How to fix "Unable to resolve the template type T" issue in library

[pkruithof]

Support question

In a recent update, Doctrine added psalm/phpstan annotations, which now makes phpstan find the following error:

https://phpstan.org/r/e462e0f9-abc4-44bc-8a9a-80aca2717980

I've tracked down the change that most likely causes this, and it seems the Doctrine people could not fix this error so they put this error in the ignore section: https://github.com/doctrine/dbal/pull/3977/files#diff-0847156bd64b0de0f4d91da2394ec0e8R89-R92

My question is: what is this error exactly, is there a way to fix or work around it and if not: do I really need to ignore an error caused by a third-party library?

[ondrejmirtes]

The full PHPDoc of the method is:

     * @param  array{wrapperClass?: class-string<T>} $params
     * @param Configuration|null                    $config       The configuration to use.
     * @param EventManager|null                     $eventManager The event manager to use.
     *
     * @throws Exception
     *
     * @phpstan-param mixed[] $params
     * @psalm-return ($params is array{wrapperClass:mixed} ? T : Connection)
     * @template T of Connection

So the T is there for the conditional @psalm-return tag. Not sure why the @param for $params is overriden for PHPStan with @phpstan-param mixed[] $params but the result is that PHPStan sees @template T of Connection but the T isn't present in @param so it doesn't have a way to infer what T should be. The signature is basically incomplete and broken from the point of view of PHPStan.

The correct way to fix this would be either to:

1. Remove @phpstan-param mixed[] $params and see what error it causes and what's the root issue, report it to PHPStan's issue tracker (here) and have it fixed :)
2. ...or add @phpstan-return Connection without any T involved which should already have been there in the first place...

The easiest way is to send a PR to doctrine/dbal with my 2nd suggestion, they should accept it.

[pkruithof]

Will do, thank you for clarifying 👍

[ondrejmirtes]

I realize that @phpstan-return Collection might still not help to get rid of the issue so maybe 1) with some investigation involved might be a better bet.

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