Run clippy first in CI (#100)

* Run clippy first in CI
* Fix clippy warnings

cloudbuild.yaml

@@ -13,15 +13,18 @@
 # limitations under the License.
 
 steps:
+  # clippy tends to rely on cached results from other cargo sub-commands so
+  # that it skips checking some files that were built previously. As a result
+  # we run it before other cargo sub-commands to ensure that it checks all files.
+  - name: gcr.io/$PROJECT_ID/ci
+    args: ["clippy"]
+    id: clippy
   - name: gcr.io/$PROJECT_ID/ci
     args: ["check", "--tests"]
     id: check-tests
   - name: gcr.io/$PROJECT_ID/ci
     args: ["fmt", "--", "--check"]
     id: fmt-check
-  - name: gcr.io/$PROJECT_ID/ci
-    args: ["clippy"]
-    id: clippy
   - name: gcr.io/$PROJECT_ID/ci
     args: ["test", "--tests"]
     id: test

src/test_utils.rs

@@ -194,7 +194,7 @@ where
     let contents = "hello".to_string().into_bytes();
 
     match filter.on_downstream_receive(&endpoints, from, contents.clone()) {
-        None => assert!(false, "should return a result"),
+        None => unreachable!("should return a result"),
         Some((result_endpoints, result_contents)) => {
             assert_eq!(endpoints, result_endpoints);
             assert_eq!(contents, result_contents);
@@ -220,7 +220,7 @@ where
         "127.0.0.1:70".parse().unwrap(),
         contents.clone(),
     ) {
-        None => assert!(false, "should return a result"),
+        None => unreachable!("should return a result"),
         Some(result_contents) => assert_eq!(contents, result_contents),
     }
 }