From 36f86f9e6ab0ed62ea3a8660deceacc4e1aa7ca1 Mon Sep 17 00:00:00 2001
From: AprilNEA <github@sku.moe>
Date: Tue, 30 Dec 2025 19:52:02 +0800
Subject: [PATCH] Adds a regression test for 137823

---
 .../recursion-issue-137823.rs                 | 39 +++++++++++++++++++
 .../recursion-issue-137823.stderr             | 14 +++++++
 2 files changed, 53 insertions(+)
 create mode 100644 tests/ui/codegen/normalization-overflow/recursion-issue-137823.rs
 create mode 100644 tests/ui/codegen/normalization-overflow/recursion-issue-137823.stderr

diff --git a/tests/ui/codegen/normalization-overflow/recursion-issue-137823.rs b/tests/ui/codegen/normalization-overflow/recursion-issue-137823.rs
new file mode 100644
index 000000000000..4ae8d84eba11
--- /dev/null
+++ b/tests/ui/codegen/normalization-overflow/recursion-issue-137823.rs
@@ -0,0 +1,39 @@
+//@ build-fail
+
+// Regression test for issue #137823
+// Tests that recursive monomorphization with associated types produces
+// a proper "recursion limit" error instead of an ICE.
+
+fn convert<S: Converter>() -> S::Out {
+    convert2::<ConvertWrap<S>>()
+    //~^ ERROR: reached the recursion limit while instantiating
+}
+
+fn convert2<S: Converter>() -> S::Out {
+    convert::<S>()
+}
+
+fn main() {
+    convert::<Ser>();
+}
+
+trait Converter {
+    type Out;
+}
+
+struct Ser;
+
+impl Converter for Ser {
+    type Out = ();
+}
+
+struct ConvertWrap<S> {
+    _d: S,
+}
+
+impl<S> Converter for ConvertWrap<S>
+where
+    S: Converter,
+{
+    type Out = S::Out;
+}
diff --git a/tests/ui/codegen/normalization-overflow/recursion-issue-137823.stderr b/tests/ui/codegen/normalization-overflow/recursion-issue-137823.stderr
new file mode 100644
index 000000000000..3d80c45685f5
--- /dev/null
+++ b/tests/ui/codegen/normalization-overflow/recursion-issue-137823.stderr
@@ -0,0 +1,14 @@
+error: reached the recursion limit while instantiating `convert2::<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<ConvertWrap<Ser>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
+  --> $DIR/recursion-issue-137823.rs:8:5
+   |
+LL |     convert2::<ConvertWrap<S>>()
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: `convert2` defined here
+  --> $DIR/recursion-issue-137823.rs:12:1
+   |
+LL | fn convert2<S: Converter>() -> S::Out {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+