Merge branch '♻️-associated-type-bounds' into 🦆

Author: yvt

doc/toolchain_limitations.md

@@ -38,29 +38,6 @@ impl<T> StGeneric<for<'a> fn(&'a T)> {
 ```
 
 
-### `[tag:trait_constraints_on_associated_types_do_not_propagate]` Trait constraints on associated types do not propagate to the trait's use sites
-
-*Upstream issue:* [rust-lang/rust#32722](https://github.com/rust-lang/rust/issues/32722)
-
-According to [this comment](https://github.com/rust-lang/rust/issues/32722#issuecomment-618044689), this is a symptom of [rust-lang/rust#20671](https://github.com/rust-lang/rust/issues/20671).
-
-```rust,compile_fail,E0277
-trait KernelMutex {}
-
-trait CfgBase {
-    type System;
-}
-
-trait CfgMutex: CfgBase
-where
-    Self::System: KernelMutex,
-{}
-
-// error[E0277]: the trait bound `<C as CfgBase>::System: KernelMutex` is not satisfied
-fn foo<C: CfgMutex>() {}
-```
-
-
 ### `[tag:impl_trait_false_type_alias_bounds]` `type_alias_bounds` misfires when `impl Trait` is used in a portion of a type alias
 
 *Upstream issue:* [rust-lang/rust#94395](https://github.com/rust-lang/rust/issues/94395)

src/r3/src/bind/mod.rs

@@ -119,7 +119,7 @@
 /// ```
 )]
 #![doc = include_str!("../common.md")]
-use r3_core::kernel::{cfg, raw, raw_cfg};
+use r3_core::kernel::{cfg, raw_cfg};
 
 pub use r3_core::bind::{
     fn_bind_map, Bind, BindBorrow, BindBorrowMut, BindDefiner, BindRef, BindTable, BindTake,
@@ -196,8 +196,8 @@ pub const fn bind_uninit<'pool, T, C>(
 ) -> Bind<'pool, C::System, core::mem::MaybeUninit<T>>
 where
     T: 'static,
-    C: ~const raw_cfg::CfgBase,
-    C::System: raw::KernelBase + cfg::KernelStatic,
+    // `~const CfgBase` not implied due to [ref:const_supertraits]
+    C: ~const raw_cfg::CfgBase + ~const cfg::CfgStatic,
 {
     // Safety: `MaybeUninit` is safe to leave uninitialized
     unsafe { Bind::define().uninit_unchecked().finish(cfg) }
@@ -234,8 +234,8 @@ where
 pub const fn bind_default<'pool, T, C>(cfg: &mut cfg::Cfg<'pool, C>) -> Bind<'pool, C::System, T>
 where
     T: Default + 'static,
-    C: ~const raw_cfg::CfgBase,
-    C::System: raw::KernelBase + cfg::KernelStatic,
+    // `~const CfgBase` not implied due to [ref:const_supertraits]
+    C: ~const raw_cfg::CfgBase + ~const cfg::CfgStatic,
 {
     Bind::define().init(Default::default).finish(cfg)
 }

src/r3_core/CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Added
+
+- The new blanket-implemented `CfgStatic` trait can be used to simplify some trait bounds of configuration functions.
+
+### Fixed
+
+- The `Cfg*` traits now imply the corresponding `Kernel*` traits (e.g., `C: CfgTimer` implies `C::System: KernelTimer`), making some trait bounds in configuration functions unnecessary.
+
 ## [0.1.2] - 2022-03-30
 
 ### Changed

src/r3_core/src/bind.rs

@@ -686,8 +686,8 @@ impl<'pool, System, T> DivideBind<'pool, System, T> {
 ///
 /// const fn configure_app<C>(cfg: &mut Cfg<C>)
 /// where
-///     C: ~const traits::CfgBase,
-///     C::System: traits::KernelBase + traits::KernelStatic,
+// `~const CfgBase` not implied due to [ref:const_supertraits]
+///     C: ~const traits::CfgBase + ~const traits::CfgStatic,
 /// {
 ///     let values = Bind::define().init(|| (12, 34)).finish(cfg);
 ///     let (value0, value1) = values.unzip();
@@ -820,7 +820,7 @@ impl<'pool, const LEN: usize, System, T> const UnzipBind for Bind<'pool, System,
 /// where
 ///     C: ~const traits::CfgBase +
 ///        ~const traits::CfgTask,
-///     C::System: traits::KernelBase + traits::KernelStatic,
+///     C::System: traits::KernelStatic,
 /// {
 ///     let foo = Bind::define().init(|| {
 ///         // `BindTable::get()` will fail because some bindings might not

src/r3_core/src/kernel/cfg.rs

@@ -725,3 +725,51 @@ macro array_item_from_fn($(
         unsafe { mem::transmute(values) }
     };
 )*}
+
+/// A subtrait of [`raw_cfg::CfgBase`][] that implies
+/// `Self::System: `[`KernelStatic`][].
+///
+/// This trait by itself has no function, but it may help you keep your
+/// configuration functions clean by getting rid of trait bounds on
+/// `C::System`.
+///
+/// # Example
+///
+/// ```rust
+/// # #![feature(const_trait_impl)]
+/// # #![feature(const_mut_refs)]
+/// # use r3_core::kernel::traits;
+/// #
+/// const fn configure<C>(cfg: &mut C)
+/// where
+// `~const CfgBase` not implied due to [ref:const_supertraits]
+///     C: ~const traits::CfgBase + ~const traits::CfgStatic,
+/// {
+///     todo!()   
+/// }
+/// ```
+///
+/// The above is equivalent to:
+///
+/// ```rust
+/// # #![feature(const_trait_impl)]
+/// # #![feature(const_mut_refs)]
+/// # use r3_core::kernel::traits;
+/// #
+/// const fn configure<C>(cfg: &mut C)
+/// where
+///     C: ~const traits::CfgBase,
+///     C::System: traits::KernelStatic,
+/// {
+///     todo!()   
+/// }
+/// ```
+// The supertrait can't be `~const` due to [ref:const_supertraits]
+pub trait CfgStatic: raw_cfg::CfgBase<System: KernelStatic> {}
+
+impl<C> const CfgStatic for C
+where
+    C: ~const raw_cfg::CfgBase,
+    C::System: KernelStatic,
+{
+}

src/r3_core/src/kernel/mod.rs

@@ -72,7 +72,7 @@ pub mod prelude {
 pub mod traits {
     #[doc(no_inline)]
     pub use super::{
-        cfg::KernelStatic,
+        cfg::{CfgStatic, KernelStatic},
         event_group::{EventGroupHandle, EventGroupMethods},
         mutex::{MutexHandle, MutexMethods},
         raw::{

src/r3_core/src/kernel/mutex.rs

@@ -54,9 +54,6 @@ define_object! {
 /// const fn configure<C>(cfg: &mut Cfg<C>) -> Objects<C::System>
 /// where
 ///     C: ~const traits::CfgMutex,
-// The following bound is necessary becauase of a bug in the compiler
-// [ref:trait_constraints_on_associated_types_do_not_propagate]
-///     C::System: traits::KernelMutex,
 /// {
 ///     let mutex = StaticMutex::define()
 ///         .protocol(MutexProtocol::Ceiling(1))

src/r3_core/src/kernel/raw_cfg.rs

@@ -116,10 +116,7 @@ pub struct TaskDescriptor<System> {
 /// [3]: self#stability
 /// [4]: self#safety
 // The supertrait can't be `~const` due to [ref:const_supertraits]
-pub unsafe trait CfgEventGroup: CfgBase
-where
-    Self::System: raw::KernelEventGroup,
-{
+pub unsafe trait CfgEventGroup: CfgBase<System: raw::KernelEventGroup> {
     fn event_group_define<Properties: ~const Bag>(
         &mut self,
         descriptor: EventGroupDescriptor<Self::System>,
@@ -151,10 +148,7 @@ pub struct EventGroupDescriptor<System> {
 /// [3]: self#stability
 /// [4]: self#safety
 // The supertrait can't be `~const` due to [ref:const_supertraits]
-pub unsafe trait CfgMutex: CfgBase
-where
-    Self::System: raw::KernelMutex,
-{
+pub unsafe trait CfgMutex: CfgBase<System: raw::KernelMutex> {
     fn mutex_define<Properties: ~const Bag>(
         &mut self,
         descriptor: MutexDescriptor<Self::System>,
@@ -185,10 +179,7 @@ pub struct MutexDescriptor<System> {
 /// [3]: self#stability
 /// [4]: self#safety
 // The supertrait can't be `~const` due to [ref:const_supertraits]
-pub unsafe trait CfgSemaphore: CfgBase
-where
-    Self::System: raw::KernelSemaphore,
-{
+pub unsafe trait CfgSemaphore: CfgBase<System: raw::KernelSemaphore> {
     fn semaphore_define<Properties: ~const Bag>(
         &mut self,
         descriptor: SemaphoreDescriptor<Self::System>,
@@ -221,10 +212,7 @@ pub struct SemaphoreDescriptor<System> {
 /// [3]: self#stability
 /// [4]: self#safety
 // The supertrait can't be `~const` due to [ref:const_supertraits]
-pub unsafe trait CfgTimer: CfgBase
-where
-    Self::System: raw::KernelTimer,
-{
+pub unsafe trait CfgTimer: CfgBase<System: raw::KernelTimer> {
     fn timer_define<Properties: ~const Bag>(
         &mut self,
         descriptor: TimerDescriptor<Self::System>,
@@ -258,10 +246,7 @@ pub struct TimerDescriptor<System> {
 /// [3]: self#stability
 /// [4]: self#safety
 // The supertrait can't be `~const` due to [ref:const_supertraits]
-pub unsafe trait CfgInterruptLine: CfgBase
-where
-    Self::System: raw::KernelInterruptLine,
-{
+pub unsafe trait CfgInterruptLine: CfgBase<System: raw::KernelInterruptLine> {
     fn interrupt_line_define<Properties: ~const Bag>(
         &mut self,
         descriptor: InterruptLineDescriptor<Self::System>,

src/r3_core/src/kernel/timer.rs

@@ -279,9 +279,6 @@ define_object! {
 /// const fn configure<C>(b: &mut Cfg<C>) -> StaticTimer<C::System>
 /// where
 ///     C: ~const traits::CfgTimer,
-// The following bound is necessary becauase of a bug in the compiler
-// [ref:trait_constraints_on_associated_types_do_not_propagate]
-///     C::System: traits::KernelTimer,
 /// {
 ///     StaticTimer::define()
 ///         .delay(Duration::from_millis(70))
@@ -319,9 +316,6 @@ define_object! {
 /// const fn configure<C>(b: &mut Cfg<C>) -> StaticTimer<C::System>
 /// where
 ///     C: ~const traits::CfgTimer,
-// The following bound is necessary becauase of a bug in the compiler
-// [ref:trait_constraints_on_associated_types_do_not_propagate]
-///     C::System: traits::KernelTimer,
 /// {
 ///     StaticTimer::define()
 ///         .active(true)

src/r3_core/src/lib.rs

@@ -13,6 +13,7 @@
 #![feature(const_precise_live_drops)]
 #![feature(const_raw_ptr_comparison)]
 #![feature(generic_associated_types)]
+#![feature(associated_type_bounds)]
 #![feature(const_slice_first_last)]
 #![feature(cfg_target_has_atomic)] // `#[cfg(target_has_atomic_load_store)]`
 #![feature(const_cell_into_inner)]