From b99fb55f0fcbaabf96c1a56b0d905f41d4fe33a2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adolfo=20Ochagav=C3=ADa?= <aochagavia92@gmail.com>
Date: Fri, 12 Dec 2014 17:34:28 +0100
Subject: [PATCH 1/2] Fix #19734 (ICE)

---
 src/libsyntax/ext/expand.rs | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index a697d332d16..414241ee2bf 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -1026,16 +1026,17 @@ fn expand_method(m: P<ast::Method>, fld: &mut MacroExpander) -> SmallVector<P<as
                                  |meths, mark| meths.move_map(|m| mark_method(m, mark)),
                                  fld);
 
-            let new_methods = match maybe_new_methods {
-                Some(methods) => methods,
+            match maybe_new_methods {
+                Some(methods) => {
+                    // expand again if necessary
+                    let new_methods = methods.into_iter()
+                                             .flat_map(|m| fld.fold_method(m).into_iter())
+                                             .collect();
+                    fld.cx.bt_pop();
+                    new_methods
+                }
                 None => SmallVector::zero()
-            };
-
-            // expand again if necessary
-            let new_methods = new_methods.into_iter()
-                                  .flat_map(|m| fld.fold_method(m).into_iter()).collect();
-            fld.cx.bt_pop();
-            new_methods
+            }
         }
     })
 }

From 8788cb05c23c1d14ad22e5046bf3d3d621cf401e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adolfo=20Ochagav=C3=ADa?= <aochagavia92@gmail.com>
Date: Fri, 12 Dec 2014 17:40:32 +0100
Subject: [PATCH 2/2] Add test for issue #19734

---
 src/test/compile-fail/issue-19734.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 src/test/compile-fail/issue-19734.rs

diff --git a/src/test/compile-fail/issue-19734.rs b/src/test/compile-fail/issue-19734.rs
new file mode 100644
index 00000000000..cee92cae2aa
--- /dev/null
+++ b/src/test/compile-fail/issue-19734.rs
@@ -0,0 +1,15 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {}
+
+impl Type {
+    undef!() //~ ERROR macro undefined: 'undef!'
+}