Auto merge of rust-lang#117908 - lcnr:region-kind-rename, r=BoxyUwU

finish `RegionKind` renaming

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

continues the work from rust-lang#117876. While working on this and I encountered a bunch of further cleanup which I'll either open a tracking issue for or will do in a separate PR:
- rewrite the `RegionKind` docs, they still talk about `ReEmpty` and are generally out of date
- rename `DescriptionCtx` to `DescriptionCtxt`
- what is `CheckRegions::Bound`?
- `collect_late_bound_regions` et al
- `erase_late_bound_regions` -> `instantiate_bound_regions_with_erased`?
- `EraseEarlyRegions` visitor should be removed, feels duplicate

r? `@BoxyUwU`

compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs

@@ -50,8 +50,8 @@ impl OutlivesSuggestionBuilder {
     // naming the `'self` lifetime in methods, etc.
     fn region_name_is_suggestable(name: &RegionName) -> bool {
         match name.source {
-            RegionNameSource::NamedEarlyBoundRegion(..)
-            | RegionNameSource::NamedFreeRegion(..)
+            RegionNameSource::NamedEarlyParamRegion(..)
+            | RegionNameSource::NamedLateParamRegion(..)
             | RegionNameSource::Static => true,
 
             // Don't give suggestions for upvars, closure return types, or other unnameable

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -181,8 +181,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
     /// Returns `true` if a closure is inferred to be an `FnMut` closure.
     fn is_closure_fn_mut(&self, fr: RegionVid) -> bool {
-        if let Some(ty::ReFree(free_region)) = self.to_error_region(fr).as_deref()
-            && let ty::BoundRegionKind::BrEnv = free_region.bound_region
+        if let Some(ty::ReLateParam(late_param)) = self.to_error_region(fr).as_deref()
+            && let ty::BoundRegionKind::BrEnv = late_param.bound_region
             && let DefiningTy::Closure(_, args) = self.regioncx.universal_regions().defining_ty
         {
             return args.as_closure().kind() == ty::ClosureKind::FnMut;
@@ -995,7 +995,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             .infcx
             .tcx
             .is_suitable_region(sub)
-            .and_then(|anon_reg| find_anon_type(self.infcx.tcx, sub, &anon_reg.boundregion))
+            .and_then(|anon_reg| find_anon_type(self.infcx.tcx, sub, &anon_reg.bound_region))
         else {
             return;
         };
@@ -1004,7 +1004,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             .infcx
             .tcx
             .is_suitable_region(sup)
-            .and_then(|anon_reg| find_anon_type(self.infcx.tcx, sup, &anon_reg.boundregion))
+            .and_then(|anon_reg| find_anon_type(self.infcx.tcx, sup, &anon_reg.bound_region))
         else {
             return;
         };

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -23,14 +23,14 @@ pub(crate) struct RegionName {
 }
 
 /// Denotes the source of a region that is named by a `RegionName`. For example, a free region that
-/// was named by the user would get `NamedFreeRegion` and `'static` lifetime would get `Static`.
+/// was named by the user would get `NamedLateParamRegion` and `'static` lifetime would get `Static`.
 /// This helps to print the right kinds of diagnostics.
 #[derive(Debug, Clone)]
 pub(crate) enum RegionNameSource {
     /// A bound (not free) region that was instantiated at the def site (not an HRTB).
-    NamedEarlyBoundRegion(Span),
+    NamedEarlyParamRegion(Span),
     /// A free region that the user has a name (`'a`) for.
-    NamedFreeRegion(Span),
+    NamedLateParamRegion(Span),
     /// The `'static` region.
     Static,
     /// The free region corresponding to the environment of a closure.
@@ -69,8 +69,8 @@ pub(crate) enum RegionNameHighlight {
 impl RegionName {
     pub(crate) fn was_named(&self) -> bool {
         match self.source {
-            RegionNameSource::NamedEarlyBoundRegion(..)
-            | RegionNameSource::NamedFreeRegion(..)
+            RegionNameSource::NamedEarlyParamRegion(..)
+            | RegionNameSource::NamedLateParamRegion(..)
             | RegionNameSource::Static => true,
             RegionNameSource::SynthesizedFreeEnvRegion(..)
             | RegionNameSource::AnonRegionFromArgument(..)
@@ -85,8 +85,8 @@ impl RegionName {
     pub(crate) fn span(&self) -> Option<Span> {
         match self.source {
             RegionNameSource::Static => None,
-            RegionNameSource::NamedEarlyBoundRegion(span)
-            | RegionNameSource::NamedFreeRegion(span)
+            RegionNameSource::NamedEarlyParamRegion(span)
+            | RegionNameSource::NamedLateParamRegion(span)
             | RegionNameSource::SynthesizedFreeEnvRegion(span, _)
             | RegionNameSource::AnonRegionFromUpvar(span, _)
             | RegionNameSource::AnonRegionFromYieldTy(span, _)
@@ -104,8 +104,8 @@ impl RegionName {
 
     pub(crate) fn highlight_region_name(&self, diag: &mut Diagnostic) {
         match &self.source {
-            RegionNameSource::NamedFreeRegion(span)
-            | RegionNameSource::NamedEarlyBoundRegion(span) => {
+            RegionNameSource::NamedLateParamRegion(span)
+            | RegionNameSource::NamedEarlyParamRegion(span) => {
                 diag.span_label(*span, format!("lifetime `{self}` defined here"));
             }
             RegionNameSource::SynthesizedFreeEnvRegion(span, note) => {
@@ -280,28 +280,31 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         debug!("give_region_a_name: error_region = {:?}", error_region);
         match *error_region {
-            ty::ReEarlyBound(ebr) => ebr.has_name().then(|| {
+            ty::ReEarlyParam(ebr) => ebr.has_name().then(|| {
                 let span = tcx.hir().span_if_local(ebr.def_id).unwrap_or(DUMMY_SP);
-                RegionName { name: ebr.name, source: RegionNameSource::NamedEarlyBoundRegion(span) }
+                RegionName { name: ebr.name, source: RegionNameSource::NamedEarlyParamRegion(span) }
             }),
 
             ty::ReStatic => {
                 Some(RegionName { name: kw::StaticLifetime, source: RegionNameSource::Static })
             }
 
-            ty::ReFree(free_region) => match free_region.bound_region {
+            ty::ReLateParam(late_param) => match late_param.bound_region {
                 ty::BoundRegionKind::BrNamed(region_def_id, name) => {
                     // Get the span to point to, even if we don't use the name.
                     let span = tcx.hir().span_if_local(region_def_id).unwrap_or(DUMMY_SP);
                     debug!(
                         "bound region named: {:?}, is_named: {:?}",
                         name,
-                        free_region.bound_region.is_named()
+                        late_param.bound_region.is_named()
                     );
 
-                    if free_region.bound_region.is_named() {
+                    if late_param.bound_region.is_named() {
                         // A named region that is actually named.
-                        Some(RegionName { name, source: RegionNameSource::NamedFreeRegion(span) })
+                        Some(RegionName {
+                            name,
+                            source: RegionNameSource::NamedLateParamRegion(span),
+                        })
                     } else if tcx.asyncness(self.mir_hir_id().owner).is_async() {
                         // If we spuriously thought that the region is named, we should let the
                         // system generate a true name for error messages. Currently this can
@@ -847,7 +850,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         &self,
         fr: RegionVid,
     ) -> Option<RegionName> {
-        let ty::ReEarlyBound(region) = *self.to_error_region(fr)? else {
+        let ty::ReEarlyParam(region) = *self.to_error_region(fr)? else {
             return None;
         };
         if region.has_name() {
@@ -862,7 +865,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         let found = tcx
             .any_free_region_meets(&tcx.type_of(region_parent).instantiate_identity(), |r| {
-                *r == ty::ReEarlyBound(region)
+                *r == ty::ReEarlyParam(region)
             });
 
         Some(RegionName {
@@ -881,7 +884,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         &self,
         fr: RegionVid,
     ) -> Option<RegionName> {
-        let ty::ReEarlyBound(region) = *self.to_error_region(fr)? else {
+        let ty::ReEarlyParam(region) = *self.to_error_region(fr)? else {
             return None;
         };
         if region.has_name() {
@@ -943,7 +946,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         &self,
         clauses: &[ty::Clause<'tcx>],
         ty: Ty<'tcx>,
-        region: ty::EarlyBoundRegion,
+        region: ty::EarlyParamRegion,
     ) -> bool {
         let tcx = self.infcx.tcx;
         ty.walk().any(|arg| {
@@ -956,7 +959,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                         ty::ClauseKind::Projection(data) if data.projection_ty.self_ty() == ty => {}
                         _ => return false,
                     }
-                    tcx.any_free_region_meets(pred, |r| *r == ty::ReEarlyBound(region))
+                    tcx.any_free_region_meets(pred, |r| *r == ty::ReEarlyParam(region))
                 })
             } else {
                 false

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -36,7 +36,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// call `infer_opaque_definition_from_instantiation` to get the inferred
     /// type of `_Return<'_a>`. `infer_opaque_definition_from_instantiation`
     /// compares lifetimes directly, so we need to map the inference variables
-    /// back to concrete lifetimes: `'static`, `ReEarlyBound` or `ReFree`.
+    /// back to concrete lifetimes: `'static`, `ReEarlyParam` or `ReLateParam`.
     ///
     /// First we map all the lifetimes in the concrete type to an equal
     /// universal region that occurs in the concrete type's args, in this case
@@ -386,7 +386,7 @@ fn check_opaque_type_parameter_valid(
         let arg_is_param = match arg.unpack() {
             GenericArgKind::Type(ty) => matches!(ty.kind(), ty::Param(_)),
             GenericArgKind::Lifetime(lt) if is_ty_alias => {
-                matches!(*lt, ty::ReEarlyBound(_) | ty::ReFree(_))
+                matches!(*lt, ty::ReEarlyParam(_) | ty::ReLateParam(_))
             }
             // FIXME(#113916): we can't currently check for unique lifetime params,
             // see that issue for more. We will also have to ignore unused lifetime

compiler/rustc_borrowck/src/universal_regions.rs

@@ -462,7 +462,6 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
 
         // "Liberate" the late-bound regions. These correspond to
         // "local" free regions.
-
         let bound_inputs_and_output = self.compute_inputs_and_output(&indices, defining_ty);
 
         let inputs_and_output = self.infcx.replace_bound_regions_with_nll_infer_vars(
@@ -784,7 +783,7 @@ impl<'cx, 'tcx> InferCtxtExt<'tcx> for BorrowckInferCtxt<'cx, 'tcx> {
         let (value, _map) = self.tcx.replace_late_bound_regions(value, |br| {
             debug!(?br);
             let liberated_region =
-                ty::Region::new_free(self.tcx, all_outlive_scope.to_def_id(), br.kind);
+                ty::Region::new_late_param(self.tcx, all_outlive_scope.to_def_id(), br.kind);
             let region_vid = {
                 let name = match br.kind.get_name() {
                     Some(name) => name,
@@ -854,7 +853,7 @@ impl<'tcx> UniversalRegionIndices<'tcx> {
     /// Initially, the `UniversalRegionIndices` map contains only the
     /// early-bound regions in scope. Once that is all setup, we come
     /// in later and instantiate the late-bound regions, and then we
-    /// insert the `ReFree` version of those into the map as
+    /// insert the `ReLateParam` version of those into the map as
     /// well. These are used for error reporting.
     fn insert_late_bound_region(&mut self, r: ty::Region<'tcx>, vid: ty::RegionVid) {
         debug!("insert_late_bound_region({:?}, {:?})", r, vid);
@@ -933,7 +932,8 @@ fn for_each_late_bound_region_in_item<'tcx>(
         let ty::BoundVariableKind::Region(bound_region) = bound_var else {
             continue;
         };
-        let liberated_region = ty::Region::new_free(tcx, mir_def_id.to_def_id(), bound_region);
+        let liberated_region =
+            ty::Region::new_late_param(tcx, mir_def_id.to_def_id(), bound_region);
         f(liberated_region);
     }
 }

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -258,12 +258,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
                 let generics = tcx.generics_of(item_def_id);
                 let index = generics.param_def_id_to_index[&def_id];
-                ty::Region::new_early_bound(tcx, ty::EarlyBoundRegion { def_id, index, name })
+                ty::Region::new_early_param(tcx, ty::EarlyParamRegion { def_id, index, name })
             }
 
             Some(rbv::ResolvedArg::Free(scope, id)) => {
                 let name = lifetime_name(id.expect_local());
-                ty::Region::new_free(tcx, scope, ty::BrNamed(id, name))
+                ty::Region::new_late_param(tcx, scope, ty::BrNamed(id, name))
 
                 // (*) -- not late-bound, won't change
             }

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -532,8 +532,8 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RemapLateBound<'_, 'tcx> {
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        if let ty::ReFree(fr) = *r {
-            ty::Region::new_free(
+        if let ty::ReLateParam(fr) = *r {
+            ty::Region::new_late_param(
                 self.tcx,
                 fr.scope,
                 self.mapping.get(&fr.bound_region).copied().unwrap_or(fr.bound_region),
@@ -1078,20 +1078,20 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
         region: ty::Region<'tcx>,
     ) -> Result<ty::Region<'tcx>, Self::Error> {
         match region.kind() {
-            // Remap all free regions, which correspond to late-bound regions in the function.
-            ty::ReFree(_) => {}
+            // Remap late-bound regions from the function.
+            ty::ReLateParam(_) => {}
             // Remap early-bound regions as long as they don't come from the `impl` itself,
             // in which case we don't really need to renumber them.
-            ty::ReEarlyBound(ebr) if self.tcx.parent(ebr.def_id) != self.impl_def_id => {}
+            ty::ReEarlyParam(ebr) if self.tcx.parent(ebr.def_id) != self.impl_def_id => {}
             _ => return Ok(region),
         }
 
         let e = if let Some(region) = self.map.get(&region) {
-            if let ty::ReEarlyBound(e) = region.kind() { e } else { bug!() }
+            if let ty::ReEarlyParam(e) = region.kind() { e } else { bug!() }
         } else {
             let guar = match region.kind() {
-                ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. })
-                | ty::ReFree(ty::FreeRegion {
+                ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. })
+                | ty::ReLateParam(ty::LateParamRegion {
                     bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
                     ..
                 }) => {
@@ -1119,9 +1119,9 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
             return Err(guar);
         };
 
-        Ok(ty::Region::new_early_bound(
+        Ok(ty::Region::new_early_param(
             self.tcx,
-            ty::EarlyBoundRegion {
+            ty::EarlyParamRegion {
                 def_id: e.def_id,
                 name: e.name,
                 index: (e.index as usize - self.num_trait_args + self.num_impl_args) as u32,

compiler/rustc_hir_analysis/src/check/dropck.rs

@@ -81,8 +81,7 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
     self_type_did: DefId,
     adt_to_impl_args: GenericArgsRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
-    let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_args, CheckRegions::OnlyEarlyBound)
-    else {
+    let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_args, CheckRegions::OnlyParam) else {
         return Ok(());
     };
 

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -595,9 +595,9 @@ fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
                 // Same for the region. In our example, 'a corresponds
                 // to the 'me parameter.
                 let region_param = gat_generics.param_at(*region_a_idx, tcx);
-                let region_param = ty::Region::new_early_bound(
+                let region_param = ty::Region::new_early_param(
                     tcx,
-                    ty::EarlyBoundRegion {
+                    ty::EarlyParamRegion {
                         def_id: region_param.def_id,
                         index: region_param.index,
                         name: region_param.name,
@@ -628,19 +628,19 @@ fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
                 debug!("required clause: {region_a} must outlive {region_b}");
                 // Translate into the generic parameters of the GAT.
                 let region_a_param = gat_generics.param_at(*region_a_idx, tcx);
-                let region_a_param = ty::Region::new_early_bound(
+                let region_a_param = ty::Region::new_early_param(
                     tcx,
-                    ty::EarlyBoundRegion {
+                    ty::EarlyParamRegion {
                         def_id: region_a_param.def_id,
                         index: region_a_param.index,
                         name: region_a_param.name,
                     },
                 );
                 // Same for the region.
                 let region_b_param = gat_generics.param_at(*region_b_idx, tcx);
-                let region_b_param = ty::Region::new_early_bound(
+                let region_b_param = ty::Region::new_early_param(
                     tcx,
-                    ty::EarlyBoundRegion {
+                    ty::EarlyParamRegion {
                         def_id: region_b_param.def_id,
                         index: region_b_param.index,
                         name: region_b_param.name,

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -550,7 +550,7 @@ fn infringing_fields_error(
                                 .entry((ty.clone(), predicate.clone()))
                                 .or_default()
                                 .push(origin.span());
-                            if let ty::RegionKind::ReEarlyBound(ebr) = *b
+                            if let ty::RegionKind::ReEarlyParam(ebr) = *b
                                 && ebr.has_name()
                             {
                                 bounds.push((b.to_string(), a.to_string(), None));

compiler/rustc_hir_analysis/src/collect.rs

@@ -443,7 +443,7 @@ impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
                                     self.tcx.replace_late_bound_regions_uncached(
                                         poly_trait_ref,
                                         |_| {
-                                            ty::Region::new_early_bound(self.tcx, ty::EarlyBoundRegion {
+                                            ty::Region::new_early_param(self.tcx, ty::EarlyParamRegion {
                                                 def_id: item_def_id,
                                                 index: 0,
                                                 name: Symbol::intern(&lt_name),

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -362,10 +362,10 @@ fn compute_bidirectional_outlives_predicates<'tcx>(
 ) {
     for param in opaque_own_params {
         let orig_lifetime = tcx.map_rpit_lifetime_to_fn_lifetime(param.def_id.expect_local());
-        if let ty::ReEarlyBound(..) = *orig_lifetime {
-            let dup_lifetime = ty::Region::new_early_bound(
+        if let ty::ReEarlyParam(..) = *orig_lifetime {
+            let dup_lifetime = ty::Region::new_early_param(
                 tcx,
-                ty::EarlyBoundRegion { def_id: param.def_id, index: param.index, name: param.name },
+                ty::EarlyParamRegion { def_id: param.def_id, index: param.index, name: param.name },
             );
             let span = tcx.def_span(param.def_id);
             predicates.push((

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -2012,7 +2012,7 @@ fn is_late_bound_map(
 
         fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<!> {
             debug!("r={:?}", r.kind());
-            if let ty::RegionKind::ReEarlyBound(region) = r.kind() {
+            if let ty::RegionKind::ReEarlyParam(region) = r.kind() {
                 self.arg_is_constrained[region.index as usize] = true;
             }
 

compiler/rustc_hir_analysis/src/constrained_generic_params.rs

@@ -13,8 +13,8 @@ impl From<ty::ParamTy> for Parameter {
     }
 }
 
-impl From<ty::EarlyBoundRegion> for Parameter {
-    fn from(param: ty::EarlyBoundRegion) -> Self {
+impl From<ty::EarlyParamRegion> for Parameter {
+    fn from(param: ty::EarlyParamRegion) -> Self {
         Parameter(param.index)
     }
 }
@@ -73,7 +73,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ParameterCollector {
     }
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
-        if let ty::ReEarlyBound(data) = *r {
+        if let ty::ReEarlyParam(data) = *r {
             self.parameters.push(Parameter::from(data));
         }
         ControlFlow::Continue(())