From 218caa410aa38c29984be31a5229b9fa717560ee Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:19:13 +0200
Subject: Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 ...ection-one-region-trait-bound-static-closure.rs | 88 ++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.rs

(limited to 'tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.rs')

diff --git a/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.rs b/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.rs
new file mode 100644
index 000000000..7c0a3bc72
--- /dev/null
+++ b/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.rs
@@ -0,0 +1,88 @@
+// Test cases where we constrain `<T as Anything<'b>>::AssocType` to
+// outlive `'static`. In this case, we don't get any errors, and in fact
+// we don't even propagate constraints from the closures to the callers.
+
+// compile-flags:-Zverbose
+// check-pass
+
+#![allow(warnings)]
+#![feature(rustc_attrs)]
+
+use std::cell::Cell;
+
+trait Anything<'a> {
+    type AssocType: 'static;
+}
+
+fn with_signature<'a, T, F>(cell: Cell<&'a ()>, t: T, op: F)
+where
+    F: FnOnce(Cell<&'a ()>, T),
+{
+    op(cell, t)
+}
+
+fn require<'a, 'b, T>(_cell: Cell<&'a ()>, _t: T)
+where
+    T: Anything<'b>,
+    T::AssocType: 'a,
+{
+}
+
+#[rustc_regions]
+fn no_relationships_late<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
+where
+    T: Anything<'b>,
+{
+    with_signature(cell, t, |cell, t| require(cell, t));
+}
+
+#[rustc_regions]
+fn no_relationships_early<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
+where
+    T: Anything<'b>,
+    'a: 'a,
+{
+    with_signature(cell, t, |cell, t| require(cell, t));
+}
+
+#[rustc_regions]
+fn projection_outlives<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
+where
+    T: Anything<'b>,
+    T::AssocType: 'a,
+{
+    // This error is unfortunate. This code ought to type-check: we
+    // are projecting `<T as Anything<'b>>::AssocType`, and we know
+    // that this outlives `'a` because of the where-clause. However,
+    // the way the region checker works, we don't register this
+    // outlives obligation, and hence we get an error: this is because
+    // what we see is a projection like `<T as
+    // Anything<'?0>>::AssocType`, and we don't yet know if `?0` will
+    // equal `'b` or not, so we ignore the where-clause. Obviously we
+    // can do better here with a more involved verification step.
+
+    with_signature(cell, t, |cell, t| require(cell, t));
+}
+
+#[rustc_regions]
+fn elements_outlive<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
+where
+    T: Anything<'b>,
+    'b: 'a,
+{
+    with_signature(cell, t, |cell, t| require(cell, t));
+}
+
+#[rustc_regions]
+fn one_region<'a, T>(cell: Cell<&'a ()>, t: T)
+where
+    T: Anything<'a>,
+{
+    // Note that in this case the closure still propagates an external
+    // requirement between two variables in its signature, but the
+    // creator maps both those two region variables to `'a` on its
+    // side.
+    with_signature(cell, t, |cell, t| require(cell, t));
+}
+
+fn main() {}
-- 
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