Use a function to access the Hir map to be able to turn it into a query later

src/librustc_codegen_utils/lib.rs

@@ -53,7 +53,7 @@ pub mod symbol_names_test;
 /// reporting an error.
 pub fn check_for_rustc_errors_attr(tcx: TyCtxt) {
     if let Some((id, span, _)) = *tcx.sess.entry_fn.borrow() {
-        let main_def_id = tcx.hir.local_def_id(id);
+        let main_def_id = tcx.hir().local_def_id(id);
 
         if tcx.has_attr(main_def_id, "rustc_error") {
             tcx.sess.span_fatal(span, "compilation successful");