From b4d41b689c6c1710ce083c24860ad54ebd3ba82f Mon Sep 17 00:00:00 2001
From: Sean Bowe <ewillbefull@gmail.com>
Date: Fri, 27 Jul 2018 17:36:17 -0600
Subject: [PATCH] Add must_use to operations over Edwards/Montgomery points.

---
 src/jubjub/edwards.rs    | 5 +++++
 src/jubjub/montgomery.rs | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/src/jubjub/edwards.rs b/src/jubjub/edwards.rs
index 73f0dfc..e91455c 100644
--- a/src/jubjub/edwards.rs
+++ b/src/jubjub/edwards.rs
@@ -164,6 +164,7 @@ impl<E: JubjubEngine> Point<E, Unknown> {
     }
 
     /// This guarantees the point is in the prime order subgroup
+    #[must_use]
     pub fn mul_by_cofactor(&self, params: &E::Params) -> Point<E, PrimeOrder>
     {
         let tmp = self.double(params)
@@ -346,6 +347,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         (x, y)
     }
 
+    #[must_use]
     pub fn negate(&self) -> Self {
         let mut p = self.clone();
 
@@ -355,6 +357,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         p
     }
 
+    #[must_use]
     pub fn double(&self, _: &E::Params) -> Self {
         // See "Twisted Edwards Curves Revisited"
         //     Huseyin Hisil, Kenneth Koon-Ho Wong, Gary Carter, and Ed Dawson
@@ -423,6 +426,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         }
     }
 
+    #[must_use]
     pub fn add(&self, other: &Self, params: &E::Params) -> Self
     {
         // See "Twisted Edwards Curves Revisited"
@@ -495,6 +499,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         }
     }
 
+    #[must_use]
     pub fn mul<S: Into<<E::Fs as PrimeField>::Repr>>(
         &self,
         scalar: S,
diff --git a/src/jubjub/montgomery.rs b/src/jubjub/montgomery.rs
index 2243877..18d0fcb 100644
--- a/src/jubjub/montgomery.rs
+++ b/src/jubjub/montgomery.rs
@@ -97,6 +97,7 @@ impl<E: JubjubEngine> Point<E, Unknown> {
     }
 
     /// This guarantees the point is in the prime order subgroup
+    #[must_use]
     pub fn mul_by_cofactor(&self, params: &E::Params) -> Point<E, PrimeOrder>
     {
         let tmp = self.double(params)
@@ -216,6 +217,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         }
     }
 
+    #[must_use]
     pub fn negate(&self) -> Self {
         let mut p = self.clone();
 
@@ -224,6 +226,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         p
     }
 
+    #[must_use]
     pub fn double(&self, params: &E::Params) -> Self {
         if self.infinity {
             return Point::zero();
@@ -280,6 +283,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         }
     }
 
+    #[must_use]
     pub fn add(&self, other: &Self, params: &E::Params) -> Self
     {
         // This is a standard affine point addition formula
@@ -330,6 +334,7 @@ impl<E: JubjubEngine, Subgroup> Point<E, Subgroup> {
         }
     }
 
+    #[must_use]
     pub fn mul<S: Into<<E::Fs as PrimeField>::Repr>>(
         &self,
         scalar: S,