1 files changed, 26 insertions, 0 deletions
diff --git a/tests/ui/regions/regions-trait-object-subtyping.rs b/tests/ui/regions/regions-trait-object-subtyping.rs
new file mode 100644
index 000000000..1d7a766de
--- /dev/null
+++ b/tests/ui/regions/regions-trait-object-subtyping.rs
@@ -0,0 +1,26 @@
+trait Dummy { fn dummy(&self); }
+
+fn foo1<'a:'b,'b>(x: &'a mut (dyn Dummy+'a)) -> &'b mut (dyn Dummy+'b) {
+    // Here, we are able to coerce
+    x
+}
+
+fn foo2<'a:'b,'b>(x: &'b mut (dyn Dummy+'a)) -> &'b mut (dyn Dummy+'b) {
+    // Here, we are able to coerce
+    x
+}
+
+fn foo3<'a,'b>(x: &'a mut dyn Dummy) -> &'b mut dyn Dummy {
+    // Without knowing 'a:'b, we can't coerce
+    x
+    //~^ ERROR lifetime may not live long enough
+}
+
+struct Wrapper<T>(T);
+fn foo4<'a:'b,'b>(x: Wrapper<&'a mut dyn Dummy>) -> Wrapper<&'b mut dyn Dummy> {
+    // We can't coerce because it is packed in `Wrapper`
+    x
+    //~^ ERROR lifetime may not live long enough
+}
+
+fn main() {}