1 files changed, 51 insertions, 0 deletions
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.rs b/tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.rs
new file mode 100644
index 000000000..35a864b88
--- /dev/null
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.rs
@@ -0,0 +1,51 @@
+// Test where we fail to approximate due to demanding a postdom
+// relationship between our upper bounds.
+
+// compile-flags:-Zverbose
+
+#![feature(rustc_attrs)]
+
+use std::cell::Cell;
+
+// Callee knows that:
+//
+// 'x: 'a
+// 'x: 'b
+// 'c: 'y
+//
+// we have to prove that `'x: 'y`. We currently can only approximate
+// via a postdominator -- hence we fail to choose between `'a` and
+// `'b` here and report the error in the closure.
+fn establish_relationships<'a, 'b, 'c, F>(
+    _cell_a: Cell<&'a u32>,
+    _cell_b: Cell<&'b u32>,
+    _cell_c: Cell<&'c u32>,
+    _closure: F,
+) where
+    F: for<'x, 'y> FnMut(
+        Cell<&'a &'x u32>, // shows that 'x: 'a
+        Cell<&'b &'x u32>, // shows that 'x: 'b
+        Cell<&'y &'c u32>, // shows that 'c: 'y
+        Cell<&'x u32>,
+        Cell<&'y u32>,
+    ),
+{
+}
+
+fn demand_y<'x, 'y>(_cell_x: Cell<&'x u32>, _cell_y: Cell<&'y u32>, _y: &'y u32) {}
+
+#[rustc_regions]
+fn supply<'a, 'b, 'c>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>, cell_c: Cell<&'c u32>) {
+    establish_relationships(
+        cell_a,
+        cell_b,
+        cell_c,
+        |_outlives1, _outlives2, _outlives3, x, y| {
+            // Only works if 'x: 'y:
+            let p = x.get();
+            demand_y(x, y, p) //~ ERROR
+        },
+    );
+}
+
+fn main() {}