fix: change where TaskHandle is borrowed to prevent repeat output fetches

tests/cycle_prevention.rs

@@ -30,40 +30,11 @@ fn test_builder_consumed_by_depends_on() {
     let consumer_builder = dag.add_task(Consumer);
 
     // This consumes consumer_builder and returns a TaskHandle
-    let _consumer_handle = consumer_builder.depends_on(source);
+    let _consumer_handle = consumer_builder.depends_on(&source);
 
     // We CANNOT use consumer_builder again because it was moved
     // This would fail to compile:
-    // let _consumer2 = consumer_builder.depends_on(source);  // ERROR: use of moved value
-}
-
-/// Demonstrates that you can only get a TaskHandle by finalizing a builder,
-/// and handles are immutable references with no methods to add dependencies
-#[test]
-fn test_handle_is_immutable_reference() {
-    struct NoInput;
-    #[task]
-    impl NoInput {
-        async fn run(&self) -> i32 {
-            100
-        }
-    }
-
-    let mut dag = DagRunner::new();
-    let builder = dag.add_task(NoInput);
-
-    // Convert to handle (only works because Input = ())
-    let handle = builder;
-
-    // TaskHandle is Copy/Clone - just an ID wrapper
-    let _copy1 = handle;
-    let _copy2 = handle;
-    let _copy3 = handle;
-
-    // But TaskHandle has NO methods to modify the DAG
-    // There's no way to add dependencies to it
-    // This would fail to compile:
-    // handle.depends_on(something);  // ERROR: no method named `depends_on`
+    // let _consumer2 = consumer_builder.depends_on(&source);  // ERROR: use of moved value
 }
 
 /// Documents the ordering constraint that prevents cycles
@@ -108,8 +79,8 @@ fn test_ordering_prevents_cycles() {
 
     // Let's create a valid DAG instead: A→B (B depends on A)
     let a_handle = a_builder; // A has no deps (unit input)
-    let _b_handle = b_builder.depends_on(a_handle);
-    // Now we could try: a_handle.depends_on(b_handle)?
+    let _b_handle = b_builder.depends_on(&a_handle);
+    // Now we could try: a_handle.depends_on(&b_handle)?
     // But TaskHandle has no such method!
 }
 
@@ -182,9 +153,9 @@ fn test_three_way_cycle_impossible() {
     let _c_builder = dag.add_task(C);
 
     // To create A→C→B→A:
-    // 1. a_builder.depends_on(c_handle)  // Need c_handle
-    // 2. c_builder.depends_on(b_handle)  // Need b_handle
-    // 3. b_builder.depends_on(a_handle)  // Need a_handle (from step 1!)
+    // 1. a_builder.depends_on(&c_handle)  // Need c_handle
+    // 2. c_builder.depends_on(&b_handle)  // Need b_handle
+    // 3. b_builder.depends_on(&a_handle)  // Need a_handle (from step 1!)
     //
     // But step 3 needs a_handle which doesn't exist until step 1 completes.
     // And step 1 needs c_handle which doesn't exist until step 2 completes.
@@ -209,7 +180,7 @@ fn test_self_loop_prevented() {
     let _builder = dag.add_task(SelfReferential);
 
     // To create A→A (self-loop):
-    // builder.depends_on(builder)
+    // builder.depends_on(&builder)
     //
     // But this would fail because:
     // 1. depends_on() takes `self` by value (moves builder)
@@ -217,7 +188,7 @@ fn test_self_loop_prevented() {
     // 3. We can't also use &builder as an argument because it's being moved
     //
     // This would fail to compile:
-    // let _handle = builder.depends_on(builder);  // ERROR: use of moved value
+    // let _handle = builder.depends_on(&builder);  // ERROR: use of moved value
 }
 
 /// Comprehensive test showing all the guardrails
@@ -263,11 +234,11 @@ async fn test_type_safety_prevents_invalid_graphs() {
     let s2 = dag.add_task(Source);
 
     // Transform depends on sources
-    let t1 = dag.add_task(Transform).depends_on(s1);
-    let t2 = dag.add_task(Transform).depends_on(s2);
+    let t1 = dag.add_task(Transform).depends_on(&s1);
+    let t2 = dag.add_task(Transform).depends_on(&s2);
 
     // Aggregate depends on transforms
-    let result = dag.add_task(Aggregate).depends_on((t1, t2));
+    let result = dag.add_task(Aggregate).depends_on((&t1, &t2));
 
     // Execute and verify
     let mut output = dag
@@ -275,7 +246,7 @@ async fn test_type_safety_prevents_invalid_graphs() {
         .await
         .unwrap();
 
-    assert_eq!(output.get(result).unwrap(), 40); // (10*2) + (10*2)
+    assert_eq!(output.get(result), 40); // (10*2) + (10*2)
 
     // Now if we wanted to add a cycle, we'd need to:
     // - Make one of the Source tasks depend on the Aggregate result