Merge #80

80: replace uses of ! with Void r=japaric a=japaric

We are soon going to push for embedded *library* development on beta (1.27-beta) to minimize the
number of unstable features used in the ecosystem and ease the transition towards *application*
development on stable (1.28 or 1.29).

Unfortunately `!` didn't make it into the beta release but we still need to make this crate work on
beta because a lot of crates depend on it. So this PR replaces the single use of the `!` type (cf.
`CountDown.wait`) with the equivalent, but stable, `Void` type.

This is a [breaking-change]. Implementations of the `CountDown` trait will have to update the
signature of `wait` to return `nb::Result<(), Void>`.

cc @therealprof @hannobraun I'm going to publish v0.2.0 *soon* (ideally tonight). If there's
some **breaking**, but *uncontroversial*, change that should be included in it let me know ASAP so
we can land it before the release.

Co-authored-by: Jorge Aparicio <[email protected]>

Author: bors[bot]

.travis.yml

@@ -2,6 +2,14 @@ language: rust
 
 matrix:
   include:
+    - env: TARGET=x86_64-unknown-linux-gnu
+
+    - env: TARGET=thumbv6m-none-eabi
+      rust: beta
+
+    - env: TARGET=thumbv7m-none-eabi
+      rust: beta
+
     - env: TARGET=x86_64-unknown-linux-gnu
       rust: nightly
 
@@ -25,9 +33,8 @@ before_cache:
 
 branches:
   only:
-    - auto
-    - master
-    - try
+    - staging
+    - trying
 
 notifications:
   email:

CHANGELOG.md

@@ -7,6 +7,18 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+## [v0.2.0] - 2018-05-11
+
+### Changed
+
+- [breaking-change] The signature of `CountDown.wait` changed; it now returns `nb::Result<(),
+  Void>`. Where [`Void`] is the stable alternative to the never type, `!`, provided by the stable
+  [`void`] crate. Implementations of the `CountDown` trait will have to be updated to use the new
+  signature. With this change this crate compiles on the stable and beta channels.
+
+[`Void`]: https://docs.rs/void/1.0.2/void/enum.Void.html
+[`void`]: https://crates.io/crates/void
+
 ## [v0.1.2] - 2018-02-14
 
 ### Added
@@ -23,6 +35,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 Initial release
 
-[Unreleased]: https://github.com/japaric/embedded-hal/compare/v0.1.2...HEAD
+[Unreleased]: https://github.com/japaric/embedded-hal/compare/v0.2.0...HEAD
+[v0.2.0]: https://github.com/japaric/embedded-hal/compare/v0.1.2...v0.2.0
 [v0.1.2]: https://github.com/japaric/embedded-hal/compare/v0.1.1...v0.1.2
 [v0.1.1]: https://github.com/japaric/embedded-hal/compare/v0.1.0...v0.1.1

Cargo.toml

@@ -13,6 +13,10 @@ readme = "README.md"
 repository = "https://github.com/japaric/embedded-hal"
 version = "0.1.2"
 
+[dependencies.void]
+default-features = false
+version = "1.0.2"
+
 [dependencies.nb]
 version = "0.1.1"
 

bors.toml

@@ -0,0 +1,3 @@
+status = [
+  "continuous-integration/travis-ci/push",
+]

ci/install.sh

@@ -1,7 +1,9 @@
 set -euxo pipefail
 
 main() {
-    return
+    if [ $TARGET != x86_64-unknown-linux-gnu ]; then
+        rustup target add $TARGET
+    fi
 }
 
 main

ci/script.sh

@@ -2,7 +2,11 @@ set -euxo pipefail
 
 main() {
     cargo check --target $TARGET
-    cargo test --target $TARGET --features unproven
+    cargo check --target $TARGET --features unproven
+
+    if [ $TRAVIS_RUST_VERSION = nightly ]; then
+        cargo test --target $TARGET --features unproven
+    fi
 }
 
 main

src/lib.rs

@@ -90,19 +90,20 @@
 //! [`WouldBlock`]: https://docs.rs/nb/0.1.0/nb/enum.Error.html
 //!
 //! Some traits, like the one shown below, may expose possibly blocking APIs that can't fail. In
-//! those cases `nb::Result<_, !>` is used.
+//! those cases `nb::Result<_, Void>` is used.
 //!
 //! ```
-//! #![feature(never_type)]
-//!
 //! extern crate nb;
+//! extern crate void;
+//!
+//! use void::Void;
 //!
 //! /// A count down timer
 //! pub trait CountDown {
 //!     // ..
 //!
 //!     /// "waits" until the count down is over
-//!     fn wait(&mut self) -> nb::Result<(), !>;
+//!     fn wait(&mut self) -> nb::Result<(), Void>;
 //! }
 //!
 //! # fn main() {}
@@ -201,7 +202,6 @@
 //! fashion:
 //!
 //! ```
-//! # #![feature(never_type)]
 //! extern crate embedded_hal;
 //! #[macro_use(block)]
 //! extern crate nb;
@@ -223,9 +223,11 @@
 //! # }
 //!
 //! # mod stm32f30x_hal {
+//! #     extern crate void;
+//! #     use self::void::Void;
 //! #     pub struct Serial1;
 //! #     impl Serial1 {
-//! #         pub fn write(&mut self, _: u8) -> ::nb::Result<(), !> {
+//! #         pub fn write(&mut self, _: u8) -> ::nb::Result<(), Void> {
 //! #             Ok(())
 //! #         }
 //! #     }
@@ -238,11 +240,9 @@
 //! second. Second task: loop back data over the serial interface.
 //!
 //! ```
-//! #![feature(conservative_impl_trait)]
-//! #![feature(never_type)]
-//!
 //! extern crate embedded_hal as hal;
 //! extern crate futures;
+//! extern crate void;
 //!
 //! #[macro_use(try_nb)]
 //! extern crate nb;
@@ -255,11 +255,12 @@
 //! };
 //! use futures::future::Loop;
 //! use stm32f30x_hal::{Led, Serial1, Timer6};
+//! use void::Void;
 //!
 //! /// `futures` version of `CountDown.wait`
 //! ///
 //! /// This returns a future that must be polled to completion
-//! fn wait<T>(mut timer: T) -> impl Future<Item = T, Error = !>
+//! fn wait<T>(mut timer: T) -> impl Future<Item = T, Error = Void>
 //! where
 //!     T: hal::timer::CountDown,
 //! {
@@ -341,30 +342,32 @@
 //!
 //!     // Event loop
 //!     loop {
-//!         blinky.poll().unwrap(); // NOTE(unwrap) E = !
+//!         blinky.poll().unwrap(); // NOTE(unwrap) E = Void
 //!         loopback.poll().unwrap();
 //! #       break;
 //!     }
 //! }
 //!
 //! # mod stm32f30x_hal {
+//! #     extern crate void;
+//! #     use self::void::Void;
 //! #     pub struct Timer6;
 //! #     impl ::hal::timer::CountDown for Timer6 {
 //! #         type Time = ();
 //! #
 //! #         fn start<T>(&mut self, _: T) where T: Into<()> {}
-//! #         fn wait(&mut self) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) }
+//! #         fn wait(&mut self) -> ::nb::Result<(), Void> { Err(::nb::Error::WouldBlock) }
 //! #     }
 //! #
 //! #     pub struct Serial1;
 //! #     impl ::hal::serial::Read<u8> for Serial1 {
-//! #         type Error = !;
-//! #         fn read(&mut self) -> ::nb::Result<u8, !> { Err(::nb::Error::WouldBlock) }
+//! #         type Error = Void;
+//! #         fn read(&mut self) -> ::nb::Result<u8, Void> { Err(::nb::Error::WouldBlock) }
 //! #     }
 //! #     impl ::hal::serial::Write<u8> for Serial1 {
-//! #         type Error = !;
-//! #         fn flush(&mut self) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) }
-//! #         fn write(&mut self, _: u8) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) }
+//! #         type Error = Void;
+//! #         fn flush(&mut self) -> ::nb::Result<(), Void> { Err(::nb::Error::WouldBlock) }
+//! #         fn write(&mut self, _: u8) -> ::nb::Result<(), Void> { Err(::nb::Error::WouldBlock) }
 //! #     }
 //! #
 //! #     pub struct Led;
@@ -382,7 +385,6 @@
 //! ```
 //! #![feature(generator_trait)]
 //! #![feature(generators)]
-//! # #![feature(never_type)]
 //!
 //! extern crate embedded_hal as hal;
 //!
@@ -415,7 +417,7 @@
 //!         loop {
 //!             // `await!` means "suspend / yield here" instead of "block until
 //!             // completion"
-//!             await!(timer.wait()).unwrap(); // NOTE(unwrap) E = !
+//!             await!(timer.wait()).unwrap(); // NOTE(unwrap) E = Void
 //!
 //!             state = !state;
 //!
@@ -436,21 +438,23 @@
 //!
 //!     // Event loop
 //!     loop {
-//!         blinky.resume();
-//!         loopback.resume();
+//!         unsafe { blinky.resume(); }
+//!         unsafe { loopback.resume(); }
 //!         # break;
 //!     }
 //! }
 //!
 //! # mod stm32f30x_hal {
+//! #   extern crate void;
+//! #   use self::void::Void;
 //! #   pub struct Serial1;
 //! #   impl Serial1 {
-//! #       pub fn read(&mut self) -> ::nb::Result<u8, !> { Err(::nb::Error::WouldBlock) }
-//! #       pub fn write(&mut self, _: u8) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) }
+//! #       pub fn read(&mut self) -> ::nb::Result<u8, Void> { Err(::nb::Error::WouldBlock) }
+//! #       pub fn write(&mut self, _: u8) -> ::nb::Result<(), Void> { Err(::nb::Error::WouldBlock) }
 //! #   }
 //! #   pub struct Timer6;
 //! #   impl Timer6 {
-//! #       pub fn wait(&mut self) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) }
+//! #       pub fn wait(&mut self) -> ::nb::Result<(), Void> { Err(::nb::Error::WouldBlock) }
 //! #   }
 //! #   pub struct Led;
 //! #   impl Led {
@@ -589,15 +593,16 @@
 //! - Buffered serial interface with periodic flushing in interrupt handler
 //!
 //! ```
-//! # #![feature(never_type)]
 //! extern crate embedded_hal as hal;
 //! extern crate nb;
+//! extern crate void;
 //!
 //! use hal::prelude::*;
+//! use void::Void;
 //!
 //! fn flush<S>(serial: &mut S, cb: &mut CircularBuffer)
 //! where
-//!     S: hal::serial::Write<u8, Error = !>,
+//!     S: hal::serial::Write<u8, Error = Void>,
 //! {
 //!     loop {
 //!         if let Some(byte) = cb.peek() {
@@ -662,9 +667,9 @@
 //! # }
 //! # struct Serial1;
 //! # impl ::hal::serial::Write<u8> for Serial1 {
-//! #   type Error = !;
-//! #   fn write(&mut self, _: u8) -> nb::Result<(), !> { Err(::nb::Error::WouldBlock) }
-//! #   fn flush(&mut self) -> nb::Result<(), !> { Err(::nb::Error::WouldBlock) }
+//! #   type Error = Void;
+//! #   fn write(&mut self, _: u8) -> nb::Result<(), Void> { Err(::nb::Error::WouldBlock) }
+//! #   fn flush(&mut self) -> nb::Result<(), Void> { Err(::nb::Error::WouldBlock) }
 //! # }
 //! # struct CircularBuffer;
 //! # impl CircularBuffer {
@@ -678,11 +683,11 @@
 
 #![deny(missing_docs)]
 #![deny(warnings)]
-#![feature(never_type)]
 #![no_std]
 
 #[macro_use]
 extern crate nb;
+extern crate void;
 
 pub mod blocking;
 pub mod digital;
@@ -699,8 +704,6 @@ pub mod timer;
 /// / events
 ///
 /// ```
-/// # #![feature(never_type)]
-///
 /// extern crate embedded_hal as hal;
 /// #[macro_use(block)]
 /// extern crate nb;
@@ -723,6 +726,8 @@ pub mod timer;
 ///     println!("Period: {} ms", period);
 /// }
 ///
+/// # extern crate void;
+/// # use void::Void;
 /// # struct MilliSeconds(u32);
 /// # trait U32Ext { fn ms(self) -> MilliSeconds; }
 /// # impl U32Ext for u32 { fn ms(self) -> MilliSeconds { MilliSeconds(self) } }
@@ -731,9 +736,9 @@ pub mod timer;
 /// # impl hal::Capture for Capture1 {
 /// #     type Capture = u16;
 /// #     type Channel = Channel;
-/// #     type Error = !;
+/// #     type Error = Void;
 /// #     type Time = MilliSeconds;
-/// #     fn capture(&mut self, _: Channel) -> ::nb::Result<u16, !> { Ok(0) }
+/// #     fn capture(&mut self, _: Channel) -> ::nb::Result<u16, Void> { Ok(0) }
 /// #     fn disable(&mut self, _: Channel) { unimplemented!() }
 /// #     fn enable(&mut self, _: Channel) { unimplemented!() }
 /// #     fn get_resolution(&self) -> MilliSeconds { unimplemented!() }
@@ -908,7 +913,6 @@ pub trait PwmPin {
 /// You can use this interface to measure the speed of a motor
 ///
 /// ```
-/// # #![feature(never_type)]
 /// extern crate embedded_hal as hal;
 /// #[macro_use(block)]
 /// extern crate nb;
@@ -935,6 +939,8 @@ pub trait PwmPin {
 ///     println!("Speed: {} pulses per second", speed);
 /// }
 ///
+/// # extern crate void;
+/// # use void::Void;
 /// # struct Seconds(u32);
 /// # trait U32Ext { fn s(self) -> Seconds; }
 /// # impl U32Ext for u32 { fn s(self) -> Seconds { Seconds(self) } }
@@ -948,7 +954,7 @@ pub trait PwmPin {
 /// # impl hal::timer::CountDown for Timer6 {
 /// #     type Time = Seconds;
 /// #     fn start<T>(&mut self, _: T) where T: Into<Seconds> {}
-/// #     fn wait(&mut self) -> ::nb::Result<(), !> { Ok(()) }
+/// #     fn wait(&mut self) -> ::nb::Result<(), Void> { Ok(()) }
 /// # }
 /// ```
 #[cfg(feature = "unproven")]

src/timer.rs

@@ -1,6 +1,7 @@
 //! Timers
 
 use nb;
+use void::Void;
 
 /// A count down timer
 ///
@@ -17,7 +18,6 @@ use nb;
 /// You can use this timer to create delays
 ///
 /// ```
-/// # #![feature(never_type)]
 /// extern crate embedded_hal as hal;
 /// #[macro_use(block)]
 /// extern crate nb;
@@ -40,6 +40,8 @@ use nb;
 ///     Led.off();
 /// }
 ///
+/// # extern crate void;
+/// # use void::Void;
 /// # struct Seconds(u32);
 /// # trait U32Ext { fn s(self) -> Seconds; }
 /// # impl U32Ext for u32 { fn s(self) -> Seconds { Seconds(self) } }
@@ -52,7 +54,7 @@ use nb;
 /// # impl hal::timer::CountDown for Timer6 {
 /// #     type Time = Seconds;
 /// #     fn start<T>(&mut self, _: T) where T: Into<Seconds> {}
-/// #     fn wait(&mut self) -> ::nb::Result<(), !> { Ok(()) }
+/// #     fn wait(&mut self) -> ::nb::Result<(), Void> { Ok(()) }
 /// # }
 /// ```
 pub trait CountDown {
@@ -72,7 +74,7 @@ pub trait CountDown {
     /// finishes.
     /// - Otherwise the behavior of calling `wait` after the last call returned `Ok` is UNSPECIFIED.
     /// Implementers are suggested to panic on this scenario to signal a programmer error.
-    fn wait(&mut self) -> nb::Result<(), !>;
+    fn wait(&mut self) -> nb::Result<(), Void>;
 }
 
 /// Marker trait that indicates that a timer is periodic