To run the code just use:

git clone https://github.com/jcubic/refClass.git
cd refClass
R CMD INSTALL Package_A
R CMD INSTALL Package_B

Rscript app.R

Expected behvior is the output

lorem [1]
lorem [1]
hello [1]
hello [2]
world [1]
world [2]

Receive output:

lorem [1]
lorem [1]
hello [1]
hello [2]
Error in lorem(x) : could not find function "lorem"
Calls: <Anonymous> -> callSuper
Execution halted

In PackageA you have base ref class that call function defined in package. In PackageB you have inherit class that overwrite the method and callSuper. When calling that method base class implemention of the method doesn't see functions in package environment.

Code license is Public Domain CC-0.