[BioC] GenomicRanges functions unlist(GRangesList(x)) throw an error when used from an installed package

[Simon Coetzee]

When I install a package of my own creation that uses the
GenomicRanges package, I get an error:

Error in unlist(x) : argument not a list

the example function that throws this error is:

TestFunction <- function (z)
{
    x <- GRangesList(z)
    y <- unlist(x)
    return(list(x, y))
}

I have created a package that contains this function, and an example
dataset where this occurs.  It resides at
http://dl.dropbox.com/u/1196228/TestingGRangesListUnlist_1.0.tar.gz

There is no  problem when I enter the above commands, outside of the
context of the function, or if I load the function into R through the
source() command.  It only occurs if I install the package, and load
it in via the library() command.

example steps to recreate the issue:
1. Install package:
R CMD INSTALL TestingGRangesListUnlist_1.0.tar.gz
2. Start R
3. library(TestingGRangesListUnlist)
4. data(test.data)
5. TestFunction(test.data)
Error in unlist(x) : argument not a list

output of traceback():
2: unlist(x)
1: TestFunction(test.data)

output of sessionInfo():
R version 2.14.0 (2011-10-31)
Platform: x86_64-unknown-linux-gnu (64-bit)

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

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

other attached packages:
[1] TestingGRangesListUnlist_1.0 GenomicRanges_1.6.4
IRanges_1.12.5               setwidth_0.9-4
colorout_0.9-9

loaded via a namespace (and not attached):
[1] tools_2.14.0

Thanks for reading.

Simon Coetzee
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