Method unwind_stack_for_lineno

crates/vm/src/frame.rs:1401–1417

Perform deferred stack unwinding after set_f_lineno. set_f_lineno cannot pop the value stack directly because the execution loop holds the state mutex. Instead it records the work in `pending_stack_pops` / `pending_unwind_from_stack` and we execute it here, inside the execution loop where we already own the state.

(&mut self, pop_count: usize, from_stack: i64, vm: &VirtualMachine)

    /// `pending_stack_pops` / `pending_unwind_from_stack` and we execute it
    /// here, inside the execution loop where we already own the state.
    fn unwind_stack_for_lineno(&mut self, pop_count: usize, from_stack: i64, vm: &VirtualMachine) {
        let mut cur_stack = from_stack;
        for _ in 0..pop_count {
            let val = self.pop_value_opt();
            if stack_analysis::top_of_stack(cur_stack) == stack_analysis::Kind::Except as i64
                && let Some(exc_obj) = val
            {
                if vm.is_none(&exc_obj) {
                    vm.set_exception(None);
                } else {
                    let exc = exc_obj.downcast::<PyBaseException>().ok();
                    vm.set_exception(exc);
                }
            }
            cur_stack = stack_analysis::pop_value(cur_stack);
        }
    }

    /// Fire 'exception' trace event (sys.settrace) with (type, value, traceback) tuple.
    /// Matches `_PyEval_MonitorRaise` → `PY_MONITORING_EVENT_RAISE` →