Using PathLayer with PathStyleExtension

[comatory]

How can I convince the type system to recognize property getDashArray on PathLayer if I add PathStyleExtension to it?¹ It seems like Layer interface could have optional 3rd generic parameter to somehow extend the interface. I could probably cast the created layer to my own custom type that extends PathLayer interface but casting is not something I'd use if I can avoid it.

Footnotes

1. I followed instructions here on adding the extension ↩