Pop the expansion context after expanding a method macro

We were leaving these on the stack, causing spurious backtraces.

I've confirmed that this test fails without the fix.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 4ff9912645a..892213e684f 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -897,7 +897,10 @@ fn expand_method(m: P<ast::Method>, fld: &mut MacroExpander) -> SmallVector<P<as
             };
 
             // expand again if necessary
-            new_methods.into_iter().flat_map(|m| fld.fold_method(m).into_iter()).collect()
+            let new_methods = new_methods.move_iter()
+                                  .flat_map(|m| fld.fold_method(m).into_iter()).collect();
+            fld.cx.bt_pop();
+            new_methods
         }
     })
 }