Fix most of clippy warnings (#914)

* Fix clippy: cast_lossless

* Fix clippy: match_ref_pats

* Fix clippy: extra_unused_lifetimes

* Fix clippy: needless_lifetimes

* Fix clippy: new_without_default

* Fix clippy: or_fun_call

* Fix clippy: should_implement_trait

* Fix clippy: redundant_closure

* Fix clippy: const_static_lifetime

* Fix clippy: redundant_pattern_matching

* Fix clippy: unused_io_amount

* Fix clippy: string_lit_as_bytes

* Fix clippy: needless_update

* Fix clippy: blacklisted_name

* Fix clippy: collapsible_if

* Fix clippy: match_wild_err_arm

* Fix clippy: single_match

* Fix clippy: useless_vec

* Fix clippy: single_char_pattern

* Fix clippy: float_cmp

* Fix clippy: approx_constant

14 files changed, 85 insertions, 74 deletions

diff --git a/examples/nop-preprocessor.rs b/examples/nop-preprocessor.rs
index 374ee60f..8ee2c250 100644
--- a/examples/nop-preprocessor.rs
+++ b/examples/nop-preprocessor.rs
@@ -28,11 +28,9 @@ fn main() {
 
     if let Some(sub_args) = matches.subcommand_matches("supports") {
         handle_supports(&preprocessor, sub_args);
-    } else {
-        if let Err(e) = handle_preprocessing(&preprocessor) {
-            eprintln!("{}", e);
-            process::exit(1);
-        }
+    } else if let Err(e) = handle_preprocessing(&preprocessor) {
+        eprintln!("{}", e);
+        process::exit(1);
     }
 }
 
diff --git a/src/book/book.rs b/src/book/book.rs
index 62af2d92..c98c03c2 100644
--- a/src/book/book.rs
+++ b/src/book/book.rs
@@ -116,7 +116,7 @@ where
     I: IntoIterator<Item = &'a mut BookItem>,
 {
     for item in items {
-        if let &mut BookItem::Chapter(ref mut ch) = item {
+        if let BookItem::Chapter(ch) = item {
             for_each_mut(func, &mut ch.sub_items);
         }
 
@@ -301,7 +301,7 @@ mod tests {
     use std::io::Write;
     use tempfile::{Builder as TempFileBuilder, TempDir};
 
-    const DUMMY_SRC: &'static str = "
+    const DUMMY_SRC: &str = "
 # Dummy Chapter
 
 this is some dummy text.
@@ -317,7 +317,7 @@ And here is some \
         let chapter_path = temp.path().join("chapter_1.md");
         File::create(&chapter_path)
             .unwrap()
-            .write(DUMMY_SRC.as_bytes())
+            .write_all(DUMMY_SRC.as_bytes())
             .unwrap();
 
         let link = Link::new("Chapter 1", chapter_path);
@@ -333,7 +333,7 @@ And here is some \
 
         File::create(&second_path)
             .unwrap()
-            .write_all("Hello World!".as_bytes())
+            .write_all(b"Hello World!")
             .unwrap();
 
         let mut second = Link::new("Nested Chapter 1", &second_path);
diff --git a/src/book/mod.rs b/src/book/mod.rs
index 5002c353..41ae50d9 100644
--- a/src/book/mod.rs
+++ b/src/book/mod.rs
@@ -16,6 +16,7 @@ pub use self::summary::{parse_summary, Link, SectionNumber, Summary, SummaryItem
 use std::io::Write;
 use std::path::PathBuf;
 use std::process::Command;
+use std::string::ToString;
 use tempfile::Builder as TempFileBuilder;
 use toml::Value;
 
@@ -346,7 +347,7 @@ impl MDBook {
 fn determine_renderers(config: &Config) -> Vec<Box<Renderer>> {
     let mut renderers: Vec<Box<Renderer>> = Vec::new();
 
-    if let Some(output_table) = config.get("output").and_then(|o| o.as_table()) {
+    if let Some(output_table) = config.get("output").and_then(Value::as_table) {
         for (key, table) in output_table.iter() {
             // the "html" backend has its own Renderer
             if key == "html" {
@@ -386,7 +387,7 @@ fn determine_preprocessors(config: &Config) -> Result<Vec<Box<Preprocessor>>> {
         preprocessors.extend(default_preprocessors());
     }
 
-    if let Some(preprocessor_table) = config.get("preprocessor").and_then(|v| v.as_table()) {
+    if let Some(preprocessor_table) = config.get("preprocessor").and_then(Value::as_table) {
         for key in preprocessor_table.keys() {
             match key.as_ref() {
                 "links" => preprocessors.push(Box::new(LinkPreprocessor::new())),
@@ -405,8 +406,8 @@ fn determine_preprocessors(config: &Config) -> Result<Vec<Box<Preprocessor>>> {
 fn interpret_custom_preprocessor(key: &str, table: &Value) -> Box<CmdPreprocessor> {
     let command = table
         .get("command")
-        .and_then(|c| c.as_str())
-        .map(|s| s.to_string())
+        .and_then(Value::as_str)
+        .map(ToString::to_string)
         .unwrap_or_else(|| format!("mdbook-{}", key));
 
     Box::new(CmdPreprocessor::new(key.to_string(), command.to_string()))
@@ -417,8 +418,8 @@ fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
     // prepended by "mdbook-"
     let table_dot_command = table
         .get("command")
-        .and_then(|c| c.as_str())
-        .map(|s| s.to_string());
+        .and_then(Value::as_str)
+        .map(ToString::to_string);
 
     let command = table_dot_command.unwrap_or_else(|| format!("mdbook-{}", key));
 
@@ -443,7 +444,7 @@ fn preprocessor_should_run(preprocessor: &Preprocessor, renderer: &Renderer, cfg
     if let Some(Value::Array(ref explicit_renderers)) = cfg.get(&key) {
         return explicit_renderers
             .iter()
-            .filter_map(|val| val.as_str())
+            .filter_map(Value::as_str)
             .any(|name| name == renderer_name);
     }
 
@@ -453,6 +454,7 @@ fn preprocessor_should_run(preprocessor: &Preprocessor, renderer: &Renderer, cfg
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::str::FromStr;
     use toml::value::{Table, Value};
 
     #[test]
@@ -570,9 +572,9 @@ mod tests {
         let html = cfg
             .get_preprocessor("links")
             .and_then(|links| links.get("renderers"))
-            .and_then(|renderers| renderers.as_array())
+            .and_then(Value::as_array)
             .and_then(|renderers| renderers.get(0))
-            .and_then(|renderer| renderer.as_str())
+            .and_then(Value::as_str)
             .unwrap();
         assert_eq!(html, "html");
         let html_renderer = HtmlHandlebars::default();
diff --git a/src/cmd/test.rs b/src/cmd/test.rs
index 63e1910d..cad0ae14 100644
--- a/src/cmd/test.rs
+++ b/src/cmd/test.rs
@@ -31,7 +31,7 @@ pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let library_paths: Vec<&str> = args
         .values_of("library-path")
-        .map(|v| v.collect())
+        .map(std::iter::Iterator::collect)
         .unwrap_or_default();
     let book_dir = get_book_dir(args);
     let mut book = MDBook::load(&book_dir)?;
diff --git a/src/config.rs b/src/config.rs
index c6b37094..8e20bd7e 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -13,6 +13,7 @@
 //! # use mdbook::errors::*;
 //! # extern crate toml;
 //! use std::path::PathBuf;
+//! use std::str::FromStr;
 //! use mdbook::Config;
 //! use toml::Value;
 //!
@@ -56,6 +57,7 @@ use std::env;
 use std::fs::File;
 use std::io::Read;
 use std::path::{Path, PathBuf};
+use std::str::FromStr;
 use toml::value::Table;
 use toml::{self, Value};
 use toml_query::delete::TomlValueDeleteExt;
@@ -75,12 +77,16 @@ pub struct Config {
     rest: Value,
 }
 
-impl Config {
+impl FromStr for Config {
+    type Err = Error;
+
     /// Load a `Config` from some string.
-    pub fn from_str(src: &str) -> Result<Config> {
+    fn from_str(src: &str) -> Result<Self> {
         toml::from_str(src).chain_err(|| Error::from("Invalid configuration file"))
     }
+}
 
+impl Config {
     /// Load the configuration file from disk.
     pub fn from_disk<P: AsRef<Path>>(config_file: P) -> Result<Config> {
         let mut buffer = String::new();
@@ -212,13 +218,13 @@ impl Config {
     /// Get the table associated with a particular renderer.
     pub fn get_renderer<I: AsRef<str>>(&self, index: I) -> Option<&Table> {
         let key = format!("output.{}", index.as_ref());
-        self.get(&key).and_then(|v| v.as_table())
+        self.get(&key).and_then(Value::as_table)
     }
 
     /// Get the table associated with a particular preprocessor.
     pub fn get_preprocessor<I: AsRef<str>>(&self, index: I) -> Option<&Table> {
         let key = format!("preprocessor.{}", index.as_ref());
-        self.get(&key).and_then(|v| v.as_table())
+        self.get(&key).and_then(Value::as_table)
     }
 
     fn from_legacy(mut table: Value) -> Config {
@@ -560,7 +566,7 @@ impl<'de, T> Updateable<'de> for T where T: Serialize + Deserialize<'de> {}
 mod tests {
     use super::*;
 
-    const COMPLEX_CONFIG: &'static str = r#"
+    const COMPLEX_CONFIG: &str = r#"
         [book]
         title = "Some Book"
         authors = ["Michael-F-Bryan <michaelfbryan@gmail.com>"]
@@ -601,7 +607,6 @@ mod tests {
             description: Some(String::from("A completely useless book")),
             multilingual: true,
             src: PathBuf::from("source"),
-            ..Default::default()
         };
         let build_should_be = BuildConfig {
             build_dir: PathBuf::from("outputs"),
@@ -658,10 +663,10 @@ mod tests {
 
         assert_eq!(got, should_be);
 
-        let baz: Vec<bool> = cfg.get_deserialized("output.random.baz").unwrap();
+        let got_baz: Vec<bool> = cfg.get_deserialized("output.random.baz").unwrap();
         let baz_should_be = vec![true, true, false];
 
-        assert_eq!(baz, baz_should_be);
+        assert_eq!(got_baz, baz_should_be);
     }
 
     #[test]
@@ -753,7 +758,7 @@ mod tests {
 
         for (src, should_be) in inputs {
             let got = parse_env(src);
-            let should_be = should_be.map(|s| s.to_string());
+            let should_be = should_be.map(ToString::to_string);
 
             assert_eq!(got, should_be);
         }
@@ -783,6 +788,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(clippy::approx_constant)]
     fn update_config_using_env_var_and_complex_value() {
         let mut cfg = Config::default();
         let key = "foo-bar.baz";
diff --git a/src/preprocess/index.rs b/src/preprocess/index.rs
index a8818518..d8e00fc1 100644
--- a/src/preprocess/index.rs
+++ b/src/preprocess/index.rs
@@ -8,6 +8,7 @@ use book::{Book, BookItem};
 
 /// A preprocessor for converting file name `README.md` to `index.md` since
 /// `README.md` is the de facto index file in markdown-based documentation.
+#[derive(Default)]
 pub struct IndexPreprocessor;
 
 impl IndexPreprocessor {
@@ -45,7 +46,10 @@ impl Preprocessor for IndexPreprocessor {
 
 fn warn_readme_name_conflict<P: AsRef<Path>>(readme_path: P, index_path: P) {
     let file_name = readme_path.as_ref().file_name().unwrap_or_default();
-    let parent_dir = index_path.as_ref().parent().unwrap_or(index_path.as_ref());
+    let parent_dir = index_path
+        .as_ref()
+        .parent()
+        .unwrap_or_else(|| index_path.as_ref());
     warn!(
         "It seems that there are both {:?} and index.md under \"{}\".",
         file_name,
@@ -67,7 +71,7 @@ fn is_readme_file<P: AsRef<Path>>(path: P) -> bool {
     RE.is_match(
         path.as_ref()
             .file_stem()
-            .and_then(|s| s.to_str())
+            .and_then(std::ffi::OsStr::to_str)
             .unwrap_or_default(),
     )
 }
diff --git a/src/preprocess/links.rs b/src/preprocess/links.rs
index 2e3a88e3..d852f706 100644
--- a/src/preprocess/links.rs
+++ b/src/preprocess/links.rs
@@ -13,6 +13,7 @@ const MAX_LINK_NESTED_DEPTH: usize = 10;
 
 /// A preprocessor for expanding the `{{# playpen}}` and `{{# include}}`
 /// helpers in a chapter.
+#[derive(Default)]
 pub struct LinkPreprocessor;
 
 impl LinkPreprocessor {
diff --git a/src/renderer/html_handlebars/hbs_renderer.rs b/src/renderer/html_handlebars/hbs_renderer.rs
index 956b8125..74358fb0 100644
--- a/src/renderer/html_handlebars/hbs_renderer.rs
+++ b/src/renderer/html_handlebars/hbs_renderer.rs
@@ -611,7 +611,7 @@ fn partition_source(s: &str) -> (String, String) {
 
     for line in s.lines() {
         let trimline = line.trim();
-        let header = trimline.chars().all(|c| c.is_whitespace()) || trimline.starts_with("#![");
+        let header = trimline.chars().all(char::is_whitespace) || trimline.starts_with("#![");
         if !header || after_header {
             after_header = true;
             after.push_str(line);
diff --git a/src/renderer/html_handlebars/helpers/theme.rs b/src/renderer/html_handlebars/helpers/theme.rs
index 24c0dda1..44a4f85f 100644
--- a/src/renderer/html_handlebars/helpers/theme.rs
+++ b/src/renderer/html_handlebars/helpers/theme.rs
@@ -9,12 +9,9 @@ pub fn theme_option(
 ) -> Result<(), RenderError> {
     trace!("theme_option (handlebars helper)");
 
-    let param = h
-        .param(0)
-        .and_then(|v| v.value().as_str())
-        .ok_or(RenderError::new(
-            "Param 0 with String type is required for theme_option helper.",
-        ))?;
+    let param = h.param(0).and_then(|v| v.value().as_str()).ok_or_else(|| {
+        RenderError::new("Param 0 with String type is required for theme_option helper.")
+    })?;
 
     let theme_name = rc
         .evaluate_absolute(ctx, "default_theme", true)?
diff --git a/src/renderer/html_handlebars/helpers/toc.rs b/src/renderer/html_handlebars/helpers/toc.rs
index 190a3470..ae085e5f 100644
--- a/src/renderer/html_handlebars/helpers/toc.rs
+++ b/src/renderer/html_handlebars/helpers/toc.rs
@@ -16,11 +16,11 @@ pub struct RenderToc {
 impl HelperDef for RenderToc {
     fn call<'reg: 'rc, 'rc>(
         &self,
-        _h: &Helper,
-        _: &Handlebars,
-        ctx: &Context,
-        rc: &mut RenderContext,
-        out: &mut Output,
+        _h: &Helper<'reg, 'rc>,
+        _r: &'reg Handlebars,
+        ctx: &'rc Context,
+        rc: &mut RenderContext<'reg>,
+        out: &mut dyn Output,
     ) -> Result<(), RenderError> {
         // get value from context data
         // rc.get_path() is current json parent path, you should always use it like this
diff --git a/src/renderer/html_handlebars/search.rs b/src/renderer/html_handlebars/search.rs
index c27977e1..df7a698f 100644
--- a/src/renderer/html_handlebars/search.rs
+++ b/src/renderer/html_handlebars/search.rs
@@ -91,7 +91,7 @@ fn render_item(
     let p = Parser::new_ext(&chapter.content, opts);
 
     let mut in_header = false;
-    let max_section_depth = search_config.heading_split_level as i32;
+    let max_section_depth = i32::from(search_config.heading_split_level);
     let mut section_id = None;
     let mut heading = String::new();
     let mut body = String::new();
diff --git a/src/utils/fs.rs b/src/utils/fs.rs
index 4ac59127..4e0aeb7d 100644
--- a/src/utils/fs.rs
+++ b/src/utils/fs.rs
@@ -1,4 +1,5 @@
 use errors::*;
+use std::convert::Into;
 use std::fs::{self, File};
 use std::io::{Read, Write};
 use std::path::{Component, Path, PathBuf};
@@ -28,7 +29,7 @@ pub fn normalize_path(path: &str) -> String {
 pub fn write_file<P: AsRef<Path>>(build_dir: &Path, filename: P, content: &[u8]) -> Result<()> {
     let path = build_dir.join(filename);
 
-    create_file(&path)?.write_all(content).map_err(|e| e.into())
+    create_file(&path)?.write_all(content).map_err(Into::into)
 }
 
 /// Takes a path and returns a path containing just enough `../` to point to
@@ -85,7 +86,7 @@ pub fn create_file(path: &Path) -> Result<File> {
         fs::create_dir_all(p)?;
     }
 
-    File::create(path).map_err(|e| e.into())
+    File::create(path).map_err(Into::into)
 }
 
 /// Removes all the content of a directory but not the directory itself
@@ -196,43 +197,44 @@ mod tests {
     fn copy_files_except_ext_test() {
         let tmp = match tempfile::TempDir::new() {
             Ok(t) => t,
-            Err(_) => panic!("Could not create a temp dir"),
+            Err(e) => panic!("Could not create a temp dir: {}", e),
         };
 
         // Create a couple of files
-        if let Err(_) = fs::File::create(&tmp.path().join("file.txt")) {
-            panic!("Could not create file.txt")
+        if let Err(err) = fs::File::create(&tmp.path().join("file.txt")) {
+            panic!("Could not create file.txt: {}", err);
         }
-        if let Err(_) = fs::File::create(&tmp.path().join("file.md")) {
-            panic!("Could not create file.md")
+        if let Err(err) = fs::File::create(&tmp.path().join("file.md")) {
+            panic!("Could not create file.md: {}", err);
         }
-        if let Err(_) = fs::File::create(&tmp.path().join("file.png")) {
-            panic!("Could not create file.png")
+        if let Err(err) = fs::File::create(&tmp.path().join("file.png")) {
+            panic!("Could not create file.png: {}", err);
         }
-        if let Err(_) = fs::create_dir(&tmp.path().join("sub_dir")) {
-            panic!("Could not create sub_dir")
+        if let Err(err) = fs::create_dir(&tmp.path().join("sub_dir")) {
+            panic!("Could not create sub_dir: {}", err);
         }
-        if let Err(_) = fs::File::create(&tmp.path().join("sub_dir/file.png")) {
-            panic!("Could not create sub_dir/file.png")
+        if let Err(err) = fs::File::create(&tmp.path().join("sub_dir/file.png")) {
+            panic!("Could not create sub_dir/file.png: {}", err);
         }
-        if let Err(_) = fs::create_dir(&tmp.path().join("sub_dir_exists")) {
-            panic!("Could not create sub_dir_exists")
+        if let Err(err) = fs::create_dir(&tmp.path().join("sub_dir_exists")) {
+            panic!("Could not create sub_dir_exists: {}", err);
         }
-        if let Err(_) = fs::File::create(&tmp.path().join("sub_dir_exists/file.txt")) {
-            panic!("Could not create sub_dir_exists/file.txt")
+        if let Err(err) = fs::File::create(&tmp.path().join("sub_dir_exists/file.txt")) {
+            panic!("Could not create sub_dir_exists/file.txt: {}", err);
         }
 
         // Create output dir
-        if let Err(_) = fs::create_dir(&tmp.path().join("output")) {
-            panic!("Could not create output")
+        if let Err(err) = fs::create_dir(&tmp.path().join("output")) {
+            panic!("Could not create output: {}", err);
         }
-        if let Err(_) = fs::create_dir(&tmp.path().join("output/sub_dir_exists")) {
-            panic!("Could not create output/sub_dir_exists")
+        if let Err(err) = fs::create_dir(&tmp.path().join("output/sub_dir_exists")) {
+            panic!("Could not create output/sub_dir_exists: {}", err);
         }
 
-        match copy_files_except_ext(&tmp.path(), &tmp.path().join("output"), true, &["md"]) {
-            Err(e) => panic!("Error while executing the function:\n{:?}", e),
-            Ok(_) => {}
+        if let Err(e) =
+            copy_files_except_ext(&tmp.path(), &tmp.path().join("output"), true, &["md"])
+        {
+            panic!("Error while executing the function:\n{:?}", e);
         }
 
         // Check if the correct files where created
diff --git a/src/utils/mod.rs b/src/utils/mod.rs
index 2a6324f1..7c7aeb51 100644
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -14,7 +14,7 @@ use std::borrow::Cow;
 pub use self::string::{take_lines, RangeArgument};
 
 /// Replaces multiple consecutive whitespace characters with a single space character.
-pub fn collapse_whitespace<'a>(text: &'a str) -> Cow<'a, str> {
+pub fn collapse_whitespace(text: &str) -> Cow<'_, str> {
     lazy_static! {
         static ref RE: Regex = Regex::new(r"\s\s+").unwrap();
     }
diff --git a/tests/rendered_output.rs b/tests/rendered_output.rs
index 2449498c..8766ed88 100644
--- a/tests/rendered_output.rs
+++ b/tests/rendered_output.rs
@@ -22,15 +22,15 @@ use std::path::Path;
 use tempfile::Builder as TempFileBuilder;
 use walkdir::{DirEntry, WalkDir};
 
-const BOOK_ROOT: &'static str = concat!(env!("CARGO_MANIFEST_DIR"), "/tests/dummy_book");
-const TOC_TOP_LEVEL: &[&'static str] = &[
+const BOOK_ROOT: &str = concat!(env!("CARGO_MANIFEST_DIR"), "/tests/dummy_book");
+const TOC_TOP_LEVEL: &[&str] = &[
     "1. First Chapter",
     "2. Second Chapter",
     "Conclusion",
     "Dummy Book",
     "Introduction",
 ];
-const TOC_SECOND_LEVEL: &[&'static str] = &[
+const TOC_SECOND_LEVEL: &[&str] = &[
     "1.1. Nested Chapter",
     "1.2. Includes",
     "2.1. Nested Chapter",
@@ -187,7 +187,7 @@ fn chapter_files_were_rendered_to_html() {
     let chapter_files = WalkDir::new(&src)
         .into_iter()
         .filter_entry(|entry| entry_ends_with(entry, ".md"))
-        .filter_map(|entry| entry.ok())
+        .filter_map(std::result::Result::ok)
         .map(|entry| entry.path().to_path_buf())
         .filter(|path| path.file_name().and_then(OsStr::to_str) != Some("SUMMARY.md"));
 
@@ -390,7 +390,7 @@ fn by_default_mdbook_use_index_preprocessor_to_convert_readme_to_index() {
         "First README",
     ];
     assert_contains_strings(&first_index, &expected_strings);
-    assert_doesnt_contain_strings(&first_index, &vec!["README.html"]);
+    assert_doesnt_contain_strings(&first_index, &["README.html"]);
 
     let second_index = temp.path().join("book").join("second").join("index.html");
     let unexpected_strings = vec!["Second README"];
@@ -428,11 +428,12 @@ mod search {
         let index = root.join("book/searchindex.js");
         let index = file_to_string(index).unwrap();
         let index = index.trim_start_matches("window.search = ");
-        let index = index.trim_end_matches(";");
+        let index = index.trim_end_matches(';');
         serde_json::from_str(&index).unwrap()
     }
 
     #[test]
+    #[allow(clippy::float_cmp)]
     fn book_creates_reasonable_search_index() {
         let temp = DummyBook::new().build().unwrap();
         let md = MDBook::load(temp.path()).unwrap();