GeezerVison

Is type(Placeholder)() acceptable? I would have actually expected that type(MySentinel)() returned the sentinel as for type(None)() but it's not the case since MySentinel is an instance of a sentinel!

Actually, since we're launching beta, it may be ok to change this and see if it breaks something

It's difficult to imagine why people would be doing things like type(Placeholder)() outside of test code, but you never know.

I can see people doing type(Placeholder) for maybe their mypy plugin or whatever, or even for checking if a default is a placeholder instance and do something else with it (though they should assume that it's a singleton so there is no real need to check placeholders through isinstance checks). I think there was a discussion when introducing placeholders about type(P)() returning P but I can't find it (and maybe I remembered wrongly). One could argue that type(Placeholder) could also be used for type annotations =/

This PR is stale because it has been open for 90 days with no activity.

I'm not worried about the type(Placeholder) issue. That is an undocumented, unimportant, and unintended implementation detail.

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