Replace Rc with Lrc for shared data

src/libproc_macro/Cargo.toml

@@ -11,3 +11,4 @@ crate-type = ["dylib"]
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 rustc_errors = { path = "../librustc_errors" }
+rustc_data_structures = { path = "../librustc_data_structures" }

src/libproc_macro/lib.rs

@@ -43,6 +43,7 @@
 extern crate syntax;
 extern crate syntax_pos;
 extern crate rustc_errors;
+extern crate rustc_data_structures;
 
 mod diagnostic;
 
@@ -50,7 +51,7 @@ mod diagnostic;
 pub use diagnostic::{Diagnostic, Level};
 
 use std::{ascii, fmt, iter};
-use std::rc::Rc;
+use rustc_data_structures::sync::Lrc;
 use std::str::FromStr;
 
 use syntax::ast;
@@ -306,7 +307,7 @@ pub struct LineColumn {
 #[unstable(feature = "proc_macro", issue = "38356")]
 #[derive(Clone)]
 pub struct SourceFile {
-    filemap: Rc<FileMap>,
+    filemap: Lrc<FileMap>,
 }
 
 impl SourceFile {
@@ -356,7 +357,7 @@ impl fmt::Debug for SourceFile {
 #[unstable(feature = "proc_macro", issue = "38356")]
 impl PartialEq for SourceFile {
     fn eq(&self, other: &Self) -> bool {
-        Rc::ptr_eq(&self.filemap, &other.filemap)
+        Lrc::ptr_eq(&self.filemap, &other.filemap)
     }
 }