Fix async fn in trait warning

crates/compute_graph/src/rule.rs

@@ -2,6 +2,7 @@ use crate::node::NodeValue;
 use crate::NodeId;
 pub use compute_graph_macros::InputVisitable;
 use std::cell::{Ref, RefCell};
+use std::future::Future;
 use std::ops::Deref;
 use std::rc::Rc;
 
@@ -62,7 +63,7 @@ pub trait AsyncRule: InputVisitable + 'static {
     /// Asynchronously produces the value of this rule using its inputs.
     ///
     /// See [`Rule::evaluate`] for additional details; the same considerations apply.
-    async fn evaluate(&mut self) -> Self::Output;
+    fn evaluate(&mut self) -> impl Future<Output = Self::Output> + '_;
 }
 
 /// Common supertrait of [`Rule`] and [`AsyncRule`] that defines how rule inputs are visited.