The vctrs package defines new notions of prototype and size that are used to provide tools for consistent and well-founded type-coercion and size-recycling, and are in turn connected to ideas of type- and size-stability useful for analyzing function interfaces. See the vctrs site at https://vctrs.r-lib.org/ for more information.
This package is imported directly to encourage development using the standardized helpers it provides. This decision may be re-thought at a later date.