1 files changed, 43 insertions, 0 deletions
diff --git a/src/test/ui/dynamically-sized-types/dst-coerce-custom.rs b/src/test/ui/dynamically-sized-types/dst-coerce-custom.rs
new file mode 100644
index 000000000..24d83eb53
--- /dev/null
+++ b/src/test/ui/dynamically-sized-types/dst-coerce-custom.rs
@@ -0,0 +1,43 @@
+// run-pass
+// Test a very simple custom DST coercion.
+
+#![feature(unsize, coerce_unsized)]
+
+use std::ops::CoerceUnsized;
+use std::marker::Unsize;
+
+struct Bar<T: ?Sized> {
+    x: *const T,
+}
+
+impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<Bar<U>> for Bar<T> {}
+
+trait Baz {
+    fn get(&self) -> i32;
+}
+
+impl Baz for i32 {
+    fn get(&self) -> i32 {
+        *self
+    }
+}
+
+fn main() {
+    // Arrays.
+    let a: Bar<[i32; 3]> = Bar { x: &[1, 2, 3] };
+    // This is the actual coercion.
+    let b: Bar<[i32]> = a;
+
+    unsafe {
+        assert_eq!((*b.x)[0], 1);
+        assert_eq!((*b.x)[1], 2);
+        assert_eq!((*b.x)[2], 3);
+    }
+
+    // Trait objects.
+    let a: Bar<i32> = Bar { x: &42 };
+    let b: Bar<dyn Baz> = a;
+    unsafe {
+        assert_eq!((*b.x).get(), 42);
+    }
+}