Remove extern crate rustc_macros from rustc_middle.

compiler/rustc_middle/src/ty/mod.rs

@@ -47,7 +47,9 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap};
 use rustc_index::IndexVec;
-use rustc_macros::HashStable;
+use rustc_macros::{
+    Decodable, Encodable, HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable,
+};
 use rustc_query_system::ich::StableHashingContext;
 use rustc_serialize::{Decodable, Encodable};
 use rustc_session::lint::LintBuffer;