Merge #407

407: async: switch to async-fn-in-traits, release v0.2.0-alpha.0 r=eldruin a=Dirbaio

Latest Rust nightlies have somewhat usable async-fn-in-trait support already! 🎉 

embassy-nrf updated here embassy-rs/embassy#974

Paprecuts encountered:

- there's this annoying error [playground](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=f04fca1f2a3d643c323fb49c05bd3ed3), workaround is to use the concrete type instead of `Self::Error`. This is a limitation of all `async fn`s, not just in traits, but it hits especially hard within traits, so I dunno if there's plans to improve it.

> `async fn` return type cannot contain a projection or `Self` that references lifetimes from a parent scope

- The SpiDevice trait ICEs, issue filed rust-lang/rust#102310
- default methods don't work, but there's a PR already rust-lang/rust#102308

Due to the last 2 I've left `SpiDevice` alone for now.

Co-authored-by: Dario Nieuwenhuis <[email protected]>

Author: bors[bot]

.github/workflows/clippy.yml

@@ -14,7 +14,7 @@ jobs:
           profile: minimal
           # embedded-hal-async needs nightly.
           # Use a pinned version to avoid spontaneous breakages (new clippy lints are added often)
-          toolchain: nightly-2022-09-25
+          toolchain: nightly-2022-11-22
           override: true
           components: clippy
       - run: cargo clippy -- --deny=warnings

embedded-hal-async/CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+## [v0.2.0-alpha.0] - 2022-11-23
+
+- Switch all traits to use [`async_fn_in_trait`](https://blog.rust-lang.org/inside-rust/2022/11/17/async-fn-in-trait-nightly.html) (AFIT). Requires `nightly-2022-11-22` or newer.
 
 ## [v0.1.0-alpha.3] - 2022-10-26
 
@@ -34,7 +37,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 First release to crates.io
 
 
-[Unreleased]: https://github.com/rust-embedded/embedded-hal/compare/embedded-hal-async-v0.1.0-alpha.3...HEAD
+[Unreleased]: https://github.com/rust-embedded/embedded-hal/compare/embedded-hal-async-v0.2.0-alpha.0...HEAD
+[v0.2.0-alpha.0]: https://github.com/rust-embedded/embedded-hal/compare/embedded-hal-async-v0.1.0-alpha.3...embedded-hal-async-v0.2.0-alpha.0
 [v0.1.0-alpha.3]: https://github.com/rust-embedded/embedded-hal/compare/embedded-hal-async-v0.1.0-alpha.2...embedded-hal-async-v0.1.0-alpha.3
 [v0.1.0-alpha.2]: https://github.com/rust-embedded/embedded-hal/compare/embedded-hal-async-v0.1.0-alpha.1...embedded-hal-async-v0.1.0-alpha.2
 [v0.1.0-alpha.1]: https://github.com/rust-embedded/embedded-hal/compare/embedded-hal-async-v0.1.0-alpha.0...embedded-hal-async-v0.1.0-alpha.1

embedded-hal-async/Cargo.toml

@@ -11,7 +11,7 @@ license = "MIT OR Apache-2.0"
 name = "embedded-hal-async"
 readme = "README.md"
 repository = "https://github.com/rust-embedded/embedded-hal"
-version = "0.1.0-alpha.3"
+version = "0.2.0-alpha.0"
 
 [dependencies]
 embedded-hal = { version = "=1.0.0-alpha.9", path = "../embedded-hal" }

embedded-hal-async/src/delay.rs

@@ -1,29 +1,17 @@
 //! Delays
 
-use core::future::Future;
-
 /// Microsecond delay
 pub trait DelayUs {
     /// Enumeration of errors
     type Error: core::fmt::Debug;
 
-    /// The future returned by the `delay_us` function.
-    type DelayUsFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
-
     /// Pauses execution for at minimum `us` microseconds. Pause can be longer
     /// if the implementation requires it due to precision/timing issues.
-    fn delay_us(&mut self, us: u32) -> Self::DelayUsFuture<'_>;
-
-    /// The future returned by the `delay_ms` function.
-    type DelayMsFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
+    async fn delay_us(&mut self, us: u32) -> Result<(), Self::Error>;
 
     /// Pauses execution for at minimum `ms` milliseconds. Pause can be longer
     /// if the implementation requires it due to precision/timing issues.
-    fn delay_ms(&mut self, ms: u32) -> Self::DelayMsFuture<'_>;
+    async fn delay_ms(&mut self, ms: u32) -> Result<(), Self::Error>;
 }
 
 impl<T> DelayUs for &mut T
@@ -32,15 +20,11 @@ where
 {
     type Error = T::Error;
 
-    type DelayUsFuture<'a> = T::DelayUsFuture<'a> where Self: 'a;
-
-    fn delay_us(&mut self, us: u32) -> Self::DelayUsFuture<'_> {
-        T::delay_us(self, us)
+    async fn delay_us(&mut self, us: u32) -> Result<(), Self::Error> {
+        T::delay_us(self, us).await
     }
 
-    type DelayMsFuture<'a> = T::DelayMsFuture<'a> where Self: 'a;
-
-    fn delay_ms(&mut self, ms: u32) -> Self::DelayMsFuture<'_> {
-        T::delay_ms(self, ms)
+    async fn delay_ms(&mut self, ms: u32) -> Result<(), Self::Error> {
+        T::delay_ms(self, ms).await
     }
 }

embedded-hal-async/src/digital.rs

@@ -16,93 +16,56 @@
 //! }
 //! ```
 
-use core::future::Future;
-
 /// Asynchronously wait for GPIO pin state.
 pub trait Wait: embedded_hal::digital::ErrorType {
-    /// The future returned by the `wait_for_high` function.
-    type WaitForHighFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
-
     /// Wait until the pin is high. If it is already high, return immediately.
     ///
     /// # Note for implementers
     /// The pin may have switched back to low before the task was run after
     /// being woken. The future should still resolve in that case.
-    fn wait_for_high(&mut self) -> Self::WaitForHighFuture<'_>;
-
-    /// The future returned by `wait_for_low`.
-    type WaitForLowFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
+    async fn wait_for_high(&mut self) -> Result<(), Self::Error>;
 
     /// Wait until the pin is low. If it is already low, return immediately.
     ///
     /// # Note for implementers
     /// The pin may have switched back to high before the task was run after
     /// being woken. The future should still resolve in that case.
-    fn wait_for_low(&mut self) -> Self::WaitForLowFuture<'_>;
-
-    /// The future returned from `wait_for_rising_edge`.
-    type WaitForRisingEdgeFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
+    async fn wait_for_low(&mut self) -> Result<(), Self::Error>;
 
     /// Wait for the pin to undergo a transition from low to high.
     ///
     /// If the pin is already high, this does *not* return immediately, it'll wait for the
     /// pin to go low and then high again.
-    fn wait_for_rising_edge(&mut self) -> Self::WaitForRisingEdgeFuture<'_>;
-
-    /// The future returned from `wait_for_falling_edge`.
-    type WaitForFallingEdgeFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
+    async fn wait_for_rising_edge(&mut self) -> Result<(), Self::Error>;
 
     /// Wait for the pin to undergo a transition from high to low.
     ///
     /// If the pin is already low, this does *not* return immediately, it'll wait for the
     /// pin to go high and then low again.
-    fn wait_for_falling_edge(&mut self) -> Self::WaitForFallingEdgeFuture<'_>;
-
-    /// The future returned from `wait_for_any_edge`.
-    type WaitForAnyEdgeFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
+    async fn wait_for_falling_edge(&mut self) -> Result<(), Self::Error>;
 
     /// Wait for the pin to undergo any transition, i.e low to high OR high to low.
-    fn wait_for_any_edge(&mut self) -> Self::WaitForAnyEdgeFuture<'_>;
+    async fn wait_for_any_edge(&mut self) -> Result<(), Self::Error>;
 }
 
 impl<T: Wait> Wait for &mut T {
-    type WaitForHighFuture<'a> = T::WaitForHighFuture<'a> where Self: 'a;
-
-    fn wait_for_high(&mut self) -> Self::WaitForHighFuture<'_> {
-        T::wait_for_high(self)
+    async fn wait_for_high(&mut self) -> Result<(), Self::Error> {
+        T::wait_for_high(self).await
     }
 
-    type WaitForLowFuture<'a> = T::WaitForLowFuture<'a> where Self: 'a;
-
-    fn wait_for_low(&mut self) -> Self::WaitForLowFuture<'_> {
-        T::wait_for_low(self)
+    async fn wait_for_low(&mut self) -> Result<(), Self::Error> {
+        T::wait_for_low(self).await
     }
 
-    type WaitForRisingEdgeFuture<'a> = T::WaitForRisingEdgeFuture<'a> where Self: 'a;
-
-    fn wait_for_rising_edge(&mut self) -> Self::WaitForRisingEdgeFuture<'_> {
-        T::wait_for_rising_edge(self)
+    async fn wait_for_rising_edge(&mut self) -> Result<(), Self::Error> {
+        T::wait_for_rising_edge(self).await
     }
 
-    type WaitForFallingEdgeFuture<'a> = T::WaitForFallingEdgeFuture<'a> where Self: 'a;
-
-    fn wait_for_falling_edge(&mut self) -> Self::WaitForFallingEdgeFuture<'_> {
-        T::wait_for_falling_edge(self)
+    async fn wait_for_falling_edge(&mut self) -> Result<(), Self::Error> {
+        T::wait_for_falling_edge(self).await
     }
 
-    type WaitForAnyEdgeFuture<'a> = T::WaitForAnyEdgeFuture<'a> where Self: 'a;
-
-    fn wait_for_any_edge(&mut self) -> Self::WaitForAnyEdgeFuture<'_> {
-        T::wait_for_any_edge(self)
+    async fn wait_for_any_edge(&mut self) -> Result<(), Self::Error> {
+        T::wait_for_any_edge(self).await
     }
 }

embedded-hal-async/src/i2c.rs

@@ -16,19 +16,13 @@
 //! Since 7-bit addressing is the mode of the majority of I2C devices,
 //! `SevenBitAddress` has been set as default mode and thus can be omitted if desired.
 
-use core::future::Future;
 pub use embedded_hal::i2c::Operation;
 pub use embedded_hal::i2c::{
     AddressMode, Error, ErrorKind, ErrorType, NoAcknowledgeSource, SevenBitAddress, TenBitAddress,
 };
 
 /// Async i2c
 pub trait I2c<A: AddressMode = SevenBitAddress>: ErrorType {
-    /// Future returned by the `read` method.
-    type ReadFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
-
     /// Reads enough bytes from slave with `address` to fill `buffer`
     ///
     /// # I2C Events (contract)
@@ -47,12 +41,7 @@ pub trait I2c<A: AddressMode = SevenBitAddress>: ErrorType {
     /// - `MAK` = master acknowledge
     /// - `NMAK` = master no acknowledge
     /// - `SP` = stop condition
-    fn read<'a>(&'a mut self, address: A, read: &'a mut [u8]) -> Self::ReadFuture<'a>;
-
-    /// Future returned by the `write` method.
-    type WriteFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
+    async fn read<'a>(&'a mut self, address: A, read: &'a mut [u8]) -> Result<(), Self::Error>;
 
     /// Writes bytes to slave with address `address`
     ///
@@ -70,12 +59,7 @@ pub trait I2c<A: AddressMode = SevenBitAddress>: ErrorType {
     /// - `SAK` = slave acknowledge
     /// - `Bi` = ith byte of data
     /// - `SP` = stop condition
-    fn write<'a>(&'a mut self, address: A, write: &'a [u8]) -> Self::WriteFuture<'a>;
-
-    /// Future returned by the `write_read` method.
-    type WriteReadFuture<'a>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a;
+    async fn write<'a>(&'a mut self, address: A, write: &'a [u8]) -> Result<(), Self::Error>;
 
     /// Writes bytes to slave with address `address` and then reads enough bytes to fill `read` *in a
     /// single transaction*.
@@ -99,18 +83,12 @@ pub trait I2c<A: AddressMode = SevenBitAddress>: ErrorType {
     /// - `MAK` = master acknowledge
     /// - `NMAK` = master no acknowledge
     /// - `SP` = stop condition
-    fn write_read<'a>(
+    async fn write_read<'a>(
         &'a mut self,
         address: A,
         write: &'a [u8],
         read: &'a mut [u8],
-    ) -> Self::WriteReadFuture<'a>;
-
-    /// Future returned by the `transaction` method.
-    type TransactionFuture<'a, 'b>: Future<Output = Result<(), Self::Error>>
-    where
-        Self: 'a,
-        'b: 'a;
+    ) -> Result<(), Self::Error>;
 
     /// Execute the provided operations on the I2C bus as a single transaction.
     ///
@@ -125,44 +103,36 @@ pub trait I2c<A: AddressMode = SevenBitAddress>: ErrorType {
     /// - `SAD+R/W` = slave address followed by bit 1 to indicate reading or 0 to indicate writing
     /// - `SR` = repeated start condition
     /// - `SP` = stop condition
-    fn transaction<'a, 'b>(
+    async fn transaction<'a, 'b>(
         &'a mut self,
         address: A,
         operations: &'a mut [Operation<'b>],
-    ) -> Self::TransactionFuture<'a, 'b>;
+    ) -> Result<(), Self::Error>;
 }
 
 impl<A: AddressMode, T: I2c<A>> I2c<A> for &mut T {
-    type ReadFuture<'a> = T::ReadFuture<'a> where Self: 'a;
-
-    fn read<'a>(&'a mut self, address: A, buffer: &'a mut [u8]) -> Self::ReadFuture<'a> {
-        T::read(self, address, buffer)
+    async fn read<'a>(&'a mut self, address: A, buffer: &'a mut [u8]) -> Result<(), Self::Error> {
+        T::read(self, address, buffer).await
     }
 
-    type WriteFuture<'a> = T::WriteFuture<'a> where Self: 'a;
-
-    fn write<'a>(&'a mut self, address: A, bytes: &'a [u8]) -> Self::WriteFuture<'a> {
-        T::write(self, address, bytes)
+    async fn write<'a>(&'a mut self, address: A, bytes: &'a [u8]) -> Result<(), Self::Error> {
+        T::write(self, address, bytes).await
     }
 
-    type WriteReadFuture<'a> = T::WriteReadFuture<'a> where Self: 'a;
-
-    fn write_read<'a>(
+    async fn write_read<'a>(
         &'a mut self,
         address: A,
         bytes: &'a [u8],
         buffer: &'a mut [u8],
-    ) -> Self::WriteReadFuture<'a> {
-        T::write_read(self, address, bytes, buffer)
+    ) -> Result<(), Self::Error> {
+        T::write_read(self, address, bytes, buffer).await
     }
 
-    type TransactionFuture<'a, 'b> = T::TransactionFuture<'a, 'b> where Self: 'a, 'b: 'a;
-
-    fn transaction<'a, 'b>(
+    async fn transaction<'a, 'b>(
         &'a mut self,
         address: A,
         operations: &'a mut [Operation<'b>],
-    ) -> Self::TransactionFuture<'a, 'b> {
-        T::transaction(self, address, operations)
+    ) -> Result<(), Self::Error> {
+        T::transaction(self, address, operations).await
     }
 }

embedded-hal-async/src/lib.rs

@@ -9,7 +9,8 @@
 
 #![warn(missing_docs)]
 #![no_std]
-#![feature(type_alias_impl_trait)]
+#![allow(incomplete_features)]
+#![feature(async_fn_in_trait, impl_trait_projections)]
 
 pub mod delay;
 pub mod digital;