Remove extern crate tracing.

`use` is a nicer way of doing things.

compiler/rustc_data_structures/src/flock/windows.rs

@@ -2,6 +2,7 @@ use std::fs::{File, OpenOptions};
 use std::io;
 use std::os::windows::prelude::*;
 use std::path::Path;
+use tracing::debug;
 
 use windows::{
     Win32::Foundation::{ERROR_INVALID_FUNCTION, HANDLE},

compiler/rustc_data_structures/src/graph/implementation/mod.rs

@@ -22,6 +22,7 @@
 
 use rustc_index::bit_set::BitSet;
 use std::fmt::Debug;
+use tracing::debug;
 
 #[cfg(test)]
 mod tests;

compiler/rustc_data_structures/src/graph/implementation/tests.rs

@@ -1,4 +1,5 @@
 use crate::graph::implementation::*;
+use tracing::debug;
 
 type TestGraph = Graph<&'static str, &'static str>;
 

compiler/rustc_data_structures/src/graph/scc/mod.rs

@@ -10,6 +10,7 @@ use crate::graph::vec_graph::VecGraph;
 use crate::graph::{DirectedGraph, NumEdges, Successors};
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use std::ops::Range;
+use tracing::{debug, instrument};
 
 #[cfg(test)]
 mod tests;

compiler/rustc_data_structures/src/lib.rs

@@ -42,9 +42,6 @@
 #![feature(unwrap_infallible)]
 // tidy-alphabetical-end
 
-#[macro_use]
-extern crate tracing;
-
 pub use atomic_ref::AtomicRef;
 pub use ena::snapshot_vec;
 pub use ena::undo_log;

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -70,12 +70,12 @@
 //! aren't needed anymore.
 
 use crate::fx::{FxHashMap, FxHashSet};
-
 use std::cell::Cell;
 use std::collections::hash_map::Entry;
 use std::fmt::Debug;
 use std::hash;
 use std::marker::PhantomData;
+use tracing::debug;
 
 mod graphviz;
 

compiler/rustc_data_structures/src/profiling.rs

@@ -99,6 +99,7 @@ pub use measureme::EventId;
 use measureme::{EventIdBuilder, Profiler, SerializableString, StringId};
 use parking_lot::RwLock;
 use smallvec::SmallVec;
+use tracing::warn;
 
 bitflags::bitflags! {
     #[derive(Clone, Copy)]