From 44a7eb01fcedd4c42ea9b8cb76be71aa72bf8a4a Mon Sep 17 00:00:00 2001
From: inq <gofiri@gmail.com>
Date: Mon, 4 May 2026 03:27:18 +0700
Subject: [PATCH 1/2] Regression test for trait-system-refactor#7

---
 .../alias-relate/transitive-inference.rs      | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 tests/ui/traits/next-solver/alias-relate/transitive-inference.rs

diff --git a/tests/ui/traits/next-solver/alias-relate/transitive-inference.rs b/tests/ui/traits/next-solver/alias-relate/transitive-inference.rs
new file mode 100644
index 0000000000000..e41ea736e950d
--- /dev/null
+++ b/tests/ui/traits/next-solver/alias-relate/transitive-inference.rs
@@ -0,0 +1,38 @@
+//@ revisions: old next
+//@[next] compile-flags: -Znext-solver=globally
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@ check-pass
+// Regression test for trait-system-refactor-initiative#7
+
+use std::marker::PhantomData;
+
+#[derive(Default)]
+struct Foo<T, U>(PhantomData<(T, U)>);
+
+trait Trait {
+    type Assoc;
+
+    fn to_assoc(self) -> Self::Assoc;
+}
+
+impl Trait for Foo<u32, i32> {
+    type Assoc = Foo<u32, i32>;
+    fn to_assoc(self) -> Self::Assoc {
+        Foo(PhantomData)
+    }
+}
+impl Trait for Foo<i32, u32> {
+    type Assoc = Foo<i32, u32>;
+    fn to_assoc(self) -> Self::Assoc {
+        Foo(PhantomData)
+    }
+}
+
+#[allow(unused_assignments)]
+fn main() {
+    let mut x: Foo<_, _> = Default::default();
+    let mut assoc = x.to_assoc();
+    assoc = Foo::<u32, _>(PhantomData);
+    assoc = Foo::<_, i32>(PhantomData);
+    x = assoc;
+}

From d4c413e34873e0f0c384a9fd7274d09228d10319 Mon Sep 17 00:00:00 2001
From: inkyu <gofiri@gmail.com>
Date: Mon, 4 May 2026 15:05:04 +0700
Subject: [PATCH 2/2] Apply suggestion from @lcnr

Co-authored-by: lcnr <rust@lcnr.de>
---
 .../traits/next-solver/alias-relate/transitive-inference.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tests/ui/traits/next-solver/alias-relate/transitive-inference.rs b/tests/ui/traits/next-solver/alias-relate/transitive-inference.rs
index e41ea736e950d..207cf71c0b3a4 100644
--- a/tests/ui/traits/next-solver/alias-relate/transitive-inference.rs
+++ b/tests/ui/traits/next-solver/alias-relate/transitive-inference.rs
@@ -2,7 +2,11 @@
 //@[next] compile-flags: -Znext-solver=globally
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@ check-pass
-// Regression test for trait-system-refactor-initiative#7
+// Regression test for trait-system-refactor-initiative#7. This test
+// would error if we were to rely on lazy normalization here.
+//
+// We eagerly normalize the associated types, here, causing this to
+// compile.
 
 use std::marker::PhantomData;