From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/test/ui/associated-types/issue-47139-1.rs | 78 +++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 src/test/ui/associated-types/issue-47139-1.rs

(limited to 'src/test/ui/associated-types/issue-47139-1.rs')

diff --git a/src/test/ui/associated-types/issue-47139-1.rs b/src/test/ui/associated-types/issue-47139-1.rs
new file mode 100644
index 000000000..c55fc3434
--- /dev/null
+++ b/src/test/ui/associated-types/issue-47139-1.rs
@@ -0,0 +1,78 @@
+// run-pass
+// Regression test for issue #47139:
+//
+// Coherence was encountering an (unnecessary) overflow trying to
+// decide if the two impls of dummy overlap.
+//
+// The overflow went something like:
+//
+// - `&'a ?T: Insertable` ?
+// - let ?T = Option<?U> ?
+// - `Option<?U>: Insertable` ?
+// - `Option<&'a ?U>: Insertable` ?
+// - `&'a ?U: Insertable` ?
+//
+// While somewhere in the middle, a projection would occur, which
+// broke cycle detection.
+//
+// It turned out that this cycle was being kicked off due to some
+// extended diagnostic attempts in coherence, so removing those
+// sidestepped the issue for now.
+
+#![allow(dead_code)]
+
+pub trait Insertable {
+    type Values;
+
+    fn values(self) -> Self::Values;
+}
+
+impl<T> Insertable for Option<T>
+    where
+    T: Insertable,
+    T::Values: Default,
+{
+    type Values = T::Values;
+
+    fn values(self) -> Self::Values {
+        self.map(Insertable::values).unwrap_or_default()
+    }
+}
+
+impl<'a, T> Insertable for &'a Option<T>
+    where
+    Option<&'a T>: Insertable,
+{
+    type Values = <Option<&'a T> as Insertable>::Values;
+
+    fn values(self) -> Self::Values {
+        self.as_ref().values()
+    }
+}
+
+impl<'a, T> Insertable for &'a [T]
+{
+    type Values = Self;
+
+    fn values(self) -> Self::Values {
+        self
+    }
+}
+
+trait Unimplemented { }
+
+trait Dummy { }
+
+struct Foo<T> { t: T }
+
+impl<'a, U> Dummy for Foo<&'a U>
+    where &'a U: Insertable
+{
+}
+
+impl<T> Dummy for T
+    where T: Unimplemented
+{ }
+
+fn main() {
+}
-- 
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