/cc @kbond :)
Note that wiring union|intersection types might very well belong to AutowirePass (reordering and filtering what TypeReference::getType() returns to resolve them there.

@gmichard, to clarify, are you trying to "autowire" getSomethingOrOther?

@nicolas-grekas can you confirm that union types are not supported by ServiceSubscriberInterface? I never got a clear answer here: #42238 (comment) (quick test in 5.4 shows me no)

I'm thinking to skip methods without \ReflectionNamedType in 4.4+ and in 5.4+, when using the SubscribedService trait, throw an exception. At least until a time that ServiceSubscriberInterface supports union/intersection services.

can you confirm that union types are not supported by ServiceSubscriberInterface

it's never been specified, but it's trivial to define them so I think we should consider them as defined actually:
?Foo|Bar / ?Foo&Bar.

the leading ? is needed as a flag to express that a key is optional.
Then AutowirePass could parse those, remove built-in types, order, and relying the existing logic to autowire

Ok, this will be in 5.4+ only, correct?

In 4.4+ and 5.4's deprecation layer I'm thinking we should ignore union/intersection types.

to clarify, are you trying to "autowire" getSomethingOrOther?

@kbond

• autowire is enabled (autoconfigure is enabled too, for what it's worth)
• But this method is not a really a service location. It's a regular method for internal usage, with no argument and with many return types.

A more complete example could be:

<?php
// File: src/Service/ExampleHandler.php

// use [...]

class ExampleHandler implements ServiceSubscriberInterface
{
    use ServiceSubscriberTrait;

    /**
     * A regular method that return a object type or another.
     * 
     * This method doesn't need to use the service locator.
     */
    private function getSomethingOrOther(): SomethingInterface|Other
    {
        /** @var $something SomethingInterface|null */
        $something = $this->somethingProvider()->load();

        if (null !== $something) {
            return $something;
        }

        return new Other();
    }

    /**
     * A Service Locator (thanks to the autowiring and the ServiceSubscriberTrait)
     */
    private function somethingProvider(): SomethingProviderInterface
    {
        return $this->container->get(__METHOD__);
    }
}

The both methods matches the criteria to add it as subscribed services (non-static, non-internal, etc.).
Perhaps there is a way to indicate that a method is not a service locator (and that its return type doesn't need to be added to the subscribed services array)?

I hope this words are clarifying and not confusing.
(And really really thank you for all your work and your reactivity!)

For 5.4+ yes @kbond

@gmichard Ok, that's what I thought. Keep in mind that you'll also have trouble with non-union return types (ie getSomethingOrOther(): UserInterface). #42238 fixes but only on 5.4 and when using the new attribute. Really, this issue would be fixed by #42238 as well - you wouldn't put the attribute on getSomethingOrOther().

@nicolas-grekas, #43922 provides a fix for this specific issue on 4.4 - do you not want to fix on that branch?