749: Fixed polymorphic variants type issue

[LucasUnplugged]

NOTE: PR #893 should be merged before this one; if that gets rejected, I can redo this one in a fresh branch*.

Tiny PR to address #749; I'm not sure if the typing is quite right, but based on what I'm seeing in the code, it should be. I've manually tested it where I'm seeing the issue, in my local development, and this resolved it, with no adverse side-effects (that I have seen).

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* — I did this for my own convenience, to be able to create a build that has both of these fixes, which are disrupting my TS workflow. As long as #893 gets merged first, this should have no impact on the final result.

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[LucasUnplugged]

Not sure why this isn't picking up that the base branch changed, @hadihallak 🙈

Let me know if you'd rather a do a fresh rebase off canary, to only show this actual change.

[csantos-nydig]

#893 is merged, could this one be merged now? Thanks

[hadihallak]

Hey @LucasUnplugged Thanks for your effort working on this PR. I did some tests and found some cases where the behaviour of the polymorphic as changed so I dug deeper and was able to solve the issue from the area it originated from in #954

Thanks again for your effort and for helping me fix this issue 🙏

Closing in favor of #954