Prevent out-of-memory errors while regex array shape inference

[staabm]

closes phpstan/phpstan#11292

before this PR the following snippet..

<?php

require 'vendor/autoload.php';

// 1. Read the grammar.
$grammar  = new Hoa\File\Read('hoa://Library/Regex/Grammar.pp');

// 2. Load the compiler.
$compiler = Hoa\Compiler\Llk\Llk::load($grammar);

$nonUrl = "[^\x7f-\xff]";
$pattern = '{(' . $nonUrl . ')}';


// 3. Lex, parse and produce the AST.
$ast      = $compiler->parse($pattern);

// 4. Dump the result.
$dump     = new Hoa\Compiler\Visitor\Dump();
echo $dump->visit($ast);

.. mistakenly detected a non-parseable regex string as a lexeme, because errors in preg_match were not reported back properly in https://github.com/staabm/HoaCompiler/blob/c620f44deff0b4c2d0c27560a3b0f5e7e376e001/Llk/Lexer.php#L275-L302

this in turn lead to a wall of warnings like

Warning: Undefined array key 0 in /Users/staabm/workspace/phpstan-src/vendor/hoa/compiler/Llk/Lexer.php on line 288
PHP Warning:  Undefined array key 0 in /Users/staabm/workspace/phpstan-src/vendor/hoa/compiler/Llk/Lexer.php on line 299

Warning: Undefined array key 0 in /Users/staabm/workspace/phpstan-src/vendor/hoa/compiler/Llk/Lexer.php on line 299
PHP Warning:  Undefined array key 0 in /Users/staabm/workspace/phpstan-src/vendor/hoa/compiler/Llk/Lexer.php on line 300

and the lexer running into a infinite loop

[phpstan-bot]

This pull request has been marked as ready for review.

[ondrejmirtes]

Please also test what kind of array shape is inferred here.

[ondrejmirtes]

Also can you please explain what happened and why this fix helps?

[staabm]

added a PR description above

[ondrejmirtes]

Thank you.