There are two uses I'm not converting here, that seem to want the
"shortest" behavior. For everything else, I'm going to `zip_equal` since
it's more restrictive.
I wish `zip` were named `zip_shortest`.
Only update the canonical for itself if it has no value, otherwise a
"better" canonical was previously added and the chain will be followed
when deleting specifics.
When a pair of specifics is found to be equivalent, the current logic
would always remove the second one (j indexed) from further processing,
assuming that i was the canonical. That's not always the case, when the
j is the canonical, the i indexed specific should be the one removed.
Update logic to reflect that.
Adding testcase.
Geoff Romer
Jon Ross-Perkins
Alina Sbirlea