From c454c1d4ac9ad19a03b892a6173419e8b95849d1 Mon Sep 17 00:00:00 2001
From: Jeffrey Seyfried <jeffrey.seyfried@gmail.com>
Date: Mon, 4 Jul 2016 03:10:04 +0000
Subject: [PATCH 1/2] Strip unconfigured items from `MultiModifier`-expanded
 AST

---
 src/libsyntax/ext/expand.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index c670283e559d9..877293bac54f7 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -769,7 +769,11 @@ fn expand_annotatable(mut item: Annotatable, fld: &mut MacroExpander) -> SmallVe
             };
 
             fld.cx.bt_pop();
-            modified.into_iter().flat_map(|it| expand_annotatable(it, fld)).collect()
+            let configured = modified.into_iter().flat_map(|it| {
+                it.fold_with(&mut fld.strip_unconfigured())
+            }).collect::<SmallVector<_>>();
+
+            configured.into_iter().flat_map(|it| expand_annotatable(it, fld)).collect()
         }
     }
 }

From bf4911b9560a20d1861627a2db3de33843f964b1 Mon Sep 17 00:00:00 2001
From: Jeffrey Seyfried <jeffrey.seyfried@gmail.com>
Date: Tue, 5 Jul 2016 00:22:13 +0000
Subject: [PATCH 2/2] Add regression test

---
 src/test/run-pass-fulldeps/auxiliary/macro_crate_test.rs | 1 +
 src/test/run-pass-fulldeps/macro-crate.rs                | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/src/test/run-pass-fulldeps/auxiliary/macro_crate_test.rs b/src/test/run-pass-fulldeps/auxiliary/macro_crate_test.rs
index 11d81eda55625..3f50811f826e0 100644
--- a/src/test/run-pass-fulldeps/auxiliary/macro_crate_test.rs
+++ b/src/test/run-pass-fulldeps/auxiliary/macro_crate_test.rs
@@ -72,6 +72,7 @@ fn expand_into_foo_multi(cx: &mut ExtCtxt,
                 ..(*quote_item!(cx, enum Foo2 { Bar2, Baz2 }).unwrap()).clone()
             })),
             Annotatable::Item(quote_item!(cx, enum Foo3 { Bar }).unwrap()),
+            Annotatable::Item(quote_item!(cx, #[cfg(any())] fn foo2() {}).unwrap()),
         ],
         Annotatable::ImplItem(it) => vec![
             quote_item!(cx, impl X { fn foo(&self) -> i32 { 42 } }).unwrap().and_then(|i| {
diff --git a/src/test/run-pass-fulldeps/macro-crate.rs b/src/test/run-pass-fulldeps/macro-crate.rs
index d17adff007c63..fe2317aabea68 100644
--- a/src/test/run-pass-fulldeps/macro-crate.rs
+++ b/src/test/run-pass-fulldeps/macro-crate.rs
@@ -21,6 +21,9 @@ extern crate macro_crate_test;
 #[derive(PartialEq, Clone, Debug)]
 fn foo() -> AnotherFakeTypeThatHadBetterGoAway {}
 
+// Check that the `#[into_multi_foo]`-generated `foo2` is configured away
+fn foo2() {}
+
 trait Qux {
     #[into_multi_foo]
     fn bar();