when running scripts via mruby -e or file, return values are unused.
this adds a no_return_value flag to skip generating unnecessary code.
for parallel assignment like a,b = 1,2:
- before: 18 bytes, 5 registers, creates temporary array
- after: 5 bytes, 3 registers, direct register assignment, no RETURN
the flag is set only for the main program, not for libraries loaded
with -r option. eval() and mirb continue returning values correctly.
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto
613b03ac18