> df <- tibble(a = 1, b = 2)
> names(df) <- NULL
> names(df) <- "c"
Warning: The `value` argument of ``names<-`()` must have the same length as `x` as of tibble 3.0.0.
`names` must have length 2, not 1.

Warning: The `value` argument of ``names<-`()` can't be empty as of tibble 3.0.0.
Column 2 must be named.

> names(df) <- c("..1", "..2")
