Feature request

This code is invalid in PHP 8.3 and PHPStan does not detect the problem:

enum Language: string
{
	case ENG = 'eng';
	case FRE = 'fre';
	case GER = 'ger';
	case ITA = 'ita';
	case SPA = 'spa';
	case DUT = 'dut';
	case DAN = 'dan';
}

$langs = [
	Language::ENG, 
	Language::GER,
	Language::DAN,
];

$array = array_fill_keys($langs, null);

(see https://phpstan.org/r/08852987-50be-4812-9e61-c27c36d9cb36)

Actually running the code leads to this error: Object of class Language could not be converted to string

A new rule to detect this kind of mis-use would be nice.

We could also check other invalid accesses:

• Reading access: var_dump($array[Language::GER]); --> Cannot access offset of type Language on array
• Write: $array[Language::ITA] = 'foobar'; --> Cannot access offset of type Language on array
• Unset: unset($array[Language::GER]); --> Cannot unset offset of type Language on array

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