vctrs_list_of and subset assignment

[krlmlr]

Do I need to implement more methods to make subset assignment work with "list of" classes? I wonder why my vec_cast() implementation doesn't fire.

Works with atomic vector

library(vctrs)
new_percent <- function(x = double()) {
  vec_assert(x, double())
  new_vctr(x, class = "vctrs_percent")
}

vec_ptype2.vctrs_percent.vctrs_percent <- function(x, y, ...) new_percent()

vec_cast.vctrs_percent.vctrs_percent <- function(x, to, ...) x

pct <- new_percent(1.5:10)
pct[1] <- 2

Fails with list_of

library(vctrs)
new_percent <- function(x = list()) {
  vec_assert(x, list())
  new_list_of(x, double(), class = "vctrs_percent")
}

vec_ptype2.vctrs_percent.vctrs_percent <- function(x, y, ...) new_percent()

vec_cast.vctrs_percent.vctrs_percent <- function(x, to, ...) {
  message("Casting")
  x
}

pct <- new_percent(as.list(1.5:10))
pct[1] <- new_percent(list(2))
#> Error: Can't convert <list_of<double>> to <list_of<double>>.

^{Created on 2021-04-26 by the reprex package (v2.0.0)}