refined error model (#2253)

actix-http/src/body/mod.rs

@@ -191,11 +191,15 @@ mod tests {
     }
 
     #[actix_rt::test]
-    async fn test_box() {
+    async fn test_box_and_pin() {
         let val = Box::new(());
         pin!(val);
         assert_eq!(val.size(), BodySize::Empty);
         assert!(poll_fn(|cx| val.as_mut().poll_next(cx)).await.is_none());
+
+        let mut val = Box::pin(());
+        assert_eq!(val.size(), BodySize::Empty);
+        assert!(poll_fn(|cx| val.as_mut().poll_next(cx)).await.is_none());
     }
 
     #[actix_rt::test]