Move mir::Field → abi::FieldIdx

The first PR for https://github.com/rust-lang/compiler-team/issues/606

This is just the move-and-rename, because it's plenty big-and-bitrotty already.  Future PRs will start using `FieldIdx` more broadly, and concomitantly removing `FieldIdx::new`s.

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -9,15 +9,15 @@ use rustc_hir::GeneratorKind;
 use rustc_infer::infer::{LateBoundRegionConversionTime, TyCtxtInferExt};
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
-    AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
-    Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
+    AggregateKind, Constant, FakeReadCause, Local, LocalInfo, LocalKind, Location, Operand, Place,
+    PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
 };
 use rustc_middle::ty::print::Print;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, VariantIdx};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::{
     type_known_to_meet_bound_modulo_regions, Obligation, ObligationCause,
@@ -302,7 +302,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     fn describe_field(
         &self,
         place: PlaceRef<'tcx>,
-        field: Field,
+        field: FieldIdx,
         including_tuple_field: IncludingTupleField,
     ) -> Option<String> {
         let place_ty = match place {
@@ -331,7 +331,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     fn describe_field_from_ty(
         &self,
         ty: Ty<'_>,
-        field: Field,
+        field: FieldIdx,
         variant_index: Option<VariantIdx>,
         including_tuple_field: IncludingTupleField,
     ) -> Option<String> {

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -12,6 +12,7 @@ use rustc_middle::{
 use rustc_span::source_map::DesugaringKind;
 use rustc_span::symbol::{kw, Symbol};
 use rustc_span::{sym, BytePos, Span};
+use rustc_target::abi::FieldIdx;
 
 use crate::diagnostics::BorrowedContentSource;
 use crate::MirBorrowckCtxt;
@@ -1275,7 +1276,7 @@ fn is_closure_or_generator(ty: Ty<'_>) -> bool {
 fn get_mut_span_in_struct_field<'tcx>(
     tcx: TyCtxt<'tcx>,
     ty: Ty<'tcx>,
-    field: mir::Field,
+    field: FieldIdx,
 ) -> Option<Span> {
     // Expect our local to be a reference to a struct of some kind.
     if let ty::Ref(_, ty, _) = ty.kind()

compiler/rustc_borrowck/src/lib.rs

@@ -33,12 +33,13 @@ use rustc_middle::mir::{
     Place, PlaceElem, PlaceRef, VarDebugInfoContents,
 };
 use rustc_middle::mir::{AggregateKind, BasicBlock, BorrowCheckResult, BorrowKind};
-use rustc_middle::mir::{Field, ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
 use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind};
+use rustc_middle::mir::{ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, CapturedPlace, ParamEnv, RegionVid, TyCtxt};
 use rustc_session::lint::builtin::UNUSED_MUT;
 use rustc_span::{Span, Symbol};
+use rustc_target::abi::FieldIdx;
 
 use either::Either;
 use smallvec::SmallVec;
@@ -597,7 +598,7 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
     used_mut: FxIndexSet<Local>,
     /// If the function we're checking is a closure, then we'll need to report back the list of
     /// mutable upvars that have been used. This field keeps track of them.
-    used_mut_upvars: SmallVec<[Field; 8]>,
+    used_mut_upvars: SmallVec<[FieldIdx; 8]>,
     /// Region inference context. This contains the results from region inference and lets us e.g.
     /// find out which CFG points are contained in each borrow region.
     regioncx: Rc<RegionInferenceContext<'tcx>>,
@@ -2277,7 +2278,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     /// then returns the index of the field being projected. Note that this closure will always
     /// be `self` in the current MIR, because that is the only time we directly access the fields
     /// of a closure type.
-    fn is_upvar_field_projection(&self, place_ref: PlaceRef<'tcx>) -> Option<Field> {
+    fn is_upvar_field_projection(&self, place_ref: PlaceRef<'tcx>) -> Option<FieldIdx> {
         path_utils::is_upvar_field_projection(self.infcx.tcx, &self.upvars, place_ref, self.body())
     }
 

compiler/rustc_borrowck/src/path_utils.rs

@@ -7,8 +7,9 @@ use crate::BorrowIndex;
 use crate::Upvar;
 use rustc_data_structures::graph::dominators::Dominators;
 use rustc_middle::mir::BorrowKind;
-use rustc_middle::mir::{BasicBlock, Body, Field, Location, Place, PlaceRef, ProjectionElem};
+use rustc_middle::mir::{BasicBlock, Body, Location, Place, PlaceRef, ProjectionElem};
 use rustc_middle::ty::TyCtxt;
+use rustc_target::abi::FieldIdx;
 
 /// Returns `true` if the borrow represented by `kind` is
 /// allowed to be split into separate Reservation and
@@ -148,7 +149,7 @@ pub(crate) fn is_upvar_field_projection<'tcx>(
     upvars: &[Upvar<'tcx>],
     place_ref: PlaceRef<'tcx>,
     body: &Body<'tcx>,
-) -> Option<Field> {
+) -> Option<FieldIdx> {
     let mut place_ref = place_ref;
     let mut by_ref = false;
 

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -36,7 +36,7 @@ use rustc_middle::ty::{
 };
 use rustc_span::def_id::CRATE_DEF_ID;
 use rustc_span::{Span, DUMMY_SP};
-use rustc_target::abi::FIRST_VARIANT;
+use rustc_target::abi::{FieldIdx, FIRST_VARIANT};
 use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints;
 use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
 use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
@@ -786,7 +786,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         &mut self,
         parent: &dyn fmt::Debug,
         base_ty: PlaceTy<'tcx>,
-        field: Field,
+        field: FieldIdx,
         location: Location,
     ) -> Result<Ty<'tcx>, FieldAccessError> {
         let tcx = self.tcx();