3 files changed, 77 insertions, 4 deletions

diff --git a/embassy-executor/src/lib.rs b/embassy-executor/src/lib.rs
index dfe420bab..e174a0594 100644
--- a/embassy-executor/src/lib.rs
+++ b/embassy-executor/src/lib.rs
@@ -65,8 +65,17 @@ pub mod _export {
 
     use crate::raw::TaskPool;
 
+    trait TaskReturnValue {}
+    impl TaskReturnValue for () {}
+    impl TaskReturnValue for Never {}
+
+    #[diagnostic::on_unimplemented(
+        message = "task futures must resolve to `()` or `!`",
+        note = "use `async fn` or change the return type to `impl Future<Output = ()>`"
+    )]
+    #[allow(private_bounds)]
     pub trait TaskFn<Args>: Copy {
-        type Fut: Future + 'static;
+        type Fut: Future<Output: TaskReturnValue> + 'static;
     }
 
     macro_rules! task_fn_impl {
@@ -74,7 +83,7 @@ pub mod _export {
             impl<F, Fut, $($Tn,)*> TaskFn<($($Tn,)*)> for F
             where
                 F: Copy + FnOnce($($Tn,)*) -> Fut,
-                Fut: Future + 'static,
+                Fut: Future<Output: TaskReturnValue> + 'static,
             {
                 type Fut = Fut;
             }
@@ -205,4 +214,42 @@ pub mod _export {
         Align268435456: 268435456,
         Align536870912: 536870912,
     );
+
+    #[allow(dead_code)]
+    trait HasOutput {
+        type Output;
+    }
+
+    impl<O> HasOutput for fn() -> O {
+        type Output = O;
+    }
+
+    #[allow(dead_code)]
+    type Never = <fn() -> ! as HasOutput>::Output;
+}
+
+/// Implementation details for embassy macros.
+/// Do not use. Used for macros and HALs only. Not covered by semver guarantees.
+#[doc(hidden)]
+#[cfg(feature = "nightly")]
+pub mod _export {
+    #[diagnostic::on_unimplemented(
+        message = "task futures must resolve to `()` or `!`",
+        note = "use `async fn` or change the return type to `impl Future<Output = ()>`"
+    )]
+    pub trait TaskReturnValue {}
+    impl TaskReturnValue for () {}
+    impl TaskReturnValue for Never {}
+
+    #[allow(dead_code)]
+    trait HasOutput {
+        type Output;
+    }
+
+    impl<O> HasOutput for fn() -> O {
+        type Output = O;
+    }
+
+    #[allow(dead_code)]
+    type Never = <fn() -> ! as HasOutput>::Output;
 }
diff --git a/embassy-executor/src/raw/trace.rs b/embassy-executor/src/raw/trace.rs
index 6c9cfda25..aa27ab37e 100644
--- a/embassy-executor/src/raw/trace.rs
+++ b/embassy-executor/src/raw/trace.rs
@@ -283,7 +283,17 @@ pub(crate) fn task_new(executor: &SyncExecutor, task: &TaskRef) {
     }
 
     #[cfg(feature = "rtos-trace")]
-    rtos_trace::trace::task_new(task.as_ptr() as u32);
+    {
+        rtos_trace::trace::task_new(task.as_ptr() as u32);
+        let name = task.name().unwrap_or("unnamed task\0");
+        let info = rtos_trace::TaskInfo {
+            name,
+            priority: 0,
+            stack_base: 0,
+            stack_size: 0,
+        };
+        rtos_trace::trace::task_send_info(task.id(), info);
+    }
 
     #[cfg(feature = "rtos-trace")]
     TASK_TRACKER.add(*task);
diff --git a/embassy-executor/src/spawner.rs b/embassy-executor/src/spawner.rs
index 522d97db3..2909d19a0 100644
--- a/embassy-executor/src/spawner.rs
+++ b/embassy-executor/src/spawner.rs
@@ -122,10 +122,26 @@ impl Spawner {
     /// This function is `async` just to get access to the current async
     /// context. It returns instantly, it does not block/yield.
     ///
+    /// Using this method is discouraged due to it being unsafe. Consider the following
+    /// alternatives instead:
+    ///
+    /// - Pass the initial `Spawner` as an argument to tasks. Note that it's `Copy`, so you can
+    ///   make as many copies of it as you want.
+    /// - Use `SendSpawner::for_current_executor()` instead, which is safe but can only be used
+    ///   if task arguments are `Send`.
+    ///
+    /// The only case where using this method is absolutely required is obtaining the `Spawner`
+    /// for an `InterruptExecutor`.
+    ///
+    /// # Safety
+    ///
+    /// You must only execute this with an async `Context` created by the Embassy executor.
+    /// You must not execute it with manually-created `Context`s.
+    ///
     /// # Panics
     ///
     /// Panics if the current executor is not an Embassy executor.
-    pub fn for_current_executor() -> impl Future<Output = Self> {
+    pub unsafe fn for_current_executor() -> impl Future<Output = Self> {
         poll_fn(|cx| {
             let task = raw::task_from_waker(cx.waker());
             let executor = unsafe {