use replace value

logger/src/lib.rs

@@ -26,7 +26,7 @@ fn replace_logger(logger: env_logger::Logger) {
     let max_level = logger.filter();
     log::set_max_level(max_level);
     let mut rw = LOGGER.write().unwrap();
-    std::mem::replace(&mut *rw, logger);
+    let _ = std::mem::replace(&mut *rw, logger);
     let _ = log::set_boxed_logger(Box::new(LoggerShim {}));
 }