rustc: Remove the session dependency from front::attr

src/rustc/back/link.rs

@@ -302,7 +302,7 @@ fn provided_link_metas(sess: session, c: ast::crate) ->
         let mut vers: option<str> = none;
         let mut cmh_items: [@ast::meta_item] = [];
         let linkage_metas = attr::find_linkage_metas(c.node.attrs);
-        attr::require_unique_names(sess, linkage_metas);
+        attr::require_unique_names(sess.diagnostic(), linkage_metas);
         for meta: @ast::meta_item in linkage_metas {
             if attr::get_meta_item_name(meta) == "name" {
                 alt attr::get_meta_item_value_str(meta) {

src/rustc/front/attr.rs

@@ -4,7 +4,7 @@
 import std::map::hashmap;
 import either::either;
 import syntax::{ast, ast_util};
-import driver::session::session;
+import driver::diagnostic::span_handler;
 
 export attr_meta;
 export attr_metas;
@@ -220,13 +220,14 @@ fn remove_meta_items_by_name(items: [@ast::meta_item], name: str) ->
     ret vec::filter_map(items, filter);
 }
 
-fn require_unique_names(sess: session, metas: [@ast::meta_item]) {
+fn require_unique_names(diagnostic: span_handler,
+                        metas: [@ast::meta_item]) {
     let map = map::str_hash();
     for meta: @ast::meta_item in metas {
         let name = get_meta_item_name(meta);
         if map.contains_key(name) {
-            sess.span_fatal(meta.span,
-                            #fmt["duplicate meta item `%s`", name]);
+            diagnostic.span_fatal(meta.span,
+                                  #fmt["duplicate meta item `%s`", name]);
         }
         map.insert(name, ());
     }

src/rustc/metadata/creader.rs

@@ -137,7 +137,7 @@ fn find_library_crate(sess: session::session, ident: ast::ident,
                       metas: [@ast::meta_item])
    -> option<{ident: str, data: @[u8]}> {
 
-    attr::require_unique_names(sess, metas);
+    attr::require_unique_names(sess.diagnostic(), metas);
     let metas = metas;
 
     let crate_name =