implement RFCs 147 and 155, etc.

This commit:

- Implements RFC 147: "all functions must be safe"

- Implements RFC 155: "explicit Context parameter"

- Implements the pending breaking change #141: reject assign syntax in `init`
  (which was used to initialize late resources)

- Refactors code generation to make it more readable -- there are no more random
  identifiers in the output -- and align it with the book description of RTFM
  internals.

- Makes the framework hard depend on `core::mem::MaybeUninit` and thus will
  require nightly until that API is stabilized.

- Fixes a ceiling analysis bug where the priority of the system timer was not
  considered in the analysis.

- Shrinks the size of all the internal queues by turning `AtomicUsize` indices
  into `AtomicU8`s.

- Removes the integration with `owned_singleton`.

1 files changed, 6 insertions, 15 deletions

diff --git a/macros/src/check.rs b/macros/src/check.rs
index 4adc2c17..6ba7d375 100644
--- a/macros/src/check.rs
+++ b/macros/src/check.rs
@@ -35,21 +35,12 @@ pub fn app(app: &App) -> parse::Result<()> {
         }
     }
 
-    // Check that all late resources have been initialized in `#[init]` if `init` has signature
-    // `fn()`
-    if !app.init.returns_late_resources {
-        for res in
-            app.resources
-                .iter()
-                .filter_map(|(name, res)| if res.expr.is_none() { Some(name) } else { None })
-        {
-            if app.init.assigns.iter().all(|assign| assign.left != *res) {
-                return Err(parse::Error::new(
-                    res.span(),
-                    "late resources MUST be initialized at the end of `init`",
-                ));
-            }
-        }
+    // Check that `init` returns `LateResources` if there's any declared late resource
+    if !app.init.returns_late_resources && app.resources.iter().any(|(_, res)| res.expr.is_none()) {
+        return Err(parse::Error::new(
+            app.init.span,
+            "late resources have been specified so `init` must return `init::LateResources`",
+        ));
     }
 
     // Check that all referenced tasks have been declared