Informational 15 Bitcoin Committed Dec 7, 2025 · 00:05 UTC

Add generic Sub/AddAssign impl over NumOpResult

456aad19 View source ↗

Public commit record

What the developer wrote

Authored by Mitchell Bagot

68/100 · Adequate

Add generic Sub/AddAssign impl over NumOpResult

Currently, we have an internal macro impl_(sub|add)_assign to implement
Sub/AddAssign for a type with itself, or a ref of itself. Since many
ops on units types yield NumOpResult<T> wrappers, it's convenient for
users to provide AddAssign and SubAssign over those wrappers for types
that already provide Sub/AddAssign.

Add generic implementation of Sub/AddAssign over NumOpResult<T> for
types in units that implement Sub/AddAssign on the base type.

✓ Descriptive subject✓ Names a concrete action or component✓ Provides detailed explanatory context

The short version

What changed, and why it matters

This commit adds convenience Rust traits (+= and -= operators) for a wrapper type called NumOpResult. It does not fix a bug or change existing behavior; it only makes it easier to add or subtract values that are already wrapped in a NumOpResult. There is no security relevance in the change itself.

Recommended action

No security action needed. Review as a normal API addition.

Security signals we found

No strong security signals were identified.

Technical analysis

Evidence from the diff

The patch adds generic AddAssign and SubAssign implementations for NumOpResult in rust-bitcoin’s units crate. If the wrapped value is Valid, the operation is forwarded to the underlying T; if either operand is Error, the result becomes Error. This is a pure API ergonomics addition and does not alter any existing arithmetic semantics or fix a vulnerability.

Changed components

units/src/result.rsunits/src/fee_rate/mod.rs

Inspect captured patch +72 / −0

diff --git a/api/units/all-features.txt b/api/units/all-features.txt
index 07889bdf..cd908025 100644
--- a/api/units/all-features.txt
+++ b/api/units/all-features.txt
@@ -1344,6 +1344,10 @@ impl<T: core::cmp::PartialEq> core::cmp::PartialEq for bitcoin_units::result::Nu
 impl<T: core::fmt::Debug> bitcoin_units::result::NumOpResult<T>
 impl<T: core::fmt::Debug> core::fmt::Debug for bitcoin_units::result::NumOpResult<T>
 impl<T: core::marker::Copy> core::marker::Copy for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::AddAssign + core::marker::Copy> core::ops::arith::AddAssign for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::AddAssign> core::ops::arith::AddAssign<T> for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::SubAssign + core::marker::Copy> core::ops::arith::SubAssign for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::SubAssign> core::ops::arith::SubAssign<T> for bitcoin_units::result::NumOpResult<T>
 impl<T> bitcoin_units::result::NumOpResult<T>
 impl<T> core::marker::Freeze for bitcoin_units::result::NumOpResult<T> where T: core::marker::Freeze
 impl<T> core::marker::Send for bitcoin_units::result::NumOpResult<T> where T: core::marker::Send
@@ -2355,6 +2359,8 @@ pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: &T) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: &bitcoin_units::result::NumOpResult<T>) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: Self) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: T) -> Self::Output
+pub fn bitcoin_units::result::NumOpResult<T>::add_assign(&mut self, rhs: Self)
+pub fn bitcoin_units::result::NumOpResult<T>::add_assign(&mut self, rhs: T)
 pub fn bitcoin_units::result::NumOpResult<T>::and_then<F>(self, op: F) -> Self where F: core::ops::function::FnOnce(T) -> Self
 pub fn bitcoin_units::result::NumOpResult<T>::arbitrary(u: &mut arbitrary::unstructured::Unstructured<'a>) -> arbitrary::error::Result<Self>
 pub fn bitcoin_units::result::NumOpResult<T>::clone(&self) -> bitcoin_units::result::NumOpResult<T>
@@ -2370,6 +2376,8 @@ pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: &T) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: &bitcoin_units::result::NumOpResult<T>) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: Self) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: T) -> Self::Output
+pub fn bitcoin_units::result::NumOpResult<T>::sub_assign(&mut self, rhs: Self)
+pub fn bitcoin_units::result::NumOpResult<T>::sub_assign(&mut self, rhs: T)
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap(self) -> T
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap_err(self) -> bitcoin_units::result::NumOpError
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap_or(self, default: T) -> T
diff --git a/api/units/alloc-only.txt b/api/units/alloc-only.txt
index de665ac2..b6333f98 100644
--- a/api/units/alloc-only.txt
+++ b/api/units/alloc-only.txt
@@ -1105,6 +1105,10 @@ impl<T: core::cmp::PartialEq> core::cmp::PartialEq for bitcoin_units::result::Nu
 impl<T: core::fmt::Debug> bitcoin_units::result::NumOpResult<T>
 impl<T: core::fmt::Debug> core::fmt::Debug for bitcoin_units::result::NumOpResult<T>
 impl<T: core::marker::Copy> core::marker::Copy for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::AddAssign + core::marker::Copy> core::ops::arith::AddAssign for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::AddAssign> core::ops::arith::AddAssign<T> for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::SubAssign + core::marker::Copy> core::ops::arith::SubAssign for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::SubAssign> core::ops::arith::SubAssign<T> for bitcoin_units::result::NumOpResult<T>
 impl<T> bitcoin_units::result::NumOpResult<T>
 impl<T> core::marker::Freeze for bitcoin_units::result::NumOpResult<T> where T: core::marker::Freeze
 impl<T> core::marker::Send for bitcoin_units::result::NumOpResult<T> where T: core::marker::Send
@@ -1996,6 +2000,8 @@ pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: &T) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: &bitcoin_units::result::NumOpResult<T>) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: Self) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: T) -> Self::Output
+pub fn bitcoin_units::result::NumOpResult<T>::add_assign(&mut self, rhs: Self)
+pub fn bitcoin_units::result::NumOpResult<T>::add_assign(&mut self, rhs: T)
 pub fn bitcoin_units::result::NumOpResult<T>::and_then<F>(self, op: F) -> Self where F: core::ops::function::FnOnce(T) -> Self
 pub fn bitcoin_units::result::NumOpResult<T>::clone(&self) -> bitcoin_units::result::NumOpResult<T>
 pub fn bitcoin_units::result::NumOpResult<T>::eq(&self, other: &bitcoin_units::result::NumOpResult<T>) -> bool
@@ -2010,6 +2016,8 @@ pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: &T) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: &bitcoin_units::result::NumOpResult<T>) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: Self) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: T) -> Self::Output
+pub fn bitcoin_units::result::NumOpResult<T>::sub_assign(&mut self, rhs: Self)
+pub fn bitcoin_units::result::NumOpResult<T>::sub_assign(&mut self, rhs: T)
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap(self) -> T
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap_err(self) -> bitcoin_units::result::NumOpError
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap_or(self, default: T) -> T
diff --git a/api/units/no-features.txt b/api/units/no-features.txt
index 369e5d91..4dbb5000 100644
--- a/api/units/no-features.txt
+++ b/api/units/no-features.txt
@@ -1081,6 +1081,10 @@ impl<T: core::cmp::PartialEq> core::cmp::PartialEq for bitcoin_units::result::Nu
 impl<T: core::fmt::Debug> bitcoin_units::result::NumOpResult<T>
 impl<T: core::fmt::Debug> core::fmt::Debug for bitcoin_units::result::NumOpResult<T>
 impl<T: core::marker::Copy> core::marker::Copy for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::AddAssign + core::marker::Copy> core::ops::arith::AddAssign for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::AddAssign> core::ops::arith::AddAssign<T> for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::SubAssign + core::marker::Copy> core::ops::arith::SubAssign for bitcoin_units::result::NumOpResult<T>
+impl<T: core::ops::arith::SubAssign> core::ops::arith::SubAssign<T> for bitcoin_units::result::NumOpResult<T>
 impl<T> bitcoin_units::result::NumOpResult<T>
 impl<T> core::marker::Freeze for bitcoin_units::result::NumOpResult<T> where T: core::marker::Freeze
 impl<T> core::marker::Send for bitcoin_units::result::NumOpResult<T> where T: core::marker::Send
@@ -1938,6 +1942,8 @@ pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: &T) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: &bitcoin_units::result::NumOpResult<T>) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: Self) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::add(self, rhs: T) -> Self::Output
+pub fn bitcoin_units::result::NumOpResult<T>::add_assign(&mut self, rhs: Self)
+pub fn bitcoin_units::result::NumOpResult<T>::add_assign(&mut self, rhs: T)
 pub fn bitcoin_units::result::NumOpResult<T>::and_then<F>(self, op: F) -> Self where F: core::ops::function::FnOnce(T) -> Self
 pub fn bitcoin_units::result::NumOpResult<T>::clone(&self) -> bitcoin_units::result::NumOpResult<T>
 pub fn bitcoin_units::result::NumOpResult<T>::eq(&self, other: &bitcoin_units::result::NumOpResult<T>) -> bool
@@ -1952,6 +1958,8 @@ pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: &T) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: &bitcoin_units::result::NumOpResult<T>) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: Self) -> Self::Output
 pub fn bitcoin_units::result::NumOpResult<T>::sub(self, rhs: T) -> Self::Output
+pub fn bitcoin_units::result::NumOpResult<T>::sub_assign(&mut self, rhs: Self)
+pub fn bitcoin_units::result::NumOpResult<T>::sub_assign(&mut self, rhs: T)
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap(self) -> T
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap_err(self) -> bitcoin_units::result::NumOpError
 pub fn bitcoin_units::result::NumOpResult<T>::unwrap_or(self, default: T) -> T
diff --git a/units/src/fee_rate/mod.rs b/units/src/fee_rate/mod.rs
index e94e4973..670adb9b 100644
--- a/units/src/fee_rate/mod.rs
+++ b/units/src/fee_rate/mod.rs
@@ -323,6 +323,14 @@ mod tests {
         let mut f = FeeRate::from_sat_per_kwu(1);
         f += &FeeRate::from_sat_per_kwu(2);
         assert_eq!(f, FeeRate::from_sat_per_kwu(3));
+
+        let mut f = NumOpResult::Valid(FeeRate::from_sat_per_kwu(1));
+        f += FeeRate::from_sat_per_kwu(2);
+        assert_eq!(f, NumOpResult::Valid(FeeRate::from_sat_per_kwu(3)));
+
+        let mut f = NumOpResult::Valid(FeeRate::from_sat_per_kwu(1));
+        f += NumOpResult::Valid(FeeRate::from_sat_per_kwu(2));
+        assert_eq!(f, NumOpResult::Valid(FeeRate::from_sat_per_kwu(3)));
     }
 
     #[test]
@@ -334,6 +342,14 @@ mod tests {
         let mut f = FeeRate::from_sat_per_kwu(3);
         f -= &FeeRate::from_sat_per_kwu(2);
         assert_eq!(f, FeeRate::from_sat_per_kwu(1));
+
+        let mut f = NumOpResult::Valid(FeeRate::from_sat_per_kwu(3));
+        f -= FeeRate::from_sat_per_kwu(2);
+        assert_eq!(f, NumOpResult::Valid(FeeRate::from_sat_per_kwu(1)));
+
+        let mut f = NumOpResult::Valid(FeeRate::from_sat_per_kwu(3));
+        f -= NumOpResult::Valid(FeeRate::from_sat_per_kwu(2));
+        assert_eq!(f, NumOpResult::Valid(FeeRate::from_sat_per_kwu(1)));
     }
 
     #[test]
diff --git a/units/src/result.rs b/units/src/result.rs
index 7b730d02..4d50dc82 100644
--- a/units/src/result.rs
+++ b/units/src/result.rs
@@ -269,6 +269,38 @@ crate::internal_macros::impl_op_for_references! {
     }
 }
 
+// Implement AddAssign on NumOpResults for all wrapped types that already implement AddAssign on themselves
+impl<T: ops::AddAssign> ops::AddAssign<T> for NumOpResult<T> {
+    fn add_assign(&mut self, rhs: T) {
+        if let Self::Valid(ref mut lhs) = self { *lhs += rhs }
+    }
+}
+
+impl<T: ops::AddAssign + Copy> ops::AddAssign<Self> for NumOpResult<T> {
+    fn add_assign(&mut self, rhs: Self) {
+        match (&self, rhs) {
+            (Self::Valid(_), Self::Valid(rhs)) => *self += rhs,
+            (_, _) => *self = Self::Error(NumOpError::while_doing(MathOp::Add)),
+        }
+    }
+}
+
+// Implement SubAssign on NumOpResults for all wrapped types that already implement SubAssign on themselves
+impl<T: ops::SubAssign> ops::SubAssign<T> for NumOpResult<T> {
+    fn sub_assign(&mut self, rhs: T) {
+        if let Self::Valid(ref mut lhs) = self { *lhs -= rhs }
+    }
+}
+
+impl<T: ops::SubAssign + Copy> ops::SubAssign<Self> for NumOpResult<T> {
+    fn sub_assign(&mut self, rhs: Self) {
+        match (&self, rhs) {
+            (Self::Valid(_), Self::Valid(rhs)) => *self -= rhs,
+            (_, _) => *self = Self::Error(NumOpError::while_doing(MathOp::Sub)),
+        }
+    }
+}
+
 pub(crate) trait OptionExt<T> {
     fn valid_or_error(self, op: MathOp) -> NumOpResult<T>;
 }

Risk score

Why this scored 15/100

Our methodology →

Potential impact 0/30

Exploitability 0/25

Stealth signal 0/15

Affected reach 0/15

Confidence 10/10

Evidence quality 5/5

Human-validated context

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What the developer wrote

What changed, and why it matters

Security signals we found

Evidence from the diff

Changed components

Why this scored 15/100

Community notes

Related watches

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Update API files

Merge rust-bitcoin/rust-bitcoin#6678: units: Add `Weight::to_vb_` functions, deprecating `to_vbytes_`