Pass a Symbol to check_name, emit_feature_err, and related functions.

src/libsyntax_ext/deriving/generic/mod.rs

@@ -191,7 +191,7 @@ use syntax::ext::build::AstBuilder;
 use syntax::source_map::{self, respan};
 use syntax::util::map_in_place::MapInPlace;
 use syntax::ptr::P;
-use syntax::symbol::{Symbol, keywords};
+use syntax::symbol::{Symbol, keywords, sym};
 use syntax::parse::ParseSess;
 use syntax_pos::{DUMMY_SP, Span};
 
@@ -426,7 +426,7 @@ impl<'a> TraitDef<'a> {
                     }
                 };
                 let is_always_copy =
-                    attr::contains_name(&item.attrs, "rustc_copy_clone_marker") &&
+                    attr::contains_name(&item.attrs, sym::rustc_copy_clone_marker) &&
                     has_no_type_params;
                 let use_temporaries = is_packed && is_always_copy;