Auto merge of #58081 - Centril:liballoc-2018, r=oli-obk

Transition liballoc to Rust 2018

This transitions liballoc to Rust 2018 edition and applies relevant idiom lints.
I also did a small bit of drive-by cleanup along the way.

r? @oli-obk

I started with liballoc since it seemed easiest. In particular, adding `edition = "2018"` to libcore gave me way too many errors due to stdsimd. Ideally we should be able to continue this crate-by-crate until all crates use 2018.

Author: bors

Diff for: src/liballoc/Cargo.toml

@@ -4,6 +4,7 @@ name = "alloc"
 version = "0.0.0"
 autotests = false
 autobenches = false
+edition = "2018"
 
 [lib]
 name = "alloc"

Diff for: src/liballoc/alloc.rs

@@ -227,9 +227,9 @@ pub fn handle_alloc_error(layout: Layout) -> ! {
 #[cfg(test)]
 mod tests {
     extern crate test;
-    use self::test::Bencher;
-    use boxed::Box;
-    use alloc::{Global, Alloc, Layout, handle_alloc_error};
+    use test::Bencher;
+    use crate::boxed::Box;
+    use crate::alloc::{Global, Alloc, Layout, handle_alloc_error};
 
     #[test]
     fn allocate_zeroed() {

Diff for: src/liballoc/benches/btree/map.rs

@@ -1,6 +1,7 @@
 use std::iter::Iterator;
 use std::vec::Vec;
 use std::collections::BTreeMap;
+
 use rand::{Rng, seq::SliceRandom, thread_rng};
 use test::{Bencher, black_box};
 

Diff for: src/liballoc/benches/slice.rs

@@ -1,8 +1,6 @@
-use rand::{thread_rng};
-use std::mem;
-use std::ptr;
+use std::{mem, ptr};
 
-use rand::{Rng, SeedableRng};
+use rand::{thread_rng, Rng, SeedableRng};
 use rand::distributions::{Standard, Alphanumeric};
 use rand_xorshift::XorShiftRng;
 use test::{Bencher, black_box};

Diff for: src/liballoc/borrow.rs

@@ -6,14 +6,14 @@ use core::cmp::Ordering;
 use core::hash::{Hash, Hasher};
 use core::ops::{Add, AddAssign, Deref};
 
-use fmt;
-use string::String;
-
-use self::Cow::*;
-
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::borrow::{Borrow, BorrowMut};
 
+use crate::fmt;
+use crate::string::String;
+
+use Cow::*;
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B>
     where B: ToOwned,
@@ -182,9 +182,7 @@ pub enum Cow<'a, B: ?Sized + 'a>
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, B: ?Sized> Clone for Cow<'a, B>
-    where B: ToOwned
-{
+impl<'a, B: ?Sized + ToOwned> Clone for Cow<'a, B> {
     fn clone(&self) -> Cow<'a, B> {
         match *self {
             Borrowed(b) => Borrowed(b),
@@ -207,9 +205,7 @@ impl<'a, B: ?Sized> Clone for Cow<'a, B>
     }
 }
 
-impl<'a, B: ?Sized> Cow<'a, B>
-    where B: ToOwned
-{
+impl<B: ?Sized + ToOwned> Cow<'_, B> {
     /// Acquires a mutable reference to the owned form of the data.
     ///
     /// Clones the data if it is not already owned.
@@ -285,9 +281,7 @@ impl<'a, B: ?Sized> Cow<'a, B>
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, B: ?Sized> Deref for Cow<'a, B>
-    where B: ToOwned
-{
+impl<B: ?Sized + ToOwned> Deref for Cow<'_, B> {
     type Target = B;
 
     fn deref(&self) -> &B {
@@ -299,7 +293,7 @@ impl<'a, B: ?Sized> Deref for Cow<'a, B>
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, B: ?Sized> Eq for Cow<'a, B> where B: Eq + ToOwned {}
+impl<B: ?Sized> Eq for Cow<'_, B> where B: Eq + ToOwned {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, B: ?Sized> Ord for Cow<'a, B>
@@ -333,11 +327,11 @@ impl<'a, B: ?Sized> PartialOrd for Cow<'a, B>
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, B: ?Sized> fmt::Debug for Cow<'a, B>
+impl<B: ?Sized> fmt::Debug for Cow<'_, B>
     where B: fmt::Debug + ToOwned,
           <B as ToOwned>::Owned: fmt::Debug
 {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Borrowed(ref b) => fmt::Debug::fmt(b, f),
             Owned(ref o) => fmt::Debug::fmt(o, f),
@@ -346,11 +340,11 @@ impl<'a, B: ?Sized> fmt::Debug for Cow<'a, B>
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, B: ?Sized> fmt::Display for Cow<'a, B>
+impl<B: ?Sized> fmt::Display for Cow<'_, B>
     where B: fmt::Display + ToOwned,
           <B as ToOwned>::Owned: fmt::Display
 {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Borrowed(ref b) => fmt::Display::fmt(b, f),
             Owned(ref o) => fmt::Display::fmt(o, f),
@@ -380,7 +374,7 @@ impl<'a, B: ?Sized> Hash for Cow<'a, B>
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T: ?Sized + ToOwned> AsRef<T> for Cow<'a, T> {
+impl<T: ?Sized + ToOwned> AsRef<T> for Cow<'_, T> {
     fn as_ref(&self) -> &T {
         self
     }

Diff for: src/liballoc/boxed.rs

@@ -73,9 +73,9 @@ use core::ops::{
 use core::ptr::{self, NonNull, Unique};
 use core::task::{LocalWaker, Poll};
 
-use vec::Vec;
-use raw_vec::RawVec;
-use str::from_boxed_utf8_unchecked;
+use crate::vec::Vec;
+use crate::raw_vec::RawVec;
+use crate::str::from_boxed_utf8_unchecked;
 
 /// A pointer type for heap allocation.
 ///
@@ -603,21 +603,21 @@ impl Box<dyn Any + Send> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: fmt::Display + ?Sized> fmt::Display for Box<T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(&**self, f)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: fmt::Debug + ?Sized> fmt::Debug for Box<T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(&**self, f)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized> fmt::Pointer for Box<T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // It's not possible to extract the inner Uniq directly from the Box,
         // instead we cast it to a *const which aliases the Unique
         let ptr: *const T = &**self;
@@ -737,7 +737,7 @@ impl<A, F> FnBox<A> for F
 
 #[unstable(feature = "fnbox",
            reason = "will be deprecated if and when `Box<FnOnce>` becomes usable", issue = "28796")]
-impl<'a, A, R> FnOnce<A> for Box<dyn FnBox<A, Output = R> + 'a> {
+impl<A, R> FnOnce<A> for Box<dyn FnBox<A, Output = R> + '_> {
     type Output = R;
 
     extern "rust-call" fn call_once(self, args: A) -> R {
@@ -747,7 +747,7 @@ impl<'a, A, R> FnOnce<A> for Box<dyn FnBox<A, Output = R> + 'a> {
 
 #[unstable(feature = "fnbox",
            reason = "will be deprecated if and when `Box<FnOnce>` becomes usable", issue = "28796")]
-impl<'a, A, R> FnOnce<A> for Box<dyn FnBox<A, Output = R> + Send + 'a> {
+impl<A, R> FnOnce<A> for Box<dyn FnBox<A, Output = R> + Send + '_> {
     type Output = R;
 
     extern "rust-call" fn call_once(self, args: A) -> R {

Diff for: src/liballoc/collections/binary_heap.rs

@@ -151,8 +151,8 @@ use core::mem::{swap, size_of, ManuallyDrop};
 use core::ptr;
 use core::fmt;
 
-use slice;
-use vec::{self, Vec};
+use crate::slice;
+use crate::vec::{self, Vec};
 
 use super::SpecExtend;
 
@@ -227,16 +227,16 @@ pub struct PeekMut<'a, T: 'a + Ord> {
 }
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
-impl<'a, T: Ord + fmt::Debug> fmt::Debug for PeekMut<'a, T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+impl<T: Ord + fmt::Debug> fmt::Debug for PeekMut<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("PeekMut")
          .field(&self.heap.data[0])
          .finish()
     }
 }
 
 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
-impl<'a, T: Ord> Drop for PeekMut<'a, T> {
+impl<T: Ord> Drop for PeekMut<'_, T> {
     fn drop(&mut self) {
         if self.sift {
             self.heap.sift_down(0);
@@ -245,15 +245,15 @@ impl<'a, T: Ord> Drop for PeekMut<'a, T> {
 }
 
 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
-impl<'a, T: Ord> Deref for PeekMut<'a, T> {
+impl<T: Ord> Deref for PeekMut<'_, T> {
     type Target = T;
     fn deref(&self) -> &T {
         &self.heap.data[0]
     }
 }
 
 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
-impl<'a, T: Ord> DerefMut for PeekMut<'a, T> {
+impl<T: Ord> DerefMut for PeekMut<'_, T> {
     fn deref_mut(&mut self) -> &mut T {
         &mut self.heap.data[0]
     }
@@ -291,7 +291,7 @@ impl<T: Ord> Default for BinaryHeap<T> {
 
 #[stable(feature = "binaryheap_debug", since = "1.4.0")]
 impl<T: fmt::Debug + Ord> fmt::Debug for BinaryHeap<T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self.iter()).finish()
     }
 }
@@ -349,7 +349,7 @@ impl<T: Ord> BinaryHeap<T> {
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn iter(&self) -> Iter<T> {
+    pub fn iter(&self) -> Iter<'_, T> {
         Iter { iter: self.data.iter() }
     }
 
@@ -400,7 +400,7 @@ impl<T: Ord> BinaryHeap<T> {
     /// assert_eq!(heap.peek(), Some(&2));
     /// ```
     #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
-    pub fn peek_mut(&mut self) -> Option<PeekMut<T>> {
+    pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>> {
         if self.is_empty() {
             None
         } else {
@@ -761,7 +761,7 @@ impl<T: Ord> BinaryHeap<T> {
     /// ```
     #[inline]
     #[stable(feature = "drain", since = "1.6.0")]
-    pub fn drain(&mut self) -> Drain<T> {
+    pub fn drain(&mut self) -> Drain<'_, T> {
         Drain { iter: self.data.drain(..) }
     }
 
@@ -908,7 +908,7 @@ impl<'a, T> Hole<'a, T> {
     }
 }
 
-impl<'a, T> Drop for Hole<'a, T> {
+impl<T> Drop for Hole<'_, T> {
     #[inline]
     fn drop(&mut self) {
         // fill the hole again
@@ -932,8 +932,8 @@ pub struct Iter<'a, T: 'a> {
 }
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
-impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("Iter")
          .field(&self.iter.as_slice())
          .finish()
@@ -972,14 +972,14 @@ impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T> ExactSizeIterator for Iter<'a, T> {
+impl<T> ExactSizeIterator for Iter<'_, T> {
     fn is_empty(&self) -> bool {
         self.iter.is_empty()
     }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
-impl<'a, T> FusedIterator for Iter<'a, T> {}
+impl<T> FusedIterator for Iter<'_, T> {}
 
 /// An owning iterator over the elements of a `BinaryHeap`.
 ///
@@ -996,7 +996,7 @@ pub struct IntoIter<T> {
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
 impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("IntoIter")
          .field(&self.iter.as_slice())
          .finish()
@@ -1050,7 +1050,7 @@ pub struct Drain<'a, T: 'a> {
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<'a, T: 'a> Iterator for Drain<'a, T> {
+impl<T> Iterator for Drain<'_, T> {
     type Item = T;
 
     #[inline]
@@ -1065,22 +1065,22 @@ impl<'a, T: 'a> Iterator for Drain<'a, T> {
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
+impl<T> DoubleEndedIterator for Drain<'_, T> {
     #[inline]
     fn next_back(&mut self) -> Option<T> {
         self.iter.next_back()
     }
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {
+impl<T> ExactSizeIterator for Drain<'_, T> {
     fn is_empty(&self) -> bool {
         self.iter.is_empty()
     }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
-impl<'a, T: 'a> FusedIterator for Drain<'a, T> {}
+impl<T> FusedIterator for Drain<'_, T> {}
 
 #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
 impl<T: Ord> From<Vec<T>> for BinaryHeap<T> {