Provide a supertrait_def_ids() function in rustc_type_ir's interner

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)

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();

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,

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;