Comment by dvt

> That made me wonder if ABCs could “hijack” a pattern match. Something like this:

I guess the word "hijack" is used loosely for rhetorical effect here because this seems to be working as intended, and it's not even remotely the most dangerous footgun in Python. The problem (if any) is with `isinstance`, and not the pattern matching. `isinstance` should probably explicitly work with ABCs (via flag or something) because I do agree it's a bit weird that it takes the ABC's `__subclasshook__` as gospel by default.