Fix ArrayColumnFunctionReturnTypeExtension producing array key types

[jlherren]

Fixes phpstan/phpstan#6682

[ondrejmirtes]

Also - what happens when the column isn't a valid array key? Maybe an opportunity for a new rule later?

[ondrejmirtes]

I don't get it. Array gets cast to integer?

[BitScout]

See https://sandbox.onlinephpfunctions.com/code/381d0182b85cc698b02b18b82cd9dae0da3f7a00
I intentionally used 'foo' instead of 'type' in the array_column call in this example. So this seems to be the behaviour.

[jlherren]

Yes exactly. In PHP < 8, whenever a value cannot be used as an array key (either because it is an array, or the value is missing entirely), the next available integer array key is used (as if you'd do $arr[] = $value). In PHP >= 8, using an array value as key causes a fatal error, which of course is an opportunity for PHPStan to detect in the future.

[ondrejmirtes]

FYI I miss an if for this behaviour in this extension. Feel free to add in a future PR :)

[ondrejmirtes]

Thank you!