Erroneous return type matched when using multiple interfaces using self as return type

[Ocramius]

See https://psalm.dev/r/8170d89c39:

<?php

interface Id {}
interface Foo
{
    public function id() : Id;
}

class ImplementsFoo implements Foo, Id
{
     public function id() : self
     {
          return $this;
     }
}

Reports:

Psalm output (using commit ae2c671):

ERROR: MethodSignatureMismatch - 9:7 - Method ImplementsFoo::id with return type 'ImplementsFoo' is different to return type 'Id' of inherited method Foo::id

Even simpler in https://psalm.dev/r/494e02869f:

Psalm output (using commit ae2c671):

ERROR: MethodSignatureMismatch - 8:7 - Method ImplementsFoo::id with return type 'ImplementsFoo' is different to return type 'Foo' of inherited method Foo::id

Reports:

<?php

interface Foo
{
    public function id() : self;
}

class ImplementsFoo implements Foo
{
     public function id() : self
     {
          return $this;
     }
}

Related: sebastianbergmann/phpunit#3120

[Ocramius]

Ah... this is a PHP 7.4 thing, my bad.

Working on bleeding edge spoiled me.

[muglug]

Yeah I'll disable this when Psalm detects it's running on 7.4

[muglug]

I have other features (e.g. arrow functions) ready to ship, but I don't want to bump the upstream dependency (nikic/php-parser) version until necessary, once 7.4 is publicly available

[zmitic]

@muglug Can you put arrow functions support in master or fork? I would really like to get rid of errors like this:

[Ocramius]

@zmitic a bit of patience: PHP 7.4 isn't even out yet :-)

[zmitic]

@Ocramius I know, I know... but I love it 😄

Above example is just one small thing. More complex are coming tomorrow when I put entity accessors: https://github.com/hitechcoding/strict-form-mapper-bundle/blob/master/docs/accessors.md

Arrow functions really makes these things easier.

[muglug]

@zmitic the branch (arrow-functions) already exists, I've just rebased it on top of latest master.

I'll add Psalm compatibility about a week before PHP's 7.4 release date.

[zmitic]

@muglug Thank you, a lot! My errors are gone now.