Better documentation for the new Default trait bound

egui_node_graph/src/editor_ui.rs

@@ -473,9 +473,9 @@ where
                     } else {
                         // NOTE: We want to pass the `user_data` to
                         // `value_widget`, but we can't since that would require
-                        // borrowing the graph twice. Here, we take the
-                        // assumption that the value is cheaply replace, and use
-                        // `std::mem::take` to temporarily replace it with a
+                        // borrowing the graph twice. Here, we make the
+                        // assumption that the value is cheaply replaced, and
+                        // use `std::mem::take` to temporarily replace it with a
                         // dummy value. This requires `ValueType` to implement
                         // Default, but results in a totally safe alternative.
                         let mut value = std::mem::take(&mut self.graph[param_id].value);

egui_node_graph/src/traits.rs

@@ -3,6 +3,12 @@ use super::*;
 /// This trait must be implemented by the `ValueType` generic parameter of the
 /// [`Graph`]. The trait allows drawing custom inline widgets for the different
 /// types of the node graph.
+///
+/// The [`Default`] trait bound is required to circumvent borrow checker issues
+/// using `std::mem::take` Otherwise, it would be impossible to pass the
+/// `node_data` parameter during `value_widget`. The default value is never
+/// used, so the implementation is not important, but it should be reasonably
+/// cheap to construct.
 pub trait WidgetValueTrait : Default {
     type Response;
     type UserState;