Remove RegionckMode in favor of calling new skip_region_resolution

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

@@ -7,7 +7,6 @@ use crate::infer::region_constraints::VarInfos;
 use crate::infer::region_constraints::VerifyBound;
 use crate::infer::RegionRelations;
 use crate::infer::RegionVariableOrigin;
-use crate::infer::RegionckMode;
 use crate::infer::SubregionOrigin;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::graph::implementation::{
@@ -33,32 +32,23 @@ pub(crate) fn resolve<'tcx>(
     region_rels: &RegionRelations<'_, 'tcx>,
     var_infos: VarInfos,
     data: RegionConstraintData<'tcx>,
-    mode: RegionckMode,
 ) -> (LexicalRegionResolutions<'tcx>, Vec<RegionResolutionError<'tcx>>) {
     let mut errors = vec![];
     let mut resolver = LexicalResolver { region_rels, var_infos, data };
-    match mode {
-        RegionckMode::Solve => {
-            let values = resolver.infer_variable_values(&mut errors);
-            (values, errors)
-        }
-        RegionckMode::Erase => {
-            // Skip region inference entirely.
-            (resolver.erased_data(region_rels.tcx), Vec::new())
-        }
-    }
+    let values = resolver.infer_variable_values(&mut errors);
+    (values, errors)
 }
 
 /// Contains the result of lexical region resolution. Offers methods
 /// to lookup up the final value of a region variable.
 #[derive(Clone)]
 pub struct LexicalRegionResolutions<'tcx> {
-    values: IndexVec<RegionVid, VarValue<'tcx>>,
-    error_region: ty::Region<'tcx>,
+    pub(crate) values: IndexVec<RegionVid, VarValue<'tcx>>,
+    pub(crate) error_region: ty::Region<'tcx>,
 }
 
 #[derive(Copy, Clone, Debug)]
-enum VarValue<'tcx> {
+pub(crate) enum VarValue<'tcx> {
     Value(Region<'tcx>),
     ErrorValue,
 }
@@ -162,19 +152,6 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         }
     }
 
-    /// An erased version of the lexical region resolutions. Used when we're
-    /// erasing regions and suppressing errors: in item bodies with
-    /// `-Zborrowck=mir`.
-    fn erased_data(&self, tcx: TyCtxt<'tcx>) -> LexicalRegionResolutions<'tcx> {
-        LexicalRegionResolutions {
-            error_region: tcx.lifetimes.re_static,
-            values: IndexVec::from_elem_n(
-                VarValue::Value(tcx.lifetimes.re_erased),
-                self.num_vars(),
-            ),
-        }
-    }
-
     fn dump_constraints(&self, free_regions: &RegionRelations<'_, 'tcx>) {
         debug!("----() Start constraint listing (context={:?}) ()----", free_regions.context);
         for (idx, (constraint, _)) in self.data.constraints.iter().enumerate() {

compiler/rustc_infer/src/infer/mod.rs

@@ -84,20 +84,6 @@ pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable<
     ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut InferCtxtUndoLogs<'tcx>>,
 >;
 
-/// How we should handle region solving.
-///
-/// This is used so that the region values inferred by HIR region solving are
-/// not exposed, and so that we can avoid doing work in HIR typeck that MIR
-/// typeck will also do.
-#[derive(Copy, Clone, Debug, Default)]
-pub enum RegionckMode {
-    /// The default mode: report region errors, don't erase regions.
-    #[default]
-    Solve,
-    /// Erase the results of region after solving.
-    Erase,
-}
-
 /// This type contains all the things within `InferCtxt` that sit within a
 /// `RefCell` and are involved with taking/rolling back snapshots. Snapshot
 /// operations are hot enough that we want only one call to `borrow_mut` per
@@ -1248,6 +1234,33 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         self.tainted_by_errors_flag.set(true)
     }
 
+    pub fn skip_region_resolution(&self) {
+        let (var_infos, _) = {
+            let mut inner = self.inner.borrow_mut();
+            let inner = &mut *inner;
+            // Note: `inner.region_obligations` may not be empty, because we
+            // didn't necessarily call `process_registered_region_obligations`.
+            // This is okay, because that doesn't introduce new vars.
+            inner
+                .region_constraint_storage
+                .take()
+                .expect("regions already resolved")
+                .with_log(&mut inner.undo_log)
+                .into_infos_and_data()
+        };
+
+        let lexical_region_resolutions = LexicalRegionResolutions {
+            error_region: self.tcx.lifetimes.re_static,
+            values: rustc_index::vec::IndexVec::from_elem_n(
+                crate::infer::lexical_region_resolve::VarValue::Value(self.tcx.lifetimes.re_erased),
+                var_infos.len(),
+            ),
+        };
+
+        let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
+        assert!(old_value.is_none());
+    }
+
     /// Process the region constraints and return any any errors that
     /// result. After this, no more unification operations should be
     /// done -- or the compiler will panic -- but it is legal to use
@@ -1256,7 +1269,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         &self,
         region_context: DefId,
         outlives_env: &OutlivesEnvironment<'tcx>,
-        mode: RegionckMode,
     ) -> Vec<RegionResolutionError<'tcx>> {
         let (var_infos, data) = {
             let mut inner = self.inner.borrow_mut();
@@ -1278,7 +1290,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             &RegionRelations::new(self.tcx, region_context, outlives_env.free_region_map());
 
         let (lexical_region_resolutions, errors) =
-            lexical_region_resolve::resolve(region_rels, var_infos, data, mode);
+            lexical_region_resolve::resolve(region_rels, var_infos, data);
 
         let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
         assert!(old_value.is_none());
@@ -1294,9 +1306,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         &self,
         region_context: DefId,
         outlives_env: &OutlivesEnvironment<'tcx>,
-        mode: RegionckMode,
     ) {
-        let errors = self.resolve_regions(region_context, outlives_env, mode);
+        let errors = self.resolve_regions(region_context, outlives_env);
 
         if !self.is_tainted_by_errors() {
             // As a heuristic, just skip reporting region errors

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -5,7 +5,7 @@
 //! [trait-specialization]: https://rustc-dev-guide.rust-lang.org/traits/specialization.html
 
 use crate::infer::outlives::env::OutlivesEnvironment;
-use crate::infer::{CombinedSnapshot, InferOk, RegionckMode};
+use crate::infer::{CombinedSnapshot, InferOk};
 use crate::traits::select::IntercrateAmbiguityCause;
 use crate::traits::util::impl_subject_and_oblig;
 use crate::traits::SkipLeakCheck;
@@ -413,7 +413,7 @@ fn resolve_negative_obligation<'cx, 'tcx>(
         param_env,
     );
 
-    let errors = infcx.resolve_regions(region_context, &outlives_env, RegionckMode::default());
+    let errors = infcx.resolve_regions(region_context, &outlives_env);
 
     if !errors.is_empty() {
         return false;

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -23,7 +23,7 @@ mod util;
 pub mod wf;
 
 use crate::infer::outlives::env::OutlivesEnvironment;
-use crate::infer::{InferCtxt, RegionckMode, TyCtxtInferExt};
+use crate::infer::{InferCtxt, TyCtxtInferExt};
 use crate::traits::error_reporting::InferCtxtExt as _;
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
 use rustc_errors::ErrorGuaranteed;
@@ -240,11 +240,7 @@ fn do_normalize_predicates<'tcx>(
         // cares about declarations like `'a: 'b`.
         let outlives_env = OutlivesEnvironment::new(elaborated_env);
 
-        infcx.resolve_regions_and_report_errors(
-            region_context,
-            &outlives_env,
-            RegionckMode::default(),
-        );
+        infcx.resolve_regions_and_report_errors(region_context, &outlives_env);
 
         let predicates = match infcx.fully_resolve(predicates) {
             Ok(predicates) => predicates,

compiler/rustc_typeck/src/check/regionck.rs

@@ -82,7 +82,7 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::PatKind;
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
-use rustc_infer::infer::{self, InferCtxt, RegionObligation, RegionckMode};
+use rustc_infer::infer::{self, InferCtxt, RegionObligation};
 use rustc_middle::hir::place::{PlaceBase, PlaceWithHirId};
 use rustc_middle::ty::adjustment;
 use rustc_middle::ty::{self, Ty};
@@ -163,7 +163,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             rcx.visit_body(body);
             rcx.visit_region_obligations(id);
         }
-        rcx.resolve_regions_and_report_errors(RegionckMode::Erase);
+        // Checked by NLL
+        rcx.fcx.skip_region_resolution();
     }
 
     /// Region checking during the WF phase for items. `wf_tys` are the
@@ -175,7 +176,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         rcx.outlives_environment.add_implied_bounds(self, wf_tys, item_id, span);
         rcx.outlives_environment.save_implied_bounds(item_id);
         rcx.visit_region_obligations(item_id);
-        rcx.resolve_regions_and_report_errors(RegionckMode::default());
+        rcx.resolve_regions_and_report_errors();
     }
 
     /// Region check a function body. Not invoked on closures, but
@@ -206,7 +207,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             rcx.visit_fn_body(fn_id, body, self.tcx.hir().span(fn_id));
         }
 
-        rcx.resolve_regions_and_report_errors(RegionckMode::Erase);
+        // Checked by NLL
+        rcx.fcx.skip_region_resolution();
     }
 }
 
@@ -361,7 +363,7 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
         self.select_all_obligations_or_error();
     }
 
-    fn resolve_regions_and_report_errors(&self, mode: RegionckMode) {
+    fn resolve_regions_and_report_errors(&self) {
         self.infcx.process_registered_region_obligations(
             self.outlives_environment.region_bound_pairs_map(),
             Some(self.tcx.lifetimes.re_root_empty),
@@ -371,7 +373,6 @@ impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
         self.fcx.resolve_regions_and_report_errors(
             self.subject_def_id.to_def_id(),
             &self.outlives_environment,
-            mode,
         );
     }
 

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -15,8 +15,7 @@ use rustc_hir::ItemKind;
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::outlives::obligations::TypeOutlives;
 use rustc_infer::infer::region_constraints::GenericKind;
-use rustc_infer::infer::{self, RegionckMode};
-use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
+use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts, Subst};
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
@@ -650,11 +649,7 @@ fn resolve_regions_with_wf_tys<'tcx>(
 
         add_constraints(&infcx, region_bound_pairs);
 
-        let errors = infcx.resolve_regions(
-            id.expect_owner().to_def_id(),
-            &outlives_environment,
-            RegionckMode::default(),
-        );
+        let errors = infcx.resolve_regions(id.expect_owner().to_def_id(), &outlives_environment);
 
         debug!(?errors, "errors");
 

compiler/rustc_typeck/src/coherence/builtin.rs

@@ -9,7 +9,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_hir::ItemKind;
 use rustc_infer::infer;
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
-use rustc_infer::infer::{RegionckMode, TyCtxtInferExt};
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::ty::adjustment::CoerceUnsizedInfo;
 use rustc_middle::ty::{self, suggest_constraining_type_params, Ty, TyCtxt, TypeFoldable};
 use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
@@ -349,11 +349,7 @@ fn visit_implementation_of_dispatch_from_dyn<'tcx>(tcx: TyCtxt<'tcx>, impl_did:
 
                     // Finally, resolve all regions.
                     let outlives_env = OutlivesEnvironment::new(param_env);
-                    infcx.resolve_regions_and_report_errors(
-                        impl_did.to_def_id(),
-                        &outlives_env,
-                        RegionckMode::default(),
-                    );
+                    infcx.resolve_regions_and_report_errors(impl_did.to_def_id(), &outlives_env);
                 }
             }
             _ => {
@@ -610,11 +606,7 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: DefId) -> CoerceUn
 
         // Finally, resolve all regions.
         let outlives_env = OutlivesEnvironment::new(param_env);
-        infcx.resolve_regions_and_report_errors(
-            impl_did.to_def_id(),
-            &outlives_env,
-            RegionckMode::default(),
-        );
+        infcx.resolve_regions_and_report_errors(impl_did.to_def_id(), &outlives_env);
 
         CoerceUnsizedInfo { custom_kind: kind }
     })

compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs

@@ -71,7 +71,7 @@ use crate::errors::SubstsOnOverriddenImpl;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
-use rustc_infer::infer::{InferCtxt, RegionckMode, TyCtxtInferExt};
+use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::specialization_graph::Node;
 use rustc_middle::ty::subst::{GenericArg, InternalSubsts, SubstsRef};
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
@@ -164,7 +164,7 @@ fn get_impl_substs<'tcx>(
 
     // Conservatively use an empty `ParamEnv`.
     let outlives_env = OutlivesEnvironment::new(ty::ParamEnv::empty());
-    infcx.resolve_regions_and_report_errors(impl1_def_id, &outlives_env, RegionckMode::default());
+    infcx.resolve_regions_and_report_errors(impl1_def_id, &outlives_env);
     let Ok(impl2_substs) = infcx.fully_resolve(impl2_substs) else {
         tcx.sess.emit_err(SubstsOnOverriddenImpl { span });
         return None;