Fix clippy lints for Rust 1.68

graphics/src/primitive.rs

@@ -9,9 +9,10 @@ use crate::triangle;
 use std::sync::Arc;
 
 /// A rendering primitive.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub enum Primitive {
     /// An empty primitive
+    #[default]
     None,
     /// A group of primitives
     Group {
@@ -117,9 +118,3 @@ pub enum Primitive {
         cache: Arc<Primitive>,
     },
 }
-
-impl Default for Primitive {
-    fn default() -> Primitive {
-        Primitive::None
-    }
-}