Auto merge of #110036 - jackh726:placeholder_boundvar, r=nnethercote

Remove u32 on BrAnon and BoundTyKind::Anon in favor of BoundVar on Placeholder types

r? `@nnethercote`

Better alternative to #110025

compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs

@@ -181,8 +181,8 @@ trait TypeOpInfo<'tcx> {
         };
 
         let placeholder_region = tcx.mk_re_placeholder(ty::Placeholder {
-            name: placeholder.name,
             universe: adjusted_universe.into(),
+            bound: placeholder.bound,
         });
 
         let error_region =
@@ -191,8 +191,8 @@ trait TypeOpInfo<'tcx> {
                     error_placeholder.universe.as_u32().checked_sub(base_universe.as_u32());
                 adjusted_universe.map(|adjusted| {
                     tcx.mk_re_placeholder(ty::Placeholder {
-                        name: error_placeholder.name,
                         universe: adjusted.into(),
+                        bound: error_placeholder.bound,
                     })
                 })
             } else {

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -467,9 +467,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         if let ty::Ref(region, ..) = ty.kind() {
             match **region {
                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
-                | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
+                | ty::RePlaceholder(ty::PlaceholderRegion {
-                    printer.region_highlight_mode.highlighting_bound_region(br, counter)
+                    bound: ty::BoundRegion { kind: br, .. },
-                }
+                    ..
+                }) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
                 _ => {}
             }
         }
@@ -485,9 +486,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let region = if let ty::Ref(region, ..) = ty.kind() {
             match **region {
                 ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
-                | ty::RePlaceholder(ty::PlaceholderRegion { name: br, .. }) => {
+                | ty::RePlaceholder(ty::PlaceholderRegion {
-                    printer.region_highlight_mode.highlighting_bound_region(br, counter)
+                    bound: ty::BoundRegion { kind: br, .. },
-                }
+                    ..
+                }) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
                 _ => {}
             }
             region

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -207,7 +207,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             .regioncx
             .placeholders_contained_in(lower_bound)
             .map(|placeholder| {
-                if let Some(id) = placeholder.name.get_id()
+                if let Some(id) = placeholder.bound.kind.get_id()
                     && let Some(placeholder_id) = id.as_local()
                     && let gat_hir_id = hir.local_def_id_to_hir_id(placeholder_id)
                     && let Some(generics_impl) = hir.get_parent(gat_hir_id).generics()

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1342,9 +1342,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                     let region_ctxt_fn = || {
                         let reg_info = match br.kind {
-                            ty::BoundRegionKind::BrAnon(_, Some(span)) => {
+                            ty::BoundRegionKind::BrAnon(Some(span)) => BoundRegionInfo::Span(span),
-                                BoundRegionInfo::Span(span)
-                            }
                             ty::BoundRegionKind::BrAnon(..) => {
                                 BoundRegionInfo::Name(Symbol::intern("anon"))
                             }

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -123,8 +123,8 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
             .constraints
             .placeholder_region(self.type_checker.infcx, placeholder);
 
-        let reg_info = match placeholder.name {
+        let reg_info = match placeholder.bound.kind {
-            ty::BoundRegionKind::BrAnon(_, Some(span)) => BoundRegionInfo::Span(span),
+            ty::BoundRegionKind::BrAnon(Some(span)) => BoundRegionInfo::Span(span),
             ty::BoundRegionKind::BrAnon(..) => BoundRegionInfo::Name(Symbol::intern("anon")),
             ty::BoundRegionKind::BrNamed(_, name) => BoundRegionInfo::Name(name),
             ty::BoundRegionKind::BrEnv => BoundRegionInfo::Name(Symbol::intern("env")),

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2336,10 +2336,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 FnMutDelegate {
                     regions: &mut |_| tcx.lifetimes.re_erased,
                     types: &mut |bv| {
-                        tcx.mk_placeholder(ty::PlaceholderType { universe, name: bv.kind })
+                        tcx.mk_placeholder(ty::PlaceholderType { universe, bound: bv })
                     },
                     consts: &mut |bv, ty| {
-                        tcx.mk_const(ty::PlaceholderConst { universe, name: bv }, ty)
+                        tcx.mk_const(ty::PlaceholderConst { universe, bound: bv }, ty)
                     },
                 },
             );
@@ -2525,11 +2525,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                             regions: &mut |_| tcx.lifetimes.re_erased,
                                             types: &mut |bv| tcx.mk_placeholder(ty::PlaceholderType {
                                                 universe,
-                                                name: bv.kind,
+                                                bound: bv,
                                             }),
                                             consts: &mut |bv, ty| tcx.mk_const(ty::PlaceholderConst {
                                                 universe,
-                                                name: bv
+                                                bound: bv,
                                             }, ty),
                                         })
                                     )

compiler/rustc_hir_analysis/src/check/intrinsic.rs

@@ -139,14 +139,14 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
     let name_str = intrinsic_name.as_str();
 
     let bound_vars = tcx.mk_bound_variable_kinds(&[
-        ty::BoundVariableKind::Region(ty::BrAnon(0, None)),
+        ty::BoundVariableKind::Region(ty::BrAnon(None)),
         ty::BoundVariableKind::Region(ty::BrEnv),
     ]);
     let mk_va_list_ty = |mutbl| {
         tcx.lang_items().va_list().map(|did| {
             let region = tcx.mk_re_late_bound(
                 ty::INNERMOST,
-                ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon(0, None) },
+                ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon(None) },
             );
             let env_region = tcx.mk_re_late_bound(
                 ty::INNERMOST,
@@ -387,8 +387,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
                 );
                 let discriminant_def_id = assoc_items[0];
 
-                let br =
+                let br = ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon(None) };
-                    ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon(0, None) };
                 (
                     1,
                     vec![tcx.mk_imm_ref(tcx.mk_re_late_bound(ty::INNERMOST, br), param(0))],
@@ -440,8 +439,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
             sym::nontemporal_store => (1, vec![tcx.mk_mut_ptr(param(0)), param(0)], tcx.mk_unit()),
 
             sym::raw_eq => {
-                let br =
+                let br = ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon(None) };
-                    ty::BoundRegion { var: ty::BoundVar::from_u32(0), kind: ty::BrAnon(0, None) };
                 let param_ty = tcx.mk_imm_ref(tcx.mk_re_late_bound(ty::INNERMOST, br), param(0));
                 (1, vec![param_ty; 2], tcx.types.bool)
             }

compiler/rustc_hir_typeck/src/generator_interior/mod.rs

@@ -240,7 +240,7 @@ pub fn resolve_interior<'a, 'tcx>(
 
             let mut counter = 0;
             let mut mk_bound_region = |span| {
-                let kind = ty::BrAnon(counter, span);
+                let kind = ty::BrAnon(span);
                 let var = ty::BoundVar::from_u32(counter);
                 counter += 1;
                 ty::BoundRegion { var, kind }
@@ -263,7 +263,7 @@ pub fn resolve_interior<'a, 'tcx>(
                     }
                     ty::ReLateBound(_, ty::BoundRegion { kind, .. })
                     | ty::ReFree(ty::FreeRegion { bound_region: kind, .. }) => match kind {
-                        ty::BoundRegionKind::BrAnon(_, span) => mk_bound_region(span),
+                        ty::BoundRegionKind::BrAnon(span) => mk_bound_region(span),
                         ty::BoundRegionKind::BrNamed(def_id, _) => {
                             mk_bound_region(Some(fcx.tcx.def_span(def_id)))
                         }
@@ -294,7 +294,7 @@ pub fn resolve_interior<'a, 'tcx>(
             FnMutDelegate {
                 regions: &mut |br| {
                     let kind = match br.kind {
-                        ty::BrAnon(_, span) => ty::BrAnon(counter, span),
+                        ty::BrAnon(span) => ty::BrAnon(span),
                         _ => br.kind,
                     };
                     let var = ty::BoundVar::from_usize(bound_vars.len());

compiler/rustc_infer/src/errors/note_and_explain.rs

@@ -90,9 +90,8 @@ impl<'a> DescriptionCtx<'a> {
                             };
                             me.span = Some(sp);
                         }
-                        ty::BrAnon(idx, span) => {
+                        ty::BrAnon(span) => {
-                            me.kind = "anon_num_here";
+                            me.kind = "defined_here";
-                            me.num_arg = idx+1;
                             me.span = match span {
                                 Some(_) => span,
                                 None => Some(tcx.def_span(scope)),

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -772,7 +772,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
         r: ty::Region<'tcx>,
     ) -> ty::Region<'tcx> {
         let var = self.canonical_var(info, r.into());
-        let br = ty::BoundRegion { var, kind: ty::BrAnon(var.as_u32(), None) };
+        let br = ty::BoundRegion { var, kind: ty::BrAnon(None) };
         self.interner().mk_re_late_bound(self.binder_index, br)
     }
 

compiler/rustc_infer/src/infer/canonical/mod.rs

@@ -125,9 +125,9 @@ impl<'tcx> InferCtxt<'tcx> {
                 ty.into()
             }
 
-            CanonicalVarKind::PlaceholderTy(ty::PlaceholderType { universe, name }) => {
+            CanonicalVarKind::PlaceholderTy(ty::PlaceholderType { universe, bound }) => {
                 let universe_mapped = universe_map(universe);
-                let placeholder_mapped = ty::PlaceholderType { universe: universe_mapped, name };
+                let placeholder_mapped = ty::PlaceholderType { universe: universe_mapped, bound };
                 self.tcx.mk_placeholder(placeholder_mapped).into()
             }
 
@@ -138,9 +138,9 @@ impl<'tcx> InferCtxt<'tcx> {
                 )
                 .into(),
 
-            CanonicalVarKind::PlaceholderRegion(ty::PlaceholderRegion { universe, name }) => {
+            CanonicalVarKind::PlaceholderRegion(ty::PlaceholderRegion { universe, bound }) => {
                 let universe_mapped = universe_map(universe);
-                let placeholder_mapped = ty::PlaceholderRegion { universe: universe_mapped, name };
+                let placeholder_mapped = ty::PlaceholderRegion { universe: universe_mapped, bound };
                 self.tcx.mk_re_placeholder(placeholder_mapped).into()
             }
 
@@ -152,9 +152,9 @@ impl<'tcx> InferCtxt<'tcx> {
                 )
                 .into(),
 
-            CanonicalVarKind::PlaceholderConst(ty::PlaceholderConst { universe, name }, ty) => {
+            CanonicalVarKind::PlaceholderConst(ty::PlaceholderConst { universe, bound }, ty) => {
                 let universe_mapped = universe_map(universe);
-                let placeholder_mapped = ty::PlaceholderConst { universe: universe_mapped, name };
+                let placeholder_mapped = ty::PlaceholderConst { universe: universe_mapped, bound };
                 self.tcx.mk_const(placeholder_mapped, ty).into()
             }
         }

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -170,15 +170,15 @@ fn msg_span_from_named_region<'tcx>(
         }
         ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
         ty::RePlaceholder(ty::PlaceholderRegion {
-            name: ty::BoundRegionKind::BrNamed(def_id, name),
+            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrNamed(def_id, name), .. },
             ..
         }) => (format!("the lifetime `{name}` as defined here"), Some(tcx.def_span(def_id))),
         ty::RePlaceholder(ty::PlaceholderRegion {
-            name: ty::BoundRegionKind::BrAnon(_, Some(span)),
+            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(Some(span)), .. },
             ..
         }) => (format!("the anonymous lifetime defined here"), Some(span)),
         ty::RePlaceholder(ty::PlaceholderRegion {
-            name: ty::BoundRegionKind::BrAnon(_, None),
+            bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(None), .. },
             ..
         }) => (format!("an anonymous lifetime"), None),
         _ => bug!("{:?}", region),
@@ -226,8 +226,8 @@ fn msg_span_from_early_bound_and_free_regions<'tcx>(
                         };
                         (text, sp)
                     }
-                    ty::BrAnon(idx, span) => (
+                    ty::BrAnon(span) => (
-                        format!("the anonymous lifetime #{} defined here", idx + 1),
+                        "the anonymous lifetime as defined here".to_string(),
                         match span {
                             Some(span) => span,
                             None => tcx.def_span(scope)

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_relation.rs

@@ -16,22 +16,34 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         match &self.error {
             Some(RegionResolutionError::ConcreteFailure(
                 SubregionOrigin::RelateRegionParamBound(span),
-                Region(Interned(RePlaceholder(ty::Placeholder { name: sub_name, .. }), _)),
+                Region(Interned(
-                Region(Interned(RePlaceholder(ty::Placeholder { name: sup_name, .. }), _)),
+                    RePlaceholder(ty::Placeholder {
+                        bound: ty::BoundRegion { kind: sub_name, .. },
+                        ..
+                    }),
+                    _,
+                )),
+                Region(Interned(
+                    RePlaceholder(ty::Placeholder {
+                        bound: ty::BoundRegion { kind: sup_name, .. },
+                        ..
+                    }),
+                    _,
+                )),
             )) => {
                 let span = *span;
                 let (sub_span, sub_symbol) = match sub_name {
                     ty::BrNamed(def_id, symbol) => {
                         (Some(self.tcx().def_span(def_id)), Some(symbol))
                     }
-                    ty::BrAnon(_, span) => (*span, None),
+                    ty::BrAnon(span) => (*span, None),
                     ty::BrEnv => (None, None),
                 };
                 let (sup_span, sup_symbol) = match sup_name {
                     ty::BrNamed(def_id, symbol) => {
                         (Some(self.tcx().def_span(def_id)), Some(symbol))
                     }
-                    ty::BrAnon(_, span) => (*span, None),
+                    ty::BrAnon(span) => (*span, None),
                     ty::BrEnv => (None, None),
                 };
                 let diag = match (sub_span, sup_span, sub_symbol, sup_symbol) {

compiler/rustc_infer/src/infer/higher_ranked/mod.rs

@@ -82,20 +82,20 @@ impl<'tcx> InferCtxt<'tcx> {
 
         let delegate = FnMutDelegate {
             regions: &mut |br: ty::BoundRegion| {
-                self.tcx.mk_re_placeholder(ty::PlaceholderRegion {
+                self.tcx
-                    universe: next_universe,
+                    .mk_re_placeholder(ty::PlaceholderRegion { universe: next_universe, bound: br })
-                    name: br.kind,
-                })
             },
             types: &mut |bound_ty: ty::BoundTy| {
                 self.tcx.mk_placeholder(ty::PlaceholderType {
                     universe: next_universe,
-                    name: bound_ty.kind,
+                    bound: bound_ty,
                 })
             },
             consts: &mut |bound_var: ty::BoundVar, ty| {
-                self.tcx
+                self.tcx.mk_const(
-                    .mk_const(ty::PlaceholderConst { universe: next_universe, name: bound_var }, ty)
+                    ty::PlaceholderConst { universe: next_universe, bound: bound_var },
+                    ty,
+                )
             },
         };
 

compiler/rustc_infer/src/infer/mod.rs

@@ -2130,13 +2130,17 @@ fn replace_param_and_infer_substs_with_placeholder<'tcx>(
 
         fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
             if let ty::Infer(_) = t.kind() {
+                let idx = {
+                    let idx = self.idx;
+                    self.idx += 1;
+                    idx
+                };
                 self.tcx.mk_placeholder(ty::PlaceholderType {
                     universe: ty::UniverseIndex::ROOT,
-                    name: ty::BoundTyKind::Anon({
+                    bound: ty::BoundTy {
-                        let idx = self.idx;
+                        var: ty::BoundVar::from_u32(idx),
-                        self.idx += 1;
+                        kind: ty::BoundTyKind::Anon,
-                        idx
+                    },
-                    }),
                 })
             } else {
                 t.super_fold_with(self)
@@ -2153,7 +2157,7 @@ fn replace_param_and_infer_substs_with_placeholder<'tcx>(
                 self.tcx.mk_const(
                     ty::PlaceholderConst {
                         universe: ty::UniverseIndex::ROOT,
-                        name: ty::BoundVar::from_u32({
+                        bound: ty::BoundVar::from_u32({
                             let idx = self.idx;
                             self.idx += 1;
                             idx

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -296,7 +296,7 @@ where
                     universe
                 });
 
-                let placeholder = ty::PlaceholderRegion { universe, name: br.kind };
+                let placeholder = ty::PlaceholderRegion { universe, bound: br };
                 debug!(?placeholder);
                 let placeholder_reg = nll_delegate.next_placeholder_region(placeholder);
                 debug!(?placeholder_reg);

compiler/rustc_infer/src/infer/region_constraints/leak_check.rs

@@ -290,9 +290,9 @@ impl<'me, 'tcx> LeakCheck<'me, 'tcx> {
     ) -> TypeError<'tcx> {
         debug!("error: placeholder={:?}, other_region={:?}", placeholder, other_region);
         if self.overly_polymorphic {
-            TypeError::RegionsOverlyPolymorphic(placeholder.name, other_region)
+            TypeError::RegionsOverlyPolymorphic(placeholder.bound.kind, other_region)
         } else {
-            TypeError::RegionsInsufficientlyPolymorphic(placeholder.name, other_region)
+            TypeError::RegionsInsufficientlyPolymorphic(placeholder.bound.kind, other_region)
         }
     }
 }

compiler/rustc_middle/src/infer/canonical.rs

@@ -149,15 +149,15 @@ impl<'tcx> CanonicalVarInfo<'tcx> {
         }
     }
 
-    pub fn expect_anon_placeholder(self) -> u32 {
+    pub fn expect_placeholder_index(self) -> usize {
         match self.kind {
             CanonicalVarKind::Ty(_)
             | CanonicalVarKind::Region(_)
             | CanonicalVarKind::Const(_, _) => bug!("expected placeholder: {self:?}"),
 
-            CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.name.expect_anon(),
+            CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.bound.var.as_usize(),
-            CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.name.expect_anon(),
+            CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.bound.var.as_usize(),
-            CanonicalVarKind::PlaceholderConst(placeholder, _) => placeholder.name.as_u32(),
+            CanonicalVarKind::PlaceholderConst(placeholder, _) => placeholder.bound.as_usize(),
         }
     }
 }
@@ -411,7 +411,7 @@ impl<'tcx> CanonicalVarValues<'tcx> {
                         CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
                             let br = ty::BoundRegion {
                                 var: ty::BoundVar::from_usize(i),
-                                kind: ty::BrAnon(i as u32, None),
+                                kind: ty::BrAnon(None),
                             };
                             tcx.mk_re_late_bound(ty::INNERMOST, br).into()
                         }

compiler/rustc_middle/src/mir/query.rs

@@ -411,10 +411,8 @@ impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
     pub fn bind(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
         let inner = tcx.fold_regions(ty, |r, depth| match r.kind() {
             ty::ReVar(vid) => {
-                let br = ty::BoundRegion {
+                let br =
-                    var: ty::BoundVar::new(vid.index()),
+                    ty::BoundRegion { var: ty::BoundVar::new(vid.index()), kind: ty::BrAnon(None) };
-                    kind: ty::BrAnon(vid.as_u32(), None),
-                };
                 tcx.mk_re_late_bound(depth, br)
             }
             _ => bug!("unexpected region in ClosureOutlivesSubjectTy: {r:?}"),

compiler/rustc_middle/src/ty/context.rs

@@ -311,7 +311,7 @@ pub struct CommonLifetimes<'tcx> {
     pub re_vars: Vec<Region<'tcx>>,
 
     /// Pre-interned values of the form:
-    /// `ReLateBound(DebruijnIndex(i), BoundRegion { var: v, kind: BrAnon(v, None) })`
+    /// `ReLateBound(DebruijnIndex(i), BoundRegion { var: v, kind: BrAnon(None) })`
     /// for small values of `i` and `v`.
     pub re_late_bounds: Vec<Vec<Region<'tcx>>>,
 }
@@ -386,10 +386,7 @@ impl<'tcx> CommonLifetimes<'tcx> {
                     .map(|v| {
                         mk(ty::ReLateBound(
                             ty::DebruijnIndex::from(i),
-                            ty::BoundRegion {
+                            ty::BoundRegion { var: ty::BoundVar::from(v), kind: ty::BrAnon(None) },
-                                var: ty::BoundVar::from(v),
-                                kind: ty::BrAnon(v, None),
-                            },
                         ))
                     })
                     .collect()
@@ -2075,10 +2072,9 @@ impl<'tcx> TyCtxt<'tcx> {
         bound_region: ty::BoundRegion,
     ) -> Region<'tcx> {
         // Use a pre-interned one when possible.
-        if let ty::BoundRegion { var, kind: ty::BrAnon(v, None) } = bound_region
+        if let ty::BoundRegion { var, kind: ty::BrAnon(None) } = bound_region
-            && var.as_u32() == v
             && let Some(inner) = self.lifetimes.re_late_bounds.get(debruijn.as_usize())
-            && let Some(re) = inner.get(v as usize).copied()
+            && let Some(re) = inner.get(var.as_usize()).copied()
         {
             re
         } else {

compiler/rustc_middle/src/ty/fold.rs

@@ -379,9 +379,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let kind = entry
-                    .or_insert_with(|| {
+                    .or_insert_with(|| ty::BoundVariableKind::Region(ty::BrAnon(None)))
-                        ty::BoundVariableKind::Region(ty::BrAnon(index as u32, None))
-                    })
                     .expect_region();
                 let br = ty::BoundRegion { var, kind };
                 self.tcx.mk_re_late_bound(ty::INNERMOST, br)
@@ -391,9 +389,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let kind = entry
-                    .or_insert_with(|| {
+                    .or_insert_with(|| ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon))
-                        ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon(index as u32))
-                    })
                     .expect_ty();
                 self.tcx.mk_bound(ty::INNERMOST, BoundTy { var, kind })
             }

compiler/rustc_middle/src/ty/mod.rs

@@ -1454,12 +1454,12 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
 #[derive(HashStable, TyEncodable, TyDecodable)]
 pub struct Placeholder<T> {
     pub universe: UniverseIndex,
-    pub name: T,
+    pub bound: T,
 }
 
-pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
+pub type PlaceholderRegion = Placeholder<BoundRegion>;
 
-pub type PlaceholderType = Placeholder<BoundTyKind>;
+pub type PlaceholderType = Placeholder<BoundTy>;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]

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

@@ -701,9 +701,7 @@ pub trait PrettyPrinter<'tcx>:
             ty::Error(_) => p!("[type error]"),
             ty::Param(ref param_ty) => p!(print(param_ty)),
             ty::Bound(debruijn, bound_ty) => match bound_ty.kind {
-                ty::BoundTyKind::Anon(bv) => {
+                ty::BoundTyKind::Anon => self.pretty_print_bound_var(debruijn, bound_ty.var)?,
-                    self.pretty_print_bound_var(debruijn, ty::BoundVar::from_u32(bv))?
-                }
                 ty::BoundTyKind::Param(_, s) => match self.should_print_verbose() {
                     true if debruijn == ty::INNERMOST => p!(write("^{}", s)),
                     true => p!(write("^{}_{}", debruijn.index(), s)),
@@ -739,8 +737,8 @@ pub trait PrettyPrinter<'tcx>:
                     p!(print(data))
                 }
             }
-            ty::Placeholder(placeholder) => match placeholder.name {
+            ty::Placeholder(placeholder) => match placeholder.bound.kind {
-                ty::BoundTyKind::Anon(_) => p!(write("Placeholder({:?})", placeholder)),
+                ty::BoundTyKind::Anon => p!(write("Placeholder({:?})", placeholder)),
                 ty::BoundTyKind::Param(_, name) => p!(write("{}", name)),
             },
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
@@ -2104,7 +2102,9 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
 
             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
-            | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
+            | ty::RePlaceholder(ty::Placeholder {
+                bound: ty::BoundRegion { kind: br, .. }, ..
+            }) => {
                 if br.is_named() {
                     return true;
                 }
@@ -2181,7 +2181,9 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             }
             ty::ReLateBound(_, ty::BoundRegion { kind: br, .. })
             | ty::ReFree(ty::FreeRegion { bound_region: br, .. })
-            | ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
+            | ty::RePlaceholder(ty::Placeholder {
+                bound: ty::BoundRegion { kind: br, .. }, ..
+            }) => {
                 if let ty::BrNamed(_, name) = br && br.is_named() {
                     p!(write("{}", name));
                     return Ok(self);
@@ -2259,7 +2261,10 @@ impl<'a, 'tcx> ty::TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
             ty::ReLateBound(db, br) if db >= self.current_index => {
                 *self.region_map.entry(br).or_insert_with(|| name(Some(db), self.current_index, br))
             }
-            ty::RePlaceholder(ty::PlaceholderRegion { name: kind, .. }) => {
+            ty::RePlaceholder(ty::PlaceholderRegion {
+                bound: ty::BoundRegion { kind, .. },
+                ..
+            }) => {
                 // If this is an anonymous placeholder, don't rename. Otherwise, in some
                 // async fns, we get a `for<'r> Send` bound
                 match kind {

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -68,7 +68,7 @@ impl<'tcx> fmt::Debug for ty::adjustment::Adjustment<'tcx> {
 impl fmt::Debug for ty::BoundRegionKind {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
-            ty::BrAnon(n, span) => write!(f, "BrAnon({n:?}, {span:?})"),
+            ty::BrAnon(span) => write!(f, "BrAnon({span:?})"),
             ty::BrNamed(did, name) => {
                 if did.is_crate_root() {
                     write!(f, "BrNamed({})", name)
@@ -254,8 +254,8 @@ TrivialTypeTraversalAndLiftImpls! {
     crate::ty::AssocKind,
     crate::ty::AliasKind,
     crate::ty::AliasRelationDirection,
-    crate::ty::Placeholder<crate::ty::BoundRegionKind>,
+    crate::ty::Placeholder<crate::ty::BoundRegion>,
-    crate::ty::Placeholder<crate::ty::BoundTyKind>,
+    crate::ty::Placeholder<crate::ty::BoundTy>,
     crate::ty::ClosureKind,
     crate::ty::FreeRegion,
     crate::ty::InferTy,

compiler/rustc_middle/src/ty/sty.rs

@@ -60,7 +60,7 @@ pub struct FreeRegion {
 #[derive(HashStable)]
 pub enum BoundRegionKind {
     /// An anonymous region parameter for a given fn (&T)
-    BrAnon(u32, Option<Span>),
+    BrAnon(Option<Span>),
 
     /// Named region parameters for functions (a in &'a T)
     ///
@@ -107,15 +107,6 @@ impl BoundRegionKind {
             _ => None,
         }
     }
-
-    pub fn expect_anon(&self) -> u32 {
-        match *self {
-            BoundRegionKind::BrNamed(_, _) | BoundRegionKind::BrEnv => {
-                bug!("expected anon region: {self:?}")
-            }
-            BoundRegionKind::BrAnon(idx, _) => idx,
-        }
-    }
 }
 
 pub trait Article {
@@ -136,10 +127,6 @@ impl<'tcx> Article for TyKind<'tcx> {
     }
 }
 
-// `TyKind` is used a lot. Make sure it doesn't unintentionally get bigger.
-#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-static_assert_size!(TyKind<'_>, 32);
-
 /// A closure can be modeled as a struct that looks like:
 /// ```ignore (illustrative)
 /// struct Closure<'l0...'li, T0...Tj, CK, CS, U>(...U);
@@ -1533,22 +1520,13 @@ pub struct BoundTy {
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub enum BoundTyKind {
-    Anon(u32),
+    Anon,
     Param(DefId, Symbol),
 }
 
-impl BoundTyKind {
-    pub fn expect_anon(self) -> u32 {
-        match self {
-            BoundTyKind::Anon(i) => i,
-            _ => bug!(),
-        }
-    }
-}
-
 impl From<BoundVar> for BoundTy {
     fn from(var: BoundVar) -> Self {
-        BoundTy { var, kind: BoundTyKind::Anon(var.as_u32()) }
+        BoundTy { var, kind: BoundTyKind::Anon }
     }
 }
 
@@ -1632,7 +1610,7 @@ impl<'tcx> Region<'tcx> {
                 ty::ReLateBound(_, br) => br.kind.get_name(),
                 ty::ReFree(fr) => fr.bound_region.get_name(),
                 ty::ReStatic => Some(kw::StaticLifetime),
-                ty::RePlaceholder(placeholder) => placeholder.name.get_name(),
+                ty::RePlaceholder(placeholder) => placeholder.bound.kind.get_name(),
                 _ => None,
             };
 
@@ -1650,7 +1628,7 @@ impl<'tcx> Region<'tcx> {
             ty::ReFree(fr) => fr.bound_region.is_named(),
             ty::ReStatic => true,
             ty::ReVar(..) => false,
-            ty::RePlaceholder(placeholder) => placeholder.name.is_named(),
+            ty::RePlaceholder(placeholder) => placeholder.bound.kind.is_named(),
             ty::ReErased => false,
             ty::ReError(_) => false,
         }
@@ -2514,3 +2492,14 @@ impl<'tcx> VarianceDiagInfo<'tcx> {
         }
     }
 }
+
+// Some types are used a lot. Make sure they don't unintentionally get bigger.
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+mod size_asserts {
+    use super::*;
+    use rustc_data_structures::static_assert_size;
+    // tidy-alphabetical-start
+    static_assert_size!(RegionKind<'_>, 28);
+    static_assert_size!(TyKind<'_>, 32);
+    // tidy-alphabetical-end
+}

compiler/rustc_symbol_mangling/src/v0.rs

@@ -1,5 +1,5 @@
 use rustc_data_structures::base_n;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::intern::Interned;
 use rustc_hir as hir;
 use rustc_hir::def::CtorKind;
@@ -81,9 +81,9 @@ pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
 struct BinderLevel {
     /// The range of distances from the root of what's
     /// being printed, to the lifetimes in a binder.
-    /// Specifically, a `BrAnon(i)` lifetime has depth
+    /// Specifically, a `BrAnon` lifetime has depth
-    /// `lifetime_depths.start + i`, going away from the
+    /// `lifetime_depths.start + index`, going away from the
-    /// the root and towards its use site, as `i` increases.
+    /// the root and towards its use site, as the var index increases.
     /// This is used to flatten rustc's pairing of `BrAnon`
     /// (intra-binder disambiguation) with a `DebruijnIndex`
     /// (binder addressing), to "true" de Bruijn indices,
@@ -208,24 +208,15 @@ impl<'tcx> SymbolMangler<'tcx> {
     where
         T: TypeVisitable<TyCtxt<'tcx>>,
     {
-        // FIXME(non-lifetime-binders): What to do here?
-        let regions = if value.has_late_bound_regions() {
-            self.tcx.collect_referenced_late_bound_regions(value)
-        } else {
-            FxHashSet::default()
-        };
-
         let mut lifetime_depths =
             self.binders.last().map(|b| b.lifetime_depths.end).map_or(0..0, |i| i..i);
 
-        let lifetimes = regions
+        // FIXME(non-lifetime-binders): What to do here?
-            .into_iter()
+        let lifetimes = value
-            .map(|br| match br {
+            .bound_vars()
-                ty::BrAnon(i, _) => i,
+            .iter()
-                _ => bug!("symbol_names: non-anonymized region `{:?}` in `{:?}`", br, value),
+            .filter(|var| matches!(var, ty::BoundVariableKind::Region(..)))
-            })
+            .count() as u32;
-            .max()
-            .map_or(0, |max| max + 1);
 
         self.push_opt_integer_62("G", lifetimes as u64);
         lifetime_depths.end += lifetimes;
@@ -338,9 +329,9 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
 
             // Late-bound lifetimes use indices starting at 1,
             // see `BinderLevel` for more details.
-            ty::ReLateBound(debruijn, ty::BoundRegion { kind: ty::BrAnon(i, _), .. }) => {
+            ty::ReLateBound(debruijn, ty::BoundRegion { var, kind: ty::BrAnon(_) }) => {
                 let binder = &self.binders[self.binders.len() - 1 - debruijn.index()];
-                let depth = binder.lifetime_depths.start + i;
+                let depth = binder.lifetime_depths.start + var.as_u32();
 
                 1 + (self.binders.last().unwrap().lifetime_depths.end - 1 - depth)
             }

compiler/rustc_trait_selection/src/solve/canonicalize.rs

@@ -257,7 +257,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
             self.primitive_var_infos.push(CanonicalVarInfo { kind });
             var
         });
-        let br = ty::BoundRegion { var, kind: BrAnon(var.as_u32(), None) };
+        let br = ty::BoundRegion { var, kind: BrAnon(None) };
         self.interner().mk_re_late_bound(self.binder_index, br)
     }
 
@@ -300,14 +300,20 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
             ty::Placeholder(placeholder) => match self.canonicalize_mode {
                 CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(ty::Placeholder {
                     universe: placeholder.universe,
-                    name: BoundTyKind::Anon(self.variables.len() as u32),
+                    bound: ty::BoundTy {
+                        var: ty::BoundVar::from_usize(self.variables.len()),
+                        kind: ty::BoundTyKind::Anon,
+                    },
                 }),
                 CanonicalizeMode::Response { .. } => CanonicalVarKind::PlaceholderTy(placeholder),
             },
             ty::Param(_) => match self.canonicalize_mode {
                 CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(ty::Placeholder {
                     universe: ty::UniverseIndex::ROOT,
-                    name: ty::BoundTyKind::Anon(self.variables.len() as u32),
+                    bound: ty::BoundTy {
+                        var: ty::BoundVar::from_usize(self.variables.len()),
+                        kind: ty::BoundTyKind::Anon,
+                    },
                 }),
                 CanonicalizeMode::Response { .. } => bug!("param ty in response: {t:?}"),
             },
@@ -345,7 +351,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
                 var
             }),
         );
-        let bt = ty::BoundTy { var, kind: BoundTyKind::Anon(var.index() as u32) };
+        let bt = ty::BoundTy { var, kind: BoundTyKind::Anon };
         self.interner().mk_bound(self.binder_index, bt)
     }
 
@@ -373,7 +379,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
                 CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
                     ty::Placeholder {
                         universe: placeholder.universe,
-                        name: ty::BoundVar::from(self.variables.len()),
+                        bound: ty::BoundVar::from(self.variables.len()),
                     },
                     c.ty(),
                 ),
@@ -385,7 +391,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
                 CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
                     ty::Placeholder {
                         universe: ty::UniverseIndex::ROOT,
-                        name: ty::BoundVar::from(self.variables.len()),
+                        bound: ty::BoundVar::from(self.variables.len()),
                     },
                     c.ty(),
                 ),

compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs

@@ -188,7 +188,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 } else {
                     // For placeholders which were already part of the input, we simply map this
                     // universal bound variable back the placeholder of the input.
-                    original_values[info.expect_anon_placeholder() as usize]
+                    original_values[info.expect_placeholder_index()]
                 }
             },
         ));

compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs

@@ -95,17 +95,15 @@ fn replace_erased_lifetimes_with_bound_vars<'tcx>(
     let mut counter = 0;
     let ty = tcx.fold_regions(ty, |mut r, current_depth| {
         if let ty::ReErased = r.kind() {
-            let br = ty::BoundRegion {
+            let br =
-                var: ty::BoundVar::from_u32(counter),
+                ty::BoundRegion { var: ty::BoundVar::from_u32(counter), kind: ty::BrAnon(None) };
-                kind: ty::BrAnon(counter, None),
-            };
             counter += 1;
             r = tcx.mk_re_late_bound(current_depth, br);
         }
         r
     });
     let bound_vars = tcx.mk_bound_variable_kinds_from_iter(
-        (0..counter).map(|i| ty::BoundVariableKind::Region(ty::BrAnon(i, None))),
+        (0..counter).map(|_| ty::BoundVariableKind::Region(ty::BrAnon(None))),
     );
     ty::Binder::bind_with_vars(ty, bound_vars)
 }

compiler/rustc_trait_selection/src/traits/project.rs

@@ -772,7 +772,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarReplacer<'_, 'tcx> {
             }
             ty::ReLateBound(debruijn, br) if debruijn >= self.current_index => {
                 let universe = self.universe_for(debruijn);
-                let p = ty::PlaceholderRegion { universe, name: br.kind };
+                let p = ty::PlaceholderRegion { universe, bound: br };
                 self.mapped_regions.insert(p, br);
                 self.infcx.tcx.mk_re_placeholder(p)
             }
@@ -790,7 +790,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarReplacer<'_, 'tcx> {
             }
             ty::Bound(debruijn, bound_ty) if debruijn >= self.current_index => {
                 let universe = self.universe_for(debruijn);
-                let p = ty::PlaceholderType { universe, name: bound_ty.kind };
+                let p = ty::PlaceholderType { universe, bound: bound_ty };
                 self.mapped_types.insert(p, bound_ty);
                 self.infcx.tcx.mk_placeholder(p)
             }
@@ -809,7 +809,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarReplacer<'_, 'tcx> {
             }
             ty::ConstKind::Bound(debruijn, bound_const) if debruijn >= self.current_index => {
                 let universe = self.universe_for(debruijn);
-                let p = ty::PlaceholderConst { universe, name: bound_const };
+                let p = ty::PlaceholderConst { universe, bound: bound_const };
                 self.mapped_consts.insert(p, bound_const);
                 self.infcx.tcx.mk_const(p, ct.ty())
             }

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -3017,7 +3017,7 @@ fn bind_generator_hidden_types_above<'tcx>(
                     if let ty::ReErased = r.kind() {
                         let br = ty::BoundRegion {
                             var: ty::BoundVar::from_u32(counter),
-                            kind: ty::BrAnon(counter, None),
+                            kind: ty::BrAnon(None),
                         };
                         counter += 1;
                         r = tcx.mk_re_late_bound(current_depth, br);
@@ -3033,7 +3033,7 @@ fn bind_generator_hidden_types_above<'tcx>(
         debug_assert!(!hidden_types.has_erased_regions());
     }
     let bound_vars = tcx.mk_bound_variable_kinds_from_iter(bound_vars.iter().chain(
-        (num_bound_variables..counter).map(|i| ty::BoundVariableKind::Region(ty::BrAnon(i, None))),
+        (num_bound_variables..counter).map(|_| ty::BoundVariableKind::Region(ty::BrAnon(None))),
     ));
     ty::Binder::bind_with_vars(hidden_types, bound_vars)
 }

compiler/rustc_traits/src/chalk/db.rs

@@ -730,7 +730,7 @@ fn bound_vars_for_item(tcx: TyCtxt<'_>, def_id: DefId) -> SubstsRef<'_> {
         ty::GenericParamDefKind::Lifetime => {
             let br = ty::BoundRegion {
                 var: ty::BoundVar::from_usize(substs.len()),
-                kind: ty::BrAnon(substs.len() as u32, None),
+                kind: ty::BrAnon(None),
             };
             tcx.mk_re_late_bound(ty::INNERMOST, br).into()
         }

compiler/rustc_traits/src/chalk/lowering.rs

@@ -376,7 +376,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Ty<RustInterner<'tcx>>> for Ty<'tcx> {
             ty::Placeholder(_placeholder) => {
                 chalk_ir::TyKind::Placeholder(chalk_ir::PlaceholderIndex {
                     ui: chalk_ir::UniverseIndex { counter: _placeholder.universe.as_usize() },
-                    idx: _placeholder.name.expect_anon() as usize,
+                    idx: _placeholder.bound.var.as_usize(),
                 })
             }
             ty::Infer(_infer) => unimplemented!(),
@@ -479,12 +479,15 @@ impl<'tcx> LowerInto<'tcx, Ty<'tcx>> for &chalk_ir::Ty<RustInterner<'tcx>> {
                 ty::DebruijnIndex::from_usize(bound.debruijn.depth() as usize),
                 ty::BoundTy {
                     var: ty::BoundVar::from_usize(bound.index),
-                    kind: ty::BoundTyKind::Anon(bound.index as u32),
+                    kind: ty::BoundTyKind::Anon,
                 },
             ),
             TyKind::Placeholder(placeholder) => ty::Placeholder(ty::Placeholder {
                 universe: ty::UniverseIndex::from_usize(placeholder.ui.counter),
-                name: ty::BoundTyKind::Anon(placeholder.idx as u32),
+                bound: ty::BoundTy {
+                    var: ty::BoundVar::from_usize(placeholder.idx),
+                    kind: ty::BoundTyKind::Anon,
+                },
             }),
             TyKind::InferenceVar(_, _) => unimplemented!(),
             TyKind::Dyn(_) => unimplemented!(),
@@ -530,13 +533,16 @@ impl<'tcx> LowerInto<'tcx, Region<'tcx>> for &chalk_ir::Lifetime<RustInterner<'t
                 ty::DebruijnIndex::from_u32(var.debruijn.depth()),
                 ty::BoundRegion {
                     var: ty::BoundVar::from_usize(var.index),
-                    kind: ty::BrAnon(var.index as u32, None),
+                    kind: ty::BrAnon(None),
                 },
             ),
             chalk_ir::LifetimeData::InferenceVar(_var) => unimplemented!(),
             chalk_ir::LifetimeData::Placeholder(p) => tcx.mk_re_placeholder(ty::Placeholder {
                 universe: ty::UniverseIndex::from_usize(p.ui.counter),
-                name: ty::BoundRegionKind::BrAnon(p.idx as u32, None),
+                bound: ty::BoundRegion {
+                    var: ty::BoundVar::from_usize(p.idx),
+                    kind: ty::BoundRegionKind::BrAnon(None),
+                },
             }),
             chalk_ir::LifetimeData::Static => tcx.lifetimes.re_static,
             chalk_ir::LifetimeData::Erased => tcx.lifetimes.re_erased,
@@ -685,7 +691,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<Ru
         let self_ty = interner.tcx.mk_bound(
             // This is going to be wrapped in a binder
             ty::DebruijnIndex::from_usize(1),
-            ty::BoundTy { var: ty::BoundVar::from_usize(0), kind: ty::BoundTyKind::Anon(0) },
+            ty::BoundTy { var: ty::BoundVar::from_usize(0), kind: ty::BoundTyKind::Anon },
         );
         let where_clauses = predicates.into_iter().map(|predicate| {
             let (predicate, binders, _named_regions) =
@@ -970,7 +976,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for BoundVarsCollector<'tcx> {
                     }
                 }
 
-                ty::BoundRegionKind::BrAnon(var, _) => match self.parameters.entry(var) {
+                ty::BoundRegionKind::BrAnon(_) => match self.parameters.entry(br.var.as_u32()) {
                     Entry::Vacant(entry) => {
                         entry.insert(chalk_ir::VariableKind::Lifetime);
                     }
@@ -1030,8 +1036,8 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for NamedBoundVarSubstitutor<'a, 'tcx> {
         match *r {
             ty::ReLateBound(index, br) if index == self.binder_index => match br.kind {
                 ty::BrNamed(def_id, _name) => match self.named_parameters.get(&def_id) {
-                    Some(idx) => {
+                    Some(_) => {
-                        let new_br = ty::BoundRegion { var: br.var, kind: ty::BrAnon(*idx, None) };
+                        let new_br = ty::BoundRegion { var: br.var, kind: ty::BrAnon(None) };
                         return self.tcx.mk_re_late_bound(index, new_br);
                     }
                     None => panic!("Missing `BrNamed`."),
@@ -1090,7 +1096,10 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ParamsSubstitutor<'tcx> {
             ty::Param(param) => match self.list.iter().position(|r| r == &param) {
                 Some(idx) => self.tcx.mk_placeholder(ty::PlaceholderType {
                     universe: ty::UniverseIndex::from_usize(0),
-                    name: ty::BoundTyKind::Anon(idx as u32),
+                    bound: ty::BoundTy {
+                        var: ty::BoundVar::from_usize(idx),
+                        kind: ty::BoundTyKind::Anon,
+                    },
                 }),
                 None => {
                     self.list.push(param);
@@ -1098,7 +1107,10 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ParamsSubstitutor<'tcx> {
                     self.params.insert(idx as u32, param);
                     self.tcx.mk_placeholder(ty::PlaceholderType {
                         universe: ty::UniverseIndex::from_usize(0),
-                        name: ty::BoundTyKind::Anon(idx as u32),
+                        bound: ty::BoundTy {
+                            var: ty::BoundVar::from_usize(idx),
+                            kind: ty::BoundTyKind::Anon,
+                        },
                     })
                 }
             },
@@ -1115,7 +1127,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ParamsSubstitutor<'tcx> {
                 Some(idx) => {
                     let br = ty::BoundRegion {
                         var: ty::BoundVar::from_u32(*idx),
-                        kind: ty::BrAnon(*idx, None),
+                        kind: ty::BrAnon(None),
                     };
                     self.tcx.mk_re_late_bound(self.binder_index, br)
                 }
@@ -1123,7 +1135,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ParamsSubstitutor<'tcx> {
                     let idx = self.named_regions.len() as u32;
                     let br = ty::BoundRegion {
                         var: ty::BoundVar::from_u32(idx),
-                        kind: ty::BrAnon(idx, None),
+                        kind: ty::BrAnon(None),
                     };
                     self.named_regions.insert(_re.def_id, idx);
                     self.tcx.mk_re_late_bound(self.binder_index, br)
@@ -1156,8 +1168,8 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseParamsSubstitutor<'tcx> {
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
         match *t.kind() {
-            ty::Placeholder(ty::PlaceholderType { universe: ty::UniverseIndex::ROOT, name }) => {
+            ty::Placeholder(ty::PlaceholderType { universe: ty::UniverseIndex::ROOT, bound }) => {
-                match self.params.get(&name.expect_anon()) {
+                match self.params.get(&bound.var.as_u32()) {
                     Some(&ty::ParamTy { index, name }) => self.tcx.mk_ty_param(index, name),
                     None => t,
                 }
@@ -1189,8 +1201,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for PlaceholdersCollector {
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         match t.kind() {
             ty::Placeholder(p) if p.universe == self.universe_index => {
-                self.next_ty_placeholder =
+                self.next_ty_placeholder = self.next_ty_placeholder.max(p.bound.var.as_usize() + 1);
-                    self.next_ty_placeholder.max(p.name.expect_anon() as usize + 1);
             }
 
             _ => (),
@@ -1202,8 +1213,9 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for PlaceholdersCollector {
     fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy> {
         match *r {
             ty::RePlaceholder(p) if p.universe == self.universe_index => {
-                if let ty::BoundRegionKind::BrAnon(anon, _) = p.name {
+                if let ty::BoundRegionKind::BrAnon(_) = p.bound.kind {
-                    self.next_anon_region_placeholder = self.next_anon_region_placeholder.max(anon);
+                    self.next_anon_region_placeholder =
+                        self.next_anon_region_placeholder.max(p.bound.var.as_u32());
                 }
                 // FIXME: This doesn't seem to handle BrNamed at all?
             }

tests/ui/impl-trait/impl-fn-hrtb-bounds-2.stderr

@@ -6,7 +6,7 @@ LL | fn a() -> impl Fn(&u8) -> impl Debug {
 LL |     |x| x
    |     --- ^
    |     |
-   |     hidden type `&u8` captures the anonymous lifetime #1 defined here
+   |     hidden type `&u8` captures the anonymous lifetime as defined here
 
 error: aborting due to previous error
 

tests/ui/nll/closure-requirements/escape-argument-callee.stderr

@@ -6,7 +6,7 @@ LL |         let mut closure = expect_sig(|p, y| *p = y);
    |
    = note: defining type: test::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None)), Region(BrAnon(2, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) mut &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(2, None) }) i32)),
+               for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) mut &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) i32)),
                (),
            ]
 

tests/ui/nll/closure-requirements/escape-argument.stderr

@@ -6,7 +6,7 @@ LL |         let mut closure = expect_sig(|p, y| *p = y);
    |
    = note: defining type: test::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) mut &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) i32)),
+               for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) mut &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32)),
                (),
            ]
 

tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.stderr

@@ -6,7 +6,7 @@ LL |         |_outlives1, _outlives2, _outlives3, x, y| {
    |
    = note: defining type: supply::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None))> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>, std::cell::Cell<&'_#2r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) &'_#3r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&'_#2r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'_#3r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#4r

tests/ui/nll/closure-requirements/propagate-approximated-ref.stderr

@@ -6,7 +6,7 @@ LL |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y
    |
    = note: defining type: supply::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None)), Region(BrAnon(2, None)), Region(BrAnon(3, None)), Region(BrAnon(4, None)), Region(BrAnon(5, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(2, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) &'_#2r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(4, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(5, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) &'_#2r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#3r

tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr

@@ -6,7 +6,7 @@ LL |     foo(cell, |cell_a, cell_x| {
    |
    = note: defining type: case1::{closure#0} with closure substs [
                i32,
-               for<Region(BrAnon(0, None))> extern "rust-call" fn((std::cell::Cell<&'_#1r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>)),
+               for<Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'_#1r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>)),
                (),
            ]
 
@@ -36,7 +36,7 @@ LL |     foo(cell, |cell_a, cell_x| {
    |
    = note: defining type: case2::{closure#0} with closure substs [
                i32,
-               for<Region(BrAnon(0, None))> extern "rust-call" fn((std::cell::Cell<&'_#1r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>)),
+               for<Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'_#1r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: number of external vids: 2

tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr

@@ -6,7 +6,7 @@ LL |     establish_relationships(&cell_a, &cell_b, |_outlives, x, y| {
    |
    = note: defining type: supply::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None)), Region(BrAnon(2, None)), Region(BrAnon(3, None)), Region(BrAnon(4, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(2, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(4, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#2r

tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr

@@ -6,7 +6,7 @@ LL |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y
    |
    = note: defining type: supply::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None)), Region(BrAnon(2, None)), Region(BrAnon(3, None)), Region(BrAnon(4, None)), Region(BrAnon(5, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(2, None) }) std::cell::Cell<&'_#2r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(4, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(5, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&'_#2r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#3r

tests/ui/nll/closure-requirements/propagate-approximated-val.stderr

@@ -6,7 +6,7 @@ LL |     establish_relationships(cell_a, cell_b, |outlives1, outlives2, x, y| {
    |
    = note: defining type: test::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None))> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#3r

tests/ui/nll/closure-requirements/propagate-despite-same-free-region.stderr

@@ -6,7 +6,7 @@ LL |         |_outlives1, _outlives2, x, y| {
    |
    = note: defining type: supply::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None))> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'_#2r u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#3r

tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-no-bounds.stderr

@@ -6,7 +6,7 @@ LL |     establish_relationships(&cell_a, &cell_b, |_outlives, x, y| {
    |
    = note: defining type: supply::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None)), Region(BrAnon(2, None)), Region(BrAnon(3, None)), Region(BrAnon(4, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) &'_#1r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(2, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(4, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'_#1r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#2r

tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.stderr

@@ -6,7 +6,7 @@ LL |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y
    |
    = note: defining type: supply::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None)), Region(BrAnon(2, None)), Region(BrAnon(3, None)), Region(BrAnon(4, None)), Region(BrAnon(5, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) &'_#1r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(2, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) &'_#2r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(4, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(5, None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(3, None) }) u32>)),
+               for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'_#1r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) &'_#2r u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>)),
                (),
            ]
    = note: late-bound region is '_#3r

tests/ui/nll/closure-requirements/return-wrong-bound-region.stderr

@@ -6,7 +6,7 @@ LL |     expect_sig(|a, b| b); // ought to return `a`
    |
    = note: defining type: test::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) i32)) -> &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) i32,
+               for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32)) -> &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) i32,
                (),
            ]
 

tests/ui/nll/ty-outlives/ty-param-closure-approximate-lower-bound.stderr

@@ -6,7 +6,7 @@ LL |     twice(cell, value, |a, b| invoke(a, b));
    |
    = note: defining type: generic::<T>::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None))> extern "rust-call" fn((std::option::Option<std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) ()>>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) T)),
+               for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::option::Option<std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) ()>>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) T)),
                (),
            ]
    = note: number of external vids: 2
@@ -28,7 +28,7 @@ LL |     twice(cell, value, |a, b| invoke(a, b));
    |
    = note: defining type: generic_fail::<T>::{closure#0} with closure substs [
                i16,
-               for<Region(BrAnon(0, None)), Region(BrAnon(1, None))> extern "rust-call" fn((std::option::Option<std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(0, None) }) ()>>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(1, None) }) T)),
+               for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::option::Option<std::cell::Cell<&'_#1r &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) ()>>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) T)),
                (),
            ]
    = note: late-bound region is '_#2r