diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index c464c159c34cd..0bd65aec10f49 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -448,8 +448,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         generic_args.args.insert_many(
             0,
-            (start.as_u32()..end.as_u32()).map(|i| {
-                let id = NodeId::from_u32(i);
+            (start..end).map(|id| {
                 let l = self.lower_lifetime_anon_in_path(id, elided_lifetime_span);
                 GenericArg::Lifetime(l)
             }),
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index c82c7341f0287..f8af9e59f6357 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -338,8 +338,7 @@ fn sccs_info<'tcx>(infcx: &BorrowckInferCtxt<'tcx>, sccs: &ConstraintSccs) {
     let num_components = sccs.num_sccs();
     let mut components = vec![FxIndexSet::default(); num_components];
 
-    for (reg_var_idx, scc_idx) in sccs.scc_indices().iter().enumerate() {
-        let reg_var = ty::RegionVid::from_usize(reg_var_idx);
+    for (reg_var, scc_idx) in sccs.scc_indices().iter_enumerated() {
         let origin = var_to_origin.get(&reg_var).unwrap_or(&RegionCtxt::Unknown);
         components[scc_idx.as_usize()].insert((reg_var, *origin));
     }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
index f52991b369797..d2591139d6edc 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
@@ -3,7 +3,6 @@ use std::collections::hash_map::Entry;
 use rustc_codegen_ssa::mir::debuginfo::{DebugScope, FunctionDebugContext};
 use rustc_codegen_ssa::traits::*;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_index::Idx;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::mir::{Body, SourceScope};
 use rustc_middle::ty::layout::{FnAbiOf, HasTypingEnv};
@@ -43,8 +42,7 @@ pub(crate) fn compute_mir_scopes<'ll, 'tcx>(
     let mut instantiated = DenseBitSet::new_empty(mir.source_scopes.len());
     let mut discriminators = FxHashMap::default();
     // Instantiate all scopes.
-    for idx in 0..mir.source_scopes.len() {
-        let scope = SourceScope::new(idx);
+    for scope in mir.source_scopes.indices() {
         make_mir_scope(
             cx,
             instance,
diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index 34f3c169505ff..bf7b1eefcf68c 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -47,12 +47,9 @@ impl DefPathTable {
         debug_assert_eq!(self.stable_crate_id, def_path_hash.stable_crate_id());
         let local_hash = def_path_hash.local_hash();
 
-        let index = {
-            let index = DefIndex::from(self.index_to_key.len());
-            debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
-            self.index_to_key.push(key);
-            index
-        };
+        let index = self.index_to_key.push(key);
+        debug!("DefPathTable::insert() - {key:?} <-> {index:?}");
+
         self.def_path_hashes.push(local_hash);
         debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
 
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 29a9931696ffa..106e9ca155489 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -606,7 +606,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     // with placeholders, which imply nothing about outlives bounds, and then
     // prove below that the hidden types are well formed.
     let universe = infcx.create_next_universe();
-    let mut idx = 0;
+    let mut idx = ty::BoundVar::ZERO;
     let mapping: FxIndexMap<_, _> = collector
         .types
         .iter()
@@ -623,10 +623,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
                     tcx,
                     ty::Placeholder {
                         universe,
-                        bound: ty::BoundTy {
-                            var: ty::BoundVar::from_usize(idx),
-                            kind: ty::BoundTyKind::Anon,
-                        },
+                        bound: ty::BoundTy { var: idx, kind: ty::BoundTyKind::Anon },
                     },
                 ),
             )
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 8366aa6ec4228..40e2e654b2ea7 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -618,9 +618,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
             RegionVid::from(value_count)..RegionVid::from(self.storage.unification_table.len());
         (
             range.clone(),
-            (range.start.index()..range.end.index())
-                .map(|index| self.storage.var_infos[ty::RegionVid::from(index)].origin)
-                .collect(),
+            (range.start..range.end).map(|index| self.storage.var_infos[index].origin).collect(),
         )
     }
 
diff --git a/compiler/rustc_infer/src/infer/snapshot/fudge.rs b/compiler/rustc_infer/src/infer/snapshot/fudge.rs
index b5d3c26b05e0b..39c8c40ea7d8b 100644
--- a/compiler/rustc_infer/src/infer/snapshot/fudge.rs
+++ b/compiler/rustc_infer/src/infer/snapshot/fudge.rs
@@ -30,11 +30,12 @@ fn const_vars_since_snapshot<'tcx>(
     snapshot_var_len: usize,
 ) -> (Range<ConstVid>, Vec<ConstVariableOrigin>) {
     let range = vars_since_snapshot(table, snapshot_var_len);
+    let range = range.start.vid..range.end.vid;
 
     (
-        range.start.vid..range.end.vid,
-        (range.start.index()..range.end.index())
-            .map(|index| match table.probe_value(ConstVid::from_u32(index)) {
+        range.clone(),
+        range
+            .map(|index| match table.probe_value(index) {
                 ConstVariableValue::Known { value: _ } => {
                     ConstVariableOrigin { param_def_id: None, span: rustc_span::DUMMY_SP }
                 }
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 5a038b27337cf..e7bd2cb27fa75 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -531,12 +531,12 @@ fn write_mir_intro<'tcx>(
 
     // construct a scope tree and write it out
     let mut scope_tree: FxHashMap<SourceScope, Vec<SourceScope>> = Default::default();
-    for (index, scope_data) in body.source_scopes.iter().enumerate() {
+    for (index, scope_data) in body.source_scopes.iter_enumerated() {
         if let Some(parent) = scope_data.parent_scope {
-            scope_tree.entry(parent).or_default().push(SourceScope::new(index));
+            scope_tree.entry(parent).or_default().push(index);
         } else {
             // Only the argument scope has no parent, because it's the root.
-            assert_eq!(index, OUTERMOST_SOURCE_SCOPE.index());
+            assert_eq!(index, OUTERMOST_SOURCE_SCOPE);
         }
     }
 
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 8dc73e4ce85ee..8d6871d2f1fee 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -278,7 +278,7 @@ impl<'tcx> TyCtxt<'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        let shift_bv = |bv: ty::BoundVar| ty::BoundVar::from_usize(bv.as_usize() + bound_vars);
+        let shift_bv = |bv: ty::BoundVar| bv + bound_vars;
         self.replace_escaping_bound_vars_uncached(
             value,
             FnMutDelegate {
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs
index b341b30af6acf..44c7b6a7c9e8d 100644
--- a/compiler/rustc_middle/src/ty/visit.rs
+++ b/compiler/rustc_middle/src/ty/visit.rs
@@ -231,9 +231,7 @@ impl MaxUniverse {
 impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
     fn visit_ty(&mut self, t: Ty<'tcx>) {
         if let ty::Placeholder(placeholder) = t.kind() {
-            self.max_universe = ty::UniverseIndex::from_u32(
-                self.max_universe.as_u32().max(placeholder.universe.as_u32()),
-            );
+            self.max_universe = self.max_universe.max(placeholder.universe);
         }
 
         t.super_visit_with(self)
@@ -241,9 +239,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
 
     fn visit_const(&mut self, c: ty::consts::Const<'tcx>) {
         if let ty::ConstKind::Placeholder(placeholder) = c.kind() {
-            self.max_universe = ty::UniverseIndex::from_u32(
-                self.max_universe.as_u32().max(placeholder.universe.as_u32()),
-            );
+            self.max_universe = self.max_universe.max(placeholder.universe);
         }
 
         c.super_visit_with(self)
@@ -251,9 +247,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
         if let ty::RePlaceholder(placeholder) = r.kind() {
-            self.max_universe = ty::UniverseIndex::from_u32(
-                self.max_universe.as_u32().max(placeholder.universe.as_u32()),
-            );
+            self.max_universe = self.max_universe.max(placeholder.universe);
         }
     }
 }
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 31e22e69111be..fde23413972b6 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -191,7 +191,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
                 let pointer_target = ExprKind::Field {
                     lhs: self.thir.exprs.push(expr),
                     variant_index: FIRST_VARIANT,
-                    name: FieldIdx::from(0u32),
+                    name: FieldIdx::ZERO,
                 };
                 let arg = Expr { temp_lifetime, ty: pin_ty, span, kind: pointer_target };
                 let arg = self.thir.exprs.push(arg);
@@ -226,7 +226,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
                     adt_def: self.tcx.adt_def(pin_did),
                     variant_index: FIRST_VARIANT,
                     args,
-                    fields: Box::new([FieldExpr { name: FieldIdx::from(0u32), expr }]),
+                    fields: Box::new([FieldExpr { name: FieldIdx::ZERO, expr }]),
                     user_ty: None,
                     base: AdtExprBase::None,
                 }));
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index 4405bd82410e3..92d5e152f58e6 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -203,7 +203,7 @@ struct TransformVisitor<'tcx> {
 
 impl<'tcx> TransformVisitor<'tcx> {
     fn insert_none_ret_block(&self, body: &mut Body<'tcx>) -> BasicBlock {
-        let block = BasicBlock::new(body.basic_blocks.len());
+        let block = body.basic_blocks.next_index();
         let source_info = SourceInfo::outermost(body.span);
 
         let none_value = match self.coroutine_kind {
@@ -1193,7 +1193,7 @@ fn insert_panic_block<'tcx>(
     body: &mut Body<'tcx>,
     message: AssertMessage<'tcx>,
 ) -> BasicBlock {
-    let assert_block = BasicBlock::new(body.basic_blocks.len());
+    let assert_block = body.basic_blocks.next_index();
     let kind = TerminatorKind::Assert {
         cond: Operand::Constant(Box::new(ConstOperand {
             span: body.span,
diff --git a/compiler/rustc_mir_transform/src/elaborate_drop.rs b/compiler/rustc_mir_transform/src/elaborate_drop.rs
index fa476f961235d..e3057a2f648f2 100644
--- a/compiler/rustc_mir_transform/src/elaborate_drop.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_drop.rs
@@ -258,17 +258,16 @@ where
     ) -> Vec<(Place<'tcx>, Option<D::Path>)> {
         variant
             .fields
-            .iter()
-            .enumerate()
-            .map(|(i, f)| {
-                let field = FieldIdx::new(i);
-                let subpath = self.elaborator.field_subpath(variant_path, field);
+            .iter_enumerated()
+            .map(|(field_idx, field)| {
+                let subpath = self.elaborator.field_subpath(variant_path, field_idx);
                 let tcx = self.tcx();
 
                 assert_eq!(self.elaborator.typing_env().typing_mode, ty::TypingMode::PostAnalysis);
-                let field_ty = match tcx
-                    .try_normalize_erasing_regions(self.elaborator.typing_env(), f.ty(tcx, args))
-                {
+                let field_ty = match tcx.try_normalize_erasing_regions(
+                    self.elaborator.typing_env(),
+                    field.ty(tcx, args),
+                ) {
                     Ok(t) => t,
                     Err(_) => Ty::new_error(
                         self.tcx(),
@@ -279,7 +278,7 @@ where
                     ),
                 };
 
-                (tcx.mk_place_field(base_place, field, field_ty), subpath)
+                (tcx.mk_place_field(base_place, field_idx, field_ty), subpath)
             })
             .collect()
     }
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 0ab24e48d443c..69e80ed54eae7 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -903,9 +903,9 @@ fn inline_call<'tcx, I: Inliner<'tcx>>(
 
     let mut integrator = Integrator {
         args: &args,
-        new_locals: Local::new(caller_body.local_decls.len())..,
-        new_scopes: SourceScope::new(caller_body.source_scopes.len())..,
-        new_blocks: BasicBlock::new(caller_body.basic_blocks.len())..,
+        new_locals: caller_body.local_decls.next_index()..,
+        new_scopes: caller_body.source_scopes.next_index()..,
+        new_blocks: caller_body.basic_blocks.next_index()..,
         destination: destination_local,
         callsite_scope: caller_body.source_scopes[callsite.source_info.scope].clone(),
         callsite,
@@ -1169,7 +1169,7 @@ impl Integrator<'_, '_> {
             if idx < self.args.len() {
                 self.args[idx]
             } else {
-                Local::new(self.new_locals.start.index() + (idx - self.args.len()))
+                self.new_locals.start + (idx - self.args.len())
             }
         };
         trace!("mapping local `{:?}` to `{:?}`", local, new);
@@ -1177,13 +1177,13 @@ impl Integrator<'_, '_> {
     }
 
     fn map_scope(&self, scope: SourceScope) -> SourceScope {
-        let new = SourceScope::new(self.new_scopes.start.index() + scope.index());
+        let new = self.new_scopes.start + scope.index();
         trace!("mapping scope `{:?}` to `{:?}`", scope, new);
         new
     }
 
     fn map_block(&self, block: BasicBlock) -> BasicBlock {
-        let new = BasicBlock::new(self.new_blocks.start.index() + block.index());
+        let new = self.new_blocks.start + block.index();
         trace!("mapping block `{:?}` to `{:?}`", block, new);
         new
     }
diff --git a/compiler/rustc_mir_transform/src/patch.rs b/compiler/rustc_mir_transform/src/patch.rs
index 6a177faeac81f..12ace04c5e267 100644
--- a/compiler/rustc_mir_transform/src/patch.rs
+++ b/compiler/rustc_mir_transform/src/patch.rs
@@ -181,7 +181,7 @@ impl<'tcx> MirPatch<'tcx> {
 
     /// Queues the addition of a new basic block.
     pub(crate) fn new_block(&mut self, data: BasicBlockData<'tcx>) -> BasicBlock {
-        let block = BasicBlock::new(self.term_patch_map.len());
+        let block = self.term_patch_map.next_index();
         debug!("MirPatch: new_block: {:?}: {:?}", block, data);
         self.new_blocks.push(data);
         self.term_patch_map.push(None);
diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/compiler/rustc_mir_transform/src/promote_consts.rs
index c8d8dc147e94f..47d4383097008 100644
--- a/compiler/rustc_mir_transform/src/promote_consts.rs
+++ b/compiler/rustc_mir_transform/src/promote_consts.rs
@@ -18,7 +18,7 @@ use either::{Left, Right};
 use rustc_const_eval::check_consts::{ConstCx, qualifs};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
-use rustc_index::{Idx, IndexSlice, IndexVec};
+use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, GenericArgs, List, Ty, TyCtxt, TypeVisitableExt};
@@ -864,17 +864,21 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
         new_temp
     }
 
-    fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) -> Body<'tcx> {
+    fn promote_candidate(
+        mut self,
+        candidate: Candidate,
+        next_promoted_index: Promoted,
+    ) -> Body<'tcx> {
         let def = self.source.source.def_id();
         let (mut rvalue, promoted_op) = {
             let promoted = &mut self.promoted;
-            let promoted_id = Promoted::new(next_promoted_id);
             let tcx = self.tcx;
             let mut promoted_operand = |ty, span| {
                 promoted.span = span;
                 promoted.local_decls[RETURN_PLACE] = LocalDecl::new(ty, span);
                 let args = tcx.erase_regions(GenericArgs::identity_for_item(tcx, def));
-                let uneval = mir::UnevaluatedConst { def, args, promoted: Some(promoted_id) };
+                let uneval =
+                    mir::UnevaluatedConst { def, args, promoted: Some(next_promoted_index) };
 
                 ConstOperand { span, user_ty: None, const_: Const::Unevaluated(uneval, ty) }
             };
@@ -1034,7 +1038,7 @@ fn promote_candidates<'tcx>(
             required_consts: Vec::new(),
         };
 
-        let mut promoted = promoter.promote_candidate(candidate, promotions.len());
+        let mut promoted = promoter.promote_candidate(candidate, promotions.next_index());
         promoted.source.promoted = Some(promotions.next_index());
         promotions.push(promoted);
     }
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index 4edc293ad807d..d56b0e5847e57 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
@@ -355,7 +355,7 @@ where
                     // exist at all (see the FIXME at the start of this method), we have to deal with
                     // them for now.
                     delegate.instantiate_canonical_var_with_infer(info, span, |idx| {
-                        ty::UniverseIndex::from(prev_universe.index() + idx.index())
+                        prev_universe + idx.index()
                     })
                 } else if info.is_existential() {
                     // As an optimization we sometimes avoid creating a new inference variable here.
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 06eb76c30c5fb..7054bbf468b9b 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -578,8 +578,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
     where
         F: FnMut(Variable) -> bool,
     {
-        for var_idx in 0..self.ir.var_kinds.len() {
-            let var = Variable::from(var_idx);
+        for var in self.ir.var_kinds.indices() {
             if test(var) {
                 write!(wr, " {var:?}")?;
             }
@@ -609,8 +608,8 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         debug!(
             "^^ liveness computation results for body {} (entry={:?})",
             {
-                for ln_idx in 0..self.ir.lnks.len() {
-                    debug!("{:?}", self.ln_str(LiveNode::from(ln_idx)));
+                for ln_idx in self.ir.lnks.indices() {
+                    debug!("{:?}", self.ln_str(ln_idx));
                 }
                 hir_id
             },
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index a7170edb98673..13de816848844 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -1948,7 +1948,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
 
         self.record_lifetime_res(
             anchor_id,
-            LifetimeRes::ElidedAnchor { start: id, end: NodeId::from_u32(id.as_u32() + 1) },
+            LifetimeRes::ElidedAnchor { start: id, end: id + 1 },
             LifetimeElisionCandidate::Ignore,
         );
         self.resolve_anonymous_lifetime(&lt, anchor_id, true);
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index de337710b5ef7..8ac8dc67fbd81 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -643,7 +643,7 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
 ) -> GenericArgsRef<'tcx> {
     struct ReplaceParamAndInferWithPlaceholder<'tcx> {
         tcx: TyCtxt<'tcx>,
-        idx: u32,
+        idx: ty::BoundVar,
     }
 
     impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceParamAndInferWithPlaceholder<'tcx> {
@@ -653,19 +653,13 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
 
         fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
             if let ty::Infer(_) = t.kind() {
-                let idx = {
-                    let idx = self.idx;
-                    self.idx += 1;
-                    idx
-                };
+                let idx = self.idx;
+                self.idx += 1;
                 Ty::new_placeholder(
                     self.tcx,
                     ty::PlaceholderType {
                         universe: ty::UniverseIndex::ROOT,
-                        bound: ty::BoundTy {
-                            var: ty::BoundVar::from_u32(idx),
-                            kind: ty::BoundTyKind::Anon,
-                        },
+                        bound: ty::BoundTy { var: idx, kind: ty::BoundTyKind::Anon },
                     },
                 )
             } else {
@@ -675,16 +669,11 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
 
         fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
             if let ty::ConstKind::Infer(_) = c.kind() {
+                let idx = self.idx;
+                self.idx += 1;
                 ty::Const::new_placeholder(
                     self.tcx,
-                    ty::PlaceholderConst {
-                        universe: ty::UniverseIndex::ROOT,
-                        bound: ty::BoundVar::from_u32({
-                            let idx = self.idx;
-                            self.idx += 1;
-                            idx
-                        }),
-                    },
+                    ty::PlaceholderConst { universe: ty::UniverseIndex::ROOT, bound: idx },
                 )
             } else {
                 c.super_fold_with(self)
@@ -692,7 +681,7 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
         }
     }
 
-    args.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: 0 })
+    args.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: ty::BoundVar::ZERO })
 }
 
 /// Normalizes the predicates and checks whether they hold in an empty environment. If this