Add test for issue-27697

src/test/ui/issues/issue-27697.rs

@@ -0,0 +1,21 @@
+// run-pass
+
+use std::ops::Deref;
+
+trait MyTrait {
+    fn do_something(&self);
+    fn as_str(&self) -> &str;
+}
+
+impl Deref for dyn MyTrait {
+    type Target = str;
+    fn deref(&self) -> &Self::Target {
+        self.as_str()
+    }
+}
+
+fn trait_object_does_something(t: &dyn MyTrait) {
+    t.do_something()
+}
+
+fn main() {}