Remove extern crate rustc_macros from rustc_middle.

compiler/rustc_middle/src/infer/canonical.rs

@@ -23,7 +23,7 @@
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lock;
-use rustc_macros::HashStable;
+use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_type_ir::Canonical as IrCanonical;
 use rustc_type_ir::CanonicalVarInfo as IrCanonicalVarInfo;
 pub use rustc_type_ir::{CanonicalTyVarKind, CanonicalVarKind};

compiler/rustc_middle/src/infer/mod.rs

@@ -4,6 +4,7 @@ pub mod unify_key;
 use crate::ty::Region;
 use crate::ty::{OpaqueTypeKey, Ty};
 use rustc_data_structures::sync::Lrc;
+use rustc_macros::{HashStable, TypeFoldable, TypeVisitable};
 use rustc_span::Span;
 
 /// Requires that `region` must be equal to one of the regions in `choice_regions`.