I guess it's just late, but I cannot get my head around why the original collection
gets modified :).

FMMultivalue is actually copying itself:

f := FMMultivalueLink new.
f copy == f "==> false"
f copy = f "==> false"

Why do you say that " FM*MultivalueLink instances which are keeping a link to the old
collection..."?

What kind of semantics do we expect when owner and opposite are not the same?

Of course, when you copy a FMMultivalueLink  you get a copy of the FMMultivalueLink.
But don't forget that, by nature, the FMMultivalueLink is liked to an method accessor
to update itself.

In moose you don't do  FMMultivalueLink new. But "FMMultivalueLink on: aFamixClass
opposite: #parentType:"  for instance.

So "," do a copy of the receiver and add to this copy each element of the argument.
But the add method in FMMultivalueLink is updating aFamixClass parentType (if we take
the example). But parentType is an other FMMultivalueLink that is updating the "attribute"
value of aFamixClass. And this value is the old FMMultivalue link (the old collection)
and not the new one you just copied !
To summarize, by doing "," :
- you just add nothing to your new collection
- and you add something to a collection that you don't wanted to change...
That is why I propose to remove it.

And it's not late ! For the next using this method, it will be useful !

Does your head feel better? :)

Ok. It seems that sleeping does make wonders :).

I would suggest to have it implemented like this:

, aCollection
    ^ self asOrderedCollection , aCollection 

What do you think?

That is good for me.

Commited in 
Name: Fame-Core-VincentBlondeau.24
Author: VincentBlondeau
Time: 24 July 2014, 10:19:43.303281 am
UUID: fffa0632-3b49-2f4e-b3e0-b682bc721a65