From 4922210ea6ff5fa7143330729ff322b829bc3fa8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Rakic?= <remy.rakic@arm.com>
Date: Wed, 6 May 2026 19:04:58 +0200
Subject: [PATCH] add normalization test with field with diverging alias

Another example from https://github.com/rust-lang/trait-system-refactor-initiative/issues/139
and which was likely fixed by https://github.com/rust-lang/rust/pull/140672 as well.
---
 ...e-diverging-alias-in-struct.current.stderr |  9 +++++++
 ...lize-diverging-alias-in-struct.next.stderr | 18 +++++++++++++
 .../normalize-diverging-alias-in-struct.rs    | 27 +++++++++++++++++++
 3 files changed, 54 insertions(+)
 create mode 100644 tests/ui/traits/normalize/normalize-diverging-alias-in-struct.current.stderr
 create mode 100644 tests/ui/traits/normalize/normalize-diverging-alias-in-struct.next.stderr
 create mode 100644 tests/ui/traits/normalize/normalize-diverging-alias-in-struct.rs

diff --git a/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.current.stderr b/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.current.stderr
new file mode 100644
index 000000000000..7787d6b68f25
--- /dev/null
+++ b/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.current.stderr
@@ -0,0 +1,9 @@
+error[E0275]: overflow evaluating the requirement `<u8 as Trait>::Diverges<u8> == _`
+  --> $DIR/normalize-diverging-alias-in-struct.rs:21:12
+   |
+LL |     field: Box<<u8 as Trait>::Diverges<u8>>,
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0275`.
diff --git a/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.next.stderr b/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.next.stderr
new file mode 100644
index 000000000000..d7046d2b058b
--- /dev/null
+++ b/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.next.stderr
@@ -0,0 +1,18 @@
+error[E0271]: type mismatch resolving `<u8 as Trait>::Diverges<u8> normalizes-to _`
+  --> $DIR/normalize-diverging-alias-in-struct.rs:21:12
+   |
+LL |     field: Box<<u8 as Trait>::Diverges<u8>>,
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ types differ
+
+error[E0271]: type mismatch resolving `<u8 as Trait>::Diverges<u8> normalizes-to _`
+  --> $DIR/normalize-diverging-alias-in-struct.rs:21:12
+   |
+LL |     field: Box<<u8 as Trait>::Diverges<u8>>,
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ types differ
+   |
+note: required by a bound in `Box`
+  --> $SRC_DIR/alloc/src/boxed.rs:LL:COL
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0271`.
diff --git a/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.rs b/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.rs
new file mode 100644
index 000000000000..45b2cb56c25f
--- /dev/null
+++ b/tests/ui/traits/normalize/normalize-diverging-alias-in-struct.rs
@@ -0,0 +1,27 @@
+// Ensure that structs with fields whose types contain diverging aliases are properly caught with
+// both solvers.
+// MCVE from https://github.com/rust-lang/trait-system-refactor-initiative/issues/139#issuecomment-2703127026.
+
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@ [next] compile-flags: -Znext-solver
+
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
+
+trait Trait {
+    type Diverges<D: Trait>;
+}
+
+impl<T> Trait for T {
+    type Diverges<D: Trait> = D::Diverges<D>;
+}
+
+struct Foo {
+    field: Box<<u8 as Trait>::Diverges<u8>>,
+    //[current]~^ ERROR: overflow evaluating the requirement `<u8 as Trait>::Diverges<u8> == _`
+    //[next]~^^ ERROR: type mismatch resolving `<u8 as Trait>::Diverges<u8> normalizes-to _`
+    //[next]~| ERROR: type mismatch resolving `<u8 as Trait>::Diverges<u8> normalizes-to _`
+}
+
+fn main() {}