Resolve deferred size comparisons before allocating span slots

core/src/widget/widgets.rs

@@ -129,7 +129,7 @@ impl Widgets {
 
     /// The length rules whoever draws this widget applies to its box.
     pub fn size_rules(&self, id: impl IdLike) -> SizeRules {
-        self.data(id).unwrap().size
+        self.data(id).unwrap().size.clone()
     }
 
     /// Sets one axis's rule. The widget is marked rather than its parent