Make sure that non-pretty-printing usages are using the correct elaborator

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -26,7 +26,6 @@
     RegionVariableOrigin,
 };
 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
-use rustc_middle::traits::util::supertraits;
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::fast_reject::{simplify_type, TreatParams};
 use rustc_middle::ty::print::{with_crate_prefix, with_forced_trimmed_paths};
@@ -40,7 +39,7 @@
 use rustc_trait_selection::traits::error_reporting::on_unimplemented::TypeErrCtxtExt as _;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
 use rustc_trait_selection::traits::{
-    FulfillmentError, Obligation, ObligationCause, ObligationCauseCode,
+    supertraits, FulfillmentError, Obligation, ObligationCause, ObligationCauseCode,
 };
 use std::borrow::Cow;
 

compiler/rustc_infer/src/traits/util.rs

@@ -2,7 +2,7 @@
 
 use crate::infer::outlives::components::{push_outlives_components, Component};
 use crate::traits::{self, Obligation, PredicateObligation};
-use rustc_data_structures::fx::{FxHashSet};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
@@ -423,7 +423,7 @@ fn next(&mut self) -> Option<Self::Item> {
 pub fn supertraits<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_ref: ty::PolyTraitRef<'tcx>,
-) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> {
+) -> FilterToTraits<Elaborator<'tcx, ty::Predicate<'tcx>>> {
     elaborate(tcx, [trait_ref.to_predicate(tcx)]).filter_only_self().filter_to_traits()
 }
 

compiler/rustc_lint/src/deref_into_dyn_supertrait.rs

@@ -4,9 +4,10 @@
 };
 
 use rustc_hir as hir;
-use rustc_middle::{traits::util::supertraits, ty};
+use rustc_middle::ty;
 use rustc_session::lint::FutureIncompatibilityReason;
 use rustc_span::sym;
+use rustc_trait_selection::traits::supertraits;
 
 declare_lint! {
     /// The `deref_into_dyn_supertrait` lint is output whenever there is a use of the

compiler/rustc_middle/src/traits/util.rs

@@ -3,9 +3,10 @@
 use crate::ty::{PolyTraitRef, TyCtxt};
 
 /// Given a PolyTraitRef, get the PolyTraitRefs of the trait's (transitive) supertraits.
-///
-/// A simplified version of the same function at `rustc_infer::traits::util::supertraits`.
-pub fn supertraits<'tcx>(
+/// This only exists in `rustc_middle` because the more powerful elaborator depends on
+/// `rustc_infer` for elaborating outlives bounds -- this should only be used for pretty
+/// printing.
+pub fn supertraits_for_pretty_printing<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_ref: PolyTraitRef<'tcx>,
 ) -> impl Iterator<Item = PolyTraitRef<'tcx>> {

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1,6 +1,7 @@
 use crate::mir::interpret::{AllocRange, GlobalAlloc, Pointer, Provenance, Scalar};
 use crate::query::IntoQueryParam;
 use crate::query::Providers;
+use crate::traits::util::supertraits_for_pretty_printing;
 use crate::ty::{
     self, ConstInt, ParamConst, ScalarInt, Term, TermKind, Ty, TyCtxt, TypeFoldable,
     TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
@@ -1166,14 +1167,14 @@ fn insert_trait_and_projection(
                 entry.has_fn_once = true;
                 return;
             } else if Some(trait_def_id) == self.tcx().lang_items().fn_mut_trait() {
-                let super_trait_ref = crate::traits::util::supertraits(self.tcx(), trait_ref)
+                let super_trait_ref = supertraits_for_pretty_printing(self.tcx(), trait_ref)
                     .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
                     .unwrap();
 
                 fn_traits.entry(super_trait_ref).or_default().fn_mut_trait_ref = Some(trait_ref);
                 return;
             } else if Some(trait_def_id) == self.tcx().lang_items().fn_trait() {
-                let super_trait_ref = crate::traits::util::supertraits(self.tcx(), trait_ref)
+                let super_trait_ref = supertraits_for_pretty_printing(self.tcx(), trait_ref)
                     .find(|super_trait_ref| super_trait_ref.def_id() == fn_once_trait)
                     .unwrap();