/// [`Pin<P>`]: ../pin/struct.Pin.html
/// [`pin module`]: ../../std/pin/index.html
#[stable(feature = "pin", since = "1.33.0")]
+#[rustc_on_unimplemented(
+ on(_Self = "std::future::Future", note = "consider using `Box::pin`",),
+ message = "`{Self}` cannot be unpinned"
+)]
#[lang = "unpin"]
pub auto trait Unpin {}