Using @psalm-if-this-is for generic class conversion

[shira-374]

Hello.

I'm trying to to add some conversion utility methods to a generic Collection class, such as asObjects() returning a more specific collection type.

I've tried to use @psalm-if-this-is self<object> to prevent asObjects() from being called on an incompatible collection type, but I've ran into issues when the template is invariant:

https://psalm.dev/r/485bd7707a

The InvalidTemplateParam could be ignored, but I'm also getting IfThisIsMismatch on the call site which is a problem.

Since @psalm-if-this-is doesn't change the type of $this after the call, shouldn't it be able to assert any type regardless of variance?