split up `#[rustc_deny_explicit_impl]` attribute

This commit splits the `#[rustc_deny_explicit_impl(implement_via_object = ...)]` attribute
into two attributes `#[rustc_deny_explicit_impl]` and `#[rustc_do_not_implement_via_object]`.

This allows us to have special traits that can have user-defined impls but do not have the
automatic trait impl for trait objects (`impl Trait for dyn Trait`).

1 files changed, 3 insertions, 1 deletions

diff --git a/library/core/src/future/async_drop.rs b/library/core/src/future/async_drop.rs
index 7de5fe67cd0..ea6d3b800e6 100644
--- a/library/core/src/future/async_drop.rs
+++ b/library/core/src/future/async_drop.rs
@@ -133,7 +133,9 @@ pub trait AsyncDrop {
 }
 
 #[lang = "async_destruct"]
-#[rustc_deny_explicit_impl(implement_via_object = false)]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl)]
+#[cfg_attr(not(bootstrap), rustc_do_not_implement_via_object)]
 trait AsyncDestruct {
     type AsyncDestructor: Future<Output = ()>;
 }