an overlapping by method or constructor argument takes place.
      */
     private boolean isOverlappingByArgument(DetailAST ast) {
         boolean overlapping = false;
         final DetailAST parent = ast.getParent();
         final DetailAST sibling = ast.getNextSibling();
         if (sibling != null && ASSIGN_TOKENS.get(parent.getType())) {
             if (COMPOUND_ASSIGN_TOKENS.get(parent.getType())) {
                 overlapping = true;
             }
             else {
                 final ClassFrame classFrame = (ClassFrame) findFrame(ast, true);
                 final Set<DetailAST> exprIdents = getAllTokensOfType(sibling, TokenTypes.IDENT);
                 overlapping = classFrame.containsFieldOrVariableDef(exprIdents, ast);
             }
         }
         return overlapping;
     }
 
     /**
      * Checks whether an overlapping by local variable takes place.
      *
      * @param ast an identifier.
      * @return true if an overlapping by local variable takes place.
      */
     private boolean isOverlappingByLocalVariable(DetailAST ast) {
         boolean overlapping = false;
         final DetailAST parent = ast.getParent();
         if (ASSIGN_TOKENS.get(parent.getType())) {
             final ClassFrame classFrame = (ClassFrame) findFrame(ast, true);
             final Set<DetailAST> exprIdents =
                 getAllTokensOfType(ast.getNextSibling(), TokenTypes.IDENT);
             overlapping = classFrame.containsFieldOrVariableDef(exprIdents, ast);
         }
         return overlapping;
     }
 
     /**
      * Collects all tokens of specific type starting with the current ast node.
      *
      * @param ast ast node.
      * @param tokenType token type.
      * @return a set of all tokens of specific type starting with the current ast node.
      */
     private static Set<DetailAST> getAllTokensOfType(DetailAST ast, int tokenType) {
         DetailAST vertex = ast;
         final Set<DetailAST> result = new HashSet<>();
         final Deque<DetailAST> stack = new ArrayDeque<>();
         while (vertex != null || !stack.isEmpty()) {
             if (!stack.isEmpty()) {
                 vertex = stack.pop();
             }
             while (vertex != null) {
                 if (vertex.getType() == tokenType) {
                     result.add(vertex);
                 }
                 if (vertex.getNextSibling() != null) {
                     stack.push(vertex.getNextSibling());
                 }
                 vertex = vertex.getFirstChild();
             }
         }
         return result;
     }
 
     /**
      * Collects all tokens of specific type starting with the current ast node and which line
      * number is lower or equal to the end line number.
      *
      * @param ast ast node.
      * @param tokenType token type.
      * @param endLineNumber end line number.
      * @return a set of all tokens of specific type starting with the current ast node and which
      *         line number is lower or equal to the end line number.
      */
     private static Set<DetailAST> getAllTokensOfType(DetailAST ast, int tokenType,
                                                      int endLineNumber) {
         DetailAST vertex = ast;
         final Set<DetailAST> result = new HashSet<>();
         final Deque<DetailAST> stack = new ArrayDeque<>();
         while (vertex != null || !stack.isEmpty()) {
             if (!stack.isEmpty()) {
                 vertex = stack.pop();
             }
             while (vertex != null) {
                 if (tokenType == vertex.getType()
                     && vertex.getLineNo() <= endLineNumber) {
                     result.add(vertex);
                 }
                 if (vertex.getNextSibling() != null) {
                     stack.push(vertex.getNextSibling());
                 }
                 vertex = vertex.getFirstChild();
             }
         }
         return result;
     }
 
     /**
      * Collects all tokens which are equal to current token starting with the current ast node and
      * which line number is lower or equal to the end line number.
      *
      * @param ast ast node.
      * @param token token.
      * @param endLineNumber end line number.
      * @return a set of tokens which are equal to current token starting with the current ast node
      *         and which line number is lower or equal to the end line number.
      */
     private static Set<DetailAST> getAllTokensWhichAreEqualToCurrent(DetailAST ast, DetailAST token,
                                                                      int endLineNumber) {
         DetailAST vertex = ast;
         final Set<DetailAST> result = new HashSet<>();
         final Deque<DetailAST> stack = new ArrayDeque<>();
         while (vertex != null || !stack.isEmpty()) {
             if (!stack.isEmpty()) {
                 vertex = stack.pop();
             }
             while (vertex != null) {
                 if (isAstSimilar(token, vertex)
                         && vertex.getLineNo() <= endLineNumber) {
                     result.add(vertex);
                 }
                 if (vertex.getNextSibling() != null) {
                     stack.push(vertex.getNextSibling());
                 }
                 vertex = vertex.getFirstChild();
             }
         }
         return result;
     }
 
     /**
      * Returns the frame where the method is declared, if the given method is used without
      * 'this' and null otherwise.
      *
      * @param ast the IDENT ast of the name to check.
      * @return the frame where the method is declared, if the given method is used without
      *         'this' and null otherwise.
      */
     private AbstractFrame getMethodWithoutThis(DetailAST ast) {
         AbstractFrame result = null;
         if (!validateOnlyOverlapping) {
             final AbstractFrame frame = findFrame(ast, true);
             if (frame != null
                     && ((ClassFrame) frame).hasInstanceMethod(ast)
                     && !((ClassFrame) frame).hasStaticMethod(ast)) {
                 result = frame;
             }
         }
         return result;
     }
 
     /**
      * Find the class frame containing declaration.
      *
      * @param name IDENT ast of the declaration to find.
      * @param lookForMethod whether we are looking for a method name.
      * @return AbstractFrame containing declaration or null.
      */
     private AbstractFrame findClassFrame(DetailAST name, boolean lookForMethod) {
         AbstractFrame frame = current.peek();
 
         while (true) {
             frame = findFrame(frame, name, lookForMethod);
 
             if (frame == null || frame instanceof ClassFrame) {
                 break;
             }
 
             frame = frame.getParent();
         }
 
         return frame;
     }
 
     /**
      * Find frame containing declaration.
      *
      * @param name IDENT ast of the declaration to find.
      * @param lookForMethod whether we are looking for a method name.
      * @return AbstractFrame containing declaration or null.
      */
     private AbstractFrame findFrame(DetailAST name, boolean lookForMethod) {
         return findFrame(current.peek(), name, lookForMethod);
     }
 
     /**
      * Find frame containing declaration.
      *
      * @param frame The parent frame to searching in.
      * @param name IDENT ast of the declaration to find.
      * @param lookForMethod whether we are looking for a method name.
      * @return AbstractFrame containing declaration or null.
      */
     private static AbstractFrame findFrame(AbstractFrame frame, DetailAST name,
             boolean lookForMethod) {
         return frame.getIfContains(name, lookForMethod);
     }
 
     /**
      * Gets the name of the nearest parent ClassFrame.
      *
      * @return the name of the nearest parent ClassFrame.
      */
     private String getNearestClassFrameName() {
         AbstractFrame frame = current.peek();
         while (frame.getType() != FrameType.CLASS_FRAME) {
             frame = frame.getParent();
         }
         return frame.getFrameName();
     }
 
     /**
      * Checks if the token is a Lambda parameter.
      *
      * @param ast the {@code DetailAST} value of the token to be checked
      * @return true if the token is a Lambda parameter
      */
     private static boolean isLambdaParameter(DetailAST ast) {
         boolean result = false;
         for (DetailAST parent = ast; parent != null; parent = parent.getParent()) {
             if (parent.getType() == TokenTypes.LAMBDA) {
                 result = !isInsideTypeDefInsideLambda(ast)
                         && isMatchingLambdaParam(ast, parent);
                 break;
             }
         }
         return result;
     }
 
     /**
      * Checks whether the given AST matches a parameter of the specified lambda.
      *
      * @param ast the AST node to check.
      * @param lambda the lambda expression AST node.
      * @return true if the AST matches a lambda parameter.
      */
     private static boolean isMatchingLambdaParam(DetailAST ast, DetailAST lambda) {
         final boolean isMatchingParam;
         if (ast.getType() == TokenTypes.PARAMETER_DEF) {
             isMatchingParam = true;
         }
         else {
             final DetailAST lambdaParameters = lambda.findFirstToken(TokenTypes.PARAMETERS);
             if (lambdaParameters == null) {
                 isMatchingParam = lambda.getFirstChild().getText().equals(ast.getText());
             }
             else {
                 isMatchingParam = TokenUtil.findFirstTokenByPredicate(lambdaParameters,
                     paramDef -> {
                         final DetailAST param = paramDef.findFirstToken(TokenTypes.IDENT);
                         return param != null && param.getText().equals(ast.getText());
                     }).isPresent();
             }
         }
         return isMatchingParam;
     }
 
     /**
      * Checks if the given AST is inside a type declaration (class, interface, enum,
      * record, or anonymous class) that is nested within the enclosing lambda.
      *
      * @param ast the AST node to check.
      * @return true if there is a type declaration boundary between {@code ast} and the lambda.
      */
     private static boolean isInsideTypeDefInsideLambda(DetailAST ast) {
         boolean isInside = false;
         for (DetailAST parent = ast; parent.getType() != TokenTypes.LAMBDA;
                 parent = parent.getParent()) {
             if (parent.getType() == TokenTypes.OBJBLOCK) {
                 isInside = true;
                 break;
             }
         }
         return isInside;
     }
 
     /**
      * Checks if 2 AST are similar by their type and text.
      *
      * @param left The first AST to check.
      * @param right The second AST to check.
      * @return {@code true} if they are similar.
      */
     private static boolean isAstSimilar(DetailAST left, DetailAST right) {
         return left.getType() == right.getType() && left.getText().equals(right.getText());
     }
 
     /** An AbstractFrame type. */
     private enum FrameType {
 
         /** Class frame type. */
         CLASS_FRAME,
         /** Constructor frame type. */
         CTOR_FRAME,
         /** Method frame type. */
         METHOD_FRAME,
         /** Block frame type. */
         BLOCK_FRAME,
         /** Catch frame type. */
         CATCH_FRAME,
         /** For frame type. */
         FOR_FRAME,
         /** Try with resources frame type. */
         TRY_WITH_RESOURCES_FRAME
 
     }
 
     /**
      * A declaration frame.
      */
     private abstract static class AbstractFrame {
 
         /** Set of name of variables declared in this frame. */
         private final Set<DetailAST> varIdents;
 
         /** Parent frame. */
         private final AbstractFrame parent;
 
         /** Name identifier token. */
         private final DetailAST frameNameIdent;
 
         /**
          * Constructor -- invocable only via super() from subclasses.
          *
          * @param parent parent frame.
          * @param ident frame name ident.
          */
         /* package */ AbstractFrame(AbstractFrame parent, DetailAST ident) {
             this.parent = parent;
             frameNameIdent = ident;
             varIdents = new HashSet<>();
         }
 
         /**
          * Get the type of the frame.
          *
          * @return a FrameType.
          */
         /* package */ abstract FrameType getType();
 
         /**
          * Add a name to the frame.
          *
          * @param identToAdd the name we're adding.
          */
         private void addIdent(DetailAST identToAdd) {
             varIdents.add(identToAdd);
         }
 
         /**
          * Returns the parent frame.
          *
          * @return the parent frame
          */
         /* package */ AbstractFrame getParent() {
             return parent;
         }
 
         /**
          * Returns the name identifier text.
          *
          * @return the name identifier text
          */
         /* package */ String getFrameName() {
             return frameNameIdent.getText();
         }
 
         /**
          * Returns the name identifier token.
          *
          * @return the name identifier token
          */
         /* package */ DetailAST getFrameNameIdent() {
             return frameNameIdent;
         }
 
         /**
          * Check whether the frame contains a field or a variable with the given name.
          *
          * @param identToFind the IDENT ast of the name we're looking for.
          * @return whether it was found.
          */
         /* package */ boolean containsFieldOrVariable(DetailAST identToFind) {
             return containsFieldOrVariableDef(varIdents, identToFind);
         }
 
         /**
          * Check whether the frame contains a given name.
          *
          * @param identToFind IDENT ast of the name we're looking for.
          * @param lookForMethod whether we are looking for a method name.
          * @return whether it was found.
          */
         /* package */ AbstractFrame getIfContains(DetailAST identToFind, boolean lookForMethod) {
             final AbstractFrame frame;
 
             if (!lookForMethod
                 && containsFieldOrVariable(identToFind)) {
                 frame = this;
             }
             else {
                 frame = parent.getIfContains(identToFind, lookForMethod);
             }
             return frame;
         }
 
         /**
          * Whether the set contains a declaration with the text of the specified
          * IDENT ast and it is declared in a proper position.
          *
          * @param set the set of declarations.
          * @param ident the specified IDENT ast.
          * @return true if the set contains a declaration with the text of the specified
          *         IDENT ast and it is declared in a proper position.
          */
         /* package */ boolean containsFieldOrVariableDef(Set<DetailAST> set, DetailAST ident) {
             boolean result = false;
             for (DetailAST ast: set) {
                 if (isProperDefinition(ident, ast)) {
                     result = true;
                     break;
                 }
             }
             return result;
         }
 
         /**
          * Whether the definition is correspondent to the IDENT.
          *
          * @param ident the IDENT ast to check.
          * @param ast the IDENT ast of the definition to check.
          * @return true if ast is correspondent to ident.
          */
         /* package */ boolean isProperDefinition(DetailAST ident, DetailAST ast) {
             final String identToFind = ident.getText();
             return identToFind.equals(ast.getText())
                 && CheckUtil.isBeforeInSource(ast, ident);
         }
     }
 
     /**
      * A frame initiated at method definition; holds a method definition token.
      */
     private static class MethodFrame extends AbstractFrame {
 
         /**
          * Creates method frame.
          *
          * @param parent parent frame.
          * @param ident method name identifier token.
          */
         /* package */ MethodFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
         }
 
         @Override
         protected FrameType getType() {
             return FrameType.METHOD_FRAME;
         }
 
     }
 
     /**
      * A frame initiated at constructor definition.
      */
     private static class ConstructorFrame extends AbstractFrame {
 
         /**
          * Creates a constructor frame.
          *
          * @param parent parent frame.
          * @param ident frame name ident.
          */
         /* package */ ConstructorFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
         }
 
         @Override
         protected FrameType getType() {
             return FrameType.CTOR_FRAME;
         }
 
     }
 
     /**
      * A frame initiated at class, enum or interface definition; holds instance variable names.
      */
     private static class ClassFrame extends AbstractFrame {
 
         /** Set of idents of instance members declared in this frame. */
         private final Set<DetailAST> instanceMembers;
         /** Set of idents of instance methods declared in this frame. */
         private final Set<DetailAST> instanceMethods;
         /** Set of idents of variables declared in this frame. */
         private final Set<DetailAST> staticMembers;
         /** Set of idents of static methods declared in this frame. */
         private final Set<DetailAST> staticMethods;
 
         /**
          * Creates new instance of ClassFrame.
          *
          * @param parent parent frame.
          * @param ident frame name ident.
          */
         private ClassFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
             instanceMembers = new HashSet<>();
             instanceMethods = new HashSet<>();
             staticMembers = new HashSet<>();
             staticMethods = new HashSet<>();
         }
 
         @Override
         protected FrameType getType() {
             return FrameType.CLASS_FRAME;
         }
 
         /**
          * Adds static member's ident.
          *
          * @param ident an ident of static member of the class.
          */
         /* package */ void addStaticMember(final DetailAST ident) {
             staticMembers.add(ident);
         }
 
         /**
          * Adds static method's name.
          *
          * @param ident an ident of static method of the class.
          */
         /* package */ void addStaticMethod(final DetailAST ident) {
             staticMethods.add(ident);
         }
 
         /**
          * Adds instance member's ident.
          *
          * @param ident an ident of instance member of the class.
          */
         /* package */ void addInstanceMember(final DetailAST ident) {
             instanceMembers.add(ident);
         }
 
         /**
          * Adds instance method's name.
          *
          * @param ident an ident of instance method of the class.
          */
         /* package */ void addInstanceMethod(final DetailAST ident) {
             instanceMethods.add(ident);
         }
 
         /**
          * Checks if a given name is a known instance member of the class.
          *
          * @param ident the IDENT ast of the name to check.
          * @return true is the given name is a name of a known
          *         instance member of the class.
          */
         /* package */ boolean hasInstanceMember(final DetailAST ident) {
             return containsFieldOrVariableDef(instanceMembers, ident);
         }
 
         /**
          * Checks if a given name is a known instance method of the class.
          *
          * @param ident the IDENT ast of the method call to check.
          * @return true if the given ast is correspondent to a known
          *         instance method of the class.
          */
         /* package */ boolean hasInstanceMethod(final DetailAST ident) {
             return containsMethodDef(instanceMethods, ident);
         }
 
         /**
          * Checks if a given name is a known static method of the class.
          *
          * @param ident the IDENT ast of the method call to check.
          * @return true is the given ast is correspondent to a known
          *         instance method of the class.
          */
         /* package */ boolean hasStaticMethod(final DetailAST ident) {
             return containsMethodDef(staticMethods, ident);
         }
 
         /**
          * Checks whether given instance member has final modifier.
          *
          * @param instanceMember an instance member of a class.
          * @return true if given instance member has final modifier.
          */
         /* package */ boolean hasFinalField(final DetailAST instanceMember) {
             boolean result = false;
             for (DetailAST member : instanceMembers) {
                 final DetailAST parent = member.getParent();
                 if (parent.getType() == TokenTypes.RECORD_COMPONENT_DEF) {
                     result = true;
                 }
                 else {
                     final DetailAST mods = parent.findFirstToken(TokenTypes.MODIFIERS);
                     final boolean finalMod = mods.findFirstToken(TokenTypes.FINAL) != null;
                     if (finalMod && isAstSimilar(member, instanceMember)) {
                         result = true;
                     }
                 }
             }
             return result;
         }
 
         @Override
         protected boolean containsFieldOrVariable(DetailAST identToFind) {
             return containsFieldOrVariableDef(instanceMembers, identToFind)
                     || containsFieldOrVariableDef(staticMembers, identToFind);
         }
 
         @Override
         protected boolean isProperDefinition(DetailAST ident, DetailAST ast) {
             final String identToFind = ident.getText();
             return identToFind.equals(ast.getText());
         }
 
         @Override
         protected AbstractFrame getIfContains(DetailAST identToFind, boolean lookForMethod) {
             AbstractFrame frame = null;
 
             if (containsMethod(identToFind)
                 || containsFieldOrVariable(identToFind)) {
                 frame = this;
             }
             else if (getParent() != null) {
                 frame = getParent().getIfContains(identToFind, lookForMethod);
             }
             return frame;
         }
 
         /**
          * Check whether the frame contains a given method.
          *
          * @param methodToFind the AST of the method to find.
          * @return true, if a method with the same name and number of parameters is found.
          */
         private boolean containsMethod(DetailAST methodToFind) {
             return containsMethodDef(instanceMethods, methodToFind)
                 || containsMethodDef(staticMethods, methodToFind);
         }
 
         /**
          * Whether the set contains a method definition with the
          *     same name and number of parameters.
          *
          * @param set the set of definitions.
          * @param ident the specified method call IDENT ast.
          * @return true if the set contains a definition with the
          *     same name and number of parameters.
          */
         private static boolean containsMethodDef(Set<DetailAST> set, DetailAST ident) {
             boolean result = false;
             for (DetailAST ast: set) {
                 if (isSimilarSignature(ident, ast)) {
                     result = true;
                     break;
                 }
             }
             return result;
         }
 
         /**
          * Whether the method definition has the same name and number of parameters.
          *
          * @param ident the specified method call IDENT ast.
          * @param ast the ast of a method definition to compare with.
          * @return true if a method definition has the same name and number of parameters
          *     as the method call.
          */
         private static boolean isSimilarSignature(DetailAST ident, DetailAST ast) {
             boolean result = false;
             final DetailAST elistToken = ident.getParent().findFirstToken(TokenTypes.ELIST);
             if (elistToken != null && ident.getText().equals(ast.getText())) {
                 final int paramsNumber =
                     ast.getParent().findFirstToken(TokenTypes.PARAMETERS).getChildCount();
                 final int argsNumber = elistToken.getChildCount();
                 result = paramsNumber == argsNumber;
             }
             return result;
         }
 
     }
 
     /**
      * An anonymous class frame; holds instance variable names.
      */
     private static class AnonymousClassFrame extends ClassFrame {
 
         /** The name of the frame. */
         private final String frameName;
 
         /**
          * Creates anonymous class frame.
          *
          * @param parent parent frame.
          * @param frameName name of the frame.
          */
         /* package */ AnonymousClassFrame(AbstractFrame parent, String frameName) {
             super(parent, null);
             this.frameName = frameName;
         }
 
         @Override
         protected String getFrameName() {
             return frameName;
         }
 
     }
 
     /**
      * A frame for the implicit class of a compact source file (JEP 512).
      * The class is unnamed in source code, so a reference to one of its members
      * from a nested class cannot be qualified with {@code <ClassName>.this} and is
      * not flagged, the same way references to anonymous class members are skipped.
      */
     private static class CompactCompilationUnitFrame extends ClassFrame {
 
         /**
          * Creates compact compilation unit frame.
          *
          * @param parent parent frame.
          * @param ident frame name ident.
          */
         /* package */ CompactCompilationUnitFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
         }
 
     }
 
     /**
      * A frame initiated on entering a statement list; holds local variable names.
      */
     private static class BlockFrame extends AbstractFrame {
 
         /**
          * Creates block frame.
          *
          * @param parent parent frame.
          * @param ident ident frame name ident.
          */
         /* package */ BlockFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
         }
 
         @Override
         protected FrameType getType() {
             return FrameType.BLOCK_FRAME;
         }
 
     }
 
     /**
      * A frame initiated on entering a catch block; holds local catch variable names.
      */
     private static class CatchFrame extends AbstractFrame {
 
         /**
          * Creates catch frame.
          *
          * @param parent parent frame.
          * @param ident ident frame name ident.
          */
         /* package */ CatchFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
         }
 
         @Override
         public FrameType getType() {
             return FrameType.CATCH_FRAME;
         }
 
         @Override
         protected AbstractFrame getIfContains(DetailAST identToFind, boolean lookForMethod) {
             final AbstractFrame frame;
 
             if (!lookForMethod
                     && containsFieldOrVariable(identToFind)) {
                 frame = this;
             }
             else if (getParent().getType() == FrameType.TRY_WITH_RESOURCES_FRAME) {
                 // Skip try-with-resources frame because resources cannot be accessed from catch
                 frame = getParent().getParent().getIfContains(identToFind, lookForMethod);
             }
             else {
                 frame = getParent().getIfContains(identToFind, lookForMethod);
             }
             return frame;
         }
 
     }
 
     /**
      * A frame initiated on entering a for block; holds local for variable names.
      */
     private static class ForFrame extends AbstractFrame {
 
         /**
          * Creates for frame.
          *
          * @param parent parent frame.
          * @param ident ident frame name ident.
          */
         /* package */ ForFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
         }
 
         @Override
         public FrameType getType() {
             return FrameType.FOR_FRAME;
         }
 
     }
 
     /**
      * A frame initiated on entering a try-with-resources construct;
      * holds local resources for the try block.
      */
     private static class TryWithResourcesFrame extends AbstractFrame {
 
         /**
          * Creates try-with-resources frame.
          *
          * @param parent parent frame.
          * @param ident ident frame name ident.
          */
         /* package */ TryWithResourcesFrame(AbstractFrame parent, DetailAST ident) {
             super(parent, ident);
         }
 
         @Override
         public FrameType getType() {
             return FrameType.TRY_WITH_RESOURCES_FRAME;
         }
 
     }
 
 }