Remove extern crate tracing from numerous crates.

compiler/rustc_expand/src/config.rs

@@ -20,6 +20,7 @@ use rustc_session::Session;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
 use thin_vec::ThinVec;
+use tracing::instrument;
 
 /// A folder that strips out items that do not belong in the current configuration.
 pub struct StripUnconfigured<'a> {

compiler/rustc_expand/src/lib.rs

@@ -16,9 +16,6 @@
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(internal_features)]
 
-#[macro_use]
-extern crate tracing;
-
 extern crate proc_macro as pm;
 
 mod placeholders;

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -14,6 +14,7 @@ use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::Ident;
 use rustc_span::{ErrorGuaranteed, Span};
 use std::borrow::Cow;
+use tracing::debug;
 
 use super::macro_rules::{parser_from_cx, NoopTracker};
 

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -29,6 +29,7 @@ use rustc_span::edition::Edition;
 use rustc_span::hygiene::Transparency;
 use rustc_span::symbol::{kw, sym, Ident, MacroRulesNormalizedIdent};
 use rustc_span::Span;
+use tracing::{debug, instrument, trace, trace_span};
 
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;