Create impl_mul_assign and impl_div_assign macros

The macros were called on type-rhs pairs that have an existing
implementation of ops::Mul and ops::Div, respectively, that have an
`Output` of `Self`

units/src/amount/result.rs

@@ -8,6 +8,7 @@ use NumOpResult as R;
 
 use super::{Amount, SignedAmount};
 use crate::{MathOp, NumOpError, NumOpResult, OptionExt};
+use crate::internal_macros::{impl_mul_assign, impl_div_assign};
 
 impl From<Amount> for NumOpResult<Amount> {
     fn from(a: Amount) -> Self { Self::Valid(a) }
@@ -230,6 +231,11 @@ crate::internal_macros::impl_op_for_references! {
     }
 }
 
+impl_mul_assign!(NumOpResult<Amount>, u64);
+impl_mul_assign!(NumOpResult<SignedAmount>, i64);
+impl_div_assign!(NumOpResult<Amount>, u64);
+impl_div_assign!(NumOpResult<SignedAmount>, i64);
+
 impl ops::Neg for SignedAmount {
     type Output = Self;
 

units/src/amount/tests.rs

@@ -23,6 +23,16 @@ fn sat(sat: u64) -> Amount { Amount::from_sat(sat).unwrap() }
 #[track_caller]
 fn ssat(ssat: i64) -> SignedAmount { SignedAmount::from_sat(ssat).unwrap() }
 
+#[track_caller]
+fn res(n_sat: u64) -> NumOpResult<Amount>{
+    NumOpResult::from(sat(n_sat))
+}
+
+#[track_caller]
+fn sres(n_sat: i64) -> NumOpResult<SignedAmount>{
+    NumOpResult::from(ssat(n_sat))
+}
+
 #[test]
 fn sanity_check() {
     assert_eq!(ssat(-100).abs(), ssat(100));
@@ -1191,9 +1201,6 @@ fn signed_subtraction() {
 
 #[test]
 fn op_int_combos() {
-    let res = |n_sat| NumOpResult::from(sat(n_sat));
-    let sres = |n_ssat| NumOpResult::from(ssat(n_ssat));
-
     assert_eq!(sat(23) * 31, res(713));
     assert_eq!(ssat(23) * 31, sres(713));
     assert_eq!(res(23) * 31, res(713));
@@ -1257,6 +1264,40 @@ fn signed_amount_div_by_amount_zero() {
     assert!(res.into_result().is_err());
 }
 
+#[test]
+fn mul_assign() {
+    let mut result = res(113);
+    result *= 367;
+    assert_eq!(result, res(41471));
+
+    let mut max = res(Amount::MAX.to_sat());
+    max *= 2;
+    assert!(max.is_error());
+
+    let mut signed_result = sres(-211);
+    signed_result *= 431;
+    assert_eq!(signed_result, sres(-90941));
+
+    let mut min = sres(SignedAmount::MIN.to_sat());
+    min *= 2;
+    assert!(min.is_error());
+}
+
+#[test]
+fn div_assign() {
+    let mut result = res(41471);
+    result /= 367;
+    assert_eq!(result, res(113));
+    result /= 0;
+    assert!(result.is_error());
+
+    let mut signed_result = sres(-90941);
+    signed_result /= 211;
+    assert_eq!(signed_result, sres(-431));
+    signed_result /= 0;
+    assert!(signed_result.is_error());
+}
+
 #[test]
 fn check_const() {
     assert_eq!(SignedAmount::ONE_BTC.to_sat(), 100_000_000);

units/src/internal_macros.rs

@@ -96,3 +96,31 @@ macro_rules! impl_sub_assign {
     };
 }
 pub(crate) use impl_sub_assign;
+
+/// Implement `ops::MulAssign` for `$ty` multiplied by `$rhs` and `&$rhs`.
+macro_rules! impl_mul_assign {
+    ($ty:ty, $rhs:ident) => {
+        impl core::ops::MulAssign<$rhs> for $ty {
+            fn mul_assign(&mut self, rhs: $rhs) { *self = *self * rhs }
+        }
+
+        impl core::ops::MulAssign<&$rhs> for $ty {
+            fn mul_assign(&mut self, rhs: &$rhs) { *self = *self * *rhs }
+        }
+    };
+}
+pub(crate) use impl_mul_assign;
+
+/// Implement `ops::DivAssign` for `$ty` divided by `$rhs` and `&$rhs`.
+macro_rules! impl_div_assign {
+    ($ty:ty, $rhs:ident) => {
+        impl core::ops::DivAssign<$rhs> for $ty {
+            fn div_assign(&mut self, rhs: $rhs) { *self = *self / rhs }
+        }
+
+        impl core::ops::DivAssign<&$rhs> for $ty {
+            fn div_assign(&mut self, rhs: &$rhs) { *self = *self / *rhs }
+        }
+    };
+}
+pub(crate) use impl_div_assign;