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

rustc_index: Add a `ZERO` constant to index types

It is commonly used.

7 files changed, 10 insertions, 11 deletions

diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index 53cb05198cd..72f849b534a 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/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;
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 7b65c11bc3c..acea89e4aab 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/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) => {
diff --git a/compiler/rustc_middle/src/mir/coverage.rs b/compiler/rustc_middle/src/mir/coverage.rs
index 588aa1f40d7..0c91dc6d3c6 100644
--- a/compiler/rustc_middle/src/mir/coverage.rs
+++ b/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
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 4e1baaec39e..ad59778f58f 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/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.
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 5ff98dc8c87..2a898430ce9 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/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)
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index ba0898e07c2..828e48c5be4 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/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
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index d60926bf796..0d74524276f 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/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) => {