Add must_use annotations

cgzones · cgzones · commit fe19bc501fec · 2025-11-18T14:21:11.000+01:00
Add annotations to warn about unused return values at call-sites.
Annotate `OperationResult`, similar to `std::result::Result`,
constructors, and functions with no side-effects.
diff --git a/src/delay/mod.rs b/src/delay/mod.rs
@@ -18,6 +18,7 @@ pub struct Exponential {
 impl Exponential {
     /// Create a new [`Exponential`] using the given millisecond duration as the initial delay and
     /// an exponential backoff factor of `2.0`.
+    #[must_use]
     pub fn from_millis(base: u64) -> Self {
         Exponential {
             current: base,
@@ -28,6 +29,7 @@ impl Exponential {
     /// Create a new [`Exponential`] using the given millisecond duration as the initial delay and
     /// the same duration as the exponential backoff factor. This was the behavior of
     /// [`Exponential::from_millis`] prior to version 2.0.
+    #[must_use]
     pub fn from_millis_with_base_factor(base: u64) -> Self {
         Exponential {
             current: base,
@@ -37,6 +39,7 @@ impl Exponential {
 
     /// Create a new [`Exponential`] using the given millisecond duration as the initial delay and
     /// the given exponential backoff factor.
+    #[must_use]
     pub fn from_millis_with_factor(base: u64, factor: f64) -> Self {
         Exponential {
             current: base,
@@ -102,6 +105,7 @@ pub struct Fibonacci {
 
 impl Fibonacci {
     /// Create a new [`Fibonacci`] using the given duration in milliseconds.
+    #[must_use]
     pub fn from_millis(millis: u64) -> Fibonacci {
         Fibonacci {
             curr: millis,
@@ -160,6 +164,7 @@ pub struct Fixed {
 
 impl Fixed {
     /// Create a new [`Fixed`] using the given duration in milliseconds.
+    #[must_use]
     pub fn from_millis(millis: u64) -> Self {
         Fixed {
             duration: Duration::from_millis(millis),
diff --git a/src/delay/random.rs b/src/delay/random.rs
@@ -23,6 +23,7 @@ impl Range {
     /// # Panics
     ///
     /// Panics if the minimum is greater than or equal to the maximum.
+    #[must_use]
     pub fn from_millis_exclusive(minimum: u64, maximum: u64) -> Self {
         Range {
             distribution: Uniform::new(minimum, maximum)
@@ -49,6 +50,7 @@ impl Range {
     /// # Panics
     ///
     /// Panics if the minimum is greater than or equal to the maximum.
+    #[must_use]
     pub fn from_millis_inclusive(minimum: u64, maximum: u64) -> Self {
         Range {
             distribution: Uniform::new_inclusive(minimum, maximum)
@@ -97,6 +99,7 @@ impl From<RangeInclusive<Duration>> for Range {
 }
 
 /// Apply full random jitter to a duration. (When the `random` Cargo feature is enabled.)
+#[must_use]
 pub fn jitter(duration: Duration) -> Duration {
     let jitter = random::<f64>();
     let secs = ((duration.as_secs() as f64) * jitter).ceil() as u64;
@@ -115,13 +118,13 @@ fn range_uniform() {
 #[test]
 #[should_panic]
 fn range_exclusive_uniform_wrong_input() {
-    Range::from_millis_exclusive(1, 0);
+    let _panic = Range::from_millis_exclusive(1, 0);
 }
 
 #[test]
 #[should_panic]
 fn range_inclusive_uniform_wrong_input() {
-    Range::from_millis_inclusive(1, 0);
+    let _panic = Range::from_millis_inclusive(1, 0);
 }
 
 #[test]
diff --git a/src/opresult.rs b/src/opresult.rs
@@ -19,6 +19,7 @@
 //! ```
 
 /// A result that represents either success, retryable failure, or immediately-returning failure.
+#[must_use]
 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
 pub enum OperationResult<T, E> {
     /// Contains the success value.
@@ -57,6 +58,7 @@ impl<T, E> OperationResult<T, E> {
     /// let x: OperationResult<i32, &str> = OperationResult::Err("Some other error message");
     /// assert_eq!(x.is_ok(), false);
     /// ```
+    #[must_use]
     pub fn is_ok(&self) -> bool {
         matches!(self, Self::Ok(_))
     }
@@ -79,6 +81,7 @@ impl<T, E> OperationResult<T, E> {
     /// let x: OperationResult<i32, &str> = OperationResult::Err("Some other error message");
     /// assert_eq!(x.is_retry(), false);
     /// ```
+    #[must_use]
     pub fn is_retry(&self) -> bool {
         matches!(self, Self::Retry(_))
     }
@@ -101,6 +104,7 @@ impl<T, E> OperationResult<T, E> {
     /// let x: OperationResult<i32, &str> = OperationResult::Err("Some other error message");
     /// assert_eq!(x.is_err(), true);
     /// ```
+    #[must_use]
     pub fn is_err(&self) -> bool {
         matches!(self, Self::Err(_))
     }
