Adapt the cutover to the reviewed core-types API

test.rs

@@ -0,0 +1,22 @@
+trait Attr {
+	fn name() -> &'static str
+}
+
+impl Attr for bool {
+	fn name() {"condition"}
+}
+
+struct Opacity(f64);
+
+impl Attr for Opacity {
+	fn name() {"opacity"}
+}
+
+
+#[node]
+fn opacity<T>(_: impl Ctx, input: T, x: ReadAttr<bool>, opacity: WriteAttr<Opacity>) -> T {
+	if x {
+		*opacity = 1.;
+	}
+	input
+}