diff --git a/cli/compiler.rs b/cli/compiler.rs
index 0452e08a95..085fcd820e 100644
--- a/cli/compiler.rs
+++ b/cli/compiler.rs
@@ -186,12 +186,8 @@ mod tests {
       maybe_source_map: None,
     };
 
-    out = compile_sync(
-      Arc::new(IsolateState::mock()),
-      specifier,
-      &referrer,
-      &mut out,
-    );
+    out =
+      compile_sync(Arc::new(IsolateState::mock()), specifier, &referrer, &out);
     assert!(
       out
         .maybe_output_code
diff --git a/cli/deno_dir.rs b/cli/deno_dir.rs
index 40612e9703..1055fa687a 100644
--- a/cli/deno_dir.rs
+++ b/cli/deno_dir.rs
@@ -692,7 +692,7 @@ mod tests {
   fn test_cache_path() {
     let (temp_dir, deno_dir) = test_setup(false, false);
     let filename = "hello.js";
-    let source_code = "1+2".as_bytes();
+    let source_code = b"1+2";
     let hash = source_code_hash(filename, source_code, version::DENO);
     assert_eq!(
       (
@@ -708,9 +708,9 @@ mod tests {
     let (_temp_dir, deno_dir) = test_setup(false, false);
 
     let filename = "hello.js";
-    let source_code = "1+2".as_bytes();
-    let output_code = "1+2 // output code".as_bytes();
-    let source_map = "{}".as_bytes();
+    let source_code = b"1+2";
+    let output_code = b"1+2 // output code";
+    let source_map = b"{}";
     let hash = source_code_hash(filename, source_code, version::DENO);
     let (cache_path, source_map_path) =
       deno_dir.cache_path(filename, source_code);
@@ -719,41 +719,41 @@ mod tests {
 
     let out = ModuleMetaData {
       filename: filename.to_owned(),
-      source_code: source_code.to_owned(),
+      source_code: source_code[..].to_owned(),
       module_name: "hello.js".to_owned(),
       media_type: msg::MediaType::TypeScript,
-      maybe_output_code: Some(output_code.to_owned()),
+      maybe_output_code: Some(output_code[..].to_owned()),
       maybe_output_code_filename: None,
-      maybe_source_map: Some(source_map.to_owned()),
+      maybe_source_map: Some(source_map[..].to_owned()),
       maybe_source_map_filename: None,
     };
 
     let r = deno_dir.code_cache(&out);
     r.expect("code_cache error");
     assert!(cache_path.exists());
-    assert_eq!(output_code.to_owned(), fs::read(&cache_path).unwrap());
+    assert_eq!(output_code[..].to_owned(), fs::read(&cache_path).unwrap());
   }
 
   #[test]
   fn test_source_code_hash() {
     assert_eq!(
       "7e44de2ed9e0065da09d835b76b8d70be503d276",
-      source_code_hash("hello.ts", "1+2".as_bytes(), "0.2.11")
+      source_code_hash("hello.ts", b"1+2", "0.2.11")
     );
     // Different source_code should result in different hash.
     assert_eq!(
       "57033366cf9db1ef93deca258cdbcd9ef5f4bde1",
-      source_code_hash("hello.ts", "1".as_bytes(), "0.2.11")
+      source_code_hash("hello.ts", b"1", "0.2.11")
     );
     // Different filename should result in different hash.
     assert_eq!(
       "19657f90b5b0540f87679e2fb362e7bd62b644b0",
-      source_code_hash("hi.ts", "1+2".as_bytes(), "0.2.11")
+      source_code_hash("hi.ts", b"1+2", "0.2.11")
     );
     // Different version should result in different hash.
     assert_eq!(
       "e2b4b7162975a02bf2770f16836eb21d5bcb8be1",
-      source_code_hash("hi.ts", "1+2".as_bytes(), "0.2.0")
+      source_code_hash("hi.ts", b"1+2", "0.2.0")
     );
   }
 
@@ -1456,7 +1456,7 @@ mod tests {
 
   #[test]
   fn test_filter_shebang() {
-    assert_eq!(filter_shebang("#!".as_bytes().to_owned()), "".as_bytes());
+    assert_eq!(filter_shebang(b"#!"[..].to_owned()), b"");
     assert_eq!(
       filter_shebang("#!\n\n".as_bytes().to_owned()),
       "\n\n".as_bytes()
diff --git a/cli/js_errors.rs b/cli/js_errors.rs
index 90c9f20075..1cb9cb3a19 100644
--- a/cli/js_errors.rs
+++ b/cli/js_errors.rs
@@ -209,7 +209,7 @@ pub fn apply_source_map(
 // The bundle does not get built for 'cargo check', so we don't embed the
 // bundle source map.
 #[cfg(feature = "check-only")]
-fn builtin_source_map(script_name: &str) -> Option<Vec<u8>> {
+fn builtin_source_map(_: &str) -> Option<Vec<u8>> {
   None
 }
 
diff --git a/cli/startup_data.rs b/cli/startup_data.rs
index 5ef74de066..6e636e5790 100644
--- a/cli/startup_data.rs
+++ b/cli/startup_data.rs
@@ -13,7 +13,7 @@ pub fn deno_isolate_init() -> StartupData {
 
     StartupData::Script(Script {
       filename: "gen/bundle/main.js".to_string(),
-      source: std::str::from_utf8(source_bytes).unwrap().to_string(),
+      source: std::str::from_utf8(&source_bytes[..]).unwrap().to_string(),
     })
   } else {
     debug!("Deno isolate init with snapshots.");
@@ -40,7 +40,7 @@ pub fn compiler_isolate_init() -> StartupData {
 
     StartupData::Script(Script {
       filename: "gen/bundle/compiler.js".to_string(),
-      source: std::str::from_utf8(source_bytes).unwrap().to_string(),
+      source: std::str::from_utf8(&source_bytes[..]).unwrap().to_string(),
     })
   } else {
     debug!("Deno isolate init with snapshots.");
diff --git a/core/isolate.rs b/core/isolate.rs
index b28730ba68..f8ada23d46 100644
--- a/core/isolate.rs
+++ b/core/isolate.rs
@@ -140,11 +140,10 @@ impl<B: Behavior> Isolate<B> {
     };
 
     // If we want to use execute this has to happen here sadly.
-    match startup_script {
-      Some(s) => core_isolate
+    if let Some(s) = startup_script {
+      core_isolate
         .execute(s.filename.as_str(), s.source.as_str())
-        .unwrap(),
-      None => {}
+        .unwrap()
     };
 
     core_isolate
@@ -510,9 +509,8 @@ impl IsolateHandle {
   /// the isolate.
   pub fn terminate_execution(&self) {
     unsafe {
-      match *self.shared_libdeno_isolate.lock().unwrap() {
-        Some(isolate) => libdeno::deno_terminate_execution(isolate),
-        None => (),
+      if let Some(isolate) = *self.shared_libdeno_isolate.lock().unwrap() {
+        libdeno::deno_terminate_execution(isolate)
       }
     }
   }