Generics and static type

[amorimjuliana]

Bug report

PHPStan complains about returning a subclass of a generic class that is compatible with the return type.

Code snippet that reproduces the problem

https://phpstan.org/r/df0e168c-f207-4db8-9d24-e1324e287652

Expected output

No errors.

[muglug]

Note this is only a false-positive if the class that makes Enum<static> into an explicit collection is declared final (as in the example given).

Otherwise this pattern can lead to runtime errors: https://3v4l.org/E78KQ

[amorimjuliana]

Yes, and that should be de case for all enums and enum sets :)

[muglug]

Yeah, just making a note for whoever tries to fix this :)

[Majkl578]

Another, simplified reproducer: https://phpstan.org/r/0a7c0617-a38b-42f2-b1b1-d059e0a80715

[ComiR]

I think this is the same problem, or at least related to the problem, I am having:
https://phpstan.org/r/72320485-b6ac-477d-8cac-6ffacd813de6

[ondrejmirtes]

@ComiR You're breaking the interface contract. Your code wuold only be valid if Hello was a final class (but PHPStan currently complains which is a bug but a different one).

If you create class Foo extends Hello but still return Hello from Foo::create() (which is what the method will do if not overriden) then World::createGreeter(Foo::class); will return Hello but not Foo which breaks the contract.

[ComiR]

Thanks @ondrejmirtes, I forgot to make the class Hello final in this example. The error stays the same: https://phpstan.org/r/19d1dd4a-1535-4ca5-9cd9-779743b92d5c

[ondrejmirtes]

Yeah, that's a bug, but you can work around it: https://phpstan.org/r/7e2056c0-7b2e-4cfe-bf95-3d445e542406

[phpstan-bot]

@amorimjuliana PHPStan now reports different result with your code snippet:

@@ @@
-42: Return type (CustomEnumSet) of method CustomEnum::all() should be compatible with return type (EnumSet<static(Enum)>) of method Enum::all()
+PHP 7.4 – 8.0 (1 error)
+==========
+
+42: Return type (CustomEnumSet) of method CustomEnum::all() should be compatible with return type (EnumSet<static(Enum)>) of method Enum::all()
+
+PHP 7.1 – 7.3 (1 error)
+==========
+
+42: Return type CustomEnumSet of method CustomEnum::all() is not compatible with return type EnumSet of method Enum::all().

Full report

PHP 7.4 – 8.0 (1 error)

Line	Error
42	Return type (CustomEnumSet) of method CustomEnum::all() should be compatible with return type (EnumSet<static(Enum)>) of method Enum::all()

PHP 7.1 – 7.3 (1 error)

Line	Error
42	Return type CustomEnumSet of method CustomEnum::all() is not compatible with return type EnumSet of method Enum::all().

[phpstan-bot]

@Majkl578 After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-13: Method Test::foo() should return static(Test) but returns Test.
+No errors

[phpstan-bot]

@ondrejmirtes After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-No errors
+19: Return type (Hello) of method Hello::create() should be covariant with return type (static(Greeter)) of method Greeter::create()

Full report

Line	Error
19	Return type (Hello) of method Hello::create() should be covariant with return type (static(Greeter)) of method Greeter::create()

[phpstan-bot]

@ComiR After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-19: Return type (Hello) of method Hello::create() should be covariant with return type (static(Greeter)) of method Greeter::create()
+No errors

[phpstan-bot]

@amorimjuliana After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-42: Return type (CustomEnumSet) of method CustomEnum::all() should be compatible with return type (EnumSet<static(Enum)>) of method Enum::all()
+PHP 7.4 – 8.0
+==========
+
+No errors
+
+PHP 7.1 – 7.3 (1 error)
+==========
+
+42: Return type CustomEnumSet of method CustomEnum::all() is not compatible with return type EnumSet of method Enum::all().

Full report

PHP 7.4 – 8.0

No errors

PHP 7.1 – 7.3 (1 error)

Line	Error
42	Return type CustomEnumSet of method CustomEnum::all() is not compatible with return type EnumSet of method Enum::all().

[ondrejmirtes]

Fixed by: phpstan/phpstan-src@d225a68

[github-actions]

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