impl Codegen {
    fn do_some(&mut) {
        let reg:Register;
        reg.free(self.unspill());
    }

    fn unspill(&mut self) -> Box<dyn FnMut(&ScratchRegister, StackRegister, &NEWTypes) -> ()> {
        Box::new(
            |reg: &ScratchRegister, spilled: StackRegister, type_decl: &NEWTypes| {
                writeln!(
                    self.output,
                    "\tmovq    {}, {}",
                    spilled.name(),
                    reg.name(type_decl),
                )
                .unwrap();
            },
        )
    }
}
impl ScratchRegister {
    fn free(
        &mut self,
        type_decl: &NEWTypes,
        mut unspill: Box<dyn FnMut(&ScratchRegister, StackRegister, &NEWTypes) -> ()>,
    ) {
        if self.spill_addr.len() > 0 {
            let spilled_addr = self.spill_addr.pop().unwrap();
            unspill(&*self, spilled_addr, type_decl);
        } else {
            self.in_use = false;
        }
}