Auto merge of #147299 - compiler-errors:hr-norm, r=jackh726

Don't normalize higher-ranked assumptions if they're not used

See the comment in the code.

Normalizing these assumptions may cause us to register things like new placeholder outlives obligations that cause higher-ranked lifetime errors, and this is problematic if we're not even using these assumptions in borrowck.

Fixes rust-lang/rust#147244
Fixes rust-lang/rust#147285

1 files changed, 38 insertions, 0 deletions

diff --git a/tests/ui/async-await/higher-ranked-normalize-assumptions-2.rs b/tests/ui/async-await/higher-ranked-normalize-assumptions-2.rs
new file mode 100644
index 00000000000..410d4e503b7
--- /dev/null
+++ b/tests/ui/async-await/higher-ranked-normalize-assumptions-2.rs
@@ -0,0 +1,38 @@
+//@ revisions: stock hr
+//@[hr] compile-flags: -Zhigher-ranked-assumptions
+//@ edition: 2024
+//@ check-pass
+
+// Test that we don't normalize the higher-ranked assumptions of an auto trait goal
+// unless we have `-Zhigher-ranked-assumptions`, since obligations that result from
+// this normalization may lead to higher-ranked lifetime errors when the flag is not
+// enabled.
+
+// Regression test for <https://github.com/rust-lang/rust/issues/147244>.
+
+pub fn a() -> impl Future + Send {
+    async {
+        let queries = core::iter::empty().map(Thing::f);
+        b(queries).await;
+    }
+}
+
+async fn b(queries: impl IntoIterator) {
+    c(queries).await;
+}
+
+fn c<'a, I>(_queries: I) -> impl Future
+where
+    I: IntoIterator,
+    I::IntoIter: 'a,
+{
+    async {}
+}
+
+pub struct Thing<'a>(pub &'a ());
+
+impl Thing<'_> {
+    fn f(_: &Self) {}
+}
+
+fn main() {}