Fix clippy and bump MSRV

.azure-pipelines.yml

@@ -14,7 +14,7 @@ stages:
     jobs:
       - job:
         variables:
-          rust: 1.36.0
+          rust: 1.40.0
         strategy:
           matrix:
             Windows 32-bit (MSVC):

.travis.yml

@@ -30,8 +30,8 @@ jobs:
   fast_finish: true
   include:
     - os: osx
-      rust: 1.36.0
-    - rust: 1.36.0
+      rust: 1.40.0
+    - rust: 1.40.0
     - {}
     - rust: beta
     - rust: nightly

clap_derive/tests/macro-errors.rs

@@ -5,7 +5,7 @@
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 
-#[rustversion::attr(any(not(stable), before(1.39)), ignore)]
+#[rustversion::attr(any(not(stable), before(1.42)), ignore)]
 #[test]
 fn ui() {
     let t = trybuild::TestCases::new();

src/build/app/mod.rs

@@ -146,7 +146,7 @@ impl<'b> App<'b> {
 
     /// Get the name of the binary
     pub fn get_bin_name(&self) -> Option<&str> {
-        self.bin_name.as_ref().map(String::as_str)
+        self.bin_name.as_deref()
     }
 
     /// Sets a string of author(s) that will be displayed to the user when they
@@ -1957,7 +1957,7 @@ impl<'a> From<&'a Yaml> for App<'a> {
             App::new(name)
         } else {
             let yaml_hash = yaml.as_hash().unwrap();
-            let sc_key = yaml_hash.keys().nth(0).unwrap();
+            let sc_key = yaml_hash.keys().next().unwrap();
             is_sc = Some(yaml_hash.get(sc_key).unwrap());
             App::new(sc_key.as_str().unwrap())
         };

src/build/arg/mod.rs

@@ -171,7 +171,7 @@ impl<'help> Arg<'help> {
     #[allow(clippy::cognitive_complexity)]
     pub fn from_yaml(y: &yaml_rust::yaml::Hash) -> Arg {
         // We WANT this to panic on error...so expect() is good.
-        let name_yml = y.keys().nth(0).unwrap();
+        let name_yml = y.keys().next().unwrap();
         let name_str = name_yml.as_str().unwrap();
         let mut a = Arg::with_name(name_str);
         let arg_settings = y.get(name_yml).unwrap().as_hash().unwrap();
@@ -817,7 +817,7 @@ impl<'help> Arg<'help> {
     /// assert!(res.is_err());
     /// assert_eq!(res.unwrap_err().kind, ErrorKind::ArgumentConflict);
     /// ```
-    ///     
+    ///
     /// [`Arg::conflicts_with_all(names)`]: ./struct.Arg.html#method.conflicts_with_all
     /// [`Arg::exclusive(true)`]: ./struct.Arg.html#method.exclusive
 
@@ -2115,7 +2115,7 @@ impl<'help> Arg<'help> {
         self.setb(ArgSettings::UseValueDelimiter);
         self.val_delim = Some(
             d.chars()
-                .nth(0)
+                .next()
                 .expect("Failed to get value_delimiter from arg"),
         );
         self

src/build/arg_group.rs

@@ -469,7 +469,7 @@ impl<'a> From<&'a yaml_rust::yaml::Hash> for ArgGroup<'a> {
         // We WANT this to panic on error...so expect() is good.
         let mut a = ArgGroup::default();
         let group_settings = if b.len() == 1 {
-            let name_yml = b.keys().nth(0).expect("failed to get name");
+            let name_yml = b.keys().next().expect("failed to get name");
             let name_str = name_yml
                 .as_str()
                 .expect("failed to convert arg YAML name to str");

src/macros.rs

@@ -759,7 +759,7 @@ macro_rules! clap_app {
         $crate::clap_app!{ @arg ($arg.long(stringify!($long))) $modes $($tail)* }
     };
     (@arg ($arg:expr) $modes:tt -$short:ident $($tail:tt)*) => {
-        $crate::clap_app!{ @arg ($arg.short(stringify!($short).chars().nth(0).unwrap())) $modes $($tail)* }
+        $crate::clap_app!{ @arg ($arg.short(stringify!($short).chars().next().unwrap())) $modes $($tail)* }
     };
     (@arg ($arg:expr) (-) <$var:ident> $($tail:tt)*) => {
         $crate::clap_app!{ @arg ($arg.value_name(stringify!($var))) (+) +takes_value +required $($tail)* }