Move MOO-specific stack frame pieces on Activation into their own Fra…

…me struct

crates/kernel/src/builtins/bf_objects.rs

@@ -438,8 +438,10 @@ fn bf_move(bf_args: &mut BfCallState<'_>) -> Result<BfRet, Error> {
 
                 // Accept verb has been called, and returned. Check the result. Should be on stack,
                 // unless short-circuited, in which case we assume *false*
+                // TODO directly pushing into the stack like this is going to be a problem for
+                //  non-MOO interpreters. we need a more generic way of doing this
                 let result = if !shortcircuit {
-                    bf_args.exec_state.top().peek_top().clone()
+                    bf_args.exec_state.top().frame.peek_top().clone()
                 } else {
                     v_int(0)
                 };

crates/kernel/src/tasks/vm_host.rs

@@ -341,7 +341,7 @@ impl VmHost {
     /// Resume what you were doing after suspension.
     pub fn resume_execution(&mut self, value: Var) {
         // coming back from suspend, we need a return value to feed back to `bf_suspend`
-        self.vm_exec_state.top_mut().push(value);
+        self.vm_exec_state.top_mut().frame.push(value);
         self.vm_exec_state.start_time = Some(SystemTime::now());
         self.vm_exec_state.tick_count = 0;
         self.running = true;
@@ -366,6 +366,7 @@ impl VmHost {
     pub fn set_variable(&mut self, task_id_var: &Name, value: Var) {
         self.vm_exec_state
             .top_mut()
+            .frame
             .set_var_offset(task_id_var, value)
             .expect("Could not set forked task id");
     }
@@ -384,7 +385,8 @@ impl VmHost {
     pub fn line_number(&self) -> usize {
         self.vm_exec_state
             .top()
-            .find_line_no(self.vm_exec_state.top().pc)
+            .frame
+            .find_line_no(self.vm_exec_state.top().frame.pc)
             .unwrap_or(0)
     }