From edb309f50c989925549952e2699bee5e1f8f2daa Mon Sep 17 00:00:00 2001
From: Eirik Ogilvie-Wigley <eirik@z.cash>
Date: Fri, 7 Sep 2018 10:38:51 -0600
Subject: [PATCH] Use u128 addition rather than u64 overflowing addition

---
 src/fq.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/fq.rs b/src/fq.rs
index 4223b36..8f724a6 100644
--- a/src/fq.rs
+++ b/src/fq.rs
@@ -75,8 +75,8 @@ fn adc2(a: u64, b: u64, carry: u64) -> (u64, u64) {
 /// Compute a + b, returning the result and the carry over.
 #[inline(always)]
 fn overflowing_add(a: u64, b: u64) -> (u64, u64) {
-    let (sum, overflow) = a.overflowing_add(b);
-    (sum, overflow as u64)
+    let sum = u128::from(a) + u128::from(b);
+    (sum as u64, (sum >> 64) as u64)
 }
 
 /// Compute a - (b + borrow), returning the result and setting borrow to