From 1dc8a3c9482b3a5c8bc4ec088aebb277e8d08791 Mon Sep 17 00:00:00 2001
From: Jakub Bogucki <jakub@confio.gmbh>
Date: Tue, 29 Mar 2022 11:17:19 +0200
Subject: [PATCH] Implement MulAssign and mul for refs for Decimal/Decimal256
 types

---
 CHANGELOG.md                        |  1 +
 packages/std/src/math/decimal.rs    | 33 ++++++++++++++++++++++++++++-
 packages/std/src/math/decimal256.rs | 33 ++++++++++++++++++++++++++++-
 packages/std/src/math/mod.rs        |  6 +++---
 4 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2545851449..c8e4be7f25 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ and this project adheres to
   `Uint64`/`Uint128`/`Uint256`/`Uint512`.
 - cosmwasm-std: Implement `pow`/`checked_pow` for `Uint64`/`Uint128`/`Uint512`.
 - cosmwasm-std: Implement `SubAssign`/`AddAssign` for `Decimal`/`Decimal256`.
+- cosmwasm-std: Implement `MulAssign` for `Decimal`/`Decimal256`.
 - cosmwasm-crypto: Upgrade ed25519-zebra to version 3.
 
 ### Changed
diff --git a/packages/std/src/math/decimal.rs b/packages/std/src/math/decimal.rs
index f710f799fe..c7d78c97eb 100644
--- a/packages/std/src/math/decimal.rs
+++ b/packages/std/src/math/decimal.rs
@@ -4,7 +4,7 @@ use serde::{de, ser, Deserialize, Deserializer, Serialize};
 use std::cmp::Ordering;
 use std::convert::TryInto;
 use std::fmt::{self, Write};
-use std::ops::{Add, AddAssign, Div, DivAssign, Mul, Sub, SubAssign};
+use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 use std::str::FromStr;
 use thiserror::Error;
 
@@ -377,6 +377,14 @@ impl Mul for Decimal {
         }
     }
 }
+forward_ref_binop!(impl Mul, mul for Decimal, Decimal);
+
+impl MulAssign for Decimal {
+    fn mul_assign(&mut self, rhs: Decimal) {
+        *self = *self * rhs;
+    }
+}
+forward_ref_op_assign!(impl MulAssign, mul_assign for Decimal, Decimal);
 
 /// Both d*u and u*d with d: Decimal and u: Uint128 returns an Uint128. There is no
 /// specific reason for this decision other than the initial use cases we have. If you
@@ -958,6 +966,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(clippy::op_ref)]
     fn decimal_implements_mul() {
         let one = Decimal::one();
         let two = one + one;
@@ -1064,6 +1073,28 @@ mod tests {
             max * dec("0.000000000000000001"),
             dec("340.282366920938463463")
         );
+
+        // works for refs
+        let a = Decimal::percent(20);
+        let b = Decimal::percent(30);
+        let expected = Decimal::percent(6);
+        assert_eq!(a * b, expected);
+        assert_eq!(&a * b, expected);
+        assert_eq!(a * &b, expected);
+        assert_eq!(&a * &b, expected);
+    }
+
+    #[test]
+    fn decimal_mul_assign_works() {
+        let mut a = Decimal::percent(15);
+        a *= Decimal::percent(60);
+        assert_eq!(a, Decimal::percent(9));
+
+        // works for refs
+        let mut a = Decimal::percent(50);
+        let b = Decimal::percent(20);
+        a *= &b;
+        assert_eq!(a, Decimal::percent(10));
     }
 
     #[test]
diff --git a/packages/std/src/math/decimal256.rs b/packages/std/src/math/decimal256.rs
index 02296aebd9..98c5059214 100644
--- a/packages/std/src/math/decimal256.rs
+++ b/packages/std/src/math/decimal256.rs
@@ -4,7 +4,7 @@ use serde::{de, ser, Deserialize, Deserializer, Serialize};
 use std::cmp::Ordering;
 use std::convert::TryInto;
 use std::fmt::{self, Write};
-use std::ops::{Add, AddAssign, Div, DivAssign, Mul, Sub, SubAssign};
+use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 use std::str::FromStr;
 use thiserror::Error;
 
@@ -389,6 +389,14 @@ impl Mul for Decimal256 {
         }
     }
 }
+forward_ref_binop!(impl Mul, mul for Decimal256, Decimal256);
+
+impl MulAssign for Decimal256 {
+    fn mul_assign(&mut self, rhs: Self) {
+        *self = *self * rhs;
+    }
+}
+forward_ref_op_assign!(impl MulAssign, mul_assign for Decimal256, Decimal256);
 
 /// Both d*u and u*d with d: Decimal256 and u: Uint256 returns an Uint256. There is no
 /// specific reason for this decision other than the initial use cases we have. If you
@@ -1045,6 +1053,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(clippy::op_ref)]
     fn decimal256_implements_mul() {
         let one = Decimal256::one();
         let two = one + one;
@@ -1151,6 +1160,28 @@ mod tests {
             max * dec("0.000000000000000001"),
             dec("115792089237316195423570985008687907853269.984665640564039457")
         );
+
+        // works for refs
+        let a = Decimal256::percent(20);
+        let b = Decimal256::percent(30);
+        let expected = Decimal256::percent(6);
+        assert_eq!(a * b, expected);
+        assert_eq!(&a * b, expected);
+        assert_eq!(a * &b, expected);
+        assert_eq!(&a * &b, expected);
+    }
+
+    #[test]
+    fn decimal256_mul_assign_works() {
+        let mut a = Decimal256::percent(15);
+        a *= Decimal256::percent(60);
+        assert_eq!(a, Decimal256::percent(9));
+
+        // works for refs
+        let mut a = Decimal256::percent(50);
+        let b = Decimal256::percent(20);
+        a *= &b;
+        assert_eq!(a, Decimal256::percent(10));
     }
 
     #[test]
diff --git a/packages/std/src/math/mod.rs b/packages/std/src/math/mod.rs
index 747d21704f..2190d0dccc 100644
--- a/packages/std/src/math/mod.rs
+++ b/packages/std/src/math/mod.rs
@@ -67,9 +67,9 @@ mod tests {
         + SubAssign
         + SubAssign<&'a Self>
         + Mul
-        // + Mul<&'a Self>
-        // + MulAssign
-        // + MulAssign<&'a Self>
+        + Mul<&'a Self>
+        + MulAssign
+        + MulAssign<&'a Self>
         // + Div
         // + Div<&'a Self>
         // + DivAssign