1 files changed, 43 insertions, 0 deletions
diff --git a/tests/ui/regions/regions-scope-chain-example.rs b/tests/ui/regions/regions-scope-chain-example.rs
new file mode 100644
index 00000000000..2beb20add32
--- /dev/null
+++ b/tests/ui/regions/regions-scope-chain-example.rs
@@ -0,0 +1,43 @@
+// run-pass
+#![allow(dead_code)]
+#![allow(unused_variables)]
+// This is an example where the older inference algorithm failed. The
+// specifics of why it failed are somewhat, but not entirely, tailed
+// to the algorithm. Ultimately the problem is that when computing the
+// mutual supertype of both sides of the `if` it would be faced with a
+// choice of tightening bounds or unifying variables and it took the
+// wrong path. The new algorithm avoids this problem and hence this
+// example typechecks correctly.
+
+// pretty-expanded FIXME #23616
+
+enum ScopeChain<'a> {
+    Link(Scope<'a>),
+    End
+}
+
+type Scope<'a> = &'a ScopeChain<'a>;
+
+struct OuterContext;
+
+struct Context<'a> {
+    foo: &'a OuterContext
+}
+
+impl<'a> Context<'a> {
+    fn foo(&mut self, scope: Scope) {
+        let link = if 1 < 2 {
+            let l = ScopeChain::Link(scope);
+            self.take_scope(&l);
+            l
+        } else {
+            ScopeChain::Link(scope)
+        };
+        self.take_scope(&link);
+    }
+
+    fn take_scope(&mut self, x: Scope) {
+    }
+}
+
+fn main() { }