Introduce CoerceShared lang item and trait

1 files changed, 9 insertions, 0 deletions

diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
index d03d7a43469..8541a5b91cd 100644
--- a/library/core/src/marker.rs
+++ b/library/core/src/marker.rs
@@ -1372,3 +1372,12 @@ pub trait CoercePointeeValidated {
 pub trait Reborrow {
     // Empty.
 }
+
+/// Allows reborrowable value to be reborrowed as shared, creating a copy of
+/// that disables the source for writes for the lifetime of the copy.
+#[lang = "coerce_shared"]
+#[unstable(feature = "reborrow", issue = "145612")]
+pub trait CoerceShared: Reborrow {
+    /// The type of this value when reborrowed as shared.
+    type Target: Copy;
+}