Add ui test to capture current situation of rust issue 93828

tests/ui/consider-restricting.rs

@@ -0,0 +1,26 @@
+// https://github.com/rust-lang/rust/issues/93828
+
+use async_trait::async_trait;
+
+pub trait IntoUrl {}
+
+#[async_trait]
+pub trait ClientExt {
+    async fn publish<T: IntoUrl>(&self, url: T);
+}
+
+struct Client;
+
+#[async_trait]
+impl ClientExt for Client {
+    async fn publish<T: IntoUrl>(&self, url: T) {}
+}
+
+struct Client2;
+
+#[async_trait]
+impl ClientExt for Client2 {
+    async fn publish<T>(&self, url: T) {}
+}
+
+fn main() {}

tests/ui/consider-restricting.stderr

@@ -0,0 +1,33 @@
+error: future cannot be sent between threads safely
+  --> tests/ui/consider-restricting.rs:16:49
+   |
+16 |     async fn publish<T: IntoUrl>(&self, url: T) {}
+   |                                                 ^^ future created by async block is not `Send`
+   |
+note: captured value is not `Send`
+  --> tests/ui/consider-restricting.rs:16:41
+   |
+16 |     async fn publish<T: IntoUrl>(&self, url: T) {}
+   |                                         ^^^ has type `T` which is not `Send`
+   = note: required for the cast to the object type `dyn Future<Output = ()> + Send`
+help: consider further restricting this bound
+   |
+16 |     async fn publish<T + std::marker::Send: IntoUrl>(&self, url: T) {}
+   |                        +++++++++++++++++++
+
+error: future cannot be sent between threads safely
+  --> tests/ui/consider-restricting.rs:23:40
+   |
+23 |     async fn publish<T>(&self, url: T) {}
+   |                                        ^^ future created by async block is not `Send`
+   |
+note: captured value is not `Send`
+  --> tests/ui/consider-restricting.rs:23:32
+   |
+23 |     async fn publish<T>(&self, url: T) {}
+   |                                ^^^ has type `T` which is not `Send`
+   = note: required for the cast to the object type `dyn Future<Output = ()> + Send`
+help: consider further restricting this bound
+   |
+23 |     async fn publish<T + std::marker::Send>(&self, url: T) {}
+   |                        +++++++++++++++++++