Remove extern crate.

src/libsyntax/ast.rs

@@ -37,6 +37,7 @@
 use rustc_data_structures::thin_vec::ThinVec;
 use rustc_index::vec::Idx;
 use rustc_serialize::{self, Decoder, Encoder};
+use rustc_macros::HashStable_Generic;
 
 use std::fmt;
 

src/libsyntax/attr/builtin.rs

@@ -9,6 +9,7 @@
 use std::num::NonZeroU32;
 use syntax_pos::hygiene::Transparency;
 use syntax_pos::{symbol::Symbol, symbol::sym, Span};
+use rustc_macros::HashStable_Generic;
 
 use super::{mark_used, MetaItemKind};
 

src/libsyntax/lib.rs

@@ -19,8 +19,6 @@
 
 #![recursion_limit="256"]
 
-#[macro_use] extern crate rustc_macros;
-
 pub use errors;
 use rustc_data_structures::sync::Lock;
 use rustc_index::bit_set::GrowableBitSet;

src/libsyntax/token.rs

@@ -15,6 +15,7 @@
 use std::fmt;
 use std::mem;
 use rustc_data_structures::sync::Lrc;
+use rustc_macros::HashStable_Generic;
 
 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 pub enum BinOpToken {