From b78c8acf1e22f904cef325d6fab04a2eab00dc56 Mon Sep 17 00:00:00 2001
From: Chayim Refael Friedman <chayimfr@gmail.com>
Date: Fri, 21 Aug 2026 06:22:56 +0300
Subject: [PATCH] Provide a `supertrait_def_ids()` function in rustc_type_ir's
 interner

rust-analyzer has a query for this, so we want to use it there. I don't know if using a query for this will be a perf win for rustc, but rust-analyzer already has this query for other reasons, so it feels a waste to not use it.
---
 compiler/rustc_middle/src/ty/context/impl_interner.rs     | 4 ++++
 compiler/rustc_next_trait_solver/src/solve/trait_goals.rs | 3 ++-
 compiler/rustc_type_ir/src/elaborate.rs                   | 3 +++
 compiler/rustc_type_ir/src/interner.rs                    | 3 +++
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_middle/src/ty/context/impl_interner.rs b/compiler/rustc_middle/src/ty/context/impl_interner.rs
index 2444f8513b8e4..7f10cb1994ee1 100644
--- a/compiler/rustc_middle/src/ty/context/impl_interner.rs
+++ b/compiler/rustc_middle/src/ty/context/impl_interner.rs
@@ -430,6 +430,10 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         self.impl_super_outlives(impl_def_id)
     }
 
+    fn supertrait_def_ids(self, trait_def_id: DefId) -> impl Iterator<Item = DefId> {
+        rustc_type_ir::elaborate::supertrait_def_ids(self, trait_def_id)
+    }
+
     fn impl_is_const(self, def_id: DefId) -> bool {
         debug_assert_matches!(self.def_kind(def_id), DefKind::Impl { of_trait: true });
         self.is_conditionally_const(def_id)
diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index 335263b1d169d..f9793fb6e417c 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -1109,7 +1109,8 @@ where
             .auto_traits()
             .into_iter()
             .chain(a_data.principal_def_id().into_iter().flat_map(|principal_def_id| {
-                elaborate::supertrait_def_ids(self.cx(), principal_def_id)
+                self.cx()
+                    .supertrait_def_ids(principal_def_id)
                     .filter(|def_id| self.cx().trait_is_auto(*def_id))
             }))
             .collect();
diff --git a/compiler/rustc_type_ir/src/elaborate.rs b/compiler/rustc_type_ir/src/elaborate.rs
index 912a5ac90f632..2110521eae764 100644
--- a/compiler/rustc_type_ir/src/elaborate.rs
+++ b/compiler/rustc_type_ir/src/elaborate.rs
@@ -318,6 +318,9 @@ impl<I: Interner, O: Elaboratable<I>> Iterator for Elaborator<I, O> {
 /// does not compute the full elaborated super-predicates but just the set of def-ids. It is used
 /// to identify which traits may define a given associated type to help avoid cycle errors,
 /// and to make size estimates for vtable layout computation.
+///
+/// rust-analyzer has a query for this, so don't use this function there.
+#[cfg(feature = "nightly")]
 pub fn supertrait_def_ids<I: Interner>(
     cx: I,
     trait_def_id: I::TraitId,
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index 49899147d5747..5a14b60e1d296 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -359,6 +359,9 @@ pub trait Interner:
         impl_def_id: Self::ImplId,
     ) -> ty::EarlyBinder<Self, impl IntoIterator<Item = Self::Clause>>;
 
+    fn supertrait_def_ids(self, trait_def_id: Self::TraitId)
+    -> impl Iterator<Item = Self::TraitId>;
+
     fn impl_is_const(self, def_id: Self::ImplId) -> bool;
     fn fn_is_const(self, def_id: Self::FunctionId) -> bool;
     fn closure_is_const(self, def_id: Self::ClosureId) -> bool;