From 4a891fe80dfc5c64d72ddb842751bf410dc7a3a8 Mon Sep 17 00:00:00 2001
From: Nick Cameron <ncameron@mozilla.com>
Date: Mon, 3 Mar 2014 10:12:40 -0800
Subject: [PATCH] Expand nested items within a backtrace.

Fixes a regression from #4913 which causes items to be exanded with spans lacking expn_info from the context's current backtrace.
---
 src/libsyntax/ext/expand.rs        | 13 +++++++------
 src/libsyntax/util/small_vector.rs |  8 ++++++++
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index d8b4334c867..13c340cb774 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -248,7 +248,7 @@ macro_rules! with_exts_frame (
 // When we enter a module, record it, for the sake of `module!`
 pub fn expand_item(it: @ast::Item, fld: &mut MacroExpander)
                    -> SmallVector<@ast::Item> {
-    let mut decorator_items = SmallVector::zero();
+    let mut decorator_items: SmallVector<@ast::Item> = SmallVector::zero();
     for attr in it.attrs.rev_iter() {
         let mname = attr.name();
 
@@ -262,20 +262,21 @@ pub fn expand_item(it: @ast::Item, fld: &mut MacroExpander)
                         span: None
                     }
                 });
+
                 // we'd ideally decorator_items.push_all(expand_item(item, fld)),
                 // but that double-mut-borrows fld
+                let mut items: SmallVector<@ast::Item> = SmallVector::zero();
                 dec_fn(fld.cx, attr.span, attr.node.value, it,
-                       |item| decorator_items.push(item));
+                       |item| items.push(item));
+                decorator_items.extend(&mut items.move_iter()
+                    .flat_map(|item| expand_item(item, fld).move_iter()));
+
                 fld.cx.bt_pop();
             }
             _ => {}
         }
     }
 
-    let decorator_items = decorator_items.move_iter()
-        .flat_map(|item| expand_item(item, fld).move_iter())
-        .collect();
-
     let mut new_items = match it.node {
         ast::ItemMac(..) => expand_item_mac(it, fld),
         ast::ItemMod(_) | ast::ItemForeignMod(_) => {
diff --git a/src/libsyntax/util/small_vector.rs b/src/libsyntax/util/small_vector.rs
index 9eb9871bb21..f15b7dd5563 100644
--- a/src/libsyntax/util/small_vector.rs
+++ b/src/libsyntax/util/small_vector.rs
@@ -39,6 +39,14 @@ impl<T> FromIterator<T> for SmallVector<T> {
     }
 }
 
+impl<T> Extendable<T> for SmallVector<T> {
+    fn extend<I: Iterator<T>>(&mut self, iter: &mut I) {
+        for val in *iter {
+            self.push(val);
+        }
+    }
+}
+
 impl<T> SmallVector<T> {
     pub fn zero() -> SmallVector<T> {
         Zero