Tom

> I'm assuming the typing is blowing up because of unsupported options Yes, this is the case. I've got a PR I am about to submit to OTP to resolve...

Okay, I've suppressed that Dialyzer warning for now, and commented next to it with a link to the PR to fix it. I've also added unit tests around incremental mode...

@ferd, what are your thoughts on the state of this PR now?

I am definitely quite new to this mechanism, so it's very possible that I am misusing the functionality somehow. In that case, maybe we can tweak the docs to make...

Seems related to #6117 in the sense that this is Dialyzer collapsing types together to cause an unexpected warning/error

My gut says the most robust solution is to make [`dialyzer_behaviours:check_callback/6`](https://github.com/erlang/otp/blob/master/lib/dialyzer/src/dialyzer_behaviours.erl#L122) not use subtyping (because that seemingly inherently breaks the invariant that Dialyzer "simplification" is always safe to apply), and...

> I agree that this looks like a bug, and the proposed fix is exactly on the right track. Great, thanks. I'll take a look at implementing that and putting...

I've put up #6243, where I implemented my proposal above to switch from subtype checking to overlap checking (and also special casing specs that return `none()`, as per a test...

> Please squash the commits. Oops! Thanks, done.

Thanks @michalmuskala for your suggestion to try this