droplevels on Factor produces warning

[MalteThodberg]

The new raw-based Factors are great!

However, the droplevels method produces a warning. Here's an example using the man page for Factor:

library(IRanges)
set.seed(123)
ir0 <- IRanges(sample(5, 8, replace=TRUE), width=10,
               names=letters[1:8], ID=paste0("ID", 1:8))

## Use explicit levels:
ir1 <- IRanges(1:6, width=10)
F1 <- Factor(ir0, levels=ir1)
droplevels(F1)

Gives the warning:

Warning message:
In storage.mode(index) <- "raw" :
  out-of-range values treated as 0 in coercion to raw

Session info for reference:

R version 4.4.1 (2024-06-14)
Platform: aarch64-apple-darwin20
Running under: macOS Sonoma 14.5

Matrix products: default
BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: Europe/Copenhagen
tzcode source: internal

attached base packages:
[1] stats4    stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] IRanges_2.38.1      S4Vectors_0.42.1    BiocGenerics_0.50.0

loaded via a namespace (and not attached):
[1] BiocManager_1.30.23 compiler_4.4.1      cli_3.6.3           tools_4.4.1        
[5] rstudioapi_0.16.0   pkgload_1.4.0       rlang_1.1.4