Test for a charvec
Value
`TRUE` if `x` is a `charvec` ALTREP vector, `FALSE` otherwise. Note a materialized `charvec` is still a `charvec`; serialization of a materialized `charvec` round-trips to a plain character vector.
Examples
is_charvec(charvec("a"))
#> [1] TRUE
is_charvec(letters)
#> [1] FALSE