Use call-site span for future Send check in debug_handler

axum-macros/src/debug_handler.rs

@@ -373,7 +373,7 @@ fn check_future_send(item_fn: &ItemFn) -> TokenStream {
         };
     }
 
-    let span = item_fn.span();
+    let span = item_fn.sig.ident.span();
 
     let handler_name = &item_fn.sig.ident;
 
@@ -383,28 +383,28 @@ fn check_future_send(item_fn: &ItemFn) -> TokenStream {
 
     let name = format_ident!("__axum_macros_check_{}_future", item_fn.sig.ident);
 
+    let do_check = quote! {
+        fn check<T>(_: T)
+            where T: ::std::future::Future + Send
+        {}
+        check(future);
+    };
+
     if let Some(receiver) = self_receiver(item_fn) {
-        quote_spanned! {span=>
+        quote! {
             #[allow(warnings)]
             fn #name() {
                 let future = #receiver #handler_name(#(#args),*);
-                fn check<T>(_: T)
+                #do_check
-                    where T: ::std::future::Future + Send
-                {}
-                check(future);
             }
         }
     } else {
-        quote_spanned! {span=>
+        quote! {
             #[allow(warnings)]
             fn #name() {
                 #item_fn
-
                 let future = #handler_name(#(#args),*);
-                fn check<T>(_: T)
+                #do_check
-                    where T: ::std::future::Future + Send
-                {}
-                check(future);
             }
         }
     }

axum-macros/tests/debug_handler/fail/not_send.stderr

@@ -1,11 +1,8 @@
 error: future cannot be sent between threads safely
- --> tests/debug_handler/fail/not_send.rs:4:1
+ --> tests/debug_handler/fail/not_send.rs:3:1
   |
-4 | / async fn handler() {
+3 | #[debug_handler]
-5 | |     let rc = std::rc::Rc::new(());
+  | ^^^^^^^^^^^^^^^^ future returned by `handler` is not `Send`
-6 | |     async {}.await;
-7 | | }
-  | |_^ future returned by `handler` is not `Send`
   |
   = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `Rc<()>`
 note: future is not `Send` as this value is used across an await
@@ -18,10 +15,8 @@ note: future is not `Send` as this value is used across an await
 7 | }
   | - `rc` is later dropped here
 note: required by a bound in `check`
- --> tests/debug_handler/fail/not_send.rs:4:1
+ --> tests/debug_handler/fail/not_send.rs:3:1
   |
-4 | / async fn handler() {
+3 | #[debug_handler]
-5 | |     let rc = std::rc::Rc::new(());
+  | ^^^^^^^^^^^^^^^^ required by this bound in `check`
-6 | |     async {}.await;
+  = note: this error originates in the attribute macro `debug_handler` (in Nightly builds, run with -Z macro-backtrace for more info)
-7 | | }
-  | |_^ required by this bound in `check`

axum-macros/tests/debug_handler/fail/wrong_return_type.stderr

@@ -13,9 +13,9 @@ error[E0277]: the trait bound `bool: IntoResponse` is not satisfied
             (Response<()>, T1, R)
             (Response<()>, T1, T2, R)
             (Response<()>, T1, T2, T3, R)
-          and 124 others
+          and $N others
 note: required by a bound in `__axum_macros_check_handler_into_response::{closure#0}::check`
  --> tests/debug_handler/fail/wrong_return_type.rs:4:23
   |
 4 | async fn handler() -> bool {
-  |                       ^^^^ required by this bound in `__axum_macros_check_handler_into_response::{closure#0}::check`
+  |                       ^^^^ required by this bound in `check`