add Primitive type

engine/lib/cache.ts

@@ -1,3 +1,5 @@
+import type { Primitive } from "#/engine/lib/Primitive.ts";
+
 export type Cache<T> = {
 	clear(): void;
 	delete(key: unknown): boolean;
@@ -22,8 +24,10 @@ export function withCache<T, U extends (...args: Parameters<U>) => T>(
 	};
 }
 
-export function memoize<T, U>(fn: (arg: U) => T): [(arg: U) => T, Cache<T>] {
-	const cache = new Map<unknown, T>();
+export function memoize<T, U extends Primitive>(
+	fn: (arg: U) => T,
+): [(arg: U) => T, Cache<T>] {
+	const cache = new Map<Primitive, T>();
 	const callback = withCache(fn, cache);
 
 	return [