The issue with unused constants is an artifact of the peepholer running 
after the bytecode generation phase.  When constant folding was 
written, I intentionally left-out a step to remove unused constants 
because of the code complexity, the fragility of the process, because 
the benefits were inconsequential, and because it added to compilation 
time.  

It would be better to wait for the AST optimizer to replace the 
peepholer.  AST optimizations are upstream from bytecode generation, so 
the unused constant issue simply disappears.