Give the StringReader a sess: &ParseSess.

src/libsyntax/parse/mod.rs

@@ -223,7 +223,7 @@ pub fn filemap_to_tts(sess: &ParseSess, filemap: Rc<FileMap>)
     -> Vec<tokenstream::TokenTree> {
     // it appears to me that the cfg doesn't matter here... indeed,
     // parsing tt's probably shouldn't require a parser at all.
-    let srdr = lexer::StringReader::new(&sess.span_diagnostic, filemap);
+    let srdr = lexer::StringReader::new(sess, filemap);
     let mut p1 = Parser::new(sess, Box::new(srdr), None, false);
     panictry!(p1.parse_all_token_trees())
 }