Feature request

PHPStan currently allows two types of variance for template types in class-likes: @template (invariant) and @template-covariant (covariant). PHPStan also internally supports the third type: contravariant, but lacks support for specifying it for class-likes with a PHPDoc.

This is, however, sometimes useful:

/**
 * @template-contravariant T
 */
interface Comparator
{
    /**
      * @param T $e1
      * @param T $e2
      */
    public function compare($e1, $e2): int;
}

The implementation should theoretically be trivial: add support for @template-contravariant tag in phpdoc-parser, then correctly parse those tags into respective variance on phpstan side. As far as I understand, the support has been there internally for a long time already.

We'll also need to modify https://github.com/phpstan/phpstan-src/blob/f8be122188aa6721cec9872bd61676ee150a5311/src/Rules/Generics/VarianceCheck.php#L53 to check contravariance in parameters.

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