In short, the fix I submitted looked at the union ofproperties, but it
really should have looked at the intersection.
Two sytlistic notes. I couldn't find the best way to get the unique
strings of an array like `[...new Set()]` would, so I created a small
helper function, but didn't put it in a great place. Also, before the
second concatenated array of discriminators at least matched the first
in complexity, but now it's much worse. I don't think that section is
particularly easy to read, but I also don't see a significantly reusable
part.
fixes#41759
This diff extends the types checked by
discriminateContextualTypeByObjectMembers and
discriminateContextualTypeByJSXAttributes to also include any optional
components in the type union.
fixes#41759 although it doesn't address the better error reporting for
their last repro, which I'm not sure how to address.
Erik Brinkman