Add test

embassy-executor/tests/ui.rs

@@ -19,5 +19,6 @@ fn ui() {
     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");
 }

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() {}

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