Attach follows_from() before constructing future

tracing-attributes/src/expand.rs

@@ -316,9 +316,11 @@ fn gen_block<B: ToTokens>(
 
         return quote!(
             let __tracing_attr_span = #span;
-            let __tracing_instrument_future = #mk_fut;
             if !__tracing_attr_span.is_disabled() {
                 #follows_from
+            }
+            let __tracing_instrument_future = #mk_fut;
+            if !__tracing_attr_span.is_disabled() {
                 tracing::Instrument::instrument(
                     __tracing_instrument_future,
                     __tracing_attr_span

tracing-attributes/tests/follows_from.rs

@@ -11,6 +11,22 @@ async fn with_follows_from_async(causes: impl IntoIterator<Item = impl Into<Opti
 #[instrument(follows_from = [&Span::current()])]
 fn follows_from_current() {}
 
+#[derive(Debug)]
+struct NonCopyContext {
+    id: Option<Id>,
+}
+
+impl NonCopyContext {
+    fn id(&self) -> Option<tracing::Id> {
+        self.id.clone()
+    }
+}
+
+#[instrument(follows_from = [ctx.id()])]
+fn follows_from_noncopy(ctx: NonCopyContext) {
+    println!("{:?}", ctx.id());
+}
+
 #[test]
 fn follows_from_sync_test() {
     let cause_a = expect::span().named("cause_a");
@@ -99,3 +115,27 @@ fn follows_from_current_test() {
 
     handle.assert_finished();
 }
+
+#[test]
+fn follows_from_noncopy_test() {
+    let cause_a = expect::span().named("cause_a");
+    let consequence = expect::span().named("follows_from_noncopy");
+
+    let (collector, handle) = collector::mock()
+        .new_span(cause_a.clone())
+        .new_span(consequence.clone())
+        .follows_from(consequence.clone(), cause_a)
+        .enter(consequence.clone())
+        .exit(consequence)
+        .only()
+        .run_with_handle();
+
+    with_default(collector, || {
+        let cause_a = tracing::info_span!("cause_a");
+        let context = NonCopyContext { id: cause_a.id() };
+
+        follows_from_noncopy(context)
+    });
+
+    handle.assert_finished();
+}