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<?php |
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declare(strict_types=1); |
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namespace Antlr\Antlr4\Runtime; |
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use Antlr\Antlr4\Runtime\Atn\ATN; |
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use Antlr\Antlr4\Runtime\Tree\ParseTree; |
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use Antlr\Antlr4\Runtime\Tree\ParseTreeVisitor; |
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use Antlr\Antlr4\Runtime\Tree\RuleNode; |
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use Antlr\Antlr4\Runtime\Tree\Tree; |
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use Antlr\Antlr4\Runtime\Tree\Trees; |
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/** |
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* A rule context is a record of a single rule invocation. |
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* |
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* We form a stack of these context objects using the parent pointer. A parent |
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* pointer of null indicates that the current context is the bottom of the stack. |
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* The {@see ParserRuleContext} subclass as a children list so that we can turn |
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* this data structure into a tree. |
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* |
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* The root node always has a null pointer and invokingState of -1. |
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* |
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* Upon entry to parsing, the first invoked rule function creates a context object |
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* (a subclass specialized for that rule such as SContext) and makes it the root |
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* of a parse tree, recorded by field Parser->ctx. |
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* |
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* public final s(){ |
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* SContext _localctx = new SContext(_ctx, getState()); <-- create new node |
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* enterRule(_localctx, 0, RULE_s); <-- push it |
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* ... |
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* exitRule(); <-- pop back to _localctx |
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* return _localctx; |
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* } |
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* |
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* A subsequent rule invocation of r from the start rule s pushes a new |
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* context object for r whose parent points at s and use invoking state is |
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* the state with r emanating as edge label. |
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* |
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* The invokingState fields from a context object to the root together |
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* form a stack of rule indication states where the root (bottom of the stack) |
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* has a -1 sentinel value. If we invoke start symbol s then call r1, |
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* which calls r2, the would look like this: |
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* |
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* SContext[-1] <- root node (bottom of the stack) |
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* R1Context[p] <- p in rule s called r1 |
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* R2Context[q] <- q in rule r1 called r2 |
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* |
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* So the top of the stack, `_ctx`, represents a call to the current rule |
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* and it holds the return address from another rule that invoke to this rule. |
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* To invoke a rule, we must always have a current context. |
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* |
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* The parent contexts are useful for computing lookahead sets and getting |
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* error information. |
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* |
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* These objects are used during parsing and prediction. For the special case |
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* of parsers, we use the subclass {@see ParserRuleContext}. |
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*/ |
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class RuleContext implements RuleNode |
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{ |
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/** |
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* The context that invoked this rule. |
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* |
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* @var RuleContext|null |
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*/ |
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public $parentCtx; |
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/** |
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* What state invoked the rule associated with this context? |
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* The "return address" is the followState of invokingState. If parent |
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* is null, this should be -1 this context object represents the start rule. |
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* |
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* @var int |
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*/ |
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public $invokingState = -1; |
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public function __construct(?RuleContext $parent, ?int $invokingState = null) |
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{ |
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$this->parentCtx = $parent; |
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$this->invokingState = $invokingState ?? -1; |
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} |
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public static function emptyContext() : ParserRuleContext |
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{ |
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static $empty; |
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return $empty ?? ($empty = new ParserRuleContext(null)); |
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} |
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public function depth() : int |
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{ |
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$n = 0; |
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$p = $this; |
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while ($p !== null) { |
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$p = $p->parentCtx; |
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$n++; |
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} |
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return $n; |
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} |
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/** |
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* A context is empty if there is no invoking state; meaning nobody call |
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* current context. |
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*/ |
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public function isEmpty() : bool |
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{ |
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return $this->invokingState === -1; |
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} |
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public function getSourceInterval() : Interval |
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{ |
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return Interval::invalid(); |
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} |
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public function getRuleContext() : RuleContext |
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{ |
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return $this; |
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} |
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public function getPayload() : RuleContext |
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{ |
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return $this; |
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} |
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/** |
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* Return the combined text of all child nodes. This method only considers |
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* tokens which have been added to the parse tree. |
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* |
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* Since tokens on hidden channels (e.g. whitespace or comments) are not |
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* added to the parse trees, they will not appear in the output |
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* of this method. |
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*/ |
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public function getText() : string |
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{ |
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$text = ''; |
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for ($i = 0, $count = $this->getChildCount(); $i < $count; $i++) { |
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$child = $this->getChild($i); |
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if ($child !== null) { |
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$text .= $child->getText(); |
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} |
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} |
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return $text; |
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} |
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public function getRuleIndex() : int |
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{ |
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return -1; |
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} |
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/** |
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* For rule associated with this parse tree internal node, return the outer |
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* alternative number used to match the input. Default implementation |
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* does not compute nor store this alt num. Create a subclass of |
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* {@see ParserRuleContext} with backing field and set option |
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* `contextSuperClass` to set it. |
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*/ |
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public function getAltNumber() : int |
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{ |
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return ATN::INVALID_ALT_NUMBER; |
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} |
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/** |
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* Set the outer alternative number for this context node. Default |
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* implementation does nothing to avoid backing field overhead for trees |
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* that don't need it. Create a subclass of {@see ParserRuleContext} with backing |
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* field and set option `contextSuperClass`. |
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*/ |
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public function setAltNumber(int $altNumber) : void |
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{ |
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} |
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/** |
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* @return RuleContext|null |
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*/ |
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public function getParent() : ?Tree |
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{ |
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return $this->parentCtx; |
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} |
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public function setParent(?RuleContext $ctx) : void |
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{ |
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$this->parentCtx = $ctx; |
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} |
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/** |
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* @return ParseTree|null |
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*/ |
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public function getChild(int $i, ?string $type = null) : ?Tree |
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{ |
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return null; |
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} |
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public function getChildCount() : int |
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{ |
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return 0; |
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} |
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public function accept(ParseTreeVisitor $visitor) |
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{ |
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return $visitor->visitChildren($this); |
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} |
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/** |
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* Print out a whole tree, not just a node, in LISP format |
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* (root child1 .. childN). Print just a node if this is a leaf. |
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* |
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* @param array<string>|null $ruleNames |
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*/ |
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public function toStringTree(?array $ruleNames = null) : string |
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{ |
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return Trees::toStringTree($this, $ruleNames); |
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} |
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public function __toString() : string |
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{ |
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return $this->toString(); |
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} |
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/** |
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* @param array<string>|null $ruleNames |
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*/ |
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public function toString(?array $ruleNames = null, ?RuleContext $stop = null) : string |
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{ |
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$p = $this; |
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$string = '['; |
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while ($p !== null && $p !== $stop) { |
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if ($ruleNames === null) { |
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if (!$p->isEmpty()) { |
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$string .= $p->invokingState; |
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} |
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} else { |
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$ri = $p->getRuleIndex(); |
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$ruleName = $ri >= 0 && $ri < \count($ruleNames) ? $ruleNames[$ri] : (string) $ri; |
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$string .= $ruleName; |
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} |
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if ($p->parentCtx !== null && ($ruleNames !== null || !$p->parentCtx->isEmpty())) { |
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$string .= ' '; |
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} |
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$p = $p->parentCtx; |
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} |
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return $string . ']'; |
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} |
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} |
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This check looks for function or method calls that always return null and whose return value is assigned to a variable.
The method
getObject()can return nothing but null, so it makes no sense to assign that value to a variable.The reason is most likely that a function or method is imcomplete or has been reduced for debug purposes.