diff --git a/parser/.travis.yml b/parser/.travis.yml
index 5e1e170..627e527 100644
--- a/parser/.travis.yml
+++ b/parser/.travis.yml
@@ -7,5 +7,8 @@ rust:
 env:
   global:
     - secure: ZUcdcbS8xbpdII9FSPx7VtoVhEkJhWL2Hb75tDlKDHNhfXqmt1NyB9q/2qXJ5Ulp4MnYXwsI8LsDloR6gvdB4xElay3smuF/neGvMjrqcB15/2p0MSQ+kZjMsNB6mlb5kAlm8ahduXIscppmw/V+m5hn3Vo+RQz/Ng+pzv0nc8KEXPMYrfRFg+a7FaeIbRbb8ir9EfflUSqArLq2hbi2WdhM3hFMcCIAUt6DD4x5ubjEg60OnIof5FDu0mXMXzQvUfHWOeYnsNcD/DLyDnm6FuQEzk37M4EB8op2SdBUeQMQ5abR3i2rd//DZpbTTEjud0PseWohGAwTwL2aoFrqs7uYQMx+vcGlOzAyDUm4VemVUa3F2BECdzU5BiujcKOITJEVUYWongld93arQq34FuXG/TO/T1XrerxfG6LTkTkKS5Vz7W8z6Rloa99WrQLJg1ZJP6itEU7G7KsDFVgRhsg7rz4/dV/2+cV4UvIwd4HlGXKCFlH0SClqvM3/7i/qqCD0689SJW6Zip+ly38MXlGy2s/AmReEasXvFer9JkOEIuPa8QTBNAjDlw7bWXi6neQWBIZU1VhZcSssnrVmEFN8fNklShzpw5DyKCv8jPTx2O6Dw8B/LgIK8uo+eaTXiO6zz/T1c/qEdsYslvxPA2D3F+ONpPU7238ykT4eRog=
+script:
+  - cargo build --features clippy --verbose
+  - cargo test --verbose
 after_script:
   - curl http://www.rust-ci.org/artifacts/put?t=$RUSTCI_TOKEN | sh
diff --git a/parser/Cargo.toml b/parser/Cargo.toml
index d427e4b..46d8c7a 100644
--- a/parser/Cargo.toml
+++ b/parser/Cargo.toml
@@ -7,3 +7,6 @@ documentation = "http://chyh1990.github.io/yaml-rust/doc/yaml_rust/"
 license = "MIT/Apache-2.0"
 description = "The missing YAML 1.2 parser for rust"
 repository = "https://github.com/chyh1990/yaml-rust"
+
+[dependencies]
+clippy = { version = "^0.*", optional = true }
diff --git a/parser/src/emitter.rs b/parser/src/emitter.rs
index 8810c95..fe9a6e1 100644
--- a/parser/src/emitter.rs
+++ b/parser/src/emitter.rs
@@ -114,8 +114,8 @@ impl<'a> YamlEmitter<'a> {
     }
 
     fn emit_node(&mut self, node: &Yaml) -> EmitResult {
-        match node {
-            &Yaml::Array(ref v) => {
+        match *node {
+            Yaml::Array(ref v) => {
                 if v.is_empty() {
                     try!(write!(self.writer, "[]"));
                     Ok(())
@@ -124,21 +124,19 @@ impl<'a> YamlEmitter<'a> {
                         try!(write!(self.writer, "\n"));
                     }
                     self.level += 1;
-                    let mut cnt = 0usize;
-                    for x in v {
+                    for (cnt, x) in v.iter().enumerate() {
+                        if cnt > 0 {
+                            try!(write!(self.writer, "\n"));
+                        }
                         try!(self.write_indent());
                         try!(write!(self.writer, "- "));
                         try!(self.emit_node(x));
-                        cnt += 1;
-                        if cnt < v.len() {
-                            try!(write!(self.writer, "\n"));
-                        }
                     }
                     self.level -= 1;
                     Ok(())
                 }
             },
-            &Yaml::Hash(ref h) => {
+            Yaml::Hash(ref h) => {
                 if h.is_empty() {
                     try!(self.writer.write_str("{}"));
                     Ok(())
@@ -147,32 +145,30 @@ impl<'a> YamlEmitter<'a> {
                         try!(write!(self.writer, "\n"));
                     }
                     self.level += 1;
-                    let mut cnt = 0usize;
-                    for (k, v) in h {
+                    for (cnt, (k, v)) in h.iter().enumerate() {
+                        if cnt > 0 {
+                            try!(write!(self.writer, "\n"));
+                        }
                         try!(self.write_indent());
-                        match k {
+                        match *k {
                             // complex key is not supported
-                            &Yaml::Array(_) | &Yaml::Hash(_) => {
+                            Yaml::Array(_) | Yaml::Hash(_) => {
                                 return Err(EmitError::BadHashmapKey);
                             },
                             _ => { try!(self.emit_node(k)); }
                         }
                         try!(write!(self.writer, ": "));
                         try!(self.emit_node(v));
-                        cnt += 1;
-                        if cnt < h.len() {
-                            try!(write!(self.writer, "\n"));
-                        }
                     }
                     self.level -= 1;
                     Ok(())
                 }
             },
-            &Yaml::String(ref v) => {
+            Yaml::String(ref v) => {
                 try!(escape_str(self.writer, v));
                 Ok(())
             },
-            &Yaml::Boolean(v) => {
+            Yaml::Boolean(v) => {
                 if v {
                     try!(self.writer.write_str("true"));
                 } else {
@@ -180,15 +176,15 @@ impl<'a> YamlEmitter<'a> {
                 }
                 Ok(())
             },
-            &Yaml::Integer(v) => {
+            Yaml::Integer(v) => {
                 try!(write!(self.writer, "{}", v));
                 Ok(())
             },
-            &Yaml::Real(ref v) => {
+            Yaml::Real(ref v) => {
                 try!(write!(self.writer, "{}", v));
                 Ok(())
             },
-            &Yaml::Null | &Yaml::BadValue => {
+            Yaml::Null | Yaml::BadValue => {
                 try!(write!(self.writer, "~"));
                 Ok(())
             },
diff --git a/parser/src/lib.rs b/parser/src/lib.rs
index 1cba925..dc66adc 100644
--- a/parser/src/lib.rs
+++ b/parser/src/lib.rs
@@ -36,6 +36,12 @@
 //!
 //! ```
 
+#![cfg_attr(feature="clippy", feature(plugin))]
+#![cfg_attr(feature="clippy", plugin(clippy))]
+#![cfg_attr(feature="clippy", deny(clippy))]
+#![cfg_attr(feature="clippy", warn(cyclomatic_complexity))]
+#![cfg_attr(feature="clippy", allow(match_same_arms))]
+
 pub mod yaml;
 pub mod scanner;
 pub mod parser;
@@ -89,7 +95,7 @@ mod tests {
             emitter.dump(doc).unwrap();
         }
 
-        assert!(writer.len() > 0);
+        assert!(!writer.is_empty());
     }
 
     fn try_fail(s: &str) -> Result<Vec<Yaml>, ScanError> {
diff --git a/parser/src/parser.rs b/parser/src/parser.rs
index a6cdf73..65924d7 100644
--- a/parser/src/parser.rs
+++ b/parser/src/parser.rs
@@ -55,11 +55,11 @@ pub enum Event {
 impl Event {
     fn empty_scalar() -> Event {
         // a null scalar
-        Event::Scalar("~".to_string(), TScalarStyle::Plain, 0, None)
+        Event::Scalar("~".to_owned(), TScalarStyle::Plain, 0, None)
     }
 
     fn empty_scalar_with_anchor(anchor: usize, tag: TokenType) -> Event {
-        Event::Scalar("".to_string(), TScalarStyle::Plain, anchor, Some(tag))
+        Event::Scalar("".to_owned(), TScalarStyle::Plain, anchor, Some(tag))
     }
 }
 
@@ -179,10 +179,7 @@ impl<T: Iterator<Item=char>> Parser<T> {
     fn load_node<R: EventReceiver>(&mut self, first_ev: &Event, recv: &mut R)
         -> Result<(), ScanError> {
         match *first_ev {
-            Event::Alias(..) => {
-                Ok(())
-            },
-            Event::Scalar(..) => {
+            Event::Alias(..) | Event::Scalar(..) => {
                 Ok(())
             },
             Event::SequenceStart(_) => {
@@ -275,7 +272,7 @@ impl<T: Iterator<Item=char>> Parser<T> {
                 self.skip();
                 Ok(Event::StreamStart)
             },
-            _ => return Err(ScanError::new(tok.0,
+            _ => Err(ScanError::new(tok.0,
                     "did not find expected <stream-start>")),
         }
     }
@@ -283,14 +280,9 @@ impl<T: Iterator<Item=char>> Parser<T> {
     fn document_start(&mut self, implicit: bool) -> ParseResult {
         let mut tok = try!(self.peek());
         if !implicit {
-            loop {
-                match tok.1 {
-                    TokenType::DocumentEnd => {
-                        self.skip();
-                        tok = try!(self.peek());
-                    },
-                    _ => break
-                }
+            while let TokenType::DocumentEnd = tok.1 {
+                self.skip();
+                tok = try!(self.peek());
             }
         }
 
@@ -298,7 +290,7 @@ impl<T: Iterator<Item=char>> Parser<T> {
             TokenType::StreamEnd => {
                 self.state = State::End;
                 self.skip();
-                return Ok(Event::StreamEnd);
+                Ok(Event::StreamEnd)
             },
             TokenType::VersionDirective(..)
                 | TokenType::TagDirective(..)
@@ -376,12 +368,9 @@ impl<T: Iterator<Item=char>> Parser<T> {
         let tok = try!(self.peek());
         let _start_mark = tok.0;
 
-        match tok.1 {
-            TokenType::DocumentEnd => {
-                self.skip();
-                _implicit = false;
-            }
-            _ => {}
+        if let TokenType::DocumentEnd = tok.1 {
+            self.skip();
+            _implicit = false;
         }
 
         // TODO tag handling
@@ -389,7 +378,7 @@ impl<T: Iterator<Item=char>> Parser<T> {
         Ok(Event::DocumentEnd)
     }
 
-    fn register_anchor(&mut self, name: &String, _: &Marker) -> Result<usize, ScanError> {
+    fn register_anchor(&mut self, name: &str, _: &Marker) -> Result<usize, ScanError> {
         // anchors can be overrided/reused
         // if self.anchors.contains_key(name) {
         //     return Err(ScanError::new(*mark,
@@ -397,7 +386,7 @@ impl<T: Iterator<Item=char>> Parser<T> {
         // }
         let new_id = self.anchor_id;
         self.anchor_id += 1;
-        self.anchors.insert(name.clone(), new_id);
+        self.anchors.insert(name.to_owned(), new_id);
         Ok(new_id)
     }
 
diff --git a/parser/src/scanner.rs b/parser/src/scanner.rs
index 16c3b61..d0b5e2b 100644
--- a/parser/src/scanner.rs
+++ b/parser/src/scanner.rs
@@ -45,7 +45,7 @@ impl ScanError {
     pub fn new(loc: Marker, info: &str) -> ScanError {
         ScanError {
             mark: loc,
-            info: info.to_string()
+            info: info.to_owned()
         }
     }
 }
@@ -233,7 +233,7 @@ impl<T: Iterator<Item=char>> Scanner<T> {
         }
     }
 
-    #[inline(always)]
+    #[inline]
     fn lookahead(&mut self, count: usize) {
         if self.buffer.len() >= count {
             return;
@@ -386,7 +386,7 @@ impl<T: Iterator<Item=char>> Scanner<T> {
             // plain scalar
             '-' if !is_blankz(nc) => self.fetch_plain_scalar(),
             ':' | '?' if !is_blankz(nc) && self.flow_level == 0 => self.fetch_plain_scalar(),
-            '%' | '@' | '`' => return Err(ScanError::new(self.mark,
+            '%' | '@' | '`' => Err(ScanError::new(self.mark,
                     &format!("unexpected character: `{}'", c))),
             _ => self.fetch_plain_scalar(),
         }
@@ -404,9 +404,8 @@ impl<T: Iterator<Item=char>> Scanner<T> {
         self.token_available = false;
         self.tokens_parsed += 1;
 
-        match t.1 {
-            TokenType::StreamEnd => self.stream_end_produced = true,
-            _ => {}
+        if let TokenType::StreamEnd = t.1 {
+            self.stream_end_produced = true;
         }
         Ok(Some(t))
     }
@@ -697,12 +696,12 @@ impl<T: Iterator<Item=char>> Scanner<T> {
                 suffix = try!(self.scan_tag_uri(false, secondary, &String::new(), &start_mark));
             } else {
                 suffix = try!(self.scan_tag_uri(false, false, &handle, &start_mark));
-                handle = "!".to_string();
+                handle = "!".to_owned();
                 // A special case: the '!' tag.  Set the handle to '' and the
                 // suffix to '!'.
-                if suffix.len() == 0 {
+                if suffix.is_empty() {
                     handle.clear();
-                    suffix = "!".to_string();
+                    suffix = "!".to_owned();
                 }
             }
         }
@@ -739,20 +738,18 @@ impl<T: Iterator<Item=char>> Scanner<T> {
         if self.ch() == '!' {
             string.push(self.ch());
             self.skip();
-        } else {
+        } else if directive && string != "!" {
             // It's either the '!' tag or not really a tag handle.  If it's a %TAG
             // directive, it's an error.  If it's a tag token, it must be a part of
             // URI.
-            if directive && string != "!" {
-                return Err(ScanError::new(*mark,
-                    "while parsing a tag directive, did not find expected '!'"));
-            }
+            return Err(ScanError::new(*mark,
+                "while parsing a tag directive, did not find expected '!'"));
         }
         Ok(string)
     }
 
     fn scan_tag_uri(&mut self, directive: bool, _is_secondary: bool,
-                head: &String, mark: &Marker) -> Result<String, ScanError> {
+                head: &str, mark: &Marker) -> Result<String, ScanError> {
         let mut length = head.len();
         let mut string = String::new();
 
@@ -1588,10 +1585,8 @@ impl<T: Iterator<Item=char>> Scanner<T> {
 
     fn remove_simple_key(&mut self) -> ScanResult {
         let last = self.simple_keys.last_mut().unwrap();
-        if last.possible {
-            if last.required {
-                return Err(ScanError::new(self.mark, "simple key expected"));
-            }
+        if last.possible && last.required {
+            return Err(ScanError::new(self.mark, "simple key expected"));
         }
 
         last.possible = false;
diff --git a/parser/src/yaml.rs b/parser/src/yaml.rs
index d63e357..6db2a1b 100644
--- a/parser/src/yaml.rs
+++ b/parser/src/yaml.rs
@@ -94,46 +94,43 @@ impl EventReceiver for YamlLoader {
             Event::Scalar(ref v, style, aid, ref tag) => {
                 let node = if style != TScalarStyle::Plain {
                     Yaml::String(v.clone())
-                } else {
-                    match tag {
-                        &Some(TokenType::Tag(ref handle, ref suffix)) => {
-                            // XXX tag:yaml.org,2002:
-                            if handle == "!!" {
-                                match suffix.as_ref() {
-                                    "bool" => {
-                                        // "true" or "false"
-                                        match v.parse::<bool>() {
-                                            Err(_) => Yaml::BadValue,
-                                            Ok(v) => Yaml::Boolean(v)
-                                        }
-                                    },
-                                    "int" => {
-                                        match v.parse::<i64>() {
-                                            Err(_) => Yaml::BadValue,
-                                            Ok(v) => Yaml::Integer(v)
-                                        }
-                                    },
-                                    "float" => {
-                                        match v.parse::<f64>() {
-                                            Err(_) => Yaml::BadValue,
-                                            Ok(_) => Yaml::Real(v.clone())
-                                        }
-                                    },
-                                    "null" => {
-                                        match v.as_ref() {
-                                            "~" | "null" => Yaml::Null,
-                                            _ => Yaml::BadValue,
-                                        }
-                                    }
-                                    _  => Yaml::String(v.clone()),
+                } else if let Some(TokenType::Tag(ref handle, ref suffix)) = *tag {
+                    // XXX tag:yaml.org,2002:
+                    if handle == "!!" {
+                        match suffix.as_ref() {
+                            "bool" => {
+                                // "true" or "false"
+                                match v.parse::<bool>() {
+                                    Err(_) => Yaml::BadValue,
+                                    Ok(v) => Yaml::Boolean(v)
+                                }
+                            },
+                            "int" => {
+                                match v.parse::<i64>() {
+                                    Err(_) => Yaml::BadValue,
+                                    Ok(v) => Yaml::Integer(v)
+                                }
+                            },
+                            "float" => {
+                                match v.parse::<f64>() {
+                                    Err(_) => Yaml::BadValue,
+                                    Ok(_) => Yaml::Real(v.clone())
+                                }
+                            },
+                            "null" => {
+                                match v.as_ref() {
+                                    "~" | "null" => Yaml::Null,
+                                    _ => Yaml::BadValue,
                                 }
-                            } else {
-                                Yaml::String(v.clone())
                             }
-                        },
-                        // Datatype is not specified, or unrecognized
-                        _ => { Yaml::from_str(v.as_ref()) }
+                            _  => Yaml::String(v.clone()),
+                        }
+                    } else {
+                        Yaml::String(v.clone())
                     }
+                } else {
+                    // Datatype is not specified, or unrecognized
+                    Yaml::from_str(v.as_ref())
                 };
 
                 self.insert_new_node((node, aid));
@@ -245,7 +242,12 @@ impl Yaml {
             _ => None
         }
     }
+}
 
+#[cfg_attr(feature="clippy", allow(should_implement_trait))]
+impl Yaml {
+    // Not implementing FromStr because there is no possibility of Error.
+    // This function falls back to Yaml::String if nothing else matches.
     pub fn from_str(v: &str) -> Yaml {
         if v.starts_with("0x") {
             let n = i64::from_str_radix(&v[2..], 16); 
@@ -259,8 +261,8 @@ impl Yaml {
                 return Yaml::Integer(n.unwrap());
             }
         }
-        if v.starts_with("+") && v[1..].parse::<i64>().is_ok() {
-	    return Yaml::Integer(v[1..].parse::<i64>().unwrap());
+        if v.starts_with('+') && v[1..].parse::<i64>().is_ok() {
+            return Yaml::Integer(v[1..].parse::<i64>().unwrap());
         }
         match v {
             "~" | "null" => Yaml::Null,
@@ -268,8 +270,8 @@ impl Yaml {
             "false" => Yaml::Boolean(false),
             _ if v.parse::<i64>().is_ok() => Yaml::Integer(v.parse::<i64>().unwrap()),
             // try parsing as f64
-            _ if v.parse::<f64>().is_ok() => Yaml::Real(v.to_string()),
-            _ => Yaml::String(v.to_string())
+            _ if v.parse::<f64>().is_ok() => Yaml::Real(v.to_owned()),
+            _ => Yaml::String(v.to_owned())
         }
     }
 }
@@ -279,7 +281,7 @@ impl<'a> Index<&'a str> for Yaml {
     type Output = Yaml;
 
     fn index(&self, idx: &'a str) -> &Yaml {
-        let key = Yaml::String(idx.to_string());
+        let key = Yaml::String(idx.to_owned());
         match self.as_hash() {
             Some(h) => h.get(&key).unwrap_or(&BAD_VALUE),
             None => &BAD_VALUE
@@ -333,7 +335,7 @@ a4:
 a5: 'single_quoted'
 a6: \"double_quoted\"
 a7: 你好
-".to_string();
+".to_owned();
         let out = YamlLoader::load_from_str(&s).unwrap();
         let doc = &out[0];
         assert_eq!(doc["a7"].as_str().unwrap(), "你好");