1 files changed, 82 insertions, 0 deletions
diff --git a/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-where-clause.rs b/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-where-clause.rs
new file mode 100644
index 000000000..b80287610
--- /dev/null
+++ b/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-where-clause.rs
@@ -0,0 +1,82 @@
+// Test that we can propagate `T: 'a` obligations to our caller.  See
+// `correct_region` for an explanation of how this test is setup; it's
+// somewhat intricate.
+
+// compile-flags:-Zverbose
+
+#![allow(warnings)]
+#![feature(rustc_attrs)]
+
+use std::cell::Cell;
+
+fn with_signature<'a, T, F>(a: Cell<&'a ()>, b: T, op: F)
+where
+    F: FnOnce(Cell<&'a ()>, T),
+{
+    op(a, b)
+}
+
+fn require<'a, T>(_a: &Cell<&'a ()>, _b: &T)
+where
+    T: 'a,
+{
+}
+
+#[rustc_regions]
+fn no_region<'a, T>(a: Cell<&'a ()>, b: T) {
+    with_signature(a, b, |x, y| {
+        // See `correct_region`, which explains the point of this
+        // test.  The only difference is that, in the case of this
+        // function, there is no where clause *anywhere*, and hence we
+        // get an error (but reported by the closure creator).
+        require(&x, &y)
+        //~^ ERROR the parameter type `T` may not live long enough
+    })
+}
+
+#[rustc_regions]
+fn correct_region<'a, T>(a: Cell<&'a ()>, b: T)
+where
+    T: 'a,
+{
+    with_signature(a, b, |x, y| {
+        // Key point of this test:
+        //
+        // The *closure* is being type-checked with all of its free
+        // regions "universalized". In particular, it does not know
+        // that `x` has the type `Cell<&'a ()>`, but rather treats it
+        // as if the type of `x` is `Cell<&'A ()>`, where `'A` is some
+        // fresh, independent region distinct from the `'a` which
+        // appears in the environment. The call to `require` here
+        // forces us then to prove that `T: 'A`, but the closure
+        // cannot do it on its own. It has to surface this requirement
+        // to its creator (which knows that `'a == 'A`).
+        require(&x, &y)
+    })
+}
+
+#[rustc_regions]
+fn wrong_region<'a, 'b, T>(a: Cell<&'a ()>, b: T)
+where
+    T: 'b,
+{
+    with_signature(a, b, |x, y| {
+        // See `correct_region`
+        require(&x, &y)
+        //~^ ERROR the parameter type `T` may not live long enough
+    })
+}
+
+#[rustc_regions]
+fn outlives_region<'a, 'b, T>(a: Cell<&'a ()>, b: T)
+where
+    T: 'b,
+    'b: 'a,
+{
+    with_signature(a, b, |x, y| {
+        // See `correct_region`
+        require(&x, &y)
+    })
+}
+
+fn main() {}