@daniel and @Pchelolo: I found you are authors of files under \tests\phpunit\data\ParserCache, could you please check this out? Thanks!

In T279942#7011127, @Func wrote:

@daniel and @Pchelolo: I found you are authors of files under \tests\phpunit\data\ParserCache, could you please check this out? Thanks!

The integer sort keys come from ParserCacheSerializationTestCases.php:

		$parserOutputWithMetadata->addCategory( 'category2', 1 );
		$parserOutputWithMetadata->addCategory( 'category1', 2 );

I guess this test data is just wrong, I see no reason for them to be integers. Though the method doesn't document any type, so I suppose until now, this was allowd.

I'll have to take a close took to remind myself how to correctly fix the serialization backwards compatibility test. Old serialized data can in fact contain integers here, the test reports the fact that the type changes unexpectedly during deserialization. We'd have to somehow tell the test that this is OK.

Maybe we should add more comments to define parameter type and provide document for ParserOutput so that phan and other CI tests can take part in.