Regression test for rust-lang#129541

Author: zachs18

tests/ui/traits/sized-coniductive.rs

@@ -0,0 +1,14 @@
+//@ check-pass
+// https://github.com/rust-lang/rust/issues/129541
+
+#[derive(Clone)]
+struct Test {
+    field: std::borrow::Cow<'static, [Self]>,
+}
+
+#[derive(Clone)]
+struct Hello {
+    a: <[Hello] as std::borrow::ToOwned>::Owned,
+}
+
+fn main(){}