Avoid clearing the string interner.

src/librustc_driver/driver.rs

@@ -210,9 +210,6 @@ pub fn compile_input(sess: &Session,
                 tcx.print_debug_stats();
             }
 
-            // Discard interned strings as they are no longer required.
-            token::clear_ident_interner();
-
             Ok((outputs, trans))
         })??
     };

src/libsyntax/parse/token.rs

@@ -454,10 +454,6 @@ pub fn reset_ident_interner() {
     with_ident_interner(|interner| *interner = mk_fresh_ident_interner());
 }
 
-pub fn clear_ident_interner() {
-    with_ident_interner(|interner| *interner = IdentInterner::new());
-}
-
 /// Represents a string stored in the thread-local interner. Because the
 /// interner lives for the life of the thread, this can be safely treated as an
 /// immortal string, as long as it never crosses between threads.