refactor: drop constraint on Future's Output (#213)

Author: Keruspe

backon/src/blocking_sleep.rs

@@ -36,6 +36,7 @@ pub type DefaultBlockingSleeper = StdSleeper;
 ///
 /// Users should enable a feature of this crate that provides a valid [`Sleeper`] implementation when this type appears in compilation errors. Alternatively, a custom [`Sleeper`] implementation should be provided where necessary, such as in [`crate::Retry::sleeper`].
 #[doc(hidden)]
+#[allow(dead_code)]
 #[derive(Clone, Copy, Debug, Default)]
 pub struct PleaseEnableAFeatureOrProvideACustomSleeper;
 

backon/src/lib.rs

@@ -98,7 +98,7 @@
 //!     Ok("hello, world!".to_string())
 //! }
 //!
-//! #[tokio::main]
+//! #[tokio::main(flavor = "current_thread")]
 //! async fn main() -> Result<()> {
 //!     let content = fetch
 //!         // Retry with exponential backoff

backon/src/retry.rs

@@ -118,7 +118,7 @@ where
 {
     /// Set the sleeper for retrying.
     ///
-    /// The sleeper should implement the [`Sleeper`] trait. The simplest way is to use a closure that returns a `Future<Output=()>`.
+    /// The sleeper should implement the [`Sleeper`] trait. The simplest way is to use a closure that returns a `Future`.
     ///
     /// If not specified, we use the [`DefaultSleeper`].
     ///
@@ -344,7 +344,7 @@ where
 
 /// State maintains internal state of retry.
 #[derive(Default)]
-enum State<T, E, Fut: Future<Output = Result<T, E>>, SleepFut: Future<Output = ()>> {
+enum State<T, E, Fut: Future<Output = Result<T, E>>, SleepFut: Future> {
     #[default]
     Idle,
     Polling(Fut),

backon/src/retry_with_context.rs

@@ -151,7 +151,7 @@ where
 {
     /// Set the sleeper for retrying.
     ///
-    /// The sleeper should implement the [`Sleeper`] trait. The simplest way is to use a closure that returns a `Future<Output=()>`.
+    /// The sleeper should implement the [`Sleeper`] trait. The simplest way is to use a closure that returns a `Future`.
     ///
     /// If not specified, we use the [`DefaultSleeper`].
     pub fn sleep<SN: Sleeper>(
@@ -284,7 +284,7 @@ where
 }
 
 /// State maintains internal state of retry.
-enum State<T, E, Ctx, Fut: Future<Output = (Ctx, Result<T, E>)>, SleepFut: Future<Output = ()>> {
+enum State<T, E, Ctx, Fut: Future<Output = (Ctx, Result<T, E>)>, SleepFut: Future> {
     Idle(Option<Ctx>),
     Polling(Fut),
     Sleeping((Option<Ctx>, SleepFut)),

backon/src/sleep.rs

@@ -5,7 +5,7 @@ use core::time::Duration;
 /// A sleeper is used to generate a future that completes after a specified duration.
 pub trait Sleeper: 'static {
     /// The future returned by the `sleep` method.
-    type Sleep: Future<Output = ()>;
+    type Sleep: Future;
 
     /// Create a future that completes after a set period.
     fn sleep(&self, dur: Duration) -> Self::Sleep;
@@ -15,16 +15,16 @@ pub trait Sleeper: 'static {
 /// It does not provide actual functionality.
 #[doc(hidden)]
 pub trait MaybeSleeper: 'static {
-    type Sleep: Future<Output = ()>;
+    type Sleep: Future;
 }
 
 /// All `Sleeper` will implement  `MaybeSleeper`, but not vice versa.
 impl<T: Sleeper + ?Sized> MaybeSleeper for T {
     type Sleep = <T as Sleeper>::Sleep;
 }
 
-/// All `Fn(Duration) -> impl Future<Output = ()>` implements `Sleeper`.
-impl<F: Fn(Duration) -> Fut + 'static, Fut: Future<Output = ()>> Sleeper for F {
+/// All `Fn(Duration) -> impl Future` implements `Sleeper`.
+impl<F: Fn(Duration) -> Fut + 'static, Fut: Future> Sleeper for F {
     type Sleep = Fut;
 
     fn sleep(&self, dur: Duration) -> Self::Sleep {
@@ -52,6 +52,7 @@ pub type DefaultSleeper = GlooTimersSleep;
 ///
 /// Users should enable a feature of this crate that provides a valid [`Sleeper`] implementation when this type appears in compilation errors. Alternatively, a custom [`Sleeper`] implementation should be provided where necessary, such as in [`crate::Retry::sleeper`].
 #[doc(hidden)]
+#[allow(dead_code)]
 #[derive(Clone, Copy, Debug, Default)]
 pub struct PleaseEnableAFeatureOrProvideACustomSleeper;