I suspect that you consider evaluation-on-reference as an important
feature of your proposal, but could you consider explicit evaluation
as an alternative? Or at the very least address in the PEP the fact
that this would close the door on future explicit evaluation models?
I can think of ways to implement evaluation-on-reference, but they all have the effect of
making python slower.
a = b
will need to slow down so that the object in b can checked to see if it need evaluating.
How will you avoid making python slower with this feature?