Arrow function not tokenized correctly when using null in union type

[simPod]

Describe the bug

phpcs shoots:

PSR2.Methods.FunctionCallSignature.SpaceBeforeOpenBracket: Space before opening parenthesis of function call prohibited
Squiz.Arrays.ArrayDeclaration.IndexNoNewline: Each index in a multi-line array must be on a new line

when types are declared as union types. array|null triggers Squiz.Arrays.ArrayDeclaration.IndexNoNewline. ?array is fine.

Code sample

<?php

declare(strict_types=1);

return [
    'this is fine' => static fn (?DateTimeImmutable $value) : ?array => $value === null
        ? null
        : [],
    'this shoots false positives' => static fn (DateTimeImmutable|null $value) : array|null => $value === null
        ? null
        : [],
];

Custom ruleset

doctrine/coding-standard v9

To reproduce

 9 | ERROR | [x] Space before opening parenthesis of function call prohibited
   |       |     (PSR2.Methods.FunctionCallSignature.SpaceBeforeOpenBracket)
 9 | ERROR | [x] Each index in a multi-line array must be on a new line (Squiz.Arrays.ArrayDeclaration.IndexNoNewline)

Expected behavior

No errors.

Versions (please complete the following information):

• OS: [MacOS]
• PHP: [8.0]
• PHPCS: [master]
• Standard: [Doctrine]

[gsherwood]

This issue was caused by the arrow function tokenizing code not allowing for the null type in a type union. It appears this was the only place that had this issue in the codebase.

Thanks a lot for the bug report. The fix will be in 3.6.1.