Error with interface inheritance and generics #4019

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1. ondrejmirtes commented on Oct 28, 2020

   

   ondrejmirtes

   on Oct 28, 2020

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   It's a pretty complicated code. This could work once implemented in PHPStan: https://phpstan.org/r/ffea3628-c9f4-46af-92c9-cc50455b51c4

   But personally I'd do something like this: https://phpstan.org/r/083a3acf-398e-458b-a3b8-69e00ddeb1ea
2. lud commented on Oct 28, 2020

   

   lud

   on Oct 28, 2020

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   Hey thank you !

   So the answer would be to write

   /**
    * @template T of PersonInterface
    * @extends WrapperInterface<T>
    */
   

   and

   	/**
   	 * @return T
   	 */
   

   In the wrappers. You say it is not implemented, is there an issue currently ongoing that I can follow to know when it is done ?

   By the way I know it is complicated but we still need to have methods that can return only a specific type, and not a wrapper for any entity type. Oh and an object can implement two wrappers and return a different interface, hence the detailed method names.

   On the other side, the code in my example is from a serializer that does not care which wrapper type we have, it will just call the method depending on the type. But you are right, we still need a way to know which method call at some point if an object implements two wrappers. I will try to simplify the code.
3. ondrejmirtes

   added

   feature-request

   on Oct 28, 2020
4. ondrejmirtes

   added this to the Generics milestone on Oct 28, 2020
5. phpstan-bot commented on Mar 9, 2021

   

   phpstan-bot

   on Mar 9, 2021

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

   @@ @@
   -PHP 7.4 – 8.0 (1 error)
   -==========
   -
   -33: Method Unwrapper::unwrap() should return T of EntityInterface but returns PersonInterface.
   -
   -PHP 7.1 – 7.3
   -==========
   -
   -No errors
   +33: Method Unwrapper::unwrap() should return T of EntityInterface but returns PersonInterface.

   Full report

   Line	Error
   33	Method Unwrapper::unwrap() should return T of EntityInterface but returns PersonInterface.
6. colinodell commented on Jun 3, 2021

   

   colinodell

   on Jun 3, 2021

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   I think I found a related (or perhaps the exact same) issue: https://phpstan.org/r/d7a5d668-29c6-464c-9925-bf6ffb9ba826
7. ondrejmirtes commented on Jun 3, 2021

   

   ondrejmirtes

   on Jun 3, 2021

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   @colinodell Your error is expected, you need @template-covariant instead: https://phpstan.org/r/b143e754-c6cc-4841-bc0d-d50c8e2a1cfb

   👍React with 👍2Reacted by Colin O'Dell and Nicolas Reynis

   ❤️React with ❤️1Reacted by Colin O'Dell
8. ZebulanStanphill commented on Feb 27, 2022

   

   ZebulanStanphill

   on Feb 27, 2022

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   @ondrejmirtes I'm confused as to what the difference is between @template and @template-covariant. The article about generics in PHPStan doesn't even mention the latter, and the docs mention but don't explain the function of either.
9. ondrejmirtes commented on Feb 27, 2022

   

   ondrejmirtes

   on Feb 27, 2022

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   @ZebulanStanphill Check this: #5780 (comment)

   👍React with 👍1Reacted by Zebulan Stanphill
10. phpstan-bot commented on Apr 4, 2023

    

    phpstan-bot

    on Apr 4, 2023

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    @ondrejmirtes After the latest push in 1.10.x, PHPStan now reports different result with your code snippet:

    @@ @@
     PHP 7.1 – 7.3 (1 error)
     ==========
     
    -28: Return type PersonInterface of method PersonWrapperInterface::unwrap() is not compatible with return type EntityInterface of method WrapperInterface::unwrap().
    +28: Return type PersonInterface of method PersonWrapperInterface::unwrap() is not compatible with return type EntityInterface of method WrapperInterface<T of PersonInterface>::unwrap().

    Full report

    PHP 7.4 – 8.0

    No errors

    PHP 7.1 – 7.3 (1 error)

    Line	Error
    28	Return type PersonInterface of method PersonWrapperInterface::unwrap() is not compatible with return type EntityInterface of method WrapperInterface<T of PersonInterface>::unwrap().