Try fixing assigning array offsets on possibly undefined nested array offsets

[ondrejmirtes]

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[ondrejmirtes]

<?php use function PHPStan\Testing\assertType; function doFoo(int $i): void { $array = []; $array[$i]['bar'] = 1; $array[$i]['baz'] = 2; // on line 10 PHPStan assigns: // 1) $array[$i]['baz'] to 2 // 2) $array[$i] to array{bar: 1, baz: 2} // 3) $array = from non-empty-array<int, array{bar: 1}> to non-empty-array<int, array{bar: 1, baz: 2}> // but step 3) is basically wrong for most code because assigning "baz" might be on a different offset than array{bar: 1} is on // but somehow we need to continue doing this if this PR is supposed to be successful assertType('non-empty-array<int, array{bar: 1, baz: 2}>', $array); }

[ondrejmirtes]

I realized the above problem could be fixed with a new accessory "ArraySize" type. When doing $array[$i]['baz'] = 2; and by knowing that $array[$i] already exists and by knowing that $array has size 1, we could overwrite the array with a new type. So instead of:

non-empty-array<int, array{bar: 1, baz?: 2}> 

We could actually end up with:

non-empty-array<int, array{bar: 1, baz: 2}>