Auto merge of #92805 - BoxyUwU:revert-lazy-anon-const-substs, r=lcnr

partially revertish `lazily "compute" anon const default substs`

reverts #87280 except for some of the changes around `ty::Unevaluated` having a visitor and a generic for promoted
why revert: <https://github.com/rust-lang/rust/pull/92805#issuecomment-1010736049>

r? `@lcnr`

10 files changed, 34 insertions, 59 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 290426aa827..d174e00df77 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -444,7 +444,7 @@ fn orphan_check_trait_ref<'tcx>(
 ) -> Result<(), OrphanCheckErr<'tcx>> {
     debug!("orphan_check_trait_ref(trait_ref={:?}, in_crate={:?})", trait_ref, in_crate);
 
-    if trait_ref.needs_infer() && trait_ref.definitely_needs_subst(tcx) {
+    if trait_ref.needs_infer() && trait_ref.needs_subst() {
         bug!(
             "can't orphan check a trait ref with both params and inference variables {:?}",
             trait_ref
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
index 0ea3a18ca34..5a69c5d50ff 100644
--- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
+++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
@@ -84,7 +84,7 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
                     Node::Leaf(leaf) => {
                         if leaf.has_infer_types_or_consts() {
                             failure_kind = FailureKind::MentionsInfer;
-                        } else if leaf.definitely_has_param_types_or_consts(tcx) {
+                        } else if leaf.has_param_types_or_consts() {
                             failure_kind = cmp::min(failure_kind, FailureKind::MentionsParam);
                         }
 
@@ -93,7 +93,7 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
                     Node::Cast(_, _, ty) => {
                         if ty.has_infer_types_or_consts() {
                             failure_kind = FailureKind::MentionsInfer;
-                        } else if ty.definitely_has_param_types_or_consts(tcx) {
+                        } else if ty.has_param_types_or_consts() {
                             failure_kind = cmp::min(failure_kind, FailureKind::MentionsParam);
                         }
 
@@ -149,7 +149,7 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
     // See #74595 for more details about this.
     let concrete = infcx.const_eval_resolve(param_env, uv.expand(), Some(span));
 
-    if concrete.is_ok() && uv.substs(infcx.tcx).definitely_has_param_types_or_consts(infcx.tcx) {
+    if concrete.is_ok() && uv.substs.has_param_types_or_consts() {
         match infcx.tcx.def_kind(uv.def.did) {
             DefKind::AnonConst | DefKind::InlineConst => {
                 let mir_body = infcx.tcx.mir_for_ctfe_opt_const_arg(uv.def);
@@ -196,7 +196,7 @@ impl<'tcx> AbstractConst<'tcx> {
     ) -> Result<Option<AbstractConst<'tcx>>, ErrorReported> {
         let inner = tcx.thir_abstract_const_opt_const_arg(uv.def)?;
         debug!("AbstractConst::new({:?}) = {:?}", uv, inner);
-        Ok(inner.map(|inner| AbstractConst { inner, substs: uv.substs(tcx) }))
+        Ok(inner.map(|inner| AbstractConst { inner, substs: uv.substs }))
     }
 
     pub fn from_const(
@@ -271,7 +271,6 @@ impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
         struct IsThirPolymorphic<'a, 'tcx> {
             is_poly: bool,
             thir: &'a thir::Thir<'tcx>,
-            tcx: TyCtxt<'tcx>,
         }
 
         use thir::visit;
@@ -281,25 +280,25 @@ impl<'a, 'tcx> AbstractConstBuilder<'a, 'tcx> {
             }
 
             fn visit_expr(&mut self, expr: &thir::Expr<'tcx>) {
-                self.is_poly |= expr.ty.definitely_has_param_types_or_consts(self.tcx);
+                self.is_poly |= expr.ty.has_param_types_or_consts();
                 if !self.is_poly {
                     visit::walk_expr(self, expr)
                 }
             }
 
             fn visit_pat(&mut self, pat: &thir::Pat<'tcx>) {
-                self.is_poly |= pat.ty.definitely_has_param_types_or_consts(self.tcx);
+                self.is_poly |= pat.ty.has_param_types_or_consts();
                 if !self.is_poly {
                     visit::walk_pat(self, pat);
                 }
             }
 
             fn visit_const(&mut self, ct: &'tcx ty::Const<'tcx>) {
-                self.is_poly |= ct.definitely_has_param_types_or_consts(self.tcx);
+                self.is_poly |= ct.has_param_types_or_consts();
             }
         }
 
-        let mut is_poly_vis = IsThirPolymorphic { is_poly: false, thir: body, tcx };
+        let mut is_poly_vis = IsThirPolymorphic { is_poly: false, thir: body };
         visit::walk_expr(&mut is_poly_vis, &body[body_id]);
         debug!("AbstractConstBuilder: is_poly={}", is_poly_vis.is_poly);
         if !is_poly_vis.is_poly {
diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index 42e3f0db15e..346590a2de2 100644
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -538,7 +538,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                         Err(NotConstEvaluatable::MentionsInfer) => {
                             pending_obligation.stalled_on.clear();
                             pending_obligation.stalled_on.extend(
-                                uv.substs(infcx.tcx)
+                                uv.substs
                                     .iter()
                                     .filter_map(TyOrConstInferVar::maybe_from_generic_arg),
                             );
@@ -583,7 +583,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                                 Err(ErrorHandled::TooGeneric) => {
                                     stalled_on.extend(
                                         unevaluated
-                                            .substs(tcx)
+                                            .substs
                                             .iter()
                                             .filter_map(TyOrConstInferVar::maybe_from_generic_arg),
                                     );
@@ -654,7 +654,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
         stalled_on: &mut Vec<TyOrConstInferVar<'tcx>>,
     ) -> ProcessResult<PendingPredicateObligation<'tcx>, FulfillmentErrorCode<'tcx>> {
         let infcx = self.selcx.infcx();
-        if obligation.predicate.is_known_global() {
+        if obligation.predicate.is_global() {
             // no type variables present, can use evaluation for better caching.
             // FIXME: consider caching errors too.
             if infcx.predicate_must_hold_considering_regions(obligation) {
@@ -708,7 +708,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
     ) -> ProcessResult<PendingPredicateObligation<'tcx>, FulfillmentErrorCode<'tcx>> {
         let tcx = self.selcx.tcx();
 
-        if obligation.predicate.is_global(tcx) {
+        if obligation.predicate.is_global() {
             // no type variables present, can use evaluation for better caching.
             // FIXME: consider caching errors too.
             if self.selcx.infcx().predicate_must_hold_considering_regions(obligation) {
@@ -756,15 +756,14 @@ fn substs_infer_vars<'a, 'tcx>(
     selcx: &mut SelectionContext<'a, 'tcx>,
     substs: ty::Binder<'tcx, SubstsRef<'tcx>>,
 ) -> impl Iterator<Item = TyOrConstInferVar<'tcx>> {
-    let tcx = selcx.tcx();
     selcx
         .infcx()
         .resolve_vars_if_possible(substs)
         .skip_binder() // ok because this check doesn't care about regions
         .iter()
         .filter(|arg| arg.has_infer_types_or_consts())
-        .flat_map(move |arg| {
-            let mut walker = arg.walk(tcx);
+        .flat_map(|arg| {
+            let mut walker = arg.walk();
             while let Some(c) = walker.next() {
                 if !c.has_infer_types_or_consts() {
                     walker.visited.remove(&c);
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index a8f26982d2e..23f534858b8 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -465,7 +465,7 @@ fn subst_and_check_impossible_predicates<'tcx>(
     debug!("subst_and_check_impossible_predicates(key={:?})", key);
 
     let mut predicates = tcx.predicates_of(key.0).instantiate(tcx, key.1).predicates;
-    predicates.retain(|predicate| !predicate.definitely_needs_subst(tcx));
+    predicates.retain(|predicate| !predicate.needs_subst());
     let result = impossible_predicates(tcx, predicates);
 
     debug!("subst_and_check_impossible_predicates(key={:?}) = {:?}", key, result);
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index 4e84849bc1e..185d64eab70 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -274,7 +274,7 @@ fn predicate_references_self<'tcx>(
     (predicate, sp): (ty::Predicate<'tcx>, Span),
 ) -> Option<Span> {
     let self_ty = tcx.types.self_param;
-    let has_self_ty = |arg: &GenericArg<'tcx>| arg.walk(tcx).any(|arg| arg == self_ty.into());
+    let has_self_ty = |arg: &GenericArg<'_>| arg.walk().any(|arg| arg == self_ty.into());
     match predicate.kind().skip_binder() {
         ty::PredicateKind::Trait(ref data) => {
             // In the case of a trait predicate, we can skip the "self" type.
@@ -768,9 +768,6 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeFoldable<'tcx>>(
 
     impl<'tcx> TypeVisitor<'tcx> for IllegalSelfTypeVisitor<'tcx> {
         type BreakTy = ();
-        fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-            Some(self.tcx)
-        }
 
         fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
             match t.kind() {
diff --git a/compiler/rustc_trait_selection/src/traits/query/normalize.rs b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
index 26bacf787e2..81ee22c1de4 100644
--- a/compiler/rustc_trait_selection/src/traits/query/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
@@ -77,11 +77,8 @@ impl<'cx, 'tcx> AtExt<'tcx> for At<'cx, 'tcx> {
         // The rest of the code is already set up to be lazy about replacing bound vars,
         // and only when we actually have to normalize.
         if value.has_escaping_bound_vars() {
-            let mut max_visitor = MaxEscapingBoundVarVisitor {
-                tcx: self.infcx.tcx,
-                outer_index: ty::INNERMOST,
-                escaping: 0,
-            };
+            let mut max_visitor =
+                MaxEscapingBoundVarVisitor { outer_index: ty::INNERMOST, escaping: 0 };
             value.visit_with(&mut max_visitor);
             if max_visitor.escaping > 0 {
                 normalizer.universes.extend((0..max_visitor.escaping).map(|_| None));
@@ -104,18 +101,13 @@ impl<'cx, 'tcx> AtExt<'tcx> for At<'cx, 'tcx> {
 }
 
 /// Visitor to find the maximum escaping bound var
-struct MaxEscapingBoundVarVisitor<'tcx> {
-    tcx: TyCtxt<'tcx>,
+struct MaxEscapingBoundVarVisitor {
     // The index which would count as escaping
     outer_index: ty::DebruijnIndex,
     escaping: usize,
 }
 
-impl<'tcx> TypeVisitor<'tcx> for MaxEscapingBoundVarVisitor<'tcx> {
-    fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-        Some(self.tcx)
-    }
-
+impl<'tcx> TypeVisitor<'tcx> for MaxEscapingBoundVarVisitor {
     fn visit_binder<T: TypeFoldable<'tcx>>(
         &mut self,
         t: &ty::Binder<'tcx, T>,
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index b7fc578ea3b..36af78b66ed 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -997,7 +997,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 let tail_field_ty = tcx.type_of(tail_field.did);
 
                 let mut unsizing_params = GrowableBitSet::new_empty();
-                for arg in tail_field_ty.walk(tcx) {
+                for arg in tail_field_ty.walk() {
                     if let Some(i) = maybe_unsizing_param_idx(arg) {
                         unsizing_params.insert(i);
                     }
@@ -1006,7 +1006,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 // Ensure none of the other fields mention the parameters used
                 // in unsizing.
                 for field in prefix_fields {
-                    for arg in tcx.type_of(field.did).walk(tcx) {
+                    for arg in tcx.type_of(field.did).walk() {
                         if let Some(i) = maybe_unsizing_param_idx(arg) {
                             unsizing_params.remove(i);
                         }
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 32518ffb071..1414c742635 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -527,7 +527,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     // contain the "'static" lifetime (any other lifetime
                     // would either be late-bound or local), so it is guaranteed
                     // to outlive any other lifetime
-                    if pred.0.is_global(self.infcx.tcx) && !pred.0.has_late_bound_regions() {
+                    if pred.0.is_global() && !pred.0.has_late_bound_regions() {
                         Ok(EvaluatedToOk)
                     } else {
                         Ok(EvaluatedToOkModuloRegions)
@@ -712,12 +712,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         mut obligation: TraitObligation<'tcx>,
     ) -> Result<EvaluationResult, OverflowError> {
         if !self.intercrate
-            && obligation.is_global(self.tcx())
-            && obligation
-                .param_env
-                .caller_bounds()
-                .iter()
-                .all(|bound| bound.definitely_needs_subst(self.tcx()))
+            && obligation.is_global()
+            && obligation.param_env.caller_bounds().iter().all(|bound| bound.needs_subst())
         {
             // If a param env has no global bounds, global obligations do not
             // depend on its particular value in order to work, so we can clear
@@ -1537,7 +1533,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // the param_env so that it can be given the lowest priority. See
         // #50825 for the motivation for this.
         let is_global = |cand: &ty::PolyTraitPredicate<'tcx>| {
-            cand.is_global(self.infcx.tcx) && !cand.has_late_bound_regions()
+            cand.is_global() && !cand.has_late_bound_regions()
         };
 
         // (*) Prefer `BuiltinCandidate { has_nested: false }`, `PointeeCandidate`,
diff --git a/compiler/rustc_trait_selection/src/traits/structural_match.rs b/compiler/rustc_trait_selection/src/traits/structural_match.rs
index 45960bd3653..2ed7a8f9cf9 100644
--- a/compiler/rustc_trait_selection/src/traits/structural_match.rs
+++ b/compiler/rustc_trait_selection/src/traits/structural_match.rs
@@ -130,9 +130,6 @@ impl<'a, 'tcx> Search<'a, 'tcx> {
 
 impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
     type BreakTy = NonStructuralMatchTy<'tcx>;
-    fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-        Some(self.tcx())
-    }
 
     fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         debug!("Search visiting ty: {:?}", ty);
diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs
index 72ffe9085cb..f6e98f42710 100644
--- a/compiler/rustc_trait_selection/src/traits/wf.rs
+++ b/compiler/rustc_trait_selection/src/traits/wf.rs
@@ -132,11 +132,10 @@ pub fn predicate_obligations<'a, 'tcx>(
             wf.compute(b.into());
         }
         ty::PredicateKind::ConstEvaluatable(uv) => {
-            let substs = uv.substs(wf.tcx());
-            let obligations = wf.nominal_obligations(uv.def.did, substs);
+            let obligations = wf.nominal_obligations(uv.def.did, uv.substs);
             wf.out.extend(obligations);
 
-            for arg in substs.iter() {
+            for arg in uv.substs.iter() {
                 wf.compute(arg);
             }
         }
@@ -429,7 +428,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 
     /// Pushes all the predicates needed to validate that `ty` is WF into `out`.
     fn compute(&mut self, arg: GenericArg<'tcx>) {
-        let mut walker = arg.walk(self.tcx());
+        let mut walker = arg.walk();
         let param_env = self.param_env;
         let depth = self.recursion_depth;
         while let Some(arg) = walker.next() {
@@ -443,16 +442,12 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                 GenericArgKind::Const(constant) => {
                     match constant.val {
                         ty::ConstKind::Unevaluated(uv) => {
-                            assert!(uv.promoted.is_none());
-                            let substs = uv.substs(self.tcx());
-
-                            let obligations = self.nominal_obligations(uv.def.did, substs);
+                            let obligations = self.nominal_obligations(uv.def.did, uv.substs);
                             self.out.extend(obligations);
 
-                            let predicate = ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(
-                                ty::Unevaluated::new(uv.def, substs),
-                            ))
-                            .to_predicate(self.tcx());
+                            let predicate =
+                                ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
+                                    .to_predicate(self.tcx());
                             let cause = self.cause(traits::MiscObligation);
                             self.out.push(traits::Obligation::with_depth(
                                 cause,