behaviour different when loaded as toolbox

[withaar]

Hi all,

I am working on the quaternion toolbox and an running into odd 
behaviour. I like making my own folder somewhere and work on functions, 
possibly shadowing the original. In my case I originally did not have 
the quaternion toolbox installed - at the moment I do but the result is 
the same.

Question: does pkg does something special when loading/installing a toolbox?

This first section below shows the behaviour when using the installed 
toolbox:

#------------------------------------------------
rmpath ("/home/willem/octave/toolbox/octave_toolboxes/quaternion")
rehash
which quaternion
#'quaternion' is a function from the file 
/home/willem/octave/quaternion-2.2.2/@quaternion/quaternion.m

q = quaternion(randn(2,3,4),randn(2,3,4),randn(2,3,4),randn(2,3,4));
q.w(1,1,1)
q.w(1,1,1) = 0
#------------------------------------------------

This is no problem and runs as expected. Now to the version that is in a 
different folder and not in a toolbox:

#------------------------------------------------
clear all
addpath ("/home/willem/octave/toolbox/octave_toolboxes/quaternion")
rmpath("/home/willem/octave/quaternion-2.2.2")
rehash
which quaternion
#'quaternion' is a function from the file 
/home/willem/octave/toolbox/octave_toolboxes/quaternion/@quaternion/quaternion.m

q = quaternion(randn(2,3,4),randn(2,3,4),randn(2,3,4),randn(2,3,4));
q.w(1,1,1)
q.w(1,1,1) = 0

error: a cs-list cannot be further indexed
error: invalid assignment to cs-list outside multiple assignment
#------------------------------------------------

Where does the difference in behaviour come from? For the alternate 
version subsref/subsassgn never get called.

Thanks!

Willem