diff --git a/cli/deno_dir.rs b/cli/deno_dir.rs
index 69496b7019..5dc9afed36 100644
--- a/cli/deno_dir.rs
+++ b/cli/deno_dir.rs
@@ -652,7 +652,7 @@ fn fetch_remote_source_async(
               filename: filename.to_string(),
               media_type: map_content_type(
                 &p,
-                maybe_content_type.as_ref().map(|s| s.as_str()),
+                maybe_content_type.as_ref().map(String::as_str),
               ),
               source_code: source.as_bytes().to_owned(),
               maybe_output_code_filename: None,
diff --git a/cli/flags.rs b/cli/flags.rs
index 3fd3f91fbc..3aac1ecc84 100644
--- a/cli/flags.rs
+++ b/cli/flags.rs
@@ -96,7 +96,7 @@ static ENV_VARIABLES_HELP: &str = "ENVIRONMENT VARIABLES:
     NO_COLOR        Set to disable color";
 
 fn create_cli_app<'a, 'b>() -> App<'a, 'b> {
-  let cli_app = App::new("deno")
+  App::new("deno")
     .bin_name("deno")
     .global_settings(&[AppSettings::ColorNever])
     .settings(&[
@@ -194,9 +194,7 @@ fn create_cli_app<'a, 'b>() -> App<'a, 'b> {
       // AppSettings:AllowExternalSubcommand to treat it as an
       // entry point script
       SubCommand::with_name("<script>").about("Script to run"),
-    );
-
-  cli_app
+    )
 }
 
 #[cfg_attr(feature = "cargo-clippy", allow(stutter))]
diff --git a/cli/ops.rs b/cli/ops.rs
index 5e2a624391..0ce9d97a49 100644
--- a/cli/ops.rs
+++ b/cli/ops.rs
@@ -295,7 +295,7 @@ fn op_start(
   let mut builder = FlatBufferBuilder::new();
 
   let state = state;
-  let argv = state.argv.iter().map(|s| s.as_str()).collect::<Vec<_>>();
+  let argv = state.argv.iter().map(String::as_str).collect::<Vec<_>>();
   let argv_off = builder.create_vector_of_strings(argv.as_slice());
 
   let cwd_path = std::env::current_dir().unwrap();
diff --git a/cli/state.rs b/cli/state.rs
index 24f2f5053c..9a74cbfa29 100644
--- a/cli/state.rs
+++ b/cli/state.rs
@@ -90,7 +90,7 @@ impl ThreadSafeState {
     argv_rest: Vec<String>,
     dispatch_selector: ops::OpSelector,
   ) -> Self {
-    let custom_root = env::var("DENO_DIR").map(|s| s.into()).ok();
+    let custom_root = env::var("DENO_DIR").map(String::into).ok();
 
     let (worker_in_tx, worker_in_rx) = async_mpsc::channel::<Buf>(1);
     let (worker_out_tx, worker_out_rx) = async_mpsc::channel::<Buf>(1);
diff --git a/cli/tokio_util.rs b/cli/tokio_util.rs
index bf27c39f0c..5b975ff403 100644
--- a/cli/tokio_util.rs
+++ b/cli/tokio_util.rs
@@ -48,7 +48,6 @@ pub fn init<F>(f: F)
 where
   F: FnOnce(),
 {
-  use tokio_executor;
   let rt = tokio::runtime::Runtime::new().unwrap();
   let mut executor = rt.executor();
   let mut enter = tokio_executor::enter().expect("Multiple executors at once");
diff --git a/cli/worker.rs b/cli/worker.rs
index c43dbf6eea..5a42992144 100644
--- a/cli/worker.rs
+++ b/cli/worker.rs
@@ -119,7 +119,7 @@ pub fn resolve_module_spec(
   //    two-character sequence U+002E FULL STOP, U+002F SOLIDUS (./), or the
   //    three-character sequence U+002E FULL STOP, U+002E FULL STOP, U+002F
   //    SOLIDUS (../), return failure.
-  if !specifier.starts_with("/")
+  if !specifier.starts_with('/')
     && !specifier.starts_with("./")
     && !specifier.starts_with("../")
   {
@@ -158,8 +158,7 @@ impl Loader for Worker {
   type Error = DenoError;
 
   fn resolve(specifier: &str, referrer: &str) -> Result<String, Self::Error> {
-    resolve_module_spec(specifier, referrer)
-      .map_err(|url_err| DenoError::from(url_err))
+    resolve_module_spec(specifier, referrer).map_err(DenoError::from)
   }
 
   /// Given an absolute url, load its source code.
diff --git a/core/examples/http_bench.rs b/core/examples/http_bench.rs
index e4598a7b3b..7cacf79b00 100644
--- a/core/examples/http_bench.rs
+++ b/core/examples/http_bench.rs
@@ -61,6 +61,7 @@ impl Into<Buf> for Record {
 
 impl From<&[u8]> for Record {
   fn from(s: &[u8]) -> Record {
+    #[allow(clippy::cast_ptr_alignment)]
     let ptr = s.as_ptr() as *const i32;
     let ints = unsafe { std::slice::from_raw_parts(ptr, 4) };
     Record {
@@ -75,7 +76,7 @@ impl From<&[u8]> for Record {
 impl From<Buf> for Record {
   fn from(buf: Buf) -> Record {
     assert_eq!(buf.len(), 4 * 4);
-    //let byte_len = buf.len();
+    #[allow(clippy::cast_ptr_alignment)]
     let ptr = Box::into_raw(buf) as *mut [i32; 4];
     let ints: Box<[i32]> = unsafe { Box::from_raw(ptr) };
     assert_eq!(ints.len(), 4);
diff --git a/core/js_errors.rs b/core/js_errors.rs
index dcd434e485..ca5cf80850 100644
--- a/core/js_errors.rs
+++ b/core/js_errors.rs
@@ -10,6 +10,7 @@
 // It would require calling into Rust from Error.prototype.prepareStackTrace.
 
 use serde_json;
+use serde_json::value::Value;
 use std::fmt;
 use std::str;
 
@@ -214,12 +215,12 @@ impl JSError {
     let script_resource_name = obj
       .get("scriptResourceName")
       .and_then(|v| v.as_str().map(String::from));
-    let line_number = obj.get("lineNumber").and_then(|v| v.as_i64());
-    let start_position = obj.get("startPosition").and_then(|v| v.as_i64());
-    let end_position = obj.get("endPosition").and_then(|v| v.as_i64());
-    let error_level = obj.get("errorLevel").and_then(|v| v.as_i64());
-    let start_column = obj.get("startColumn").and_then(|v| v.as_i64());
-    let end_column = obj.get("endColumn").and_then(|v| v.as_i64());
+    let line_number = obj.get("lineNumber").and_then(Value::as_i64);
+    let start_position = obj.get("startPosition").and_then(Value::as_i64);
+    let end_position = obj.get("endPosition").and_then(Value::as_i64);
+    let error_level = obj.get("errorLevel").and_then(Value::as_i64);
+    let start_column = obj.get("startColumn").and_then(Value::as_i64);
+    let end_column = obj.get("endColumn").and_then(Value::as_i64);
 
     let frames_v = &obj["frames"];
     if !frames_v.is_array() {
diff --git a/core/modules.rs b/core/modules.rs
index f46ff5d741..3c74fe11d4 100644
--- a/core/modules.rs
+++ b/core/modules.rs
@@ -202,7 +202,7 @@ impl<L: Loader> Future for RecursiveLoad<L> {
       return Ok(Async::NotReady);
     }
 
-    let root_id = self.root_id.unwrap().clone();
+    let root_id = self.root_id.unwrap();
     let mut loader = self.take_loader();
     let (isolate, modules) = loader.isolate_and_modules();
     let result = {
@@ -460,13 +460,10 @@ mod tests {
 
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
       self.counter += 1;
-      if self.url == "never_ready.js" {
-        // never_ready.js is never ready.
+      if self.url == "never_ready.js"
+        || (self.url == "slow.js" && self.counter < 2)
+      {
         return Ok(Async::NotReady);
-      } else if self.url == "slow.js" {
-        if self.counter < 2 {
-          return Ok(Async::NotReady);
-        }
       }
       match mock_source_code(&self.url) {
         Some(src) => Ok(Async::Ready(src.to_string())),
@@ -560,7 +557,7 @@ mod tests {
       assert_eq!(modules.get_children(c_id), Some(&vec!["d.js".to_string()]));
       assert_eq!(modules.get_children(d_id), Some(&vec![]));
     } else {
-      assert!(false);
+      panic!("this shouldn't happen");
     }
   }
 
@@ -619,7 +616,7 @@ mod tests {
         ])
       );
     } else {
-      assert!(false);
+      panic!("this shouldn't happen");
     }
   }