From 3e3e70d529d8c7d7c4d7bc4fefc9f109393b9245 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:19:43 +0200
Subject: Merging upstream version 1.69.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 tests/ui/coinduction/canonicalization-rerun.rs | 54 ++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 tests/ui/coinduction/canonicalization-rerun.rs

(limited to 'tests/ui/coinduction')

diff --git a/tests/ui/coinduction/canonicalization-rerun.rs b/tests/ui/coinduction/canonicalization-rerun.rs
new file mode 100644
index 000000000..b10ba3a81
--- /dev/null
+++ b/tests/ui/coinduction/canonicalization-rerun.rs
@@ -0,0 +1,54 @@
+// check-pass
+// revisions: old new
+//[new] compile-flags: -Ztrait-solver=next
+
+// If we use canonical goals during trait solving we have to reevaluate
+// the root goal of a cycle until we hit a fixpoint.
+//
+// Here `main` has a goal `(?0, ?1): Trait` which is canonicalized to
+// `exists<^0, ^1> (^0, ^1): Trait`.
+//
+// - `exists<^0, ^1> (^0, ^1): Trait` -instantiate-> `(?0, ?1): Trait`
+//   -`(?1, ?0): Trait` -canonicalize-> `exists<^0, ^1> (^0, ^1): Trait`
+//     - COINDUCTIVE CYCLE OK (no constraints)
+//   - `(): ConstrainToU32<?0>` -canonicalize-> `exists<^0> (): ConstrainToU32<^0>`
+//     - OK (^0 = u32 -apply-> ?0 = u32)
+//   - OK (?0 = u32 -canonicalize-> ^0 = u32)
+//   - coinductive cycle with provisional result != final result, rerun
+//
+// - `exists<^0, ^1> (^0, ^1): Trait` -instantiate-> `(?0, ?1): Trait`
+//   -`(?1, ?0): Trait` -canonicalize-> `exists<^0, ^1> (^0, ^1): Trait`
+//     - COINDUCTIVE CYCLE OK (^0 = u32 -apply-> ?1 = u32)
+//   - `(): ConstrainToU32<?0>` -canonicalize-> `exists<^0> (): ConstrainToU32<^0>`
+//     - OK (^0 = u32 -apply-> ?1 = u32)
+//   - OK (?0 = u32, ?1 = u32 -canonicalize-> ^0 = u32, ^1 = u32)
+//   - coinductive cycle with provisional result != final result, rerun
+//
+// - `exists<^0, ^1> (^0, ^1): Trait` -instantiate-> `(?0, ?1): Trait`
+//   -`(?1, ?0): Trait` -canonicalize-> `exists<^0, ^1> (^0, ^1): Trait`
+//     - COINDUCTIVE CYCLE OK (^0 = u32, ^1 = u32 -apply-> ?1 = u32, ?0 = u32)
+//   - `(): ConstrainToU32<?0>` -canonicalize-> `exists<^0> (): ConstrainToU32<^0>`
+//     - OK (^0 = u32 -apply-> ?1 = u32)
+//   - OK (?0 = u32, ?1 = u32 -canonicalize-> ^0 = u32, ^1 = u32)
+//   - coinductive cycle with provisional result == final result, DONE
+#![feature(rustc_attrs)]
+#[rustc_coinductive]
+trait Trait {}
+
+impl<T, U> Trait for (T, U)
+where
+    (U, T): Trait,
+    (): ConstrainToU32<T>,
+{}
+
+trait ConstrainToU32<T> {}
+impl ConstrainToU32<u32> for () {}
+
+fn impls_trait<T, U>()
+where
+    (T, U): Trait,
+{}
+
+fn main() {
+    impls_trait::<_, _>();
+}
-- 
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