From f484ed6326282dc834451ae5a51cda4e60f275bf Mon Sep 17 00:00:00 2001
From: Tony Arcieri <bascule@gmail.com>
Date: Wed, 17 Nov 2021 14:22:56 -0700
Subject: [PATCH] elliptic-curve: impl `Neg` for `NonZeroScalar<C>` (#816)

---
 elliptic-curve/src/scalar/non_zero.rs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/elliptic-curve/src/scalar/non_zero.rs b/elliptic-curve/src/scalar/non_zero.rs
index 8a1749676..818f5d101 100644
--- a/elliptic-curve/src/scalar/non_zero.rs
+++ b/elliptic-curve/src/scalar/non_zero.rs
@@ -6,7 +6,7 @@ use crate::{
     rand_core::{CryptoRng, RngCore},
     Curve, Error, FieldBytes, IsHigh, Result, Scalar, ScalarArithmetic, ScalarCore, SecretKey,
 };
-use core::ops::Deref;
+use core::ops::{Deref, Neg};
 use ff::{Field, PrimeField};
 use generic_array::GenericArray;
 use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
@@ -175,6 +175,19 @@ where
     }
 }
 
+impl<C> Neg for NonZeroScalar<C>
+where
+    C: Curve + ScalarArithmetic,
+{
+    type Output = NonZeroScalar<C>;
+
+    fn neg(self) -> NonZeroScalar<C> {
+        let scalar = -self.scalar;
+        debug_assert!(!bool::from(scalar.is_zero()));
+        NonZeroScalar { scalar }
+    }
+}
+
 impl<C> TryFrom<&[u8]> for NonZeroScalar<C>
 where
     C: Curve + ScalarArithmetic,