Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/tests/ui/higher-rank-trait-bounds/issue-57639.rs b/tests/ui/higher-rank-trait-bounds/issue-57639.rs
new file mode 100644
index 000000000..392e7233b
--- /dev/null
+++ b/tests/ui/higher-rank-trait-bounds/issue-57639.rs
@@ -0,0 +1,29 @@
+// Regression test for #57639:
+//
+// In the move to universes, this test stopped working. The problem
+// was that when the trait solver was asked to prove `for<'a> T::Item:
+// Foo<'a>` as part of WF checking, it wound up "eagerly committing"
+// to the where clause, which says that `T::Item: Foo<'a>`, but it
+// should instead have been using the bound found in the trait
+// declaration. Pre-universe, this used to work out ok because we got
+// "eager errors" due to the leak check.
+//
+// See [this comment on GitHub][c] for more details.
+//
+// check-pass
+//
+// [c]: https://github.com/rust-lang/rust/issues/57639#issuecomment-455685861
+
+trait Foo<'a> {}
+
+trait Bar {
+    type Item: for<'a> Foo<'a>;
+}
+
+fn foo<'a, T>(_: T)
+where
+    T: Bar,
+    T::Item: Foo<'a>,
+{}
+
+fn main() { }