setMethods/setGeneric problem when R CMD CHECK'ing a package

R-helpers:

I'm trying to build a package, but I'm a bit new to the whole S3/S4
methods concept.  I'm trying to add a new definition of the zoo
function "as.yearmon", but I'm getting the following error when it
gets to this point during a package install:

***

R CMD INSTALL STARStools
* installing to library
?/Library/Frameworks/R.framework/Versions/2.13/Resources/library?
WARNING: omitting pointless dependence on 'R' without a version requirement
* installing *source* package ?STARStools? ...
** R
** inst
** preparing package for lazy loading
Loading required package: sp
raster version 1.9-5 (28-July-2011)
Geospatial Data Abstraction Library extensions to R successfully loaded
Loaded GDAL runtime: GDAL 1.8.0, released 2011/01/12
Path to GDAL shared files:
/Library/Frameworks/GDAL.framework/Versions/1.8/Resources/gdal
Loaded PROJ.4 runtime: Rel. 4.7.1, 23 September 2009
Path to PROJ.4 shared files: (autodetected)

Attaching package: 'zoo'

The following object(s) are masked from 'package:base':

    as.Date

Creating a new generic function for "as.Date" in "STARStools"
Creating a new generic function for "as.list" in "STARStools"
Error in setGeneric(f, where = where) :
  must supply a function skeleton, explicitly or via an existing function
Error : unable to load R code in package 'STARStools'
ERROR: lazy loading failed for package ?STARStools?
* removing ?/Library/Frameworks/R.framework/Versions/2.13/Resources/library/STARStools?
* restoring previous
?/Library/Frameworks/R.framework/Versions/2.13/Resources/library/STARStools?

***

# Note that these "require" statements do not appear in the code, but
appear in the DESCRIPTION file:
require("sp")
require("zoo")

# Here are the class definitions (filename AAAclassdefinitions.R):
setClass("SpatialPointsDataFrameList",representation(list="list"),contains=c("SpatialPointsDataFrame"))
setClass("SpatialPointsDataFrameListZoo",contains=c("SpatialPointsDataFrameList"))

# And here is where it is getting hung up. filename
"as.yearmon.SpatialPointsDataFrameListZoo_SpatialPointsDataFrameListZoo.R"

setMethod("as.yearmon",
    signature(x = "SpatialPointsDataFrameListZoo"),
	as.yearmon.SpatialPointsDataFrameListZoo
)

# Filename "as.yearmon.SpatialPointsDataFrameListZoo.R"
as.yearmon.SpatialPointsDataFrameListZoo=function(x,...)
{
	newlist=mapply(zoo:::as.yearmon,x at list,MoreArgs=list(...),simplify=FALSE)
	x at list=newlist
	return(x)
}

Thoughts?

--j

Jonathan A. Greenberg, PhD
Assistant Project Scientist
Center for Spatial Technologies and Remote Sensing (CSTARS)
Department of Land, Air and Water Resources
University of California, Davis
One Shields Avenue
Davis, CA 95616
Phone: 415-763-5476
AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307