Auto merge of #117876 - lcnr:region-kind-rename, r=BoxyUwU

`ReLateBound` -> `ReBound`

first step of rust-lang/types-team#95

already fairly large xx

there's some future work here I intentionally did not contribute as part of this PR, from my notes:
- `DescriptionCtx` to `DescriptionCtxt`
- what is `CheckRegions::Bound`?
- `collect_late_bound_regions` et al
- `erase_late_bound_regions` -> `instantiate_bound_regions_with_erased`?
- `EraseEarlyRegions` should be removed, feels duplicate

r? `@BoxyUwU`

Author: bors

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -10,7 +10,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::CoroutineKind;
 use rustc_index::IndexSlice;
-use rustc_infer::infer::LateBoundRegionConversionTime;
+use rustc_infer::infer::BoundRegionConversionTime;
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
     AggregateKind, CallSource, ConstOperand, FakeReadCause, Local, LocalInfo, LocalKind, Location,
@@ -462,7 +462,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         // lifetimes without names with the value `'0`.
         if let ty::Ref(region, ..) = ty.kind() {
             match **region {
-                ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
+                ty::ReBound(_, ty::BoundRegion { kind: br, .. })
                 | ty::RePlaceholder(ty::PlaceholderRegion {
                     bound: ty::BoundRegion { kind: br, .. },
                     ..
@@ -482,7 +482,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         let region = if let ty::Ref(region, ..) = ty.kind() {
             match **region {
-                ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
+                ty::ReBound(_, ty::BoundRegion { kind: br, .. })
                 | ty::RePlaceholder(ty::PlaceholderRegion {
                     bound: ty::BoundRegion { kind: br, .. },
                     ..
@@ -1113,7 +1113,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             && let ty::Ref(_, _, hir::Mutability::Mut) = args.type_at(0).kind()
                             && let self_ty = self.infcx.instantiate_binder_with_fresh_vars(
                                 fn_call_span,
-                                LateBoundRegionConversionTime::FnCall,
+                                BoundRegionConversionTime::FnCall,
                                 tcx.fn_sig(method_did).instantiate(tcx, method_args).input(0),
                             )
                             && self.infcx.can_eq(self.param_env, ty, self_ty)

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -357,7 +357,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                 ty::BoundRegionKind::BrAnon => None,
             },
 
-            ty::ReLateBound(..)
+            ty::ReBound(..)
             | ty::ReVar(..)
             | ty::RePlaceholder(..)
             | ty::ReErased

compiler/rustc_borrowck/src/renumber.rs

@@ -28,6 +28,9 @@ pub fn renumber_mir<'tcx>(
     renumberer.visit_body(body);
 }
 
+// FIXME(@lcnr): A lot of these variants overlap and it seems like
+// this type is only used to decide which region should be used
+// as representative. This should be cleaned up.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 pub(crate) enum RegionCtxt {
     Location(Location),

compiler/rustc_borrowck/src/type_check/input_output.rs

@@ -7,7 +7,7 @@
 //! `RETURN_PLACE` the MIR arguments) are always fully normalized (and
 //! contain revealed `impl Trait` values).
 
-use rustc_infer::infer::LateBoundRegionConversionTime;
+use rustc_infer::infer::BoundRegionConversionTime;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty};
 use rustc_span::Span;
@@ -35,7 +35,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             .instantiate_canonical_with_fresh_inference_vars(body.span, &user_provided_poly_sig);
         let user_provided_sig = self.infcx.instantiate_binder_with_fresh_vars(
             body.span,
-            LateBoundRegionConversionTime::FnCall,
+            BoundRegionConversionTime::FnCall,
             user_provided_sig,
         );
 

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -21,7 +21,7 @@ use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::region_constraints::RegionConstraintData;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::{
-    InferCtxt, LateBoundRegion, LateBoundRegionConversionTime, NllRegionVariableOrigin,
+    BoundRegion, BoundRegionConversionTime, InferCtxt, NllRegionVariableOrigin,
 };
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
@@ -1401,10 +1401,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     };
 
                     self.infcx.next_region_var(
-                        LateBoundRegion(
+                        BoundRegion(
                             term.source_info.span,
                             br.kind,
-                            LateBoundRegionConversionTime::FnCall,
+                            BoundRegionConversionTime::FnCall,
                         ),
                         region_ctxt_fn,
                     )

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -107,12 +107,12 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
     fn next_existential_region_var(
         &mut self,
         from_forall: bool,
-        _name: Option<Symbol>,
+        name: Option<Symbol>,
     ) -> ty::Region<'tcx> {
         let origin = NllRegionVariableOrigin::Existential { from_forall };
 
         let reg_var =
-            self.type_checker.infcx.next_nll_region_var(origin, || RegionCtxt::Existential(_name));
+            self.type_checker.infcx.next_nll_region_var(origin, || RegionCtxt::Existential(name));
 
         reg_var
     }

compiler/rustc_borrowck/src/universal_regions.rs

@@ -665,7 +665,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                     var: ty::BoundVar::from_usize(bound_vars.len() - 1),
                     kind: ty::BrEnv,
                 };
-                let env_region = ty::Region::new_late_bound(tcx, ty::INNERMOST, br);
+                let env_region = ty::Region::new_bound(tcx, ty::INNERMOST, br);
                 let closure_ty = tcx.closure_env_ty(def_id, args, env_region).unwrap();
 
                 // The "inputs" of the closure in the

compiler/rustc_hir_analysis/src/astconv/bounds.rs

@@ -350,7 +350,7 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
             let args =
                 candidate.skip_binder().args.extend_to(tcx, assoc_item.def_id, |param, _| {
                     let subst = match param.kind {
-                        ty::GenericParamDefKind::Lifetime => ty::Region::new_late_bound(
+                        ty::GenericParamDefKind::Lifetime => ty::Region::new_bound(
                             tcx,
                             ty::INNERMOST,
                             ty::BoundRegion {

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -250,7 +250,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     var: ty::BoundVar::from_u32(index),
                     kind: ty::BrNamed(def_id, name),
                 };
-                ty::Region::new_late_bound(tcx, debruijn, br)
+                ty::Region::new_bound(tcx, debruijn, br)
             }
 
             Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
@@ -1622,7 +1622,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 }
 
                 fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-                    if r.is_late_bound() { self.tcx.lifetimes.re_erased } else { r }
+                    // FIXME(@lcnr): This is broken, erasing bound regions
+                    // impacts selection as it results in different types.
+                    if r.is_bound() { self.tcx.lifetimes.re_erased } else { r }
                 }
 
                 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -2345,7 +2345,7 @@ fn param_env_with_gat_bounds<'tcx>(
                     let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
                     let bound_var = ty::BoundVariableKind::Region(kind);
                     bound_vars.push(bound_var);
-                    ty::Region::new_late_bound(
+                    ty::Region::new_bound(
                         tcx,
                         ty::INNERMOST,
                         ty::BoundRegion {