From 00be060daf3c38256e58360bfa591b8e22f60f7a Mon Sep 17 00:00:00 2001
From: "leonardo.yvens" <leoyvens@gmail.com>
Date: Thu, 12 Oct 2017 11:18:55 -0300
Subject: [PATCH] Teach typeck about `auto trait`

---
 src/librustc/hir/lowering.rs   | 4 ++--
 src/librustc_typeck/collect.rs | 7 +++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index 7214904887e4..a69d41d16033 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -1742,8 +1742,8 @@ impl<'a> LoweringContext<'a> {
         }
     }
 
-    fn lower_is_auto(&mut self, u: IsAuto) -> hir::IsAuto {
-        match u {
+    fn lower_is_auto(&mut self, a: IsAuto) -> hir::IsAuto {
+        match a {
             IsAuto::Yes => hir::IsAuto::Yes,
             IsAuto::No => hir::IsAuto::No,
         }
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 72b40d877085..814470974285 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -730,11 +730,14 @@ fn trait_def<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     }
 
     let def_path_hash = tcx.def_path_hash(def_id);
-    let has_auto_impl = tcx.hir.trait_is_auto(def_id);
+    let is_auto = match item.node {
+        hir::ItemTrait(hir::IsAuto::Yes, ..) => true,
+        _ => tcx.hir.trait_is_auto(def_id),
+    };
     let def = ty::TraitDef::new(def_id,
                                 unsafety,
                                 paren_sugar,
-                                has_auto_impl,
+                                is_auto,
                                 def_path_hash);
     tcx.alloc_trait_def(def)
 }