Reformat use declarations.

The previous commit updated `rustfmt.toml` appropriately. This commit is
the outcome of running `x fmt --all` with the new formatting options.

compiler/rustc_serialize/src/leb128.rs

@@ -1,9 +1,8 @@
-use crate::opaque::MemDecoder;
-use crate::serialize::Decoder;
-
 // This code is very hot and uses lots of arithmetic, avoid overflow checks for performance.
 // See https://github.com/rust-lang/rust/pull/119440#issuecomment-1874255727
 use crate::int_overflow::DebugStrictAdd;
+use crate::opaque::MemDecoder;
+use crate::serialize::Decoder;
 
 /// Returns the length of the longest LEB128 encoding for `T`, assuming `T` is an integer type
 pub const fn max_leb128_len<T>() -> usize {

compiler/rustc_serialize/src/opaque.rs

@@ -1,15 +1,14 @@
-use crate::leb128;
-use crate::serialize::{Decodable, Decoder, Encodable, Encoder};
 use std::fs::File;
 use std::io::{self, Write};
 use std::marker::PhantomData;
 use std::ops::Range;
-use std::path::Path;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 // This code is very hot and uses lots of arithmetic, avoid overflow checks for performance.
 // See https://github.com/rust-lang/rust/pull/119440#issuecomment-1874255727
 use crate::int_overflow::DebugStrictAdd;
+use crate::leb128;
+use crate::serialize::{Decodable, Decoder, Encodable, Encoder};
 
 // -----------------------------------------------------------------------------
 // Encoder

compiler/rustc_serialize/src/serialize.rs

@@ -1,6 +1,5 @@
 //! Support code for encoding and decoding types.
 
-use smallvec::{Array, SmallVec};
 use std::borrow::Cow;
 use std::cell::{Cell, RefCell};
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, VecDeque};
@@ -10,6 +9,8 @@ use std::num::NonZero;
 use std::path;
 use std::rc::Rc;
 use std::sync::Arc;
+
+use smallvec::{Array, SmallVec};
 use thin_vec::ThinVec;
 
 /// A byte that [cannot occur in UTF8 sequences][utf8]. Used to mark the end of a string.