rustc: Give a better error message when references involving the caller region fail to unify

Author: pcwalton

src/rustc/util/ppaux.rs

@@ -13,7 +13,19 @@ import driver::session::session;
 fn region_to_str(cx: ctxt, region: region) -> str {
     alt region {
       re_named(_)   { "<name>" }    // TODO: include name
-      re_caller(_)  { "<caller>" }
+      re_caller(def_id) {
+        if def_id.crate == ast::local_crate {
+            alt cx.items.get(def_id.node) {
+              ast_map::node_item(item, path) {
+                #fmt("<caller of %s::%s>", ast_map::path_to_str(*path),
+                     item.ident)
+              }
+              _ { "<caller>" }
+            }
+        } else {
+            "<caller>"
+        }
+      }
       re_block(node_id) {
         alt cx.items.get(node_id) {
             ast_map::node_block(blk) {