From c37524403827525ed3d7a359b62d7231a80a5992 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Tue, 8 Jul 2025 18:45:11 +0000
Subject: [PATCH] Add test for `default_field_values` and `const_default`

Add a test showing `#![feature(default_field_values)]` using `#[const_trait] trait Default` (`#![feature(const_default)]` + `#![feature(const_trait_impl)]`).
---
 .../const-trait-default-field-value.rs        | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 tests/ui/structs/default-field-values/const-trait-default-field-value.rs

diff --git a/tests/ui/structs/default-field-values/const-trait-default-field-value.rs b/tests/ui/structs/default-field-values/const-trait-default-field-value.rs
new file mode 100644
index 0000000000000..60c22efabc4de
--- /dev/null
+++ b/tests/ui/structs/default-field-values/const-trait-default-field-value.rs
@@ -0,0 +1,37 @@
+//@ check-pass
+
+// Ensure that `default_field_values` and `const_default` interact properly.
+
+#![feature(const_default)]
+#![feature(const_trait_impl)]
+#![feature(default_field_values)]
+#![feature(derive_const)]
+
+#[derive(PartialEq, Eq, Debug)]
+#[derive_const(Default)]
+struct S {
+    r: Option<String> = <Option<_> as Default>::default(),
+    s: String = String::default(),
+    o: Option<String> = Option::<String>::default(),
+    p: std::marker::PhantomData<()> = std::marker::PhantomData::default(),
+    q: Option<String> = <Option<String> as Default>::default(),
+    t: Option<String> = Option::default(),
+    v: Option<String> = const { Option::default() },
+}
+
+const _: S = S { .. };
+const _: S = const { S { .. } };
+const _: S = S::default();
+const _: S = const { S::default() };
+
+fn main() {
+    let s = S { .. };
+    assert_eq!(s.r, None);
+    assert_eq!(&s.s, "");
+    assert_eq!(s.o, None);
+    assert_eq!(s.p, std::marker::PhantomData);
+    assert_eq!(s.q, None);
+    assert_eq!(s.t, None);
+    assert_eq!(s.v, None);
+    assert_eq!(s, S::default());
+}