From 33712a8a10eb193e1d90c52b666a053309b7a8dc Mon Sep 17 00:00:00 2001
From: Oliver Schneider <github35764891676564198441@oli-obk.de>
Date: Wed, 25 Jul 2018 10:50:30 +0200
Subject: [PATCH] Add type system canaries for potential future bugs

---
 src/librustc/traits/specialize/specialization_graph.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/librustc/traits/specialize/specialization_graph.rs b/src/librustc/traits/specialize/specialization_graph.rs
index 8a15d700bac..6562526a2ea 100644
--- a/src/librustc/traits/specialize/specialization_graph.rs
+++ b/src/librustc/traits/specialize/specialization_graph.rs
@@ -385,7 +385,11 @@ impl<'a, 'gcx, 'tcx> Ancestors {
                 | (Type, Existential)
                 => tcx.hygienic_eq(impl_item.ident, trait_item_name, trait_def_id),
 
-                _ => false,
+                | (Const, _)
+                | (Method, _)
+                | (Type, _)
+                | (Existential, _)
+                => false,
             }).map(move |item| NodeItem { node: node, item: item })
         })
     }