Array shapes handling gets broken when there are many keys (63?)

[ArtemGoutsoul]

Bug report

There's a array param with 63 keys (condensed code ):

<?php

/**
 * @param array{
 *    a1?: string,
 *    a2?: string,
 *    a3?: string,
 *  ....
 *    a59?: string,
 *    a60?: string,
 *    a61?: string,
 *    a62?: string|string[]|int|float,
 *    a63?: string
 * } $row
 */
function doStuff(array $row): void
{
	\PHPStan\dumpType($row['a51'] ?? ''); // Dumped type: string
	\PHPStan\dumpType($row['a51'] ?? ''); // Dumped type: array<string>|float|int|string
}

Not really sure what is happening here. If I remove any key - the problem goes away: i.e. the type shows up correctly as string for both lines.

Code snippet that reproduces the problem

https://phpstan.org/r/f79adf76-c8e5-46f9-8615-c887fa4324ea

Expected output

Dumped type: string
Dumped type: string

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[VincentLanglet]

For the record

It doesn't simplify the array, without the ?? ''
https://phpstan.org/r/efb9bc75-d1dc-4dc2-bbb3-7638bb1362c9

[ArtemGoutsoul]

It doesn't simplify the array, without the ?? '' https://phpstan.org/r/efb9bc75-d1dc-4dc2-bbb3-7638bb1362c9

Without ?? it first says string which is partially true and then says Offset 'a51' does not exist on array... which is partially true.

It would be clearer if instead of both messages phpstan debug would report just one: Dumped type: string, offset 'a51' is optional in array..., but I'm not sure how complex this improvement would be.

[ondrejmirtes]

Fixed phpstan/phpstan-src#3032