ArrayDimFetch on class constant array can return null

[staabm]

A offset array fetch on a constant array can return null if the offset does not exist, see https://3v4l.org/us7UK

triggered by #3453 (comment)

closes phpstan/phpstan#10847

[staabm]

we now see errors popping up in cases, where the implementation did not verify before whether the offset actually exists before fetching it (at least not in the method local code):

phpstan-src/src/Type/Php/StrContainingTypeSpecifyingExtension.php

Lines 61 to 70 in 06ab320

	public function specifyTypes(FunctionReflection $functionReflection, FuncCall $node, Scope $scope, TypeSpecifierContext $context): SpecifiedTypes
	{
	$args = $node->getArgs();
	if (count($args) >= 2) {
	[$hackstackArg, $needleArg] = self::STR_CONTAINING_FUNCTIONS[strtolower($functionReflection->getName())];
	$haystackType = $scope->getType($args[$hackstackArg]->value);
	$needleType = $scope->getType($args[$needleArg]->value);

I am not sure this was done on purpose to prevent annoying PHPStan errors?
(or its just an oversight in the implemetations of the 2 extensions and its missing a offset-assuring narrowing?)

[staabm]

I am not sure this was done on purpose to prevent annoying PHPStan errors?
(or its just an oversight in the implemetations of the 2 extensions and its missing a offset-assuring narrowing?)

just fixed the 2 extensions. as this change also fixes phpstan/phpstan#10847 I think its the right thing todo

[phpstan-bot]

This pull request has been marked as ready for review.

[staabm]

there is another ClassConstFetch bug for scalar constants:
https://phpstan.org/r/25b31c30-04d0-4b02-bc41-f5c8d47af2dd

fix it here or in a new PR?

[VincentLanglet]

A offset array fetch on a constant array can return null if the offset does not exist, see 3v4l.org/us7UK

There is a warning Warning: Undefined array key "something", so it could be considered as an error by PHPStan instead of a valid case which can return NULL.

I feel like this PR doesn't go in the right direction since it basically enforce reportPossiblyNonexistentConstantArrayOffset: true on every project https://phpstan.org/config-reference#reportpossiblynonexistentconstantarrayoffset.

According to the doc with reportPossiblyNonexistentConstantArrayOffset: false, the code

public function doFoo(string $s): int
{
    $a = ['foo' => 1];
    return $a[$s];
}

is valid; but it won't with your PR, since it will report doFoo reports int|null.

[staabm]

I think this PR is related but different.

I am doing this logic on ClassConstFetch only, which means its about hardcoded constant arrays only. I think it won't affect your example - I will test in a few hours when in the train.

[VincentLanglet]

I think this PR is related but different.

I am doing this logic on ClassConstFetch only, which means its about hardcoded constant arrays only. I think it won't affect your example - I will test in a few hours when in the train.

I gave an example based on your example https://3v4l.org/us7UK and the PHPStan doc.

But I can give another. https://phpstan.org/r/cf71d857-d4a7-4d98-ac07-4eabf80e1623
IMHO this snippet:

• Should be valid with reportPossiblyNonexistentConstantArrayOffset: false
• Should report an error on reportPossiblyNonexistentConstantArrayOffset: true

And I assume with your PR, it will report an error because it may returns int|null (therefor reportPossiblyNonexistentConstantArrayOffset will become kinda useless)

[staabm]

less invasive fix in #3460

thanks for your feedback