merge new embassy changes

38 files changed, 423 insertions, 0 deletions

diff --git a/embassy-executor/tests/test.rs b/embassy-executor/tests/test.rs
index 348cc7dc4..78c49c071 100644
--- a/embassy-executor/tests/test.rs
+++ b/embassy-executor/tests/test.rs
@@ -40,6 +40,7 @@ fn setup() -> (&'static Executor, Trace) {
     let trace = Trace::new();
     let context = Box::leak(Box::new(trace.clone())) as *mut _ as *mut ();
     let executor = &*Box::leak(Box::new(Executor::new(context)));
+
     (executor, trace)
 }
 
@@ -137,6 +138,139 @@ fn executor_task_self_wake_twice() {
 }
 
 #[test]
+fn waking_after_completion_does_not_poll() {
+    use embassy_sync::waitqueue::AtomicWaker;
+
+    #[task]
+    async fn task1(trace: Trace, waker: &'static AtomicWaker) {
+        poll_fn(|cx| {
+            trace.push("poll task1");
+            waker.register(cx.waker());
+            Poll::Ready(())
+        })
+        .await
+    }
+
+    let waker = Box::leak(Box::new(AtomicWaker::new()));
+
+    let (executor, trace) = setup();
+    executor.spawner().spawn(task1(trace.clone(), waker)).unwrap();
+
+    unsafe { executor.poll() };
+    waker.wake();
+    unsafe { executor.poll() };
+
+    // Exited task may be waken but is not polled
+    waker.wake();
+    waker.wake();
+    unsafe { executor.poll() }; // Clears running status
+
+    // Can respawn waken-but-dead task
+    executor.spawner().spawn(task1(trace.clone(), waker)).unwrap();
+
+    unsafe { executor.poll() };
+
+    assert_eq!(
+        trace.get(),
+        &[
+            "pend",       // spawning a task pends the executor
+            "poll task1", //
+            "pend",       // manual wake, gets cleared by poll
+            "pend",       // manual wake, single pend for two wakes
+            "pend",       // respawning a task pends the executor
+            "poll task1", //
+        ]
+    )
+}
+
+#[test]
+fn waking_with_old_waker_after_respawn() {
+    use embassy_sync::waitqueue::AtomicWaker;
+
+    async fn yield_now(trace: Trace) {
+        let mut yielded = false;
+        poll_fn(|cx| {
+            if yielded {
+                Poll::Ready(())
+            } else {
+                trace.push("yield_now");
+                yielded = true;
+                cx.waker().wake_by_ref();
+                Poll::Pending
+            }
+        })
+        .await
+    }
+
+    #[task]
+    async fn task1(trace: Trace, waker: &'static AtomicWaker) {
+        yield_now(trace.clone()).await;
+        poll_fn(|cx| {
+            trace.push("poll task1");
+            waker.register(cx.waker());
+            Poll::Ready(())
+        })
+        .await;
+    }
+
+    let waker = Box::leak(Box::new(AtomicWaker::new()));
+
+    let (executor, trace) = setup();
+    executor.spawner().spawn(task1(trace.clone(), waker)).unwrap();
+
+    unsafe { executor.poll() };
+    unsafe { executor.poll() }; // progress to registering the waker
+    waker.wake();
+    unsafe { executor.poll() };
+    // Task has exited
+
+    assert_eq!(
+        trace.get(),
+        &[
+            "pend",       // spawning a task pends the executor
+            "yield_now",  //
+            "pend",       // yield_now wakes the task
+            "poll task1", //
+            "pend",       // task self-wakes
+        ]
+    );
+
+    // Can respawn task on another executor
+    let (other_executor, other_trace) = setup();
+    other_executor
+        .spawner()
+        .spawn(task1(other_trace.clone(), waker))
+        .unwrap();
+
+    unsafe { other_executor.poll() }; // just run to the yield_now
+    waker.wake(); // trigger old waker registration
+    unsafe { executor.poll() };
+    unsafe { other_executor.poll() };
+
+    // First executor's trace has not changed
+    assert_eq!(
+        trace.get(),
+        &[
+            "pend",       // spawning a task pends the executor
+            "yield_now",  //
+            "pend",       // yield_now wakes the task
+            "poll task1", //
+            "pend",       // task self-wakes
+        ]
+    );
+
+    assert_eq!(
+        other_trace.get(),
+        &[
+            "pend",       // spawning a task pends the executor
+            "yield_now",  //
+            "pend",       // manual wake, gets cleared by poll
+            "poll task1", //
+        ]
+    );
+}
+
+#[test]
 fn executor_task_cfg_args() {
     // simulate cfg'ing away argument c
     #[task]
diff --git a/embassy-executor/tests/ui.rs b/embassy-executor/tests/ui.rs
new file mode 100644
index 000000000..278a4b903
--- /dev/null
+++ b/embassy-executor/tests/ui.rs
@@ -0,0 +1,24 @@
+#[cfg(not(miri))]
+#[test]
+fn ui() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/ui/abi.rs");
+    t.compile_fail("tests/ui/bad_return.rs");
+    t.compile_fail("tests/ui/generics.rs");
+    t.compile_fail("tests/ui/impl_trait_nested.rs");
+    t.compile_fail("tests/ui/impl_trait.rs");
+    t.compile_fail("tests/ui/impl_trait_static.rs");
+    t.compile_fail("tests/ui/nonstatic_ref_anon_nested.rs");
+    t.compile_fail("tests/ui/nonstatic_ref_anon.rs");
+    t.compile_fail("tests/ui/nonstatic_ref_elided.rs");
+    t.compile_fail("tests/ui/nonstatic_ref_generic.rs");
+    t.compile_fail("tests/ui/nonstatic_struct_anon.rs");
+    #[cfg(not(feature = "nightly"))] // we can't catch this case with the macro, so the output changes on nightly.
+    t.compile_fail("tests/ui/nonstatic_struct_elided.rs");
+    t.compile_fail("tests/ui/nonstatic_struct_generic.rs");
+    t.compile_fail("tests/ui/not_async.rs");
+    t.compile_fail("tests/ui/self_ref.rs");
+    t.compile_fail("tests/ui/self.rs");
+    t.compile_fail("tests/ui/type_error.rs");
+    t.compile_fail("tests/ui/where_clause.rs");
+}
diff --git a/embassy-executor/tests/ui/abi.rs b/embassy-executor/tests/ui/abi.rs
new file mode 100644
index 000000000..fd52f7e41
--- /dev/null
+++ b/embassy-executor/tests/ui/abi.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async extern "C" fn task() {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/abi.stderr b/embassy-executor/tests/ui/abi.stderr
new file mode 100644
index 000000000..e264e371a
--- /dev/null
+++ b/embassy-executor/tests/ui/abi.stderr
@@ -0,0 +1,5 @@
+error: task functions must not have an ABI qualifier
+ --> tests/ui/abi.rs:6:1
+  |
+6 | async extern "C" fn task() {}
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/embassy-executor/tests/ui/bad_return.rs b/embassy-executor/tests/ui/bad_return.rs
new file mode 100644
index 000000000..f09a5205b
--- /dev/null
+++ b/embassy-executor/tests/ui/bad_return.rs
@@ -0,0 +1,10 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task() -> u32 {
+    5
+}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/bad_return.stderr b/embassy-executor/tests/ui/bad_return.stderr
new file mode 100644
index 000000000..e9d94dff8
--- /dev/null
+++ b/embassy-executor/tests/ui/bad_return.stderr
@@ -0,0 +1,5 @@
+error: task functions must either not return a value, return `()` or return `!`
+ --> tests/ui/bad_return.rs:6:1
+  |
+6 | async fn task() -> u32 {
+  | ^^^^^^^^^^^^^^^^^^^^^^
diff --git a/embassy-executor/tests/ui/generics.rs b/embassy-executor/tests/ui/generics.rs
new file mode 100644
index 000000000..b83123bb1
--- /dev/null
+++ b/embassy-executor/tests/ui/generics.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task<T: Sized>(_t: T) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/generics.stderr b/embassy-executor/tests/ui/generics.stderr
new file mode 100644
index 000000000..197719a7b
--- /dev/null
+++ b/embassy-executor/tests/ui/generics.stderr
@@ -0,0 +1,5 @@
+error: task functions must not be generic
+ --> tests/ui/generics.rs:6:1
+  |
+6 | async fn task<T: Sized>(_t: T) {}
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/embassy-executor/tests/ui/impl_trait.rs b/embassy-executor/tests/ui/impl_trait.rs
new file mode 100644
index 000000000..a21402aa0
--- /dev/null
+++ b/embassy-executor/tests/ui/impl_trait.rs
@@ -0,0 +1,6 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+#[embassy_executor::task]
+async fn foo(_x: impl Sized) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/impl_trait.stderr b/embassy-executor/tests/ui/impl_trait.stderr
new file mode 100644
index 000000000..099b1828f
--- /dev/null
+++ b/embassy-executor/tests/ui/impl_trait.stderr
@@ -0,0 +1,5 @@
+error: `impl Trait` is not allowed in task arguments. It is syntax sugar for generics, and tasks can't be generic.
+ --> tests/ui/impl_trait.rs:4:18
+  |
+4 | async fn foo(_x: impl Sized) {}
+  |                  ^^^^^^^^^^
diff --git a/embassy-executor/tests/ui/impl_trait_nested.rs b/embassy-executor/tests/ui/impl_trait_nested.rs
new file mode 100644
index 000000000..07442b8fa
--- /dev/null
+++ b/embassy-executor/tests/ui/impl_trait_nested.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<T>(T);
+
+#[embassy_executor::task]
+async fn foo(_x: Foo<impl Sized + 'static>) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/impl_trait_nested.stderr b/embassy-executor/tests/ui/impl_trait_nested.stderr
new file mode 100644
index 000000000..39592f958
--- /dev/null
+++ b/embassy-executor/tests/ui/impl_trait_nested.stderr
@@ -0,0 +1,5 @@
+error: `impl Trait` is not allowed in task arguments. It is syntax sugar for generics, and tasks can't be generic.
+ --> tests/ui/impl_trait_nested.rs:6:22
+  |
+6 | async fn foo(_x: Foo<impl Sized + 'static>) {}
+  |                      ^^^^^^^^^^^^^^^^^^^^
diff --git a/embassy-executor/tests/ui/impl_trait_static.rs b/embassy-executor/tests/ui/impl_trait_static.rs
new file mode 100644
index 000000000..272470f98
--- /dev/null
+++ b/embassy-executor/tests/ui/impl_trait_static.rs
@@ -0,0 +1,6 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+#[embassy_executor::task]
+async fn foo(_x: impl Sized + 'static) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/impl_trait_static.stderr b/embassy-executor/tests/ui/impl_trait_static.stderr
new file mode 100644
index 000000000..0032a20c9
--- /dev/null
+++ b/embassy-executor/tests/ui/impl_trait_static.stderr
@@ -0,0 +1,5 @@
+error: `impl Trait` is not allowed in task arguments. It is syntax sugar for generics, and tasks can't be generic.
+ --> tests/ui/impl_trait_static.rs:4:18
+  |
+4 | async fn foo(_x: impl Sized + 'static) {}
+  |                  ^^^^^^^^^^^^^^^^^^^^
diff --git a/embassy-executor/tests/ui/nonstatic_ref_anon.rs b/embassy-executor/tests/ui/nonstatic_ref_anon.rs
new file mode 100644
index 000000000..417c360a1
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_anon.rs
@@ -0,0 +1,6 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+#[embassy_executor::task]
+async fn foo(_x: &'_ u32) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/nonstatic_ref_anon.stderr b/embassy-executor/tests/ui/nonstatic_ref_anon.stderr
new file mode 100644
index 000000000..0544de843
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_anon.stderr
@@ -0,0 +1,5 @@
+error: Arguments for tasks must live forever. Try using the `'static` lifetime.
+ --> tests/ui/nonstatic_ref_anon.rs:4:19
+  |
+4 | async fn foo(_x: &'_ u32) {}
+  |                   ^^
diff --git a/embassy-executor/tests/ui/nonstatic_ref_anon_nested.rs b/embassy-executor/tests/ui/nonstatic_ref_anon_nested.rs
new file mode 100644
index 000000000..175ebccc1
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_anon_nested.rs
@@ -0,0 +1,6 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+#[embassy_executor::task]
+async fn foo(_x: &'static &'_ u32) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/nonstatic_ref_anon_nested.stderr b/embassy-executor/tests/ui/nonstatic_ref_anon_nested.stderr
new file mode 100644
index 000000000..79f262e6b
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_anon_nested.stderr
@@ -0,0 +1,5 @@
+error: Arguments for tasks must live forever. Try using the `'static` lifetime.
+ --> tests/ui/nonstatic_ref_anon_nested.rs:4:28
+  |
+4 | async fn foo(_x: &'static &'_ u32) {}
+  |                            ^^
diff --git a/embassy-executor/tests/ui/nonstatic_ref_elided.rs b/embassy-executor/tests/ui/nonstatic_ref_elided.rs
new file mode 100644
index 000000000..cf49ad709
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_elided.rs
@@ -0,0 +1,6 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+#[embassy_executor::task]
+async fn foo(_x: &u32) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/nonstatic_ref_elided.stderr b/embassy-executor/tests/ui/nonstatic_ref_elided.stderr
new file mode 100644
index 000000000..7e2b9eb7c
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_elided.stderr
@@ -0,0 +1,5 @@
+error: Arguments for tasks must live forever. Try using the `'static` lifetime.
+ --> tests/ui/nonstatic_ref_elided.rs:4:18
+  |
+4 | async fn foo(_x: &u32) {}
+  |                  ^
diff --git a/embassy-executor/tests/ui/nonstatic_ref_generic.rs b/embassy-executor/tests/ui/nonstatic_ref_generic.rs
new file mode 100644
index 000000000..3f8a26cf8
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_generic.rs
@@ -0,0 +1,6 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+#[embassy_executor::task]
+async fn foo<'a>(_x: &'a u32) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/nonstatic_ref_generic.stderr b/embassy-executor/tests/ui/nonstatic_ref_generic.stderr
new file mode 100644
index 000000000..af8491ad7
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_ref_generic.stderr
@@ -0,0 +1,11 @@
+error: task functions must not be generic
+ --> tests/ui/nonstatic_ref_generic.rs:4:1
+  |
+4 | async fn foo<'a>(_x: &'a u32) {}
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: Arguments for tasks must live forever. Try using the `'static` lifetime.
+ --> tests/ui/nonstatic_ref_generic.rs:4:23
+  |
+4 | async fn foo<'a>(_x: &'a u32) {}
+  |                       ^^
diff --git a/embassy-executor/tests/ui/nonstatic_struct_anon.rs b/embassy-executor/tests/ui/nonstatic_struct_anon.rs
new file mode 100644
index 000000000..ba95d1459
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_struct_anon.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task(_x: Foo<'_>) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/nonstatic_struct_anon.stderr b/embassy-executor/tests/ui/nonstatic_struct_anon.stderr
new file mode 100644
index 000000000..5df2a6e06
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_struct_anon.stderr
@@ -0,0 +1,5 @@
+error: Arguments for tasks must live forever. Try using the `'static` lifetime.
+ --> tests/ui/nonstatic_struct_anon.rs:6:23
+  |
+6 | async fn task(_x: Foo<'_>) {}
+  |                       ^^
diff --git a/embassy-executor/tests/ui/nonstatic_struct_elided.rs b/embassy-executor/tests/ui/nonstatic_struct_elided.rs
new file mode 100644
index 000000000..4cfe2966a
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_struct_elided.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task(_x: Foo) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/nonstatic_struct_elided.stderr b/embassy-executor/tests/ui/nonstatic_struct_elided.stderr
new file mode 100644
index 000000000..099ef8b4e
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_struct_elided.stderr
@@ -0,0 +1,10 @@
+error[E0726]: implicit elided lifetime not allowed here
+ --> tests/ui/nonstatic_struct_elided.rs:6:19
+  |
+6 | async fn task(_x: Foo) {}
+  |                   ^^^ expected lifetime parameter
+  |
+help: indicate the anonymous lifetime
+  |
+6 | async fn task(_x: Foo<'_>) {}
+  |                      ++++
diff --git a/embassy-executor/tests/ui/nonstatic_struct_generic.rs b/embassy-executor/tests/ui/nonstatic_struct_generic.rs
new file mode 100644
index 000000000..ec3d908f6
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_struct_generic.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task<'a>(_x: Foo<'a>) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/nonstatic_struct_generic.stderr b/embassy-executor/tests/ui/nonstatic_struct_generic.stderr
new file mode 100644
index 000000000..61d5231bc
--- /dev/null
+++ b/embassy-executor/tests/ui/nonstatic_struct_generic.stderr
@@ -0,0 +1,11 @@
+error: task functions must not be generic
+ --> tests/ui/nonstatic_struct_generic.rs:6:1
+  |
+6 | async fn task<'a>(_x: Foo<'a>) {}
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: Arguments for tasks must live forever. Try using the `'static` lifetime.
+ --> tests/ui/nonstatic_struct_generic.rs:6:27
+  |
+6 | async fn task<'a>(_x: Foo<'a>) {}
+  |                           ^^
diff --git a/embassy-executor/tests/ui/not_async.rs b/embassy-executor/tests/ui/not_async.rs
new file mode 100644
index 000000000..f3f7e9bd2
--- /dev/null
+++ b/embassy-executor/tests/ui/not_async.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+fn task() {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/not_async.stderr b/embassy-executor/tests/ui/not_async.stderr
new file mode 100644
index 000000000..27f040d9c
--- /dev/null
+++ b/embassy-executor/tests/ui/not_async.stderr
@@ -0,0 +1,5 @@
+error: task functions must be async
+ --> tests/ui/not_async.rs:6:1
+  |
+6 | fn task() {}
+  | ^^^^^^^^^
diff --git a/embassy-executor/tests/ui/self.rs b/embassy-executor/tests/ui/self.rs
new file mode 100644
index 000000000..f83a962d1
--- /dev/null
+++ b/embassy-executor/tests/ui/self.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task(self) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/self.stderr b/embassy-executor/tests/ui/self.stderr
new file mode 100644
index 000000000..aaf031573
--- /dev/null
+++ b/embassy-executor/tests/ui/self.stderr
@@ -0,0 +1,13 @@
+error: task functions must not have `self` arguments
+ --> tests/ui/self.rs:6:15
+  |
+6 | async fn task(self) {}
+  |               ^^^^
+
+error: `self` parameter is only allowed in associated functions
+ --> tests/ui/self.rs:6:15
+  |
+6 | async fn task(self) {}
+  |               ^^^^ not semantically valid as function parameter
+  |
+  = note: associated functions are those in `impl` or `trait` definitions
diff --git a/embassy-executor/tests/ui/self_ref.rs b/embassy-executor/tests/ui/self_ref.rs
new file mode 100644
index 000000000..5e49bba5e
--- /dev/null
+++ b/embassy-executor/tests/ui/self_ref.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task(&mut self) {}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/self_ref.stderr b/embassy-executor/tests/ui/self_ref.stderr
new file mode 100644
index 000000000..dd2052977
--- /dev/null
+++ b/embassy-executor/tests/ui/self_ref.stderr
@@ -0,0 +1,13 @@
+error: task functions must not have `self` arguments
+ --> tests/ui/self_ref.rs:6:15
+  |
+6 | async fn task(&mut self) {}
+  |               ^^^^^^^^^
+
+error: `self` parameter is only allowed in associated functions
+ --> tests/ui/self_ref.rs:6:15
+  |
+6 | async fn task(&mut self) {}
+  |               ^^^^^^^^^ not semantically valid as function parameter
+  |
+  = note: associated functions are those in `impl` or `trait` definitions
diff --git a/embassy-executor/tests/ui/type_error.rs b/embassy-executor/tests/ui/type_error.rs
new file mode 100644
index 000000000..1734bc6c4
--- /dev/null
+++ b/embassy-executor/tests/ui/type_error.rs
@@ -0,0 +1,8 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+#[embassy_executor::task]
+async fn task() {
+    5
+}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/type_error.stderr b/embassy-executor/tests/ui/type_error.stderr
new file mode 100644
index 000000000..bce315811
--- /dev/null
+++ b/embassy-executor/tests/ui/type_error.stderr
@@ -0,0 +1,7 @@
+error[E0308]: mismatched types
+ --> tests/ui/type_error.rs:5:5
+  |
+4 | async fn task() {
+  |                - help: try adding a return type: `-> i32`
+5 |     5
+  |     ^ expected `()`, found integer
diff --git a/embassy-executor/tests/ui/where_clause.rs b/embassy-executor/tests/ui/where_clause.rs
new file mode 100644
index 000000000..848d78149
--- /dev/null
+++ b/embassy-executor/tests/ui/where_clause.rs
@@ -0,0 +1,12 @@
+#![cfg_attr(feature = "nightly", feature(impl_trait_in_assoc_type))]
+
+struct Foo<'a>(&'a ());
+
+#[embassy_executor::task]
+async fn task()
+where
+    (): Sized,
+{
+}
+
+fn main() {}
diff --git a/embassy-executor/tests/ui/where_clause.stderr b/embassy-executor/tests/ui/where_clause.stderr
new file mode 100644
index 000000000..eba45af40
--- /dev/null
+++ b/embassy-executor/tests/ui/where_clause.stderr
@@ -0,0 +1,7 @@
+error: task functions must not have `where` clauses
+ --> tests/ui/where_clause.rs:6:1
+  |
+6 | / async fn task()
+7 | | where
+8 | |     (): Sized,
+  | |______________^