[OpaqueRock]

Fix undefined-array-key warning in visit() for custom Node kinds

Problem

Node::kind is not required to be one of the built-in NodeKind constants — consumers can define custom Node subclasses with arbitrary kind strings. Visitor::visit() resolved a node's child keys like this:

$keys = ($inList ? $node : $visitorKeys[$node->kind]) ?? [];

The parentheses are misplaced: ?? only suppresses an undefined-index/notice-level warning when it directly wraps the array access it's guarding. Here it wraps the whole ternary instead, so $visitorKeys[$node->kind] is evaluated as a plain array access when $inList is false, and PHP emits an undefined-array-key warning whenever a Node with a custom (non-NodeKind) kind is visited. The resulting value of $keys was already correct in that case (it still ends up []) — only the warning was spurious.

Fix

Move the ?? [] fallback directly onto the array access so ?? can suppress the warning as intended:

$keys = $inList ? $node : ($visitorKeys[$node->kind] ?? []);

No behavior change — custom-kind nodes were already treated as leaves (no children); this just removes the spurious warning.

Tests

Added regression tests covering generic and kind-specific enter/leave visitors invoked on a custom-kind Node via visit().

Context

Split out of #1948, where this pre-existing bug was noticed while optimizing Visitor::visitInParallel(). It's an independent, smaller fix so it can be reviewed/merged on its own.

Changelog

Fixed

• Avoid undefined array key warning when visiting nodes with a custom kind

[Copilot]

Pull request overview

This pull request fixes a PHP undefined array key notice/warning in Visitor::visit() when traversing AST nodes whose kind is not one of the built-in NodeKind constants (i.e., consumer-defined custom Node subclasses). It also adds tests intended to cover visiting such custom-kind nodes.

Changes:

• Adjust Visitor::visit() to apply the ?? [] fallback directly to the $visitorKeys[$node->kind] array access, preventing undefined-key warnings for unknown kinds.
• Add tests that exercise visit() with a custom-kind Node, validating generic and kind-specific enter/leave visitor invocation.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/Language/Visitor.php	Moves null-coalescing fallback onto the visitorKeys[$node->kind] access to suppress undefined-key warnings for custom kinds.
tests/Language/VisitorTest.php	Adds coverage for visiting a custom-kind Node with both generic and kind-specific visitors.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused implementation correctly suppresses the warning while preserving behavior, with adequate regression coverage.

Review effort: Balanced
Findings: None

Resolved since last review (2)

• Same issue here as the generic-visitor test: it doesn't explicitly assert that visiting a…
• These assertions verify enter/leave callbacks are invoked, but the regression this PR describes is…

[spawnia]

Thanks @OpaqueRock! Released as v15.38.2.