upgrade to rust 1.31 and 2018 edition

Author: Emerentius

exercises/doubly-linked-list/Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 name = "doubly-linked-list"
 version = "0.0.0"
+edition = "2018"
 
 [features]
 # check correct covariance and Send, Sync

exercises/doubly-linked-list/example.rs

@@ -24,7 +24,7 @@ pub struct LinkedList<T> {
 unsafe impl<T: Send> Send for LinkedList<T> {}
 unsafe impl<T: Sync> Sync for LinkedList<T> {}
 
-pub struct Cursor<'a, T: 'a> {
+pub struct Cursor<'a, T> {
     list: &'a mut LinkedList<T>,
     node: OptNodePtr<T>,
 }
@@ -174,12 +174,12 @@ impl<T> Drop for LinkedList<T> {
     }
 }
 
-pub struct Iter<'a, T: 'a> {
+pub struct Iter<'a, T> {
     next_node: OptNodePtr<T>,
     marker: std::marker::PhantomData<&'a LinkedList<T>>,
 }
 
-impl<'a, T: 'a> Iterator for Iter<'a, T> {
+impl<'a, T> Iterator for Iter<'a, T> {
     type Item = &'a T;
 
     fn next(&mut self) -> Option<Self::Item> {
@@ -192,7 +192,7 @@ impl<'a, T: 'a> Iterator for Iter<'a, T> {
     }
 }
 
-impl<'a, T: 'a> Cursor<'a, T> {
+impl<T> Cursor<'_, T> {
     pub fn peek_mut(&mut self) -> Option<&mut T> {
         unsafe {
             self.node.map(|node| &mut (*node.as_ptr()).element)

exercises/doubly-linked-list/src/lib.rs

@@ -5,9 +5,9 @@ mod pre_implemented;
 
 pub struct LinkedList<T>(std::marker::PhantomData<T>);
 
-pub struct Cursor<'a, T: 'a>(std::marker::PhantomData<&'a mut T>);
+pub struct Cursor<'a, T>(std::marker::PhantomData<&'a mut T>);
 
-pub struct Iter<'a, T: 'a>(std::marker::PhantomData<&'a T>);
+pub struct Iter<'a, T>(std::marker::PhantomData<&'a T>);
 
 impl<T> LinkedList<T> {
     pub fn new() -> Self {
@@ -76,7 +76,7 @@ impl<T> Cursor<'_, T> {
     }
 }
 
-impl<'a, T: 'a> Iterator for Iter<'a, T> {
+impl<'a, T> Iterator for Iter<'a, T> {
     type Item = &'a T;
 
     fn next(&mut self) -> Option<&'a T> {

exercises/doubly-linked-list/src/pre_implemented.rs

@@ -2,8 +2,7 @@
 //! You are free to use anything, if it suits you.
 //! They are useful for the test framework, but the implementation is trivial.
 //! We supply them to reduce work both for you and the mentors.
-use {LinkedList, Cursor};
-
+use crate::{LinkedList, Cursor};
 
 impl<T> LinkedList<T> {
     pub fn push_back(&mut self, element: T) {
@@ -31,7 +30,7 @@ impl<T> LinkedList<T> {
     }
 }
 
-impl<T> ::std::iter::FromIterator<T> for LinkedList<T> {
+impl<T> std::iter::FromIterator<T> for LinkedList<T> {
     fn from_iter<I>(iter: I) -> Self
     where
         I: IntoIterator<Item = T>,
@@ -51,7 +50,7 @@ impl<T: Clone> Clone for LinkedList<T> {
 }
 
 // seek methods, return false if end of list is reached prematurely
-impl<'a, T: 'a> Cursor<'a, T> {
+impl<T> Cursor<'_, T> {
     pub fn seek_forward(&mut self, n: usize) -> bool {
         (0..n).all(|_| self.next().is_some())
     }

exercises/doubly-linked-list/tests/doubly-linked-list.rs

@@ -1,4 +1,3 @@
-extern crate doubly_linked_list;
 use doubly_linked_list::*;
 
 #[test]