MatcherVisitor

MatcherVisitor is the generic base behind ClassNameMatcherVisitor. Use it directly when the condition you're searching for is more than just "is an instance of this class".

public function __construct(
    \Closure $matcher,
    ?\Closure $break = null,
) {}

$matcher — called for every node; the first node for which it returns true becomes the match, and traversal of that subtree stops there (Command::SkipChildren is returned automatically once found, and for every node visited afterwards).
$break — optional early-exit predicate, checked whenever $matcher itself didn't match; if it returns true, the search stops there (leaving node as null) without visiting the rest of the tree.

After a traverse() call, $matcher->node holds the matched node (or null), and $matcher->isFound is a convenience boolean for the same.

Example

Find the first named type whose name is longer than a given length:

use TypeLang\Parser\Traverser;
use TypeLang\Parser\Traverser\MatcherVisitor;
use TypeLang\Type\NamedTypeNode;
use TypeLang\Type\Node;

$type = new TypeLang\Parser\TypeParser()
    ->parse('int|non-empty-string|bool');

$finder = Traverser::through(new MatcherVisitor(
    static fn(Node $node): bool => $node instanceof NamedTypeNode
        && \strlen($node->name->toString()) > 5,
), [$type]);

// string(16) "non-empty-string"
var_dump($finder->node->name->toString());

Stopping Early with `$break`

The $break callback lets you bail out before scanning the whole tree once some other condition is met — useful when you know the node you're looking for can't possibly occur past a certain point:

use TypeLang\Type\Shape\FieldsListNode;
use TypeLang\Type\Literal\BoolLiteralNode;

$finder = Traverser::through(
    new MatcherVisitor(
        matcher: static fn(Node $node): bool 
            => $node instanceof BoolLiteralNode,
        // give up as soon as we step into a shape's field list
        break: static fn(Node $node): bool 
            => $node instanceof FieldsListNode,
    ),
    [$type],
);

ClassNameMatcherVisitor(SomeClass::class) is exactly new MatcherVisitor(static fn(Node $node): bool => $node instanceof SomeClass) with no $break — reach for it directly whenever an instanceof check is all you need.

05 July 2026

MatcherVisitor

Example

Stopping Early with $break

Stopping Early with `$break`