dbl <- vctrs::new_vctr(1,  inherit_base_type = TRUE)
int <- vctrs::new_vctr(1L, inherit_base_type = TRUE)

library(ggplot2) # CRAN version

scale_type(dbl)
#> Don't know how to automatically pick scale for object of type
#> <vctrs_vctr/double>. Defaulting to continuous.
#> [1] "continuous"
scale_type(int)
#> Don't know how to automatically pick scale for object of type
#> <vctrs_vctr/integer>. Defaulting to continuous.
#> [1] "continuous"

devtools::load_all("~/packages/ggplot2") # This PR
#> ℹ Loading ggplot2

scale_type(dbl)
#> [1] "continuous"
scale_type(int)
#> [1] "continuous"