1 files changed, 40 insertions, 0 deletions
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.rs b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.rs
new file mode 100644
index 000000000..372209075
--- /dev/null
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.rs
@@ -0,0 +1,40 @@
+// Test a case where we are trying to prove `'x: 'y` and are forced to
+// approximate the shorter end-point (`'y`) to with `'static`. This is
+// because `'y` is higher-ranked but we know of no relations to other
+// regions. Note that `'static` shows up in the stderr output as `'0`.
+
+// compile-flags:-Zverbose
+
+#![feature(rustc_attrs)]
+
+use std::cell::Cell;
+
+// Callee knows that:
+//
+// 'x: 'a
+//
+// so the only way we can ensure that `'x: 'y` is to show that
+// `'a: 'static`.
+fn establish_relationships<'a, 'b, F>(_cell_a: &Cell<&'a u32>, _cell_b: &Cell<&'b u32>, _closure: F)
+where
+    F: for<'x, 'y> FnMut(
+        &Cell<&'a &'x u32>, // shows that 'x: 'a
+        &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>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
+    establish_relationships(&cell_a, &cell_b, |_outlives, x, y| {
+        //~^ ERROR borrowed data escapes outside of function
+
+        // Only works if 'x: 'y:
+        demand_y(x, y, x.get())
+    });
+}
+
+fn main() {}