wip: feeling goodish about scheduler

packages/core/src/diff_stack.rs

@@ -55,6 +55,10 @@ impl<'bump> DiffStack<'bump> {
         }
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.instructions.is_empty()
+    }
+
     pub fn pop(&mut self) -> Option<DiffInstruction<'bump>> {
         self.instructions.pop()
     }