clippy::redundant_pattern_matching

warning: redundant pattern matching, consider using `is_err()`
   --> src/race.rs:354:20
    |
354 |             if let Err(_) = exchange {
    |             -------^^^^^^----------- help: try this: `if exchange.is_err()`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pattern_matching
    = note: `#[warn(clippy::redundant_pattern_matching)]` on by default

src/race.rs

@@ -351,7 +351,7 @@ mod once_box {
                 Ordering::AcqRel,
                 Ordering::Acquire,
             );
-            if let Err(_) = exchange {
+            if exchange.is_err() {
                 let value = unsafe { Box::from_raw(ptr) };
                 return Err(value);
             }