findMatches doesn't work correctly for DataFrames

[LTLA]

Consider the following:

library(S4Vectors)
a <- DataFrame(A=LETTERS)
b <- a[5:1,,drop=FALSE]
match(b, a) # gives me 5:1, so far so good.
findMatches(b, a)
## Error in .Call2("Hits_new", Class, from, to, nLnode, nRnode, revmap_envir,  : 
##   'to(hits)' must contain non-NA values >= 1 and <= 'nRnode(hits)'
countMatches(b, a)
## [1]  1 NA NA NA NA

If I had to guess, probably these two invocations are trying to call some kind of List method rather than using DF's match method.

Session info

R Under development (unstable) (2019-10-31 r77342)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.3 LTS

Matrix products: default
BLAS:   /home/luna/Software/R/trunk/lib/libRblas.so
LAPACK: /home/luna/Software/R/trunk/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] parallel  stats4    stats     graphics  grDevices utils     datasets 
[8] methods   base     

other attached packages:
[1] S4Vectors_0.25.8    BiocGenerics_0.33.0

loaded via a namespace (and not attached):
[1] compiler_4.0.0