Migrate to 2018 edition. (#924)

* Migrate to 2018 edition.

* Use impl Iterator at one site.

* Fix more rust 2018 idioms.

src/event_loop.rs

@@ -13,9 +13,9 @@ use std::{fmt, error};
 use std::time::Instant;
 use std::ops::Deref;
 
-use platform_impl;
-use event::Event;
-use monitor::{AvailableMonitorsIter, MonitorHandle};
+use crate::platform_impl;
+use crate::event::Event;
+use crate::monitor::{AvailableMonitorsIter, MonitorHandle};
 
 /// Provides a way to retrieve events from the system and from the windows that were registered to
 /// the events loop.
@@ -46,13 +46,13 @@ pub struct EventLoopWindowTarget<T: 'static> {
 }
 
 impl<T> fmt::Debug for EventLoop<T> {
-    fn fmt(&self, fmtr: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, fmtr: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmtr.pad("EventLoop { .. }")
     }
 }
 
 impl<T> fmt::Debug for EventLoopWindowTarget<T> {
-    fn fmt(&self, fmtr: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, fmtr: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmtr.pad("EventLoopWindowTarget { .. }")
     }
 }
@@ -146,10 +146,8 @@ impl<T> EventLoop<T> {
     }
 
     /// Returns the list of all the monitors available on the system.
-    ///
-    // Note: should be replaced with `-> impl Iterator` once stable.
     #[inline]
-    pub fn available_monitors(&self) -> AvailableMonitorsIter {
+    pub fn available_monitors(&self) -> impl Iterator<Item = MonitorHandle> {
         let data = self.event_loop.available_monitors();
         AvailableMonitorsIter{ data: data.into_iter() }
     }
@@ -186,7 +184,7 @@ impl<T: 'static> EventLoopProxy<T> {
 }
 
 impl<T: 'static> fmt::Debug for EventLoopProxy<T> {
-    fn fmt(&self, fmtr: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, fmtr: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmtr.pad("EventLoopProxy { .. }")
     }
 }
@@ -197,7 +195,7 @@ impl<T: 'static> fmt::Debug for EventLoopProxy<T> {
 pub struct EventLoopClosed;
 
 impl fmt::Display for EventLoopClosed {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", error::Error::description(self))
     }
 }