collapse version 2.1.1

• alloc(list(1), 2) now gives list(1, 1) instead of list(list(1), list(1)), which can still be generated with alloc(list(1), 2, simplify = FALSE). This change also affects ftransform()/fmutate(), making, e.g., fmutate(data, y = list(1)) consistent with dplyr::mutate(data, y = list(1)). Thanks @MattAFiedler (#753).

• fslice() now works with sf data frames.