1 files changed, 17 insertions, 0 deletions

diff --git a/tests/ui/issues/issue-39808.rs b/tests/ui/issues/issue-39808.rs
new file mode 100644
index 00000000000..a4701367373
--- /dev/null
+++ b/tests/ui/issues/issue-39808.rs
@@ -0,0 +1,17 @@
+// run-pass
+#![allow(unreachable_code)]
+
+// Regression test for #39808. The type parameter of `Owned` was
+// considered to be "unconstrained" because the type resulting from
+// `format!` (`String`) was not being propagated upward, owing to the
+// fact that the expression diverges.
+
+use std::borrow::Cow;
+
+fn main() {
+    let _ = if false {
+        Cow::Owned(format!("{:?}", panic!()))
+    } else {
+        Cow::Borrowed("")
+    };
+}