order(x, decreasing=TRUE) is broken on CompressedIntegerList objects

[hpages]

library(IRanges)
x1 <- IntegerList(15:11, 21:28, compress=TRUE)

order(x1)
# IntegerList of length 2
# [[1]] 5 4 3 2 1
# [[2]] 1 2 3 4 5 6 7 8

order(x1, decreasing=TRUE)  # BROKEN!
# IntegerList of length 2
# [[1]] 13 12 11 10 9
# [[2]] 3 2 1 -4 -3 -2 -1 0

This in turn breaks sort( , decreasing=TRUE):

sort(x1, decreasing=TRUE)
# Error in seq_len(x_NROW)[i] : 
#   only 0's may be mixed with negative subscripts

Everything looks fine with a SimpleIntegerList object:

x2 <- IntegerList(15:11, 21:28, compress=FALSE)

order(x2)
# IntegerList of length 2
# [[1]] 5 4 3 2 1
# [[2]] 1 2 3 4 5 6 7 8

order(x2, decreasing=TRUE)
# IntegerList of length 2
# [[1]] 1 2 3 4 5
# [[2]] 8 7 6 5 4 3 2 1

sort(x2, decreasing=TRUE)
# IntegerList of length 2
# [[1]] 15 14 13 12 11
# [[2]] 28 27 26 25 24 23 22 21

sessionInfo():

> sessionInfo()
R version 3.6.0 Patched (2019-05-02 r76454)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 16.04.5 LTS

Matrix products: default
BLAS:   /home/hpages/R/R-3.6.r76454/lib/libRblas.so
LAPACK: /home/hpages/R/R-3.6.r76454/lib/libRlapack.so

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

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

other attached packages:
[1] IRanges_2.19.16     S4Vectors_0.23.23   BiocGenerics_0.31.6

loaded via a namespace (and not attached):
[1] compiler_3.6.0