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.

1 files changed, 8 insertions, 9 deletions

diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index 5e4aac9ce78..dcecf9bc76d 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -7,10 +7,9 @@ use core::ops::Drop;
 use core::ptr::{self, NonNull, Unique};
 use core::slice;
 
-use alloc::{Alloc, Layout, Global, handle_alloc_error};
-use collections::CollectionAllocErr;
-use collections::CollectionAllocErr::*;
-use boxed::Box;
+use crate::alloc::{Alloc, Layout, Global, handle_alloc_error};
+use crate::collections::CollectionAllocErr::{self, *};
+use crate::boxed::Box;
 
 /// A low-level utility for more ergonomically allocating, reallocating, and deallocating
 /// a buffer of memory on the heap without having to worry about all the corner cases
@@ -621,14 +620,14 @@ enum Fallibility {
     Infallible,
 }
 
-use self::Fallibility::*;
+use Fallibility::*;
 
 enum ReserveStrategy {
     Exact,
     Amortized,
 }
 
-use self::ReserveStrategy::*;
+use ReserveStrategy::*;
 
 impl<T, A: Alloc> RawVec<T, A> {
     fn reserve_internal(
@@ -639,7 +638,7 @@ impl<T, A: Alloc> RawVec<T, A> {
         strategy: ReserveStrategy,
     ) -> Result<(), CollectionAllocErr> {
         unsafe {
-            use alloc::AllocErr;
+            use crate::alloc::AllocErr;
 
             // NOTE: we don't early branch on ZSTs here because we want this
             // to actually catch "asking for more than usize::MAX" in that case.
@@ -733,7 +732,7 @@ unsafe impl<#[may_dangle] T, A: Alloc> Drop for RawVec<T, A> {
 
 #[inline]
 fn alloc_guard(alloc_size: usize) -> Result<(), CollectionAllocErr> {
-    if mem::size_of::<usize>() < 8 && alloc_size > ::core::isize::MAX as usize {
+    if mem::size_of::<usize>() < 8 && alloc_size > core::isize::MAX as usize {
         Err(CapacityOverflow)
     } else {
         Ok(())
@@ -753,7 +752,7 @@ mod tests {
 
     #[test]
     fn allocator_param() {
-        use alloc::AllocErr;
+        use crate::alloc::AllocErr;
 
         // Writing a test of integration between third-party
         // allocators and RawVec is a little tricky because the RawVec