fix(controller/reporting):reduce unnecessary mutability exposure

kuyaseg-controller/src/reporting/tracing_evt.rs

@@ -83,8 +83,11 @@ where
     S: Subscriber + for<'a> LookupSpan<'a>,
 {
     fn on_new_span(&self, attrs: &Attributes<'_>, id: &Id, ctx: Context<'_, S>) {
+        let fields = {
             let mut fields = SpanFields::default();
             attrs.record(&mut fields);
+            fields
+        };
 
         if fields.has_any_fields()
             && let Some(span) = ctx.span(id)
@@ -104,19 +107,25 @@ where
         };
 
         // construct & check event fields
-        let mut span_fields = SpanFields::default();
+        let span_fields = {
+            let mut fields = SpanFields::default();
             for span in scope.from_root() {
-            if let Some(fields) = span.extensions().get::<SpanFields>() {
-                span_fields.under(fields);
+                if let Some(span_fields) = span.extensions().get::<SpanFields>() {
+                    fields.under(span_fields);
                 }
             }
+            fields
+        };
         if !span_fields.check_fields() {
             return;
         }
 
         // construct & check pro fields
-        let mut event_fields = EventFields::default();
-        event.record(&mut event_fields);
+        let event_fields = {
+            let mut fields = EventFields::default();
+            event.record(&mut fields);
+            fields
+        };
         if !event_fields.check_fields() {
             return;
         }