Am I expecting too much from the analyser here?

[pauljherring]

... or am I having another senior moment?

Consider (https://phpstan.org/r/3d974ed6-7d4b-4f91-8dcf-7187222d3004):

<?php declare(strict_types = 1);
/**
* @return no-return
*/
function no_return(){
    echo "Dying\n";
    die(1);
}

/**
* @param int|null $u
* @param int|null $a
* @return array<int, int>
*/
function foo($u=null, $a=null){
    if (is_null($u) && is_null($a)){
        no_return();
	return [0,0]; // line 18
    }
    if ($u){
        $a = $u;
    }else if ($a){
        $u = $a;
    }
    return [$u, $a]; // line 25
}

print_r(foo(1)); // first only
print_r(foo(null,2)); // second only
print_r(foo(1,2)); // both
print_r(foo()); // none - will die() and not return

Output from execution:

Array
(
    [0] => 1
    [1] => 1
)
Array
(
    [0] => 2
    [1] => 2
)
Array
(
    [0] => 1
    [1] => 1
)
Dying

All as I expect.

From the playground:

18 | Unreachable statement - code above always terminates.
-- | --
25 | Function foo() should return array<int, int> but returns array<int, int|null>.

Line 18, I expect - I put it in there to make sure the no-return was being 'honoured.'

But line 25? $a cannot be null if it's getting that far through the function.

Am I expecting too much of the parser here, or is there something here that I'm missing and should be wary of in my own code that's doing this?

[ondrejmirtes]

Yes, the code is very complicated. Feel free to open an issue, I'll file it under dependent types: https://github.com/phpstan/phpstan/milestone/12

[pauljherring]

What's the best way to silence the notification here for the moment, then? @phpstan-ignore-*? @var array{...} $variable?

I'm getting multiple errors for the object being returned from that function, one for each item in the array I try to access in code (cannot access offset 'xxx' on array(...)|false) where false cannot be (it it were, it would have hit the die() in the example above.)

[ondrejmirtes]

Please reproduce your actual problem, the linked playground does not contain "cannot access offset" message.

[pauljherring]

the linked playground does not contain "cannot access offset" message.

ISTR the playground doesn't give the same messages as I get on the command line, but does Offset 'a' does not exist on array<int>|null. seem close enough?

#4695 (comment)

[muglug]

@pauljherring this is a nontrivial problem – I recently wrote an article about how Psalm solves it here: https://psalm.dev/articles/the-truth-matters