gt:                 env.messages.error(HTML, tree, "dc.tag.not.allowed", treeName);
context: /*
   * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code 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 General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package com.sun.tools.doclint;
  
  import java.io.IOException;
  import java.io.StringWriter;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.util.Deque;
  import java.util.EnumSet;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import javax.lang.model.element.Element;
  import javax.lang.model.element.ElementKind;
  import javax.lang.model.element.ExecutableElement;
  import javax.lang.model.element.Name;
  import javax.lang.model.element.VariableElement;
  import javax.lang.model.type.TypeKind;
  import javax.lang.model.type.TypeMirror;
  import javax.tools.Diagnostic.Kind;
  import javax.tools.JavaFileObject;
  
  import com.sun.source.doctree.AttributeTree;
  import com.sun.source.doctree.AuthorTree;
  import com.sun.source.doctree.DocCommentTree;
  import com.sun.source.doctree.DocRootTree;
  import com.sun.source.doctree.DocTree;
  import com.sun.source.doctree.EndElementTree;
  import com.sun.source.doctree.EntityTree;
  import com.sun.source.doctree.ErroneousTree;
  import com.sun.source.doctree.IdentifierTree;
  import com.sun.source.doctree.InheritDocTree;
  import com.sun.source.doctree.LinkTree;
  import com.sun.source.doctree.LiteralTree;
  import com.sun.source.doctree.ParamTree;
  import com.sun.source.doctree.ReferenceTree;
  import com.sun.source.doctree.ReturnTree;
  import com.sun.source.doctree.SerialDataTree;
  import com.sun.source.doctree.SerialFieldTree;
  import com.sun.source.doctree.SinceTree;
  import com.sun.source.doctree.StartElementTree;
  import com.sun.source.doctree.TextTree;
  import com.sun.source.doctree.ThrowsTree;
  import com.sun.source.doctree.UnknownBlockTagTree;
  import com.sun.source.doctree.UnknownInlineTagTree;
  import com.sun.source.doctree.ValueTree;
  import com.sun.source.doctree.VersionTree;
  import com.sun.source.util.DocTreePath;
  import com.sun.source.util.DocTreePathScanner;
  import com.sun.source.util.TreePath;
  import com.sun.tools.doclint.HtmlTag.AttrKind;
  import com.sun.tools.javac.tree.DocPretty;
  import com.sun.tools.javac.util.StringUtils;
  import static com.sun.tools.doclint.Messages.Group.*;
  
  
  /**
   * Validate a doc comment.
   *
   * <p><b>This is NOT part of any supported API.
   * If you write code that depends on this, you do so at your own
   * risk.  This code and its internal interfaces are subject to change
   * or deletion without notice.</b></p>
   */
  public class Checker extends DocTreePathScanner<Void, Void> {
      final Env env;
  
      Set<Element> foundParams = new HashSet<>();
      Set<TypeMirror> foundThrows = new HashSet<>();
      Map<Element, Set<String>> foundAnchors = new HashMap<>();
      boolean foundInheritDoc = false;
      boolean foundReturn = false;
  
      public enum Flag {
          TABLE_HAS_CAPTION,
          HAS_ELEMENT,
          HAS_INLINE_TAG,
          HAS_TEXT,
          REPORTED_BAD_INLINE
      }
  
      static class TagStackItem {
          final DocTree tree; // typically, but not always, StartElementTree
          final HtmlTag tag;
          final Set<HtmlTag.Attr> attrs;
          final Set<Flag> flags;
          TagStackItem(DocTree tree, HtmlTag tag) {
              this.tree = tree;
              this.tag = tag;
              attrs = EnumSet.noneOf(HtmlTag.Attr.class);
              flags = EnumSet.noneOf(Flag.class);
          }
          @Override
          public String toString() {
              return String.valueOf(tag);
          }
      }
  
      private Deque<TagStackItem> tagStack; // TODO: maybe want to record starting tree as well
      private HtmlTag currHeaderTag;
  
      private final int implicitHeaderLevel;
  
      // <editor-fold defaultstate="collapsed" desc="Top level">
  
      Checker(Env env) {
          env.getClass();
          this.env = env;
          tagStack = new LinkedList<>();
          implicitHeaderLevel = env.implicitHeaderLevel;
      }
  
      public Void scan(DocCommentTree tree, TreePath p) {
          env.setCurrent(p, tree);
  
          boolean isOverridingMethod = !env.currOverriddenMethods.isEmpty();
  
          if (p.getLeaf() == p.getCompilationUnit()) {
              // If p points to a compilation unit, the implied declaration is the
              // package declaration (if any) for the compilation unit.
              // Handle this case specially, because doc comments are only
              // expected in package-info files.
              JavaFileObject fo = p.getCompilationUnit().getSourceFile();
              boolean isPkgInfo = fo.isNameCompatible("package-info", JavaFileObject.Kind.SOURCE);
              if (tree == null) {
                  if (isPkgInfo)
                      reportMissing("dc.missing.comment");
                  return null;
              } else {
                  if (!isPkgInfo)
                      reportReference("dc.unexpected.comment");
              }
          } else {
              if (tree == null) {
                  if (!isSynthetic() && !isOverridingMethod)
                      reportMissing("dc.missing.comment");
                  return null;
              }
          }
  
          tagStack.clear();
          currHeaderTag = null;
  
          foundParams.clear();
          foundThrows.clear();
          foundInheritDoc = false;
          foundReturn = false;
  
          scan(new DocTreePath(p, tree), null);
  
          if (!isOverridingMethod) {
              switch (env.currElement.getKind()) {
                  case METHOD:
                  case CONSTRUCTOR: {
                      ExecutableElement ee = (ExecutableElement) env.currElement;
                      checkParamsDocumented(ee.getTypeParameters());
                      checkParamsDocumented(ee.getParameters());
                      switch (ee.getReturnType().getKind()) {
                          case VOID:
                          case NONE:
                              break;
                          default:
                              if (!foundReturn
                                      && !foundInheritDoc
                                      && !env.types.isSameType(ee.getReturnType(), env.java_lang_Void)) {
                                  reportMissing("dc.missing.return");
                              }
                      }
                      checkThrowsDocumented(ee.getThrownTypes());
                  }
              }
          }
  
          return null;
      }
  
      private void reportMissing(String code, Object... args) {
          env.messages.report(MISSING, Kind.WARNING, env.currPath.getLeaf(), code, args);
      }
  
      private void reportReference(String code, Object... args) {
          env.messages.report(REFERENCE, Kind.WARNING, env.currPath.getLeaf(), code, args);
      }
  
      @Override
      public Void visitDocComment(DocCommentTree tree, Void ignore) {
          super.visitDocComment(tree, ignore);
          for (TagStackItem tsi: tagStack) {
              warnIfEmpty(tsi, null);
              if (tsi.tree.getKind() == DocTree.Kind.START_ELEMENT
                      && tsi.tag.endKind == HtmlTag.EndKind.REQUIRED) {
                  StartElementTree t = (StartElementTree) tsi.tree;
                  env.messages.error(HTML, t, "dc.tag.not.closed", t.getName());
              }
          }
          return null;
      }
      // </editor-fold>
  
      // <editor-fold defaultstate="collapsed" desc="Text and entities.">
  
      @Override
      public Void visitText(TextTree tree, Void ignore) {
          if (hasNonWhitespace(tree)) {
              checkAllowsText(tree);
              markEnclosingTag(Flag.HAS_TEXT);
          }
          return null;
      }
  
      @Override
      public Void visitEntity(EntityTree tree, Void ignore) {
          checkAllowsText(tree);
          markEnclosingTag(Flag.HAS_TEXT);
          String name = tree.getName().toString();
          if (name.startsWith("#")) {
              int v = StringUtils.toLowerCase(name).startsWith("#x")
                      ? Integer.parseInt(name.substring(2), 16)
                      : Integer.parseInt(name.substring(1), 10);
              if (!Entity.isValid(v)) {
                  env.messages.error(HTML, tree, "dc.entity.invalid", name);
              }
          } else if (!Entity.isValid(name)) {
              env.messages.error(HTML, tree, "dc.entity.invalid", name);
          }
          return null;
      }
  
      void checkAllowsText(DocTree tree) {
          TagStackItem top = tagStack.peek();
          if (top != null
                  && top.tree.getKind() == DocTree.Kind.START_ELEMENT
                  && !top.tag.acceptsText()) {
              if (top.flags.add(Flag.REPORTED_BAD_INLINE)) {
                  env.messages.error(HTML, tree, "dc.text.not.allowed",
                          ((StartElementTree) top.tree).getName());
              }
          }
      }
  
      // </editor-fold>
  
      // <editor-fold defaultstate="collapsed" desc="HTML elements">
  
      @Override
      public Void visitStartElement(StartElementTree tree, Void ignore) {
          final Name treeName = tree.getName();
          final HtmlTag t = HtmlTag.get(treeName);
          if (t == null) {
              env.messages.error(HTML, tree, "dc.tag.unknown", treeName);
          } else {
              boolean done = false;
              for (TagStackItem tsi: tagStack) {
                  if (tsi.tag.accepts(t)) {
                      while (tagStack.peek() != tsi) {
                          warnIfEmpty(tagStack.peek(), null);
                          tagStack.pop();
                      }
                      done = true;
                      break;
                  } else if (tsi.tag.endKind != HtmlTag.EndKind.OPTIONAL) {
                      done = true;
                      break;
                  }
              }
              if (!done && HtmlTag.BODY.accepts(t)) {
                  while (!tagStack.isEmpty()) {
                      warnIfEmpty(tagStack.peek(), null);
                      tagStack.pop();
                  }
              }
  
              markEnclosingTag(Flag.HAS_ELEMENT);
              checkStructure(tree, t);
  
              // tag specific checks
              switch (t) {
                  // check for out of sequence headers, such as <h1>...</h1>  <h3>...</h3>
                  case H1: case H2: case H3: case H4: case H5: case H6:
                      checkHeader(tree, t);
                      break;
              }
  
              if (t.flags.contains(HtmlTag.Flag.NO_NEST)) {
                  for (TagStackItem i: tagStack) {
                      if (t == i.tag) {
                          env.messages.warning(HTML, tree, "dc.tag.nested.not.allowed", treeName);
                          break;
                      }
                  }
              }
          }
  
          // check for self closing tags, such as <a id="name"/>
          if (tree.isSelfClosing()) {
              env.messages.error(HTML, tree, "dc.tag.self.closing", treeName);
          }
  
          try {
              TagStackItem parent = tagStack.peek();
              TagStackItem top = new TagStackItem(tree, t);
              tagStack.push(top);
  
              super.visitStartElement(tree, ignore);
  
              // handle attributes that may or may not have been found in start element
              if (t != null) {
                  switch (t) {
                      case CAPTION:
                          if (parent != null && parent.tag == HtmlTag.TABLE)
                              parent.flags.add(Flag.TABLE_HAS_CAPTION);
                          break;
  
                      case IMG:
                          if (!top.attrs.contains(HtmlTag.Attr.ALT))
                              env.messages.error(ACCESSIBILITY, tree, "dc.no.alt.attr.for.image");
                          break;
                  }
              }
  
              return null;
          } finally {
  
              if (t == null || t.endKind == HtmlTag.EndKind.NONE)
                  tagStack.pop();
          }
      }
  
      private void checkStructure(StartElementTree tree, HtmlTag t) {
          Name treeName = tree.getName();
          TagStackItem top = tagStack.peek();
          switch (t.blockType) {
              case BLOCK:
                  if (top == null || top.tag.accepts(t))
                      return;
  
                  switch (top.tree.getKind()) {
                      case START_ELEMENT: {
                          if (top.tag.blockType == HtmlTag.BlockType.INLINE) {
                              Name name = ((StartElementTree) top.tree).getName();
                              env.messages.error(HTML, tree, "dc.tag.not.allowed.inline.element",
                                      treeName, name);
                              return;
                          }
                      }
                      break;
  
                      case LINK:
                      case LINK_PLAIN: {
                          String name = top.tree.getKind().tagName;
                          env.messages.error(HTML, tree, "dc.tag.not.allowed.inline.tag",
                                  treeName, name);
                          return;
                      }
                  }
                  break;
  
              case INLINE:
                  if (top == null || top.tag.accepts(t))
                      return;
                  break;
  
              case LIST_ITEM:
              case TABLE_ITEM:
                  if (top != null) {
                      // reset this flag so subsequent bad inline content gets reported
                      top.flags.remove(Flag.REPORTED_BAD_INLINE);
                      if (top.tag.accepts(t))
                          return;
                  }
                  break;
  
              case OTHER:
  