normalize tuple pair types

src/librustc_trans/common.rs

@@ -114,7 +114,8 @@ pub fn type_pair_fields<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>)
             if tys.len() != 2 {
                 return None;
             }
-            Some([tys[0], tys[1]])
+            Some([ccx.tcx().normalize_associated_type(&tys[0]),
+                  ccx.tcx().normalize_associated_type(&tys[1])])
         }
         _ => None
     }

src/test/run-pass/issue-37109.rs

@@ -0,0 +1,25 @@
+// Copyright 2016 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.
+
+trait ToRef<'a> {
+    type Ref: 'a;
+}
+
+impl<'a, U: 'a> ToRef<'a> for U {
+    type Ref = &'a U;
+}
+
+fn example<'a, T>(value: &'a T) -> (<T as ToRef<'a>>::Ref, u32) {
+    (value, 0)
+}
+
+fn main() {
+    example(&0);
+}