It looks like this is because the default values for optional parameters are deduced from the values passed to required parameters.

I'm not sure I follow.

On second reading, this code isn't doing what I thought it was doing. I'd (mistakenly) concluded unpassed colors were filled in by referencing supplied colors - but that's not happening.

My brain must have been autocompleting with what's coming in the colorScheme generator.

Good point. I expect the complete colorScheme generator will probably be what solves this issue.

It is just following the chain. My thinking was that if the user did supply a tertiary color, but not a tertiaryContainer, it should fall back to the tertiary they gave us instead of the secondary. If they supply neither, then it will fallback to the secondary color.

I think I'm coming down on this side, as well; as long as we don't bump into any invalid const type of issues while implementing the optional parameter juggling.

I think so too. Wonder how this interacts with the idea of fallback. Is an m3 color scheme created with these constructors then: m3 baseline + provided nullable properties + fallbacks for non-provided nullable properties?