Also, the test should show that false doesn't report an error, and true does. @dataProvider is ideal for that.

I tried to find some test where checkExplicitMixed is tested but all I found is just tests for specific bugs so I was not sure how this test should look like. Should I add new testCheckImplicitMixed() with some minimal input? Or copy some basic method like

Don't copy this huge test, that's a maintenance nightmare :) Just add a small one, to show the differences.

OK I will do it tomorrow ;-)

Test added. Based on explicit mixed test I found in CallMethodsRuleTest.

I have another suggestion. I would welcome option that would allow casting implicit/explicit mixed. It is currently not allowed when checkXMixed is used. Maybe add new option allowCastMixed or two options allowCastXMixed? I think it would be enough to check it in findTypeToCheck of RuleLevelHelper right?

I really like how you made these two options independent :) Thank you very much!

About your suggestion - I don't get it, can you give me a code sample?

At level 9 casting explicit mixed to string is not allowed. With implicit mixed option it would not be allowed for implicit mixed too.

https://phpstan.org/r/33a99c16-a95b-41c9-94bf-30e8404dd8cf

If you want you can just ignore this with a regex. But IMHO it's a valid error.

That is what we do now. I just think it would be nice to have built-in support for ignoring such errors because it is often used. BUt I can live with just ignoring it.

I just found out problems with checkImplicitMixed option. See https://phpstan.org/r/fbdaf0db-cf77-4cce-827f-63ca9facfaee

It seems that access lelel-2 key access to array with undefined structure always raises error even ehoen used in context where it is valid like in isset or setting array value.

But I do not know how to fix that.

@ondrejmirtes I am not sure what to do now. I can prepare failing test but I do not know where to even start with fixing it.

It's expected, and I think it's not specific to implicit mixed. You can see the same thing with explicit mixed: https://phpstan.org/r/50a04edc-93f4-4871-981a-8d1147500d02

I think this error is desirable. You can fatal-crash PHP with some types and this construct: https://3v4l.org/oPMeC

But here it is known it is an array and it works without errors on level 9.

Because static $cache is implicit mixed on purpose. We'd have to have some analysis of the whole function body to figure out what types it can be. There's an open issue for it.

Oh I see. Problem is that you do not know if value of static is not set to someting completely different later and picked up in next call.

Please send a documentation update here: https://phpstan.org/config-reference#stricter-analysis

Editing the page: https://github.com/phpstan/phpstan/edit/1.8.x/website/src/config-reference.md

Ok I will write it

See phpstan/phpstan@1.8.x...MartinMystikJonas:phpstan:patch-1

Please open a PR :)