1 files changed, 35 insertions, 0 deletions
diff --git a/tests/ui/feature-gates/feature-gate-dispatch-from-dyn-missing-impl.rs b/tests/ui/feature-gates/feature-gate-dispatch-from-dyn-missing-impl.rs
new file mode 100644
index 000000000..23857cbac
--- /dev/null
+++ b/tests/ui/feature-gates/feature-gate-dispatch-from-dyn-missing-impl.rs
@@ -0,0 +1,35 @@
+// Check that a self parameter type requires a DispatchFromDyn impl to be object safe
+
+#![feature(arbitrary_self_types, unsize, coerce_unsized)]
+
+use std::{
+    marker::Unsize,
+    ops::{CoerceUnsized, Deref},
+};
+
+struct Ptr<T: ?Sized>(Box<T>);
+
+impl<T: ?Sized> Deref for Ptr<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &*self.0
+    }
+}
+
+impl<T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<Ptr<U>> for Ptr<T> {}
+// Because this impl is missing the coercion below fails.
+// impl<T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<Ptr<U>> for Ptr<T> {}
+
+trait Trait {
+    fn ptr(self: Ptr<Self>);
+}
+impl Trait for i32 {
+    fn ptr(self: Ptr<Self>) {}
+}
+
+fn main() {
+    Ptr(Box::new(4)) as Ptr<dyn Trait>;
+    //~^ ERROR the trait `Trait` cannot be made into an object
+    //~^^ ERROR the trait `Trait` cannot be made into an object
+}