add better example

trait-variant/examples/variant.rs

@@ -6,7 +6,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::{future::Future, ops::Add};
+use std::{fmt::Display, future::Future};
 
 #[trait_variant::make(IntFactory: Send)]
 pub trait LocalIntFactory {
@@ -37,9 +37,10 @@ where
     const CONST: usize = 3;
     type F;
     type A<const ANOTHER_CONST: u8>;
-    type B<T>: Add<T>;
+    type B<T: Display>: FromIterator<T>;
 
     async fn take(&self, s: S);
+    fn build<T: Display>(&self, items: impl Iterator<Item = T>) -> Self::B<T>;
 }
 
 fn main() {}