Automatic debugging of copy by reference errors?

[Gabriel Genellina]

> I think what you want is a namespace that requires each object to have
> exactly one reference - the namespace.  Of course, additional references
> will be created during evaluation of expressions.  So the best you can do

It's not enough. It won't catch the case where a list holds many
references to the same object - the example provided by the OP.

-- 
Gabriel Genellina