aleph1.co.uk Git - yaffs-website/blob - vendor/ezyang/htmlpurifier/library/HTMLPurifier/Strategy/MakeWellFormed.php

   1 <?php
   2
   3 /**
   4  * Takes tokens makes them well-formed (balance end tags, etc.)
   5  *
   6  * Specification of the armor attributes this strategy uses:
   7  *
   8  *      - MakeWellFormed_TagClosedError: This armor field is used to
   9  *        suppress tag closed errors for certain tokens [TagClosedSuppress],
  10  *        in particular, if a tag was generated automatically by HTML
  11  *        Purifier, we may rely on our infrastructure to close it for us
  12  *        and shouldn't report an error to the user [TagClosedAuto].
  13  */
  14 class HTMLPurifier_Strategy_MakeWellFormed extends HTMLPurifier_Strategy
  15 {
  16
  17     /**
  18      * Array stream of tokens being processed.
  19      * @type HTMLPurifier_Token[]
  20      */
  21     protected $tokens;
  22
  23     /**
  24      * Current token.
  25      * @type HTMLPurifier_Token
  26      */
  27     protected $token;
  28
  29     /**
  30      * Zipper managing the true state.
  31      * @type HTMLPurifier_Zipper
  32      */
  33     protected $zipper;
  34
  35     /**
  36      * Current nesting of elements.
  37      * @type array
  38      */
  39     protected $stack;
  40
  41     /**
  42      * Injectors active in this stream processing.
  43      * @type HTMLPurifier_Injector[]
  44      */
  45     protected $injectors;
  46
  47     /**
  48      * Current instance of HTMLPurifier_Config.
  49      * @type HTMLPurifier_Config
  50      */
  51     protected $config;
  52
  53     /**
  54      * Current instance of HTMLPurifier_Context.
  55      * @type HTMLPurifier_Context
  56      */
  57     protected $context;
  58
  59     /**
  60      * @param HTMLPurifier_Token[] $tokens
  61      * @param HTMLPurifier_Config $config
  62      * @param HTMLPurifier_Context $context
  63      * @return HTMLPurifier_Token[]
  64      * @throws HTMLPurifier_Exception
  65      */
  66     public function execute($tokens, $config, $context)
  67     {
  68         $definition = $config->getHTMLDefinition();
  69
  70         // local variables
  71         $generator = new HTMLPurifier_Generator($config, $context);
  72         $escape_invalid_tags = $config->get('Core.EscapeInvalidTags');
  73         // used for autoclose early abortion
  74         $global_parent_allowed_elements = $definition->info_parent_def->child->getAllowedElements($config);
  75         $e = $context->get('ErrorCollector', true);
  76         $i = false; // injector index
  77         list($zipper, $token) = HTMLPurifier_Zipper::fromArray($tokens);
  78         if ($token === NULL) {
  79             return array();
  80         }
  81         $reprocess = false; // whether or not to reprocess the same token
  82         $stack = array();
  83
  84         // member variables
  85         $this->stack =& $stack;
  86         $this->tokens =& $tokens;
  87         $this->token =& $token;
  88         $this->zipper =& $zipper;
  89         $this->config = $config;
  90         $this->context = $context;
  91
  92         // context variables
  93         $context->register('CurrentNesting', $stack);
  94         $context->register('InputZipper', $zipper);
  95         $context->register('CurrentToken', $token);
  96
  97         // -- begin INJECTOR --
  98
  99         $this->injectors = array();
 100
 101         $injectors = $config->getBatch('AutoFormat');
 102         $def_injectors = $definition->info_injector;
 103         $custom_injectors = $injectors['Custom'];
 104         unset($injectors['Custom']); // special case
 105         foreach ($injectors as $injector => $b) {
 106             // XXX: Fix with a legitimate lookup table of enabled filters
 107             if (strpos($injector, '.') !== false) {
 108                 continue;
 109             }
 110             $injector = "HTMLPurifier_Injector_$injector";
 111             if (!$b) {
 112                 continue;
 113             }
 114             $this->injectors[] = new $injector;
 115         }
 116         foreach ($def_injectors as $injector) {
 117             // assumed to be objects
 118             $this->injectors[] = $injector;
 119         }
 120         foreach ($custom_injectors as $injector) {
 121             if (!$injector) {
 122                 continue;
 123             }
 124             if (is_string($injector)) {
 125                 $injector = "HTMLPurifier_Injector_$injector";
 126                 $injector = new $injector;
 127             }
 128             $this->injectors[] = $injector;
 129         }
 130
 131         // give the injectors references to the definition and context
 132         // variables for performance reasons
 133         foreach ($this->injectors as $ix => $injector) {
 134             $error = $injector->prepare($config, $context);
 135             if (!$error) {
 136                 continue;
 137             }
 138             array_splice($this->injectors, $ix, 1); // rm the injector
 139             trigger_error("Cannot enable {$injector->name} injector because $error is not allowed", E_USER_WARNING);
 140         }
 141
 142         // -- end INJECTOR --
 143
 144         // a note on reprocessing:
 145         //      In order to reduce code duplication, whenever some code needs
 146         //      to make HTML changes in order to make things "correct", the
 147         //      new HTML gets sent through the purifier, regardless of its
 148         //      status. This means that if we add a start token, because it
 149         //      was totally necessary, we don't have to update nesting; we just
 150         //      punt ($reprocess = true; continue;) and it does that for us.
 151
 152         // isset is in loop because $tokens size changes during loop exec
 153         for (;;
 154              // only increment if we don't need to reprocess
 155              $reprocess ? $reprocess = false : $token = $zipper->next($token)) {
 156
 157             // check for a rewind
 158             if (is_int($i)) {
 159                 // possibility: disable rewinding if the current token has a
 160                 // rewind set on it already. This would offer protection from
 161                 // infinite loop, but might hinder some advanced rewinding.
 162                 $rewind_offset = $this->injectors[$i]->getRewindOffset();
 163                 if (is_int($rewind_offset)) {
 164                     for ($j = 0; $j < $rewind_offset; $j++) {
 165                         if (empty($zipper->front)) break;
 166                         $token = $zipper->prev($token);
 167                         // indicate that other injectors should not process this token,
 168                         // but we need to reprocess it.  See Note [Injector skips]
 169                         unset($token->skip[$i]);
 170                         $token->rewind = $i;
 171                         if ($token instanceof HTMLPurifier_Token_Start) {
 172                             array_pop($this->stack);
 173                         } elseif ($token instanceof HTMLPurifier_Token_End) {
 174                             $this->stack[] = $token->start;
 175                         }
 176                     }
 177                 }
 178                 $i = false;
 179             }
 180
 181             // handle case of document end
 182             if ($token === NULL) {
 183                 // kill processing if stack is empty
 184                 if (empty($this->stack)) {
 185                     break;
 186                 }
 187
 188                 // peek
 189                 $top_nesting = array_pop($this->stack);
 190                 $this->stack[] = $top_nesting;
 191
 192                 // send error [TagClosedSuppress]
 193                 if ($e && !isset($top_nesting->armor['MakeWellFormed_TagClosedError'])) {
 194                     $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag closed by document end', $top_nesting);
 195                 }
 196
 197                 // append, don't splice, since this is the end
 198                 $token = new HTMLPurifier_Token_End($top_nesting->name);
 199
 200                 // punt!
 201                 $reprocess = true;
 202                 continue;
 203             }
 204
 205             //echo '<br>'; printZipper($zipper, $token);//printTokens($this->stack);
 206             //flush();
 207
 208             // quick-check: if it's not a tag, no need to process
 209             if (empty($token->is_tag)) {
 210                 if ($token instanceof HTMLPurifier_Token_Text) {
 211                     foreach ($this->injectors as $i => $injector) {
 212                         if (isset($token->skip[$i])) {
 213                             // See Note [Injector skips]
 214                             continue;
 215                         }
 216                         if ($token->rewind !== null && $token->rewind !== $i) {
 217                             continue;
 218                         }
 219                         // XXX fuckup
 220                         $r = $token;
 221                         $injector->handleText($r);
 222                         $token = $this->processToken($r, $i);
 223                         $reprocess = true;
 224                         break;
 225                     }
 226                 }
 227                 // another possibility is a comment
 228                 continue;
 229             }
 230
 231             if (isset($definition->info[$token->name])) {
 232                 $type = $definition->info[$token->name]->child->type;
 233             } else {
 234                 $type = false; // Type is unknown, treat accordingly
 235             }
 236
 237             // quick tag checks: anything that's *not* an end tag
 238             $ok = false;
 239             if ($type === 'empty' && $token instanceof HTMLPurifier_Token_Start) {
 240                 // claims to be a start tag but is empty
 241                 $token = new HTMLPurifier_Token_Empty(
 242                     $token->name,
 243                     $token->attr,
 244                     $token->line,
 245                     $token->col,
 246                     $token->armor
 247                 );
 248                 $ok = true;
 249             } elseif ($type && $type !== 'empty' && $token instanceof HTMLPurifier_Token_Empty) {
 250                 // claims to be empty but really is a start tag
 251                 // NB: this assignment is required
 252                 $old_token = $token;
 253                 $token = new HTMLPurifier_Token_End($token->name);
 254                 $token = $this->insertBefore(
 255                     new HTMLPurifier_Token_Start($old_token->name, $old_token->attr, $old_token->line, $old_token->col, $old_token->armor)
 256                 );
 257                 // punt (since we had to modify the input stream in a non-trivial way)
 258                 $reprocess = true;
 259                 continue;
 260             } elseif ($token instanceof HTMLPurifier_Token_Empty) {
 261                 // real empty token
 262                 $ok = true;
 263             } elseif ($token instanceof HTMLPurifier_Token_Start) {
 264                 // start tag
 265
 266                 // ...unless they also have to close their parent
 267                 if (!empty($this->stack)) {
 268
 269                     // Performance note: you might think that it's rather
 270                     // inefficient, recalculating the autoclose information
 271                     // for every tag that a token closes (since when we
 272                     // do an autoclose, we push a new token into the
 273                     // stream and then /process/ that, before
 274                     // re-processing this token.)  But this is
 275                     // necessary, because an injector can make an
 276                     // arbitrary transformations to the autoclosing
 277                     // tokens we introduce, so things may have changed
 278                     // in the meantime.  Also, doing the inefficient thing is
 279                     // "easy" to reason about (for certain perverse definitions
 280                     // of "easy")
 281
 282                     $parent = array_pop($this->stack);
 283                     $this->stack[] = $parent;
 284
 285                     $parent_def = null;
 286                     $parent_elements = null;
 287                     $autoclose = false;
 288                     if (isset($definition->info[$parent->name])) {
 289                         $parent_def = $definition->info[$parent->name];
 290                         $parent_elements = $parent_def->child->getAllowedElements($config);
 291                         $autoclose = !isset($parent_elements[$token->name]);
 292                     }
 293
 294                     if ($autoclose && $definition->info[$token->name]->wrap) {
 295                         // Check if an element can be wrapped by another
 296                         // element to make it valid in a context (for
 297                         // example, <ul><ul> needs a <li> in between)
 298                         $wrapname = $definition->info[$token->name]->wrap;
 299                         $wrapdef = $definition->info[$wrapname];
 300                         $elements = $wrapdef->child->getAllowedElements($config);
 301                         if (isset($elements[$token->name]) && isset($parent_elements[$wrapname])) {
 302                             $newtoken = new HTMLPurifier_Token_Start($wrapname);
 303                             $token = $this->insertBefore($newtoken);
 304                             $reprocess = true;
 305                             continue;
 306                         }
 307                     }
 308
 309                     $carryover = false;
 310                     if ($autoclose && $parent_def->formatting) {
 311                         $carryover = true;
 312                     }
 313
 314                     if ($autoclose) {
 315                         // check if this autoclose is doomed to fail
 316                         // (this rechecks $parent, which his harmless)
 317                         $autoclose_ok = isset($global_parent_allowed_elements[$token->name]);
 318                         if (!$autoclose_ok) {
 319                             foreach ($this->stack as $ancestor) {
 320                                 $elements = $definition->info[$ancestor->name]->child->getAllowedElements($config);
 321                                 if (isset($elements[$token->name])) {
 322                                     $autoclose_ok = true;
 323                                     break;
 324                                 }
 325                                 if ($definition->info[$token->name]->wrap) {
 326                                     $wrapname = $definition->info[$token->name]->wrap;
 327                                     $wrapdef = $definition->info[$wrapname];
 328                                     $wrap_elements = $wrapdef->child->getAllowedElements($config);
 329                                     if (isset($wrap_elements[$token->name]) && isset($elements[$wrapname])) {
 330                                         $autoclose_ok = true;
 331                                         break;
 332                                     }
 333                                 }
 334                             }
 335                         }
 336                         if ($autoclose_ok) {
 337                             // errors need to be updated
 338                             $new_token = new HTMLPurifier_Token_End($parent->name);
 339                             $new_token->start = $parent;
 340                             // [TagClosedSuppress]
 341                             if ($e && !isset($parent->armor['MakeWellFormed_TagClosedError'])) {
 342                                 if (!$carryover) {
 343                                     $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag auto closed', $parent);
 344                                 } else {
 345                                     $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag carryover', $parent);
 346                                 }
 347                             }
 348                             if ($carryover) {
 349                                 $element = clone $parent;
 350                                 // [TagClosedAuto]
 351                                 $element->armor['MakeWellFormed_TagClosedError'] = true;
 352                                 $element->carryover = true;
 353                                 $token = $this->processToken(array($new_token, $token, $element));
 354                             } else {
 355                                 $token = $this->insertBefore($new_token);
 356                             }
 357                         } else {
 358                             $token = $this->remove();
 359                         }
 360                         $reprocess = true;
 361                         continue;
 362                     }
 363
 364                 }
 365                 $ok = true;
 366             }
 367
 368             if ($ok) {
 369                 foreach ($this->injectors as $i => $injector) {
 370                     if (isset($token->skip[$i])) {
 371                         // See Note [Injector skips]
 372                         continue;
 373                     }
 374                     if ($token->rewind !== null && $token->rewind !== $i) {
 375                         continue;
 376                     }
 377                     $r = $token;
 378                     $injector->handleElement($r);
 379                     $token = $this->processToken($r, $i);
 380                     $reprocess = true;
 381                     break;
 382                 }
 383                 if (!$reprocess) {
 384                     // ah, nothing interesting happened; do normal processing
 385                     if ($token instanceof HTMLPurifier_Token_Start) {
 386                         $this->stack[] = $token;
 387                     } elseif ($token instanceof HTMLPurifier_Token_End) {
 388                         throw new HTMLPurifier_Exception(
 389                             'Improper handling of end tag in start code; possible error in MakeWellFormed'
 390                         );
 391                     }
 392                 }
 393                 continue;
 394             }
 395
 396             // sanity check: we should be dealing with a closing tag
 397             if (!$token instanceof HTMLPurifier_Token_End) {
 398                 throw new HTMLPurifier_Exception('Unaccounted for tag token in input stream, bug in HTML Purifier');
 399             }
 400
 401             // make sure that we have something open
 402             if (empty($this->stack)) {
 403                 if ($escape_invalid_tags) {
 404                     if ($e) {
 405                         $e->send(E_WARNING, 'Strategy_MakeWellFormed: Unnecessary end tag to text');
 406                     }
 407                     $token = new HTMLPurifier_Token_Text($generator->generateFromToken($token));
 408                 } else {
 409                     if ($e) {
 410                         $e->send(E_WARNING, 'Strategy_MakeWellFormed: Unnecessary end tag removed');
 411                     }
 412                     $token = $this->remove();
 413                 }
 414                 $reprocess = true;
 415                 continue;
 416             }
 417
 418             // first, check for the simplest case: everything closes neatly.
 419             // Eventually, everything passes through here; if there are problems
 420             // we modify the input stream accordingly and then punt, so that
 421             // the tokens get processed again.
 422             $current_parent = array_pop($this->stack);
 423             if ($current_parent->name == $token->name) {
 424                 $token->start = $current_parent;
 425                 foreach ($this->injectors as $i => $injector) {
 426                     if (isset($token->skip[$i])) {
 427                         // See Note [Injector skips]
 428                         continue;
 429                     }
 430                     if ($token->rewind !== null && $token->rewind !== $i) {
 431                         continue;
 432                     }
 433                     $r = $token;
 434                     $injector->handleEnd($r);
 435                     $token = $this->processToken($r, $i);
 436                     $this->stack[] = $current_parent;
 437                     $reprocess = true;
 438                     break;
 439                 }
 440                 continue;
 441             }
 442
 443             // okay, so we're trying to close the wrong tag
 444
 445             // undo the pop previous pop
 446             $this->stack[] = $current_parent;
 447
 448             // scroll back the entire nest, trying to find our tag.
 449             // (feature could be to specify how far you'd like to go)
 450             $size = count($this->stack);
 451             // -2 because -1 is the last element, but we already checked that
 452             $skipped_tags = false;
 453             for ($j = $size - 2; $j >= 0; $j--) {
 454                 if ($this->stack[$j]->name == $token->name) {
 455                     $skipped_tags = array_slice($this->stack, $j);
 456                     break;
 457                 }
 458             }
 459
 460             // we didn't find the tag, so remove
 461             if ($skipped_tags === false) {
 462                 if ($escape_invalid_tags) {
 463                     if ($e) {
 464                         $e->send(E_WARNING, 'Strategy_MakeWellFormed: Stray end tag to text');
 465                     }
 466                     $token = new HTMLPurifier_Token_Text($generator->generateFromToken($token));
 467                 } else {
 468                     if ($e) {
 469                         $e->send(E_WARNING, 'Strategy_MakeWellFormed: Stray end tag removed');
 470                     }
 471                     $token = $this->remove();
 472                 }
 473                 $reprocess = true;
 474                 continue;
 475             }
 476
 477             // do errors, in REVERSE $j order: a,b,c with </a></b></c>
 478             $c = count($skipped_tags);
 479             if ($e) {
 480                 for ($j = $c - 1; $j > 0; $j--) {
 481                     // notice we exclude $j == 0, i.e. the current ending tag, from
 482                     // the errors... [TagClosedSuppress]
 483                     if (!isset($skipped_tags[$j]->armor['MakeWellFormed_TagClosedError'])) {
 484                         $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag closed by element end', $skipped_tags[$j]);
 485                     }
 486                 }
 487             }
 488
 489             // insert tags, in FORWARD $j order: c,b,a with </a></b></c>
 490             $replace = array($token);
 491             for ($j = 1; $j < $c; $j++) {
 492                 // ...as well as from the insertions
 493                 $new_token = new HTMLPurifier_Token_End($skipped_tags[$j]->name);
 494                 $new_token->start = $skipped_tags[$j];
 495                 array_unshift($replace, $new_token);
 496                 if (isset($definition->info[$new_token->name]) && $definition->info[$new_token->name]->formatting) {
 497                     // [TagClosedAuto]
 498                     $element = clone $skipped_tags[$j];
 499                     $element->carryover = true;
 500                     $element->armor['MakeWellFormed_TagClosedError'] = true;
 501                     $replace[] = $element;
 502                 }
 503             }
 504             $token = $this->processToken($replace);
 505             $reprocess = true;
 506             continue;
 507         }
 508
 509         $context->destroy('CurrentToken');
 510         $context->destroy('CurrentNesting');
 511         $context->destroy('InputZipper');
 512
 513         unset($this->injectors, $this->stack, $this->tokens);
 514         return $zipper->toArray($token);
 515     }
 516
 517     /**
 518      * Processes arbitrary token values for complicated substitution patterns.
 519      * In general:
 520      *
 521      * If $token is an array, it is a list of tokens to substitute for the
 522      * current token. These tokens then get individually processed. If there
 523      * is a leading integer in the list, that integer determines how many
 524      * tokens from the stream should be removed.
 525      *
 526      * If $token is a regular token, it is swapped with the current token.
 527      *
 528      * If $token is false, the current token is deleted.
 529      *
 530      * If $token is an integer, that number of tokens (with the first token
 531      * being the current one) will be deleted.
 532      *
 533      * @param HTMLPurifier_Token|array|int|bool $token Token substitution value
 534      * @param HTMLPurifier_Injector|int $injector Injector that performed the substitution; default is if
 535      *        this is not an injector related operation.
 536      * @throws HTMLPurifier_Exception
 537      */
 538     protected function processToken($token, $injector = -1)
 539     {
 540         // Zend OpCache miscompiles $token = array($token), so
 541         // avoid this pattern.  See: https://github.com/ezyang/htmlpurifier/issues/108
 542
 543         // normalize forms of token
 544         if (is_object($token)) {
 545             $tmp = $token;
 546             $token = array(1, $tmp);
 547         }
 548         if (is_int($token)) {
 549             $tmp = $token;
 550             $token = array($tmp);
 551         }
 552         if ($token === false) {
 553             $token = array(1);
 554         }
 555         if (!is_array($token)) {
 556             throw new HTMLPurifier_Exception('Invalid token type from injector');
 557         }
 558         if (!is_int($token[0])) {
 559             array_unshift($token, 1);
 560         }
 561         if ($token[0] === 0) {
 562             throw new HTMLPurifier_Exception('Deleting zero tokens is not valid');
 563         }
 564
 565         // $token is now an array with the following form:
 566         // array(number nodes to delete, new node 1, new node 2, ...)
 567
 568         $delete = array_shift($token);
 569         list($old, $r) = $this->zipper->splice($this->token, $delete, $token);
 570
 571         if ($injector > -1) {
 572             // See Note [Injector skips]
 573             // Determine appropriate skips.  Here's what the code does:
 574             //  *If* we deleted one or more tokens, copy the skips
 575             //  of those tokens into the skips of the new tokens (in $token).
 576             //  Also, mark the newly inserted tokens as having come from
 577             //  $injector.
 578             $oldskip = isset($old[0]) ? $old[0]->skip : array();
 579             foreach ($token as $object) {
 580                 $object->skip = $oldskip;
 581                 $object->skip[$injector] = true;
 582             }
 583         }
 584
 585         return $r;
 586
 587     }
 588
 589     /**
 590      * Inserts a token before the current token. Cursor now points to
 591      * this token.  You must reprocess after this.
 592      * @param HTMLPurifier_Token $token
 593      */
 594     private function insertBefore($token)
 595     {
 596         // NB not $this->zipper->insertBefore(), due to positioning
 597         // differences
 598         $splice = $this->zipper->splice($this->token, 0, array($token));
 599
 600         return $splice[1];
 601     }
 602
 603     /**
 604      * Removes current token. Cursor now points to new token occupying previously
 605      * occupied space.  You must reprocess after this.
 606      */
 607     private function remove()
 608     {
 609         return $this->zipper->delete();
 610     }
 611 }
 612
 613 // Note [Injector skips]
 614 // ~~~~~~~~~~~~~~~~~~~~~
 615 // When I originally designed this class, the idea behind the 'skip'
 616 // property of HTMLPurifier_Token was to help avoid infinite loops
 617 // in injector processing.  For example, suppose you wrote an injector
 618 // that bolded swear words.  Naively, you might write it so that
 619 // whenever you saw ****, you replaced it with <strong>****</strong>.
 620 //
 621 // When this happens, we will reprocess all of the tokens with the
 622 // other injectors.  Now there is an opportunity for infinite loop:
 623 // if we rerun the swear-word injector on these tokens, we might
 624 // see **** and then reprocess again to get
 625 // <strong><strong>****</strong></strong> ad infinitum.
 626 //
 627 // Thus, the idea of a skip is that once we process a token with
 628 // an injector, we mark all of those tokens as having "come from"
 629 // the injector, and we never run the injector again on these
 630 // tokens.
 631 //
 632 // There were two more complications, however:
 633 //
 634 //  - With HTMLPurifier_Injector_RemoveEmpty, we noticed that if
 635 //    you had <b><i></i></b>, after you removed the <i></i>, you
 636 //    really would like this injector to go back and reprocess
 637 //    the <b> tag, discovering that it is now empty and can be
 638 //    removed.  So we reintroduced the possibility of infinite looping
 639 //    by adding a "rewind" function, which let you go back to an
 640 //    earlier point in the token stream and reprocess it with injectors.
 641 //    Needless to say, we need to UN-skip the token so it gets
 642 //    reprocessed.
 643 //
 644 //  - Suppose that you successfuly process a token, replace it with
 645 //    one with your skip mark, but now another injector wants to
 646 //    process the skipped token with another token.  Should you continue
 647 //    to skip that new token, or reprocess it?  If you reprocess,
 648 //    you can end up with an infinite loop where one injector converts
 649 //    <a> to <b>, and then another injector converts it back.  So
 650 //    we inherit the skips, but for some reason, I thought that we
 651 //    should inherit the skip from the first token of the token
 652 //    that we deleted.  Why?  Well, it seems to work OK.
 653 //
 654 // If I were to redesign this functionality, I would absolutely not
 655 // go about doing it this way: the semantics are just not very well
 656 // defined, and in any case you probably wanted to operate on trees,
 657 // not token streams.
 658
 659 // vim: et sw=4 sts=4