From e54bc1c5ff7f17aa38632597719141688ee24242 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 23 May 2023 03:33:43 +0000
Subject: [PATCH] Don't ICE on RPITIT when promoting trait preds to associated
 type bounds

---
 .../rustc_hir_analysis/src/collect/predicates_of.rs   |  2 ++
 .../return-type-notation/supertrait-bound.rs          | 11 +++++++++++
 .../return-type-notation/supertrait-bound.stderr      | 11 +++++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 tests/ui/async-await/return-type-notation/supertrait-bound.rs
 create mode 100644 tests/ui/async-await/return-type-notation/supertrait-bound.stderr

diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index a33990813b8..e5b5dae551e 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -427,6 +427,8 @@ pub(super) fn explicit_predicates_of<'tcx>(
             //   supertrait).
             if let ty::Alias(ty::Projection, projection) = ty.kind() {
                 projection.substs == trait_identity_substs
+                    // FIXME(return_type_notation): This check should be more robust
+                    && !tcx.is_impl_trait_in_trait(projection.def_id)
                     && tcx.associated_item(projection.def_id).container_id(tcx)
                         == def_id.to_def_id()
             } else {
diff --git a/tests/ui/async-await/return-type-notation/supertrait-bound.rs b/tests/ui/async-await/return-type-notation/supertrait-bound.rs
new file mode 100644
index 00000000000..19bcfe3046b
--- /dev/null
+++ b/tests/ui/async-await/return-type-notation/supertrait-bound.rs
@@ -0,0 +1,11 @@
+// check-pass
+
+#![feature(return_position_impl_trait_in_trait, return_type_notation)]
+//~^ WARN the feature `return_type_notation` is incomplete and may not be safe to use
+
+trait IntFactory {
+    fn stream(&self) -> impl Iterator<Item = i32>;
+}
+trait SendIntFactory: IntFactory<stream(): Send> + Send {}
+
+fn main() {}
diff --git a/tests/ui/async-await/return-type-notation/supertrait-bound.stderr b/tests/ui/async-await/return-type-notation/supertrait-bound.stderr
new file mode 100644
index 00000000000..c8cec4946b4
--- /dev/null
+++ b/tests/ui/async-await/return-type-notation/supertrait-bound.stderr
@@ -0,0 +1,11 @@
+warning: the feature `return_type_notation` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/supertrait-bound.rs:3:49
+   |
+LL | #![feature(return_position_impl_trait_in_trait, return_type_notation)]
+   |                                                 ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #109417 <https://github.com/rust-lang/rust/issues/109417> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+