Refactor Attribute to use Path and TokenStream instead of MetaItem.

src/libsyntax/lib.rs

@@ -65,6 +65,16 @@ macro_rules! panictry {
     })
 }
 
+#[macro_export]
+macro_rules! unwrap_or {
+    ($opt:expr, $default:expr) => {
+        match $opt {
+            Some(x) => x,
+            None => $default,
+        }
+    }
+}
+
 #[macro_use]
 pub mod diagnostics {
     #[macro_use]