parent return type declaration is not handled correctly

[6ecuk]

Q	A
phpunit-mock-objects version	6.0.0
PHPUnit version	7.0.1
PHP version	7.2.2
Installation Method	Composer

Good evening. Tried run project on PHP 7.2 and unit tests failed with strange behavior
PHP Fatal error: Declaration of Mock_TestId_baa7a0d1::generate(): \TestId must be compatible with \BaseId::generate(): \Id in /var/www/html/vendor/phpunit/phpunit-mock-objects/src/Generator.php(603) : eval()'d code on line 1

Class example:

declare(strict_types=1);
abstract class Id
{
    protected $uid;

    /**
     * Id constructor.
     * @param UuidInterface $uid
     */
    public function __construct(UuidInterface $uid)
    {
        $this->uid = $uid;
    }

    abstract public static function generate();
}
class BaseId extends Id
{
    /**
     * @return Id
     */
    public static function generate(): parent
    {
        return new static(Uuid::uuid1());
    }
}
class TestId extends BaseId
{

}

Class generated from private function evalClass in Generator.php

class Mock_TestId_3b9eb4f3 extends TestId implements PHPUnit\Framework\MockObject\MockObject
{
    private $__phpunit_invocationMocker;
    private $__phpunit_originalObject;
    private $__phpunit_configurable = ['generate', 'fromstring', 'frombytes', 'fromint', 'tostring', '__tostring', 'isequalas', 'getuid'];

    public function __clone()
    {
        $this->__phpunit_invocationMocker = clone $this->__phpunit_getInvocationMocker();
    }

    public static function generate(): parent
    {
        throw new \PHPUnit\Framework\MockObject\BadMethodCallException('Static method "generate" cannot be invoked on mock object');
    }

    public static function fromString(string $Id): Id
    {
        throw new \PHPUnit\Framework\MockObject\BadMethodCallException('Static method "fromString" cannot be invoked on mock object');
    }

    public static function fromBytes(string $Id): Id
    {
        throw new \PHPUnit\Framework\MockObject\BadMethodCallException('Static method "fromBytes" cannot be invoked on mock object');
    }

    public static function fromInt(int $id): Id
    {
        throw new \PHPUnit\Framework\MockObject\BadMethodCallException('Static method "fromInt" cannot be invoked on mock object');
    }

    public function toString(): string
    {
        $arguments = [];
        $count     = func_num_args();

        if ($count > 0) {
            $_arguments = func_get_args();

            for ($i = 0; $i < $count; $i++) {
                $arguments[] = $_arguments[$i];
            }
        }

        $result = $this->__phpunit_getInvocationMocker()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation\ObjectInvocation(
                'Id', 'toString', $arguments, 'string', $this, false
            )
        );

        return $result;
    }

    public function __toString(): string
    {
        $arguments = [];
        $count     = func_num_args();

        if ($count > 0) {
            $_arguments = func_get_args();

            for ($i = 0; $i < $count; $i++) {
                $arguments[] = $_arguments[$i];
            }
        }

        $result = $this->__phpunit_getInvocationMocker()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation\ObjectInvocation(
                'Id', '__toString', $arguments, 'string', $this, false
            )
        );

        return $result;
    }

    public function isEqualAs(Id $other): bool
    {
        $arguments = [$other];
        $count     = func_num_args();

        if ($count > 1) {
            $_arguments = func_get_args();

            for ($i = 1; $i < $count; $i++) {
                $arguments[] = $_arguments[$i];
            }
        }

        $result = $this->__phpunit_getInvocationMocker()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation\ObjectInvocation(
                'Id', 'isEqualAs', $arguments, 'bool', $this, false
            )
        );

        return $result;
    }

    public function getUid(): Ramsey\Uuid\UuidInterface
    {
        $arguments = [];
        $count     = func_num_args();

        if ($count > 0) {
            $_arguments = func_get_args();

            for ($i = 0; $i < $count; $i++) {
                $arguments[] = $_arguments[$i];
            }
        }

        $result = $this->__phpunit_getInvocationMocker()->invoke(
            new \PHPUnit\Framework\MockObject\Invocation\ObjectInvocation(
                'Id', 'getUid', $arguments, 'Ramsey\Uuid\UuidInterface', $this, false
            )
        );

        return $result;
    }

    public function expects(\PHPUnit\Framework\MockObject\Matcher\Invocation $matcher)
    {
        return $this->__phpunit_getInvocationMocker()->expects($matcher);
    }

    public function method()
    {
        $any     = new \PHPUnit\Framework\MockObject\Matcher\AnyInvokedCount;
        $expects = $this->expects($any);

        return call_user_func_array([$expects, 'method'], func_get_args());
    }

    public function __phpunit_setOriginalObject($originalObject)
    {
        $this->__phpunit_originalObject = $originalObject;
    }

    public function __phpunit_getInvocationMocker()
    {
        if ($this->__phpunit_invocationMocker === null) {
            $this->__phpunit_invocationMocker = new \PHPUnit\Framework\MockObject\InvocationMocker($this->__phpunit_configurable);
        }

        return $this->__phpunit_invocationMocker;
    }

    public function __phpunit_hasMatchers()
    {
        return $this->__phpunit_getInvocationMocker()->hasMatchers();
    }

    public function __phpunit_verify($unsetInvocationMocker = true)
    {
        $this->__phpunit_getInvocationMocker()->verify();

        if ($unsetInvocationMocker) {
            $this->__phpunit_invocationMocker = null;
        }
    }
}