Generators make regular calls and regular returns

valuescript_vm/src/stack_frame.rs

@@ -31,3 +31,41 @@ impl Clone for StackFrame {
     self.clone_to_stack_frame()
   }
 }
+
+impl Default for StackFrame {
+  fn default() -> Self {
+    Box::new(VoidStackFrame {})
+  }
+}
+
+#[derive(Clone)]
+struct VoidStackFrame {}
+
+impl StackFrameTrait for VoidStackFrame {
+  fn write_this(&mut self, _const: bool, _this: Val) -> Result<(), Val> {
+    Ok(())
+  }
+
+  fn write_param(&mut self, _param: Val) {}
+
+  fn step(&mut self) -> FrameStepResult {
+    Ok(FrameStepOk::Continue)
+  }
+
+  fn apply_call_result(&mut self, _call_result: CallResult) {}
+
+  fn get_call_result(&mut self) -> CallResult {
+    CallResult {
+      return_: Val::Void,
+      this: Val::Void,
+    }
+  }
+
+  fn catch_exception(&mut self, _exception: Val) -> bool {
+    false
+  }
+
+  fn clone_to_stack_frame(&self) -> StackFrame {
+    Box::new(self.clone())
+  }
+}