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, 3 insertions, 21 deletions

diff --git a/macros/src/codegen/dispatchers.rs b/macros/src/codegen/dispatchers.rs
index 300aa996..bf6986b8 100644
--- a/macros/src/codegen/dispatchers.rs
+++ b/macros/src/codegen/dispatchers.rs
@@ -35,7 +35,7 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
             #[allow(non_camel_case_types)]
             #[derive(Clone, Copy)]
             #[doc = #doc]
-            enum #t {
+            pub enum #t {
                 #(#variants,)*
             }
         ));
@@ -57,27 +57,9 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
         );
         items.push(quote!(
             #[doc = #doc]
-            static mut #rq: #rq_ty = #rq_expr;
+            pub static mut #rq: #rq_ty = #rq_expr;
         ));
 
-        if let Some(ceiling) = channel.ceiling {
-            items.push(quote!(
-                struct #rq<'a> {
-                    priority: &'a rtic::export::Priority,
-                }
-            ));
-
-            items.push(util::impl_mutex(
-                extra,
-                &[],
-                false,
-                &rq,
-                rq_ty,
-                ceiling,
-                quote!(&mut #rq),
-            ));
-        }
-
         let arms = channel
             .tasks
             .iter()
@@ -88,7 +70,7 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
                 let inputs = util::inputs_ident(name);
                 let (_, tupled, pats, _) = util::regroup_inputs(&task.inputs);
 
-                let (let_instant, instant) = if app.uses_schedule() {
+                let (let_instant, instant) = if extra.monotonic.is_some() {
                     let instants = util::instants_ident(name);
 
                     (