Rollup merge of #123419 - petrochenkov:zeroindex, r=compiler-errors

rustc_index: Add a `ZERO` constant to index types

It is commonly used.

compiler/rustc_ast_lowering/src/index.rs

@@ -3,7 +3,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::{LocalDefId, LocalDefIdMap};
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::*;
-use rustc_index::{Idx, IndexVec};
+use rustc_index::IndexVec;
 use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::{Span, DUMMY_SP};
@@ -31,7 +31,7 @@ pub(super) fn index_hir<'hir>(
     bodies: &SortedMap<ItemLocalId, &'hir Body<'hir>>,
     num_nodes: usize,
 ) -> (IndexVec<ItemLocalId, ParentedNode<'hir>>, LocalDefIdMap<ItemLocalId>) {
-    let zero_id = ItemLocalId::new(0);
+    let zero_id = ItemLocalId::ZERO;
     let err_node = ParentedNode { parent: zero_id, node: Node::Err(item.span()) };
     let mut nodes = IndexVec::from_elem_n(err_node, num_nodes);
     // This node's parent should never be accessed: the owner's parent is computed by the

compiler/rustc_ast_lowering/src/item.rs

@@ -11,7 +11,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
 use rustc_hir::PredicateOrigin;
-use rustc_index::{Idx, IndexSlice, IndexVec};
+use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
 use rustc_span::edit_distance::find_best_match_for_name;
@@ -563,7 +563,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         let kind =
                             this.lower_use_tree(use_tree, &prefix, id, vis_span, &mut ident, attrs);
                         if let Some(attrs) = attrs {
-                            this.attrs.insert(hir::ItemLocalId::new(0), attrs);
+                            this.attrs.insert(hir::ItemLocalId::ZERO, attrs);
                         }
 
                         let item = hir::Item {

compiler/rustc_ast_lowering/src/lib.rs

@@ -157,7 +157,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             attrs: SortedMap::default(),
             children: Vec::default(),
             current_hir_id_owner: hir::CRATE_OWNER_ID,
-            item_local_id_counter: hir::ItemLocalId::new(0),
+            item_local_id_counter: hir::ItemLocalId::ZERO,
             node_id_to_local_id: Default::default(),
             trait_map: Default::default(),
 
@@ -583,7 +583,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // and the caller to refer to some of the subdefinitions' nodes' `LocalDefId`s.
 
         // Always allocate the first `HirId` for the owner itself.
-        let _old = self.node_id_to_local_id.insert(owner, hir::ItemLocalId::new(0));
+        let _old = self.node_id_to_local_id.insert(owner, hir::ItemLocalId::ZERO);
         debug_assert_eq!(_old, None);
 
         let item = f(self);
@@ -677,7 +677,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 v.insert(local_id);
                 self.item_local_id_counter.increment_by(1);
 
-                assert_ne!(local_id, hir::ItemLocalId::new(0));
+                assert_ne!(local_id, hir::ItemLocalId::ZERO);
                 if let Some(def_id) = self.opt_local_def_id(ast_node_id) {
                     self.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
                 }
@@ -696,7 +696,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn next_id(&mut self) -> hir::HirId {
         let owner = self.current_hir_id_owner;
         let local_id = self.item_local_id_counter;
-        assert_ne!(local_id, hir::ItemLocalId::new(0));
+        assert_ne!(local_id, hir::ItemLocalId::ZERO);
         self.item_local_id_counter.increment_by(1);
         hir::HirId { owner, local_id }
     }

compiler/rustc_borrowck/src/borrow_set.rs

@@ -159,7 +159,7 @@ impl<'tcx> BorrowSet<'tcx> {
     }
 
     pub(crate) fn indices(&self) -> impl Iterator<Item = BorrowIndex> {
-        BorrowIndex::from_usize(0)..BorrowIndex::from_usize(self.len())
+        BorrowIndex::ZERO..BorrowIndex::from_usize(self.len())
     }
 
     pub(crate) fn iter_enumerated(&self) -> impl Iterator<Item = (BorrowIndex, &BorrowData<'tcx>)> {

compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs

@@ -1393,7 +1393,7 @@ fn llvm_add_sub<'tcx>(
 
     // c + carry -> c + first intermediate carry or borrow respectively
     let int0 = crate::num::codegen_checked_int_binop(fx, bin_op, a, b);
-    let c = int0.value_field(fx, FieldIdx::new(0));
+    let c = int0.value_field(fx, FieldIdx::ZERO);
     let cb0 = int0.value_field(fx, FieldIdx::new(1)).load_scalar(fx);
 
     // c + carry -> c + second intermediate carry or borrow respectively

compiler/rustc_codegen_cranelift/src/vtable.rs

@@ -61,7 +61,7 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
             if ty.is_dyn_star() {
                 let inner_layout = fx.layout_of(arg.layout().ty.builtin_deref(true).unwrap().ty);
                 let dyn_star = CPlace::for_ptr(Pointer::new(arg.load_scalar(fx)), inner_layout);
-                let ptr = dyn_star.place_field(fx, FieldIdx::new(0)).to_ptr();
+                let ptr = dyn_star.place_field(fx, FieldIdx::ZERO).to_ptr();
                 let vtable =
                     dyn_star.place_field(fx, FieldIdx::new(1)).to_cvalue(fx).load_scalar(fx);
                 break 'block (ptr, vtable);

compiler/rustc_data_structures/src/graph/dominators/mod.rs

@@ -72,7 +72,7 @@ fn dominators_impl<G: ControlFlowGraph>(graph: &G) -> Inner<G::Node> {
         IndexVec::with_capacity(graph.num_nodes());
 
     let mut stack = vec![PreOrderFrame {
-        pre_order_idx: PreorderIndex::new(0),
+        pre_order_idx: PreorderIndex::ZERO,
         iter: graph.successors(graph.start_node()),
     }];
     let mut pre_order_to_real: IndexVec<PreorderIndex, G::Node> =
@@ -80,8 +80,8 @@ fn dominators_impl<G: ControlFlowGraph>(graph: &G) -> Inner<G::Node> {
     let mut real_to_pre_order: IndexVec<G::Node, Option<PreorderIndex>> =
         IndexVec::from_elem_n(None, graph.num_nodes());
     pre_order_to_real.push(graph.start_node());
-    parent.push(PreorderIndex::new(0)); // the parent of the root node is the root for now.
+    parent.push(PreorderIndex::ZERO); // the parent of the root node is the root for now.
-    real_to_pre_order[graph.start_node()] = Some(PreorderIndex::new(0));
+    real_to_pre_order[graph.start_node()] = Some(PreorderIndex::ZERO);
     let mut post_order_idx = 0;
 
     // Traverse the graph, collecting a number of things:
@@ -111,7 +111,7 @@ fn dominators_impl<G: ControlFlowGraph>(graph: &G) -> Inner<G::Node> {
 
     let reachable_vertices = pre_order_to_real.len();
 
-    let mut idom = IndexVec::from_elem_n(PreorderIndex::new(0), reachable_vertices);
+    let mut idom = IndexVec::from_elem_n(PreorderIndex::ZERO, reachable_vertices);
     let mut semi = IndexVec::from_fn_n(std::convert::identity, reachable_vertices);
     let mut label = semi.clone();
     let mut bucket = IndexVec::from_elem_n(vec![], reachable_vertices);

compiler/rustc_hir/src/hir.rs

@@ -846,9 +846,8 @@ pub struct OwnerNodes<'tcx> {
 
 impl<'tcx> OwnerNodes<'tcx> {
     pub fn node(&self) -> OwnerNode<'tcx> {
-        use rustc_index::Idx;
         // Indexing must ensure it is an OwnerNode.
-        self.nodes[ItemLocalId::new(0)].node.as_owner().unwrap()
+        self.nodes[ItemLocalId::ZERO].node.as_owner().unwrap()
     }
 }
 
@@ -856,7 +855,7 @@ impl fmt::Debug for OwnerNodes<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("OwnerNodes")
             // Do not print all the pointers to all the nodes, as it would be unreadable.
-            .field("node", &self.nodes[ItemLocalId::from_u32(0)])
+            .field("node", &self.nodes[ItemLocalId::ZERO])
             .field(
                 "parents",
                 &self

compiler/rustc_hir/src/hir_id.rs

@@ -17,7 +17,7 @@ impl Debug for OwnerId {
 
 impl From<OwnerId> for HirId {
     fn from(owner: OwnerId) -> HirId {
-        HirId { owner, local_id: ItemLocalId::from_u32(0) }
+        HirId { owner, local_id: ItemLocalId::ZERO }
     }
 }
 
@@ -110,7 +110,7 @@ impl HirId {
 
     #[inline]
     pub fn make_owner(owner: LocalDefId) -> Self {
-        Self { owner: OwnerId { def_id: owner }, local_id: ItemLocalId::from_u32(0) }
+        Self { owner: OwnerId { def_id: owner }, local_id: ItemLocalId::ZERO }
     }
 
     pub fn index(self) -> (usize, usize) {
@@ -172,6 +172,6 @@ unsafe impl StableOrd for ItemLocalId {
 
 /// The `HirId` corresponding to `CRATE_NODE_ID` and `CRATE_DEF_ID`.
 pub const CRATE_HIR_ID: HirId =
-    HirId { owner: OwnerId { def_id: CRATE_DEF_ID }, local_id: ItemLocalId::from_u32(0) };
+    HirId { owner: OwnerId { def_id: CRATE_DEF_ID }, local_id: ItemLocalId::ZERO };
 
 pub const CRATE_OWNER_ID: OwnerId = OwnerId { def_id: CRATE_DEF_ID };

compiler/rustc_hir_analysis/src/check/check.rs

@@ -899,7 +899,7 @@ pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
             struct_span_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot be empty").emit();
             return;
         }
-        let e = fields[FieldIdx::from_u32(0)].ty(tcx, args);
+        let e = fields[FieldIdx::ZERO].ty(tcx, args);
         if !fields.iter().all(|f| f.ty(tcx, args) == e) {
             struct_span_code_err!(tcx.dcx(), sp, E0076, "SIMD vector should be homogeneous")
                 .with_span_label(sp, "SIMD elements must have the same type")

compiler/rustc_hir_analysis/src/check/intrinsic.rs

@@ -183,7 +183,7 @@ pub fn check_intrinsic_type(
             let region = ty::Region::new_bound(
                 tcx,
                 ty::INNERMOST,
-                ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon },
+                ty::BoundRegion { var: ty::BoundVar::ZERO, kind: ty::BrAnon },
             );
             let env_region = ty::Region::new_bound(
                 tcx,
@@ -495,7 +495,7 @@ pub fn check_intrinsic_type(
                 );
                 let discriminant_def_id = assoc_items[0];
 
-                let br = ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon };
+                let br = ty::BoundRegion { var: ty::BoundVar::ZERO, kind: ty::BrAnon };
                 (
                     1,
                     0,
@@ -555,7 +555,7 @@ pub fn check_intrinsic_type(
             }
 
             sym::raw_eq => {
-                let br = ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon };
+                let br = ty::BoundRegion { var: ty::BoundVar::ZERO, kind: ty::BrAnon };
                 let param_ty_lhs =
                     Ty::new_imm_ref(tcx, ty::Region::new_bound(tcx, ty::INNERMOST, br), param(0));
                 let br = ty::BoundRegion { var: ty::BoundVar::from_u32(1), kind: ty::BrAnon };

compiler/rustc_hir_analysis/src/check/intrinsicck.rs

@@ -67,7 +67,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
             ty::RawPtr(ty, _) if self.is_thin_ptr_ty(ty) => Some(asm_ty_isize),
             ty::Adt(adt, args) if adt.repr().simd() => {
                 let fields = &adt.non_enum_variant().fields;
-                let elem_ty = fields[FieldIdx::from_u32(0)].ty(self.tcx, args);
+                let elem_ty = fields[FieldIdx::ZERO].ty(self.tcx, args);
 
                 let (size, ty) = match elem_ty.kind() {
                     ty::Array(ty, len) => {
@@ -146,7 +146,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                     "expected first field of `MaybeUnit` to be `ManuallyDrop`"
                 );
                 let fields = &ty.non_enum_variant().fields;
-                let ty = fields[FieldIdx::from_u32(0)].ty(self.tcx, args);
+                let ty = fields[FieldIdx::ZERO].ty(self.tcx, args);
                 self.get_asm_ty(ty)
             }
             _ => self.get_asm_ty(ty),

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -628,7 +628,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     let projection_ty = pred.skip_binder().projection_ty;
 
                     let args_with_infer_self = tcx.mk_args_from_iter(
-                        std::iter::once(Ty::new_var(tcx, ty::TyVid::from_u32(0)).into())
+                        std::iter::once(Ty::new_var(tcx, ty::TyVid::ZERO).into())
                             .chain(projection_ty.args.iter().skip(1)),
                     );
 

compiler/rustc_hir_typeck/src/check.rs

@@ -182,7 +182,7 @@ fn check_panic_info_fn(tcx: TyCtxt<'_>, fn_id: LocalDefId, fn_sig: ty::FnSig<'_>
         ty::Region::new_bound(
             tcx,
             ty::INNERMOST,
-            ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon },
+            ty::BoundRegion { var: ty::BoundVar::ZERO, kind: ty::BrAnon },
         ),
         panic_info_ty,
     );

compiler/rustc_hir_typeck/src/intrinsicck.rs

@@ -17,7 +17,7 @@ fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
         let data_idx;
 
         let one = VariantIdx::new(1);
-        let zero = VariantIdx::new(0);
+        let zero = VariantIdx::ZERO;
 
         if def.variant(zero).fields.is_empty() {
             data_idx = one;

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -774,7 +774,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let projection_ty = pred.skip_binder().projection_ty;
 
                         let args_with_infer_self = tcx.mk_args_from_iter(
-                            iter::once(Ty::new_var(tcx, ty::TyVid::from_u32(0)).into())
+                            iter::once(Ty::new_var(tcx, ty::TyVid::ZERO).into())
                                 .chain(projection_ty.args.iter().skip(1)),
                         );
 

compiler/rustc_hir_typeck/src/upvar.rs

@@ -343,10 +343,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let closure_env_region: ty::Region<'_> = ty::Region::new_bound(
                 self.tcx,
                 ty::INNERMOST,
-                ty::BoundRegion {
+                ty::BoundRegion { var: ty::BoundVar::ZERO, kind: ty::BoundRegionKind::BrEnv },
-                    var: ty::BoundVar::from_usize(0),
-                    kind: ty::BoundRegionKind::BrEnv,
-                },
             );
             let tupled_upvars_ty_for_borrow = Ty::new_tup_from_iter(
                 self.tcx,

compiler/rustc_index_macros/src/newtype.rs

@@ -174,6 +174,9 @@ impl Parse for Newtype {
                 /// Maximum value the index can take.
                 #vis const MAX: Self = Self::from_u32(#max);
 
+                /// Zero value of the index.
+                #vis const ZERO: Self = Self::from_u32(0);
+
                 /// Creates a new index from a given `usize`.
                 ///
                 /// # Panics

compiler/rustc_middle/src/hir/map/mod.rs

@@ -13,7 +13,6 @@ use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::*;
-use rustc_index::Idx;
 use rustc_middle::hir::nested_filter;
 use rustc_span::def_id::StableCrateId;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
@@ -69,7 +68,7 @@ impl<'hir> Iterator for ParentOwnerIterator<'hir> {
 
     fn next(&mut self) -> Option<Self::Item> {
         if self.current_id.local_id.index() != 0 {
-            self.current_id.local_id = ItemLocalId::new(0);
+            self.current_id.local_id = ItemLocalId::ZERO;
             let node = self.map.tcx.hir_owner_node(self.current_id.owner);
             return Some((self.current_id.owner, node));
         }
@@ -133,7 +132,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// If calling repeatedly and iterating over parents, prefer [`Map::parent_iter`].
     pub fn parent_hir_id(self, hir_id: HirId) -> HirId {
         let HirId { owner, local_id } = hir_id;
-        if local_id == ItemLocalId::from_u32(0) {
+        if local_id == ItemLocalId::ZERO {
             self.hir_owner_parent(owner)
         } else {
             let parent_local_id = self.hir_owner_nodes(owner).nodes[local_id].parent;

compiler/rustc_middle/src/infer/canonical.rs

@@ -82,7 +82,7 @@ impl CanonicalVarValues<'_> {
     }
 
     pub fn is_identity_modulo_regions(&self) -> bool {
-        let mut var = ty::BoundVar::from_u32(0);
+        let mut var = ty::BoundVar::ZERO;
         for arg in self.var_values {
             match arg.unpack() {
                 ty::GenericArgKind::Lifetime(r) => {

compiler/rustc_middle/src/mir/coverage.rs

@@ -34,7 +34,7 @@ rustc_index::newtype_index! {
 }
 
 impl CounterId {
-    pub const START: Self = Self::from_u32(0);
+    pub const START: Self = Self::ZERO;
 }
 
 rustc_index::newtype_index! {
@@ -56,7 +56,7 @@ rustc_index::newtype_index! {
 }
 
 impl ExpressionId {
-    pub const START: Self = Self::from_u32(0);
+    pub const START: Self = Self::ZERO;
 }
 
 /// Enum that can hold a constant zero value, the ID of an physical coverage

compiler/rustc_middle/src/ty/mod.rs

@@ -1324,7 +1324,7 @@ impl VariantDef {
     pub fn single_field(&self) -> &FieldDef {
         assert!(self.fields.len() == 1);
 
-        &self.fields[FieldIdx::from_u32(0)]
+        &self.fields[FieldIdx::ZERO]
     }
 
     /// Returns the last field in this variant, if present.

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

@@ -2589,7 +2589,7 @@ impl<'a, 'tcx> ty::TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
                     ty::BrAnon | ty::BrEnv => r,
                     _ => {
                         // Index doesn't matter, since this is just for naming and these never get bound
-                        let br = ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind };
+                        let br = ty::BoundRegion { var: ty::BoundVar::ZERO, kind };
                         *self
                             .region_map
                             .entry(br)

compiler/rustc_middle/src/ty/sty.rs

@@ -1958,7 +1958,7 @@ impl<'tcx> Ty<'tcx> {
             Adt(def, args) => {
                 assert!(def.repr().simd(), "`simd_size_and_type` called on non-SIMD type");
                 let variant = def.non_enum_variant();
-                let f0_ty = variant.fields[FieldIdx::from_u32(0)].ty(tcx, args);
+                let f0_ty = variant.fields[FieldIdx::ZERO].ty(tcx, args);
 
                 match f0_ty.kind() {
                     // If the first field is an array, we assume it is the only field and its

compiler/rustc_middle/src/ty/typeck_results.rs

@@ -19,7 +19,7 @@ use rustc_hir::{
     hir_id::OwnerId,
     BindingAnnotation, ByRef, HirId, ItemLocalId, ItemLocalMap, ItemLocalSet, Mutability,
 };
-use rustc_index::{Idx, IndexVec};
+use rustc_index::IndexVec;
 use rustc_macros::HashStable;
 use rustc_middle::mir::FakeReadCause;
 use rustc_session::Session;
@@ -680,7 +680,7 @@ impl<'tcx> IsIdentity for CanonicalUserType<'tcx> {
                     return false;
                 }
 
-                iter::zip(user_args.args, BoundVar::new(0)..).all(|(kind, cvar)| {
+                iter::zip(user_args.args, BoundVar::ZERO..).all(|(kind, cvar)| {
                     match kind.unpack() {
                         GenericArgKind::Type(ty) => match ty.kind() {
                             ty::Bound(debruijn, b) => {

compiler/rustc_mir_build/src/build/custom/parse.rs

@@ -215,7 +215,7 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
 
     fn parse_local_decls(&mut self, mut stmts: impl Iterator<Item = StmtId>) -> PResult<()> {
         let (ret_var, ..) = self.parse_let_statement(stmts.next().unwrap())?;
-        self.local_map.insert(ret_var, Local::from_u32(0));
+        self.local_map.insert(ret_var, Local::ZERO);
 
         for stmt in stmts {
             let (var, ty, span) = self.parse_let_statement(stmt)?;

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -573,7 +573,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     result_value,
                     Rvalue::CheckedBinaryOp(op, Box::new((lhs.to_copy(), rhs.to_copy()))),
                 );
-                let val_fld = FieldIdx::new(0);
+                let val_fld = FieldIdx::ZERO;
                 let of_fld = FieldIdx::new(1);
 
                 let tcx = self.tcx;

compiler/rustc_mir_build/src/build/scope.rs

@@ -190,7 +190,7 @@ rustc_index::newtype_index! {
     struct DropIdx {}
 }
 
-const ROOT_NODE: DropIdx = DropIdx::from_u32(0);
+const ROOT_NODE: DropIdx = DropIdx::ZERO;
 
 /// A tree of drops that we have deferred lowering. It's used for:
 ///

compiler/rustc_mir_dataflow/src/elaborate_drops.rs

@@ -420,14 +420,14 @@ where
     ) -> BasicBlock {
         // drop glue is sent straight to codegen
         // box cannot be directly dereferenced
-        let unique_ty = adt.non_enum_variant().fields[FieldIdx::new(0)].ty(self.tcx(), args);
+        let unique_ty = adt.non_enum_variant().fields[FieldIdx::ZERO].ty(self.tcx(), args);
         let unique_variant = unique_ty.ty_adt_def().unwrap().non_enum_variant();
-        let nonnull_ty = unique_variant.fields[FieldIdx::from_u32(0)].ty(self.tcx(), args);
+        let nonnull_ty = unique_variant.fields[FieldIdx::ZERO].ty(self.tcx(), args);
         let ptr_ty = Ty::new_imm_ptr(self.tcx(), args[0].expect_ty());
 
-        let unique_place = self.tcx().mk_place_field(self.place, FieldIdx::new(0), unique_ty);
+        let unique_place = self.tcx().mk_place_field(self.place, FieldIdx::ZERO, unique_ty);
-        let nonnull_place = self.tcx().mk_place_field(unique_place, FieldIdx::new(0), nonnull_ty);
+        let nonnull_place = self.tcx().mk_place_field(unique_place, FieldIdx::ZERO, nonnull_ty);
-        let ptr_place = self.tcx().mk_place_field(nonnull_place, FieldIdx::new(0), ptr_ty);
+        let ptr_place = self.tcx().mk_place_field(nonnull_place, FieldIdx::ZERO, ptr_ty);
         let interior = self.tcx().mk_place_deref(ptr_place);
 
         let interior_path = self.elaborator.deref_subpath(self.path);

compiler/rustc_mir_transform/src/coroutine.rs

@@ -168,7 +168,7 @@ impl<'tcx> MutVisitor<'tcx> for PinArgVisitor<'tcx> {
                 Place {
                     local: SELF_ARG,
                     projection: self.tcx().mk_place_elems(&[ProjectionElem::Field(
-                        FieldIdx::new(0),
+                        FieldIdx::ZERO,
                         self.ref_coroutine_ty,
                     )]),
                 },
@@ -267,7 +267,7 @@ impl<'tcx> TransformVisitor<'tcx> {
                 Rvalue::Aggregate(
                     Box::new(AggregateKind::Adt(
                         option_def_id,
-                        VariantIdx::from_usize(0),
+                        VariantIdx::ZERO,
                         self.tcx.mk_args(&[self.old_yield_ty.into()]),
                         None,
                         None,
@@ -329,7 +329,7 @@ impl<'tcx> TransformVisitor<'tcx> {
                     Rvalue::Aggregate(
                         Box::new(AggregateKind::Adt(
                             poll_def_id,
-                            VariantIdx::from_usize(0),
+                            VariantIdx::ZERO,
                             args,
                             None,
                             None,
@@ -358,7 +358,7 @@ impl<'tcx> TransformVisitor<'tcx> {
                     Rvalue::Aggregate(
                         Box::new(AggregateKind::Adt(
                             option_def_id,
-                            VariantIdx::from_usize(0),
+                            VariantIdx::ZERO,
                             args,
                             None,
                             None,
@@ -420,7 +420,7 @@ impl<'tcx> TransformVisitor<'tcx> {
                     Rvalue::Aggregate(
                         Box::new(AggregateKind::Adt(
                             coroutine_state_def_id,
-                            VariantIdx::from_usize(0),
+                            VariantIdx::ZERO,
                             args,
                             None,
                             None,

compiler/rustc_mir_transform/src/elaborate_box_derefs.rs

@@ -3,7 +3,6 @@
 //! Box is not actually a pointer so it is incorrect to dereference it directly.
 
 use rustc_hir::def_id::DefId;
-use rustc_index::Idx;
 use rustc_middle::mir::patch::MirPatch;
 use rustc_middle::mir::visit::MutVisitor;
 use rustc_middle::mir::*;
@@ -32,9 +31,9 @@ pub fn build_projection<'tcx>(
     ptr_ty: Ty<'tcx>,
 ) -> [PlaceElem<'tcx>; 3] {
     [
-        PlaceElem::Field(FieldIdx::new(0), unique_ty),
+        PlaceElem::Field(FieldIdx::ZERO, unique_ty),
-        PlaceElem::Field(FieldIdx::new(0), nonnull_ty),
+        PlaceElem::Field(FieldIdx::ZERO, nonnull_ty),
-        PlaceElem::Field(FieldIdx::new(0), ptr_ty),
+        PlaceElem::Field(FieldIdx::ZERO, ptr_ty),
     ]
 }
 
@@ -91,15 +90,14 @@ pub struct ElaborateBoxDerefs;
 impl<'tcx> MirPass<'tcx> for ElaborateBoxDerefs {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         if let Some(def_id) = tcx.lang_items().owned_box() {
-            let unique_did =
+            let unique_did = tcx.adt_def(def_id).non_enum_variant().fields[FieldIdx::ZERO].did;
-                tcx.adt_def(def_id).non_enum_variant().fields[FieldIdx::from_u32(0)].did;
 
             let Some(nonnull_def) = tcx.type_of(unique_did).instantiate_identity().ty_adt_def()
             else {
                 span_bug!(tcx.def_span(unique_did), "expected Box to contain Unique")
             };
 
-            let nonnull_did = nonnull_def.non_enum_variant().fields[FieldIdx::from_u32(0)].did;
+            let nonnull_did = nonnull_def.non_enum_variant().fields[FieldIdx::ZERO].did;
 
             let patch = MirPatch::new(body);
 

compiler/rustc_mir_transform/src/gvn.rs

@@ -355,7 +355,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
     }
 
     fn insert_tuple(&mut self, values: Vec<VnIndex>) -> VnIndex {
-        self.insert(Value::Aggregate(AggregateTy::Tuple, VariantIdx::from_u32(0), values))
+        self.insert(Value::Aggregate(AggregateTy::Tuple, VariantIdx::ZERO, values))
     }
 
     #[instrument(level = "trace", skip(self), ret)]

compiler/rustc_mir_transform/src/known_panics_lint.rs

@@ -13,7 +13,7 @@ use rustc_const_eval::interpret::{
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def::DefKind;
 use rustc_hir::HirId;
-use rustc_index::{bit_set::BitSet, Idx, IndexVec};
+use rustc_index::{bit_set::BitSet, IndexVec};
 use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
@@ -124,10 +124,8 @@ impl<'tcx> Value<'tcx> {
                     fields.ensure_contains_elem(*idx, || Value::Uninit)
                 }
                 (PlaceElem::Field(..), val @ Value::Uninit) => {
-                    *val = Value::Aggregate {
+                    *val =
-                        variant: VariantIdx::new(0),
+                        Value::Aggregate { variant: VariantIdx::ZERO, fields: Default::default() };
-                        fields: Default::default(),
-                    };
                     val.project_mut(&[*proj])?
                 }
                 _ => return None,
@@ -572,7 +570,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                     self.use_ecx(|this| this.ecx.overflowing_binary_op(bin_op, &left, &right))?;
                 let overflowed = ImmTy::from_bool(overflowed, self.tcx);
                 Value::Aggregate {
-                    variant: VariantIdx::new(0),
+                    variant: VariantIdx::ZERO,
                     fields: [Value::from(val), overflowed.into()].into_iter().collect(),
                 }
             }
@@ -607,7 +605,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                         | AggregateKind::Tuple
                         | AggregateKind::Closure(_, _)
                         | AggregateKind::Coroutine(_, _)
-                        | AggregateKind::CoroutineClosure(_, _) => VariantIdx::new(0),
+                        | AggregateKind::CoroutineClosure(_, _) => VariantIdx::ZERO,
                     },
                 }
             }

compiler/rustc_mir_transform/src/simplify.rs

@@ -415,7 +415,7 @@ fn make_local_map<V>(
     used_locals: &UsedLocals,
 ) -> IndexVec<Local, Option<Local>> {
     let mut map: IndexVec<Local, Option<Local>> = IndexVec::from_elem(None, local_decls);
-    let mut used = Local::new(0);
+    let mut used = Local::ZERO;
 
     for alive_index in local_decls.indices() {
         // `is_used` treats the `RETURN_PLACE` and arguments as used.

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -40,7 +40,7 @@ rustc_index::newtype_index! {
 }
 
 impl DepNodeIndex {
-    const SINGLETON_DEPENDENCYLESS_ANON_NODE: DepNodeIndex = DepNodeIndex::from_u32(0);
+    const SINGLETON_DEPENDENCYLESS_ANON_NODE: DepNodeIndex = DepNodeIndex::ZERO;
     pub const FOREVER_RED_NODE: DepNodeIndex = DepNodeIndex::from_u32(1);
 }
 

compiler/rustc_resolve/src/imports.rs

@@ -532,7 +532,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
         let mut seen_spans = FxHashSet::default();
         let mut errors = vec![];
-        let mut prev_root_id: NodeId = NodeId::from_u32(0);
+        let mut prev_root_id: NodeId = NodeId::ZERO;
         let determined_imports = mem::take(&mut self.determined_imports);
         let indeterminate_imports = mem::take(&mut self.indeterminate_imports);
 
@@ -556,8 +556,8 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     }
                 }
 
-                if prev_root_id.as_u32() != 0
+                if prev_root_id != NodeId::ZERO
-                    && prev_root_id.as_u32() != import.root_id.as_u32()
+                    && prev_root_id != import.root_id
                     && !errors.is_empty()
                 {
                     // In the case of a new import line, throw a diagnostic message

compiler/rustc_span/src/def_id.rs

@@ -22,7 +22,7 @@ rustc_index::newtype_index! {
 
 /// Item definitions in the currently-compiled crate would have the `CrateNum`
 /// `LOCAL_CRATE` in their `DefId`.
-pub const LOCAL_CRATE: CrateNum = CrateNum::from_u32(0);
+pub const LOCAL_CRATE: CrateNum = CrateNum::ZERO;
 
 impl CrateNum {
     #[inline]

compiler/rustc_span/src/hygiene.rs

@@ -165,7 +165,7 @@ pub enum Transparency {
 
 impl LocalExpnId {
     /// The ID of the theoretical expansion that generates freshly parsed, unexpanded AST.
-    pub const ROOT: LocalExpnId = LocalExpnId::from_u32(0);
+    pub const ROOT: LocalExpnId = LocalExpnId::ZERO;
 
     #[inline]
     fn from_raw(idx: ExpnIndex) -> LocalExpnId {
@@ -242,7 +242,7 @@ impl ExpnId {
     /// The ID of the theoretical expansion that generates freshly parsed, unexpanded AST.
     /// Invariant: we do not create any ExpnId with local_id == 0 and krate != 0.
     pub const fn root() -> ExpnId {
-        ExpnId { krate: LOCAL_CRATE, local_id: ExpnIndex::from_u32(0) }
+        ExpnId { krate: LOCAL_CRATE, local_id: ExpnIndex::ZERO }
     }
 
     #[inline]

compiler/rustc_span/src/source_map/tests.rs

@@ -243,7 +243,7 @@ fn t10() {
         src_hash,
         stable_id,
         source_len.to_u32(),
-        CrateNum::new(0),
+        CrateNum::ZERO,
         FreezeLock::new(lines.read().clone()),
         multibyte_chars,
         non_narrow_chars,

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -554,11 +554,7 @@ fn plug_infer_with_placeholders<'tcx>(
         }
     }
 
-    value.visit_with(&mut PlugInferWithPlaceholder {
+    value.visit_with(&mut PlugInferWithPlaceholder { infcx, universe, var: ty::BoundVar::ZERO });
-        infcx,
-        universe,
-        var: ty::BoundVar::from_u32(0),
-    });
 }
 
 fn try_prove_negated_where_clause<'tcx>(

compiler/rustc_ty_utils/src/layout.rs

@@ -377,7 +377,7 @@ fn layout_of_uncached<'tcx>(
             }
 
             // Type of the first ADT field:
-            let f0_ty = fields[FieldIdx::from_u32(0)].ty(tcx, args);
+            let f0_ty = fields[FieldIdx::ZERO].ty(tcx, args);
 
             // Heterogeneous SIMD vectors are not supported:
             // (should be caught by typeck)

compiler/rustc_type_ir/src/lib.rs

@@ -314,7 +314,7 @@ rustc_index::newtype_index! {
 }
 
 impl UniverseIndex {
-    pub const ROOT: UniverseIndex = UniverseIndex::from_u32(0);
+    pub const ROOT: UniverseIndex = UniverseIndex::ZERO;
 
     /// Returns the "next" universe index in order -- this new index
     /// is considered to extend all previous universes. This