Various minor Idx-related tweaks

Nothing particularly exciting here, but a couple of things I noticed as I was looking for more index conversions to simplify.

compiler/rustc_borrowck/src/diagnostics/var_name.rs

@@ -3,7 +3,7 @@
 
 use crate::region_infer::RegionInferenceContext;
 use crate::Upvar;
-use rustc_index::vec::{Idx, IndexSlice};
+use rustc_index::vec::IndexSlice;
 use rustc_middle::mir::{Body, Local};
 use rustc_middle::ty::{RegionVid, TyCtxt};
 use rustc_span::source_map::Span;
@@ -117,7 +117,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         argument_index: usize,
     ) -> (Option<Symbol>, Span) {
         let implicit_inputs = self.universal_regions().defining_ty.implicit_inputs();
-        let argument_local = Local::new(implicit_inputs + argument_index + 1);
+        let argument_local = Local::from_usize(implicit_inputs + argument_index + 1);
         debug!("get_argument_name_and_span_for_region: argument_local={argument_local:?}");
 
         let argument_name = local_names[argument_local];

compiler/rustc_borrowck/src/facts.rs

@@ -4,7 +4,6 @@ use crate::location::{LocationIndex, LocationTable};
 use crate::BorrowIndex;
 use polonius_engine::AllFacts as PoloniusFacts;
 use polonius_engine::Atom;
-use rustc_index::vec::Idx;
 use rustc_middle::mir::Local;
 use rustc_middle::ty::{RegionVid, TyCtxt};
 use rustc_mir_dataflow::move_paths::MovePathIndex;
@@ -93,13 +92,13 @@ impl AllFactsExt for AllFacts {
 
 impl Atom for BorrowIndex {
     fn index(self) -> usize {
-        Idx::index(self)
+        self.as_usize()
     }
 }
 
 impl Atom for LocationIndex {
     fn index(self) -> usize {
-        Idx::index(self)
+        self.as_usize()
     }
 }
 

compiler/rustc_borrowck/src/location.rs

@@ -1,6 +1,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::vec::IndexVec;
 use rustc_middle::mir::{BasicBlock, Body, Location};
 
 /// Maps between a MIR Location, which identifies a particular
@@ -50,19 +50,19 @@ impl LocationTable {
     }
 
     pub fn all_points(&self) -> impl Iterator<Item = LocationIndex> {
-        (0..self.num_points).map(LocationIndex::new)
+        (0..self.num_points).map(LocationIndex::from_usize)
     }
 
     pub fn start_index(&self, location: Location) -> LocationIndex {
         let Location { block, statement_index } = location;
         let start_index = self.statements_before_block[block];
-        LocationIndex::new(start_index + statement_index * 2)
+        LocationIndex::from_usize(start_index + statement_index * 2)
     }
 
     pub fn mid_index(&self, location: Location) -> LocationIndex {
         let Location { block, statement_index } = location;
         let start_index = self.statements_before_block[block];
-        LocationIndex::new(start_index + statement_index * 2 + 1)
+        LocationIndex::from_usize(start_index + statement_index * 2 + 1)
     }
 
     pub fn to_location(&self, index: LocationIndex) -> RichLocation {

compiler/rustc_borrowck/src/nll.rs

@@ -7,8 +7,8 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_index::vec::IndexSlice;
 use rustc_middle::mir::{create_dump_file, dump_enabled, dump_mir, PassWhere};
 use rustc_middle::mir::{
-    BasicBlock, Body, ClosureOutlivesSubject, ClosureRegionRequirements, LocalKind, Location,
-    Promoted,
+    Body, ClosureOutlivesSubject, ClosureRegionRequirements, LocalKind, Location, Promoted,
+    START_BLOCK,
 };
 use rustc_middle::ty::{self, OpaqueHiddenType, TyCtxt};
 use rustc_span::symbol::sym;
@@ -94,8 +94,8 @@ fn populate_polonius_move_facts(
         }
     }
 
-    let fn_entry_start = location_table
-        .start_index(Location { block: BasicBlock::from_u32(0u32), statement_index: 0 });
+    let fn_entry_start =
+        location_table.start_index(Location { block: START_BLOCK, statement_index: 0 });
 
     // initialized_at
     for init in move_data.inits.iter() {

compiler/rustc_borrowck/src/type_check/input_output.rs

@@ -7,7 +7,6 @@
 //! `RETURN_PLACE` the MIR arguments) are always fully normalized (and
 //! contain revealed `impl Trait` values).
 
-use rustc_index::vec::Idx;
 use rustc_infer::infer::LateBoundRegionConversionTime;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty};
@@ -83,7 +82,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
 
             // In MIR, argument N is stored in local N+1.
-            let local = Local::new(argument_index + 1);
+            let local = Local::from_usize(argument_index + 1);
 
             let mir_input_ty = body.local_decls[local].ty;
 

compiler/rustc_borrowck/src/universal_regions.rs

@@ -19,7 +19,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::BodyOwnerKind;
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::vec::IndexVec;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::{self, InlineConstSubsts, InlineConstSubstsParts, RegionVid, Ty, TyCtxt};
@@ -289,7 +289,7 @@ impl<'tcx> UniversalRegions<'tcx> {
     /// Returns an iterator over all the RegionVids corresponding to
     /// universally quantified free regions.
     pub fn universal_regions(&self) -> impl Iterator<Item = RegionVid> {
-        (FIRST_GLOBAL_INDEX..self.num_universals).map(RegionVid::new)
+        (FIRST_GLOBAL_INDEX..self.num_universals).map(RegionVid::from_usize)
     }
 
     /// Returns `true` if `r` is classified as an local region.