Fix 2018 edition errors

Author: varkor

src/lib.rs

@@ -514,15 +514,15 @@ impl Options {
 
     /// Derive a custom formatted message from a set of options. The formatted options provided to
     /// a closure as an iterator.
-    pub fn usage_with_format<F: FnMut(&mut Iterator<Item = String>) -> String>(
+    pub fn usage_with_format<F: FnMut(&mut dyn Iterator<Item = String>) -> String>(
         &self,
         mut formatter: F,
     ) -> String {
         formatter(&mut self.usage_items())
     }
 
     /// Derive usage items from a set of options.
-    fn usage_items<'a>(&'a self) -> Box<Iterator<Item = String> + 'a> {
+    fn usage_items<'a>(&'a self) -> Box<dyn Iterator<Item = String> + 'a> {
         let desc_sep = format!("\n{}", repeat(" ").take(24).collect::<String>());
 
         let any_short = self.grps.iter().any(|optref| !optref.short_name.is_empty());
@@ -938,7 +938,7 @@ fn find_opt(opts: &[Opt], nm: &Name) -> Option<usize> {
 }
 
 impl fmt::Display for Fail {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             ArgumentMissing(ref nm) => write!(f, "Argument to option '{}' missing", *nm),
             UnrecognizedOption(ref nm) => write!(f, "Unrecognized option: '{}'", *nm),