1 files changed, 32 insertions, 0 deletions
diff --git a/src/test/ui/derives/derive-Debug-use-ufcs-tuple.rs b/src/test/ui/derives/derive-Debug-use-ufcs-tuple.rs
new file mode 100644
index 000000000..5f786769f
--- /dev/null
+++ b/src/test/ui/derives/derive-Debug-use-ufcs-tuple.rs
@@ -0,0 +1,32 @@
+// run-pass
+#![allow(warnings)]
+
+#[derive(Debug)]
+pub struct Foo<T>(pub T);
+
+use std::fmt;
+
+impl<T> Field for T {}
+impl<T> Finish for T {}
+impl Dt for &mut fmt::Formatter<'_> {}
+
+pub trait Field {
+    fn field(&self, _: impl Sized) {
+        panic!("got into field");
+    }
+}
+pub trait Finish {
+    fn finish(&self) -> Result<(), std::fmt::Error> {
+        panic!("got into finish");
+    }
+}
+pub trait Dt {
+    fn debug_tuple(&self, _: &str) {
+        panic!("got into debug_tuple");
+    }
+}
+
+fn main() {
+    let foo = Foo(());
+    assert_eq!("Foo(())", format!("{:?}", foo));
+}