Are changes to the constructor really BC breaks?

[ondrejmirtes]

Hi, I've got these messages:

[BC] CHANGED: Default parameter value for parameter $nextAutoIndex of PHPStan\Type\Constant\ConstantArrayType#__construct() changed from 0 to array (
  0 => 0,
)
[BC] CHANGED: The parameter $nextAutoIndex of PHPStan\Type\Constant\ConstantArrayType#__construct() changed from int to a non-contravariant int|array
[BC] CHANGED: The parameter $nextAutoIndex of PHPStan\Type\Constant\ConstantArrayType#__construct() changed from int to int|array

This is how the PHP diff looks like:

 	/**
 	 * @api
 	 * @param array<int, ConstantIntegerType|ConstantStringType> $keyTypes
 	 * @param array<int, Type> $valueTypes
+	 * @param non-empty-list<int>|int $nextAutoIndexes
 	 * @param int[] $optionalKeys
 	 */
 	public function __construct(
 		private array $keyTypes,
 		private array $valueTypes,
-		private int $nextAutoIndex = 0,
+		int|array $nextAutoIndexes = [0],
 		private array $optionalKeys = [],
 	)
 	{
 		assert(count($keyTypes) === count($valueTypes));
 
+		if (is_int($nextAutoIndexes)) {
+			$nextAutoIndexes = [$nextAutoIndexes];
+		}
+
+		$this->nextAutoIndexes = $nextAutoIndexes;
+

I'm widening the type of the parameter, and if the argument is omitted from the call, or if the old type is passed to the parameter, the result is the same.

I don't see how this is a BC break, but I'm open to be corrected :) Thanks.

[Ocramius]

Probably need an exclusion for constructors, since in PHP they can be overridden

[ondrejmirtes]

Only abstract ones and those coming from interfaces can't :)

[Ocramius]

Actually, default value changes are most likely still a BC break, can't remember context though 🤔

As for type, it seems like a bug to me

[Ocramius]

Ah, brain fart: of course child classes cannot reduce the type of a parameter, so that's what is tripping this analysis.

We really just need to exclude constructors, like we do exclude methods for final classes, because the BC break is valid for inheritance, just not for __construct()