Use let else here

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -387,7 +387,10 @@ fn resolve_negative_obligation<'cx, 'tcx>(
 ) -> bool {
     let tcx = infcx.tcx;
 
-    if let Some(o) = o.flip_polarity(tcx) {
+    let Some(o) = o.flip_polarity(tcx) else {
+        return false;
+    };
+
     let mut fulfillment_cx = FulfillmentContext::new();
     fulfillment_cx.register_predicate_obligation(infcx, o);
 
@@ -419,10 +422,7 @@ fn resolve_negative_obligation<'cx, 'tcx>(
         return false;
     }
 
-        return true;
-    }
-
-    false
+    true
 }
 
 pub fn trait_ref_is_knowable<'tcx>(