Auto merge of #114130 - GuillaumeGomez:rollup-69ihuaj, r=GuillaumeGomez

Rollup of 7 pull requests

Successful merges:

 - #114032 (typos)
 - #114059 (rustdoc: fix cross-crate `impl Sized` & `impl ?Sized`)
 - #114088 (Bump syn dependency)
 - #114091 (docs: fmt::Debug*: Fix comments for finish method.)
 - #114109 (Docs: Fix URL for `rmatches`)
 - #114117 (Restore region uniquification in the new solver 🎉  )
 - #114123 (Turns out opaque types can have hidden types registered during mir validation)

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 32 insertions, 0 deletions

diff --git a/tests/ui/traits/new-solver/dont-loop-fulfill-on-region-constraints.rs b/tests/ui/traits/new-solver/dont-loop-fulfill-on-region-constraints.rs
new file mode 100644
index 00000000000..b241e3bf865
--- /dev/null
+++ b/tests/ui/traits/new-solver/dont-loop-fulfill-on-region-constraints.rs
@@ -0,0 +1,32 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+trait Eq<'a, 'b, T> {}
+
+trait Ambig {}
+impl Ambig for () {}
+
+impl<'a, T> Eq<'a, 'a, T> for () where T: Ambig {}
+
+fn eq<'a, 'b, T>(t: T)
+where
+    (): Eq<'a, 'b, T>,
+{
+}
+
+fn test<'r>() {
+    let mut x = Default::default();
+
+    // When we evaluate `(): Eq<'r, 'r, ?0>` we uniquify the regions.
+    // That leads us to evaluate `(): Eq<'?0, '?1, ?0>`. The response of this
+    // will be ambiguous (because `?0: Ambig` is ambig) and also not an "identity"
+    // response, since the region constraints will contain `'?0 == '?1` (so
+    // `is_changed` will return true). Since it's both ambig and changed,
+    // fulfillment will both re-register the goal AND loop again. This hits the
+    // overflow limit. This should neither be considered overflow, nor ICE.
+    eq::<'r, 'r, _>(x);
+
+    x = ();
+}
+
+fn main() {}