I think the idea is that's "legal" syntax in the vignettes (which people can run elsewhere, or downgrade manually), while the package only actually requires the specified version to run.

Thanks for flagging @medewitt - this is a good point.

I think from a technical sense what @pearsonca is saying is definitely true but also think we want to be presenting as consistent an experience as possible.

Personally, I would be very happy increasing the dependency to 4.1.0 - especially given that we are so dependent on cmdstanr and cmdstan and that versioning for those is currently difficult. On the other hand if we stuck with the technical dependency declaration then maybe we should update some documentation to indicate this to users (and maybe flag vignettes with a warning?).

Makes sense @pearsonca . It looks like the only non-vignette use is in enw_expectation with new lambda function syntax. That could revert the the old-style function( x, y) syntax and R3.5 minimum wouldn't fail unless someone trying to build the vignettes (i.e., install.packages( build_vignettes = TRUE)` or build from source.

It might just be a nitpick and really a non-issue?

If the >3.5 syntax is used outside vignettes (or other build/test infrastructure, etc), including documentation examples, that is an issue (for now - also on board with ratchetting up required R version).

In the vignette, I'm less fussed about it - indeed, I prefer the 4+ syntax there: its just better and we should normalize/encourage its use. I suppose we might footnote some caveats about using the 4+ syntax in the vignettes.