Merge #390

390: Spawn and schedule from anywhere r=AfoHT a=korken89

This PR moves RTIC to the spawn and schedule from anywhere syntax.

Notable changes:
 * We do no longer support non-`Send` types.
 * Some extra code is generated as any task may spawn/schedule any task. However Rust/LLVM does a great job optimizing away non used instantiations (no real code-size difference observed).
 * Worst case priority inversion has increased, but it is now predictable.

Upsides:
 * With this we should be able to support async/await.
 * RTIC tasks can now be callbacks (spawned and scheduled).
 * RTIC tasks can be stored.

Needs the following PR to land first: https://github.com/rtic-rs/rtic-syntax/pull/34

The following now works:

```rust
#[rtic::app(device = lm3s6965, monotonic = rtic::cyccnt::CYCCNT)]
mod app {
    #[init]
    fn init(mut cx: init::Context) -> init::LateResources {
        // Init stuff...

        // New spawn syntax
        foo::spawn().unwrap();

        // New schedule syntax
        bar::schedule(now + 4_000_000.cycles()).unwrap();

        init::LateResources {}
    }

    #[task]
    fn foo(_: foo::Context) {}

    #[task]
    fn bar(_: bar::Context) {}

    extern "C" {
        fn SSI0();
    }
}

```

Co-authored-by: Per Lindgren <per.lindgren@ltu.se>
Co-authored-by: Emil Fresk <emil.fresk@gmail.com>

1 files changed, 5 insertions, 14 deletions

diff --git a/examples/types.rs b/examples/types.rs
index 251d004c..b55a98c6 100644
--- a/examples/types.rs
+++ b/examples/types.rs
@@ -17,44 +17,35 @@ mod app {
         shared: u32,
     }
 
-    #[init(schedule = [foo], spawn = [foo])]
+    #[init]
     fn init(cx: init::Context) -> init::LateResources {
         let _: cyccnt::Instant = cx.start;
         let _: rtic::Peripherals = cx.core;
         let _: lm3s6965::Peripherals = cx.device;
-        let _: init::Schedule = cx.schedule;
-        let _: init::Spawn = cx.spawn;
 
         debug::exit(debug::EXIT_SUCCESS);
 
         init::LateResources {}
     }
 
-    #[idle(schedule = [foo], spawn = [foo])]
-    fn idle(cx: idle::Context) -> ! {
-        let _: idle::Schedule = cx.schedule;
-        let _: idle::Spawn = cx.spawn;
-
+    #[idle]
+    fn idle(_: idle::Context) -> ! {
         loop {
             cortex_m::asm::nop();
         }
     }
 
-    #[task(binds = UART0, resources = [shared], schedule = [foo], spawn = [foo])]
+    #[task(binds = UART0, resources = [shared])]
     fn uart0(cx: uart0::Context) {
         let _: cyccnt::Instant = cx.start;
         let _: resources::shared = cx.resources.shared;
-        let _: uart0::Schedule = cx.schedule;
-        let _: uart0::Spawn = cx.spawn;
     }
 
-    #[task(priority = 2, resources = [shared], schedule = [foo], spawn = [foo])]
+    #[task(priority = 2, resources = [shared])]
     fn foo(cx: foo::Context) {
         let _: cyccnt::Instant = cx.scheduled;
         let _: &mut u32 = cx.resources.shared;
         let _: foo::Resources = cx.resources;
-        let _: foo::Schedule = cx.schedule;
-        let _: foo::Spawn = cx.spawn;
     }
 
     // RTIC requires that unused interrupts are declared in an extern block when