Remove extern crate tracing from numerous crates.

compiler/rustc_builtin_macros/src/cfg_eval.rs

@@ -18,6 +18,7 @@ use rustc_session::Session;
 use rustc_span::symbol::sym;
 use rustc_span::Span;
 use smallvec::SmallVec;
+use tracing::instrument;
 
 pub(crate) fn expand(
     ecx: &mut ExtCtxt<'_>,

compiler/rustc_builtin_macros/src/lib.rs

@@ -19,11 +19,7 @@
 
 extern crate proc_macro;
 
-#[macro_use]
-extern crate tracing;
-
 use crate::deriving::*;
-
 use rustc_expand::base::{MacroExpanderFn, ResolverExpand, SyntaxExtensionKind};
 use rustc_expand::proc_macro::BangProcMacro;
 use rustc_span::symbol::sym;

compiler/rustc_builtin_macros/src/test.rs

@@ -12,6 +12,7 @@ use rustc_span::{ErrorGuaranteed, FileNameDisplayPreference, Span};
 use std::assert_matches::assert_matches;
 use std::iter;
 use thin_vec::{thin_vec, ThinVec};
+use tracing::debug;
 
 /// #[test_case] is used by custom test authors to mark tests
 /// When building for test, it needs to make the item public and gensym the name