Union type does not work correctly with property

[mvorisek]

continue of #4377

In extreme case, type can be defined by A|object to explicitly state we expect A, but still allow any object.

When B extends A, if a property contains A, it can contain any child of A, so mentioning B in the same type is superfluous information, that's why it's reduced to just A.

This is enough for parameter validation, but when this type is used for object access, this information is not superfluous. This is also how IDEs work (checked Netbeans and PHPStorm).

Please rethink my POV for a few seconds.

[ondrejmirtes]

You still don't get it. object means it can be any object. The fact it can sometimes be A is already contained in object.

[mvorisek]

For setting a variable/param, this is correct.

For accessing a variable/param, we need to keep the extra information. instanceof everywhere is one way to overcome this, but not practical for situations when the more specific type is expected except some special case. This is also how other tools work.

[ondrejmirtes]

You don't get you're opening yourself to type errors.

You can run PHPStan on level 6 or lower if you don't want to see union type-related errors.

But PHPStan is correct here if you want to be protected against errors when using union types.

[mvorisek]

If this normalization would be done for level >= 7, I would be super fine with it.

Unfortunatelly, it is currently applied also for level 2, see https://phpstan.org/r/35f7458d-3aa2-476f-a528-17a271db3203

[ondrejmirtes]

This type of error is severe enough in my eyes it's reported sooner.

[mvorisek]

I think this issue is related with https://phpstan.org/r/b4d55043-abda-445e-ac8b-b78f8552a745 .