From 853f6974767243e2e5defb43f5f7195ce1fb1cc7 Mon Sep 17 00:00:00 2001
From: Vadim Petrochenkov <vadim.petrochenkov@gmail.com>
Date: Thu, 19 Jan 2017 13:28:45 +0300
Subject: [PATCH] Fix regression in parsing of trait object types

---
 src/libsyntax/parse/parser.rs            | 11 +++++++++--
 src/test/parse-fail/bounds-obj-parens.rs | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 src/test/parse-fail/bounds-obj-parens.rs

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index d1a683b0bd5..b5913daaa5b 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1277,10 +1277,17 @@ pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
                           "at least one type parameter bound \
                           must be specified");
         }
-        if let TyKind::Path(None, ref path) = lhs.node {
+
+        let mut lhs = lhs.unwrap();
+        if let TyKind::Paren(ty) = lhs.node {
+            // We have to accept the first bound in parens for backward compatibility.
+            // Example: `(Bound) + Bound + Bound`
+            lhs = ty.unwrap();
+        }
+        if let TyKind::Path(None, path) = lhs.node {
             let poly_trait_ref = PolyTraitRef {
                 bound_lifetimes: Vec::new(),
-                trait_ref: TraitRef { path: path.clone(), ref_id: lhs.id },
+                trait_ref: TraitRef { path: path, ref_id: lhs.id },
                 span: lhs.span,
             };
             let poly_trait_ref = TraitTyParamBound(poly_trait_ref, TraitBoundModifier::None);
diff --git a/src/test/parse-fail/bounds-obj-parens.rs b/src/test/parse-fail/bounds-obj-parens.rs
new file mode 100644
index 00000000000..cbdffb4a255
--- /dev/null
+++ b/src/test/parse-fail/bounds-obj-parens.rs
@@ -0,0 +1,15 @@
+// Copyright 2017 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.
+
+// compile-flags: -Z parse-only
+
+type A = Box<(Fn(D::Error) -> E) + 'static + Send + Sync>; // OK
+
+FAIL //~ ERROR