Merge `BorrowCheckContext` into `TypeChecker`.

Because there is no real reason for it to be a separate struct.
- It has no methods.
- It's easy to confuse with the nearby `BorrowckInferContext` (which
  does have methods).
- The `mut` ref to it in `TypeChecker` makes it seem like any of the
  fields within might be mutable, but only two (`all_facts` and
  `constraints`) actually are.
- Two of the fields are `pub(crate)` but can be private.

This change makes a lot of code more concise and readable.

compiler/rustc_borrowck/src/type_check/canonical.rs

@@ -62,7 +62,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         {
             let universe_info = error_info.to_universe_info(old_universe);
             for u in (old_universe + 1)..=universe {
-                self.borrowck_context.constraints.universe_causes.insert(u, universe_info.clone());
+                self.constraints.universe_causes.insert(u, universe_info.clone());
             }
         }
 

compiler/rustc_borrowck/src/type_check/input_output.rs

@@ -48,9 +48,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         // FIXME(async_closures): It's kind of wacky that we must apply this
         // transformation here, since we do the same thing in HIR typeck.
         // Maybe we could just fix up the canonicalized signature during HIR typeck?
-        if let DefiningTy::CoroutineClosure(_, args) =
-            self.borrowck_context.universal_regions.defining_ty
-        {
+        if let DefiningTy::CoroutineClosure(_, args) = self.universal_regions.defining_ty {
             assert_matches!(
                 self.tcx().coroutine_kind(self.tcx().coroutine_for_closure(mir_def_id)),
                 Some(hir::CoroutineKind::Desugared(

compiler/rustc_borrowck/src/type_check/liveness/mod.rs

@@ -39,8 +39,8 @@ pub(super) fn generate<'a, 'tcx>(
 
     let free_regions = regions_that_outlive_free_regions(
         typeck.infcx.num_region_vars(),
-        typeck.borrowck_context.universal_regions,
-        &typeck.borrowck_context.constraints.outlives_constraints,
+        typeck.universal_regions,
+        &typeck.constraints.outlives_constraints,
     );
     let (relevant_live_locals, boring_locals) =
         compute_relevant_live_locals(typeck.tcx(), &free_regions, body);
@@ -59,11 +59,7 @@ pub(super) fn generate<'a, 'tcx>(
 
     // Mark regions that should be live where they appear within rvalues or within a call: like
     // args, regions, and types.
-    record_regular_live_regions(
-        typeck.tcx(),
-        &mut typeck.borrowck_context.constraints.liveness_constraints,
-        body,
-    );
+    record_regular_live_regions(typeck.tcx(), &mut typeck.constraints.liveness_constraints, body);
 }
 
 // The purpose of `compute_relevant_live_locals` is to define the subset of `Local`

compiler/rustc_borrowck/src/type_check/liveness/polonius.rs

@@ -88,9 +88,9 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
     body: &Body<'tcx>,
     move_data: &MoveData<'tcx>,
 ) {
-    if let Some(facts) = typeck.borrowck_context.all_facts.as_mut() {
+    if let Some(facts) = typeck.all_facts.as_mut() {
         debug!("populate_access_facts()");
-        let location_table = typeck.borrowck_context.location_table;
+        let location_table = typeck.location_table;
 
         let mut extractor = UseFactsExtractor {
             var_defined_at: &mut facts.var_defined_at,
@@ -108,7 +108,7 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
                 local, local_decl.ty
             );
             let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
-            let universal_regions = &typeck.borrowck_context.universal_regions;
+            let universal_regions = &typeck.universal_regions;
             typeck.infcx.tcx.for_each_free_region(&local_decl.ty, |region| {
                 let region_vid = universal_regions.to_region_vid(region);
                 facts.use_of_var_derefs_origin.push((local, region_vid.into()));
@@ -125,9 +125,9 @@ pub(super) fn add_drop_of_var_derefs_origin<'tcx>(
     kind: &GenericArg<'tcx>,
 ) {
     debug!("add_drop_of_var_derefs_origin(local={:?}, kind={:?}", local, kind);
-    if let Some(facts) = typeck.borrowck_context.all_facts.as_mut() {
+    if let Some(facts) = typeck.all_facts.as_mut() {
         let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
-        let universal_regions = &typeck.borrowck_context.universal_regions;
+        let universal_regions = &typeck.universal_regions;
         typeck.infcx.tcx.for_each_free_region(kind, |drop_live_region| {
             let region_vid = universal_regions.to_region_vid(drop_live_region);
             facts.drop_of_var_derefs_origin.push((local, region_vid.into()));

compiler/rustc_borrowck/src/type_check/liveness/trace.rs

@@ -47,13 +47,12 @@ pub(super) fn trace<'a, 'tcx>(
 
     // When using `-Zpolonius=next`, compute the set of loans that can reach a given region.
     if typeck.tcx().sess.opts.unstable_opts.polonius.is_next_enabled() {
-        let borrowck_context = &mut typeck.borrowck_context;
-        let borrow_set = &borrowck_context.borrow_set;
+        let borrow_set = &typeck.borrow_set;
         let mut live_loans = LiveLoans::new(borrow_set.len());
-        let outlives_constraints = &borrowck_context.constraints.outlives_constraints;
+        let outlives_constraints = &typeck.constraints.outlives_constraints;
         let graph = outlives_constraints.graph(typeck.infcx.num_region_vars());
         let region_graph =
-            graph.region_graph(outlives_constraints, borrowck_context.universal_regions.fr_static);
+            graph.region_graph(outlives_constraints, typeck.universal_regions.fr_static);
 
         // Traverse each issuing region's constraints, and record the loan as flowing into the
         // outlived region.
@@ -73,7 +72,7 @@ pub(super) fn trace<'a, 'tcx>(
 
         // Store the inflowing loans in the liveness constraints: they will be used to compute live
         // loans when liveness data is recorded there.
-        borrowck_context.constraints.liveness_constraints.loans = Some(live_loans);
+        typeck.constraints.liveness_constraints.loans = Some(live_loans);
     };
 
     let cx = LivenessContext {
@@ -222,7 +221,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
         // It may be necessary to just pick out the parts of
         // `add_drop_live_facts_for()` that make sense.
         let facts_to_add: Vec<_> = {
-            let drop_used = &self.cx.typeck.borrowck_context.all_facts.as_ref()?.var_dropped_at;
+            let drop_used = &self.cx.typeck.all_facts.as_ref()?.var_dropped_at;
 
             let relevant_live_locals: FxIndexSet<_> =
                 relevant_live_locals.iter().copied().collect();
@@ -235,12 +234,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
                         return None;
                     }
 
-                    let location = match self
-                        .cx
-                        .typeck
-                        .borrowck_context
-                        .location_table
-                        .to_location(*location_index)
+                    let location = match self.cx.typeck.location_table.to_location(*location_index)
                     {
                         RichLocation::Start(l) => l,
                         RichLocation::Mid(l) => l,
@@ -616,13 +610,9 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
             tcx: typeck.tcx(),
             param_env: typeck.param_env,
             op: |r| {
-                let live_region_vid = typeck.borrowck_context.universal_regions.to_region_vid(r);
+                let live_region_vid = typeck.universal_regions.to_region_vid(r);
 
-                typeck
-                    .borrowck_context
-                    .constraints
-                    .liveness_constraints
-                    .add_points(live_region_vid, live_at);
+                typeck.constraints.liveness_constraints.add_points(live_region_vid, live_at);
             },
         });
     }

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -156,25 +156,24 @@ pub(crate) fn type_check<'a, 'tcx>(
 
     debug!(?normalized_inputs_and_output);
 
-    let mut borrowck_context = BorrowCheckContext {
+    let mut checker = TypeChecker {
+        infcx,
+        param_env,
+        last_span: body.span,
+        body,
+        user_type_annotations: &body.user_type_annotations,
+        region_bound_pairs: &region_bound_pairs,
+        known_type_outlives_obligations,
+        implicit_region_bound,
+        reported_errors: Default::default(),
         universal_regions: &universal_regions,
         location_table,
-        borrow_set,
         all_facts,
+        borrow_set,
         constraints: &mut constraints,
         upvars,
     };
 
-    let mut checker = TypeChecker::new(
-        infcx,
-        body,
-        param_env,
-        &region_bound_pairs,
-        known_type_outlives_obligations,
-        implicit_region_bound,
-        &mut borrowck_context,
-    );
-
     checker.check_user_type_annotations();
 
     let mut verifier = TypeVerifier::new(&mut checker, promoted);
@@ -221,13 +220,12 @@ pub(crate) fn type_check<'a, 'tcx>(
                 infcx.tcx.fold_regions((opaque_type_key, hidden_type), |region, _| {
                     match region.kind() {
                         ty::ReVar(_) => region,
-                        ty::RePlaceholder(placeholder) => checker
-                            .borrowck_context
-                            .constraints
-                            .placeholder_region(infcx, placeholder),
+                        ty::RePlaceholder(placeholder) => {
+                            checker.constraints.placeholder_region(infcx, placeholder)
+                        }
                         _ => ty::Region::new_var(
                             infcx.tcx,
-                            checker.borrowck_context.universal_regions.to_region_vid(region),
+                            checker.universal_regions.to_region_vid(region),
                         ),
                     }
                 });
@@ -240,25 +238,26 @@ pub(crate) fn type_check<'a, 'tcx>(
 }
 
 fn translate_outlives_facts(typeck: &mut TypeChecker<'_, '_>) {
-    let cx = &mut typeck.borrowck_context;
-    if let Some(facts) = cx.all_facts {
+    if let Some(facts) = typeck.all_facts {
         let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
-        let location_table = cx.location_table;
-        facts.subset_base.extend(cx.constraints.outlives_constraints.outlives().iter().flat_map(
-            |constraint: &OutlivesConstraint<'_>| {
-                if let Some(from_location) = constraint.locations.from_location() {
-                    Either::Left(iter::once((
-                        constraint.sup.into(),
-                        constraint.sub.into(),
-                        location_table.mid_index(from_location),
-                    )))
-                } else {
-                    Either::Right(location_table.all_points().map(move |location| {
-                        (constraint.sup.into(), constraint.sub.into(), location)
-                    }))
-                }
-            },
-        ));
+        let location_table = typeck.location_table;
+        facts.subset_base.extend(
+            typeck.constraints.outlives_constraints.outlives().iter().flat_map(
+                |constraint: &OutlivesConstraint<'_>| {
+                    if let Some(from_location) = constraint.locations.from_location() {
+                        Either::Left(iter::once((
+                            constraint.sup.into(),
+                            constraint.sub.into(),
+                            location_table.mid_index(from_location),
+                        )))
+                    } else {
+                        Either::Right(location_table.all_points().map(move |location| {
+                            (constraint.sup.into(), constraint.sub.into(), location)
+                        }))
+                    }
+                },
+            ),
+        );
     }
 }
 
@@ -303,13 +302,8 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
         let ty = self.sanitize_type(constant, constant.const_.ty());
 
         self.cx.infcx.tcx.for_each_free_region(&ty, |live_region| {
-            let live_region_vid =
-                self.cx.borrowck_context.universal_regions.to_region_vid(live_region);
-            self.cx
-                .borrowck_context
-                .constraints
-                .liveness_constraints
-                .add_location(live_region_vid, location);
+            let live_region_vid = self.cx.universal_regions.to_region_vid(live_region);
+            self.cx.constraints.liveness_constraints.add_location(live_region_vid, location);
         });
 
         // HACK(compiler-errors): Constants that are gathered into Body.required_consts
@@ -561,15 +555,9 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         // Don't try to add borrow_region facts for the promoted MIR
 
         let mut swap_constraints = |this: &mut Self| {
-            mem::swap(this.cx.borrowck_context.all_facts, all_facts);
-            mem::swap(
-                &mut this.cx.borrowck_context.constraints.outlives_constraints,
-                &mut constraints,
-            );
-            mem::swap(
-                &mut this.cx.borrowck_context.constraints.liveness_constraints,
-                &mut liveness_constraints,
-            );
+            mem::swap(this.cx.all_facts, all_facts);
+            mem::swap(&mut this.cx.constraints.outlives_constraints, &mut constraints);
+            mem::swap(&mut this.cx.constraints.liveness_constraints, &mut liveness_constraints);
         };
 
         swap_constraints(self);
@@ -594,7 +582,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                 // temporary from the user's point of view.
                 constraint.category = ConstraintCategory::Boring;
             }
-            self.cx.borrowck_context.constraints.outlives_constraints.push(constraint)
+            self.cx.constraints.outlives_constraints.push(constraint)
         }
         // If the region is live at least one location in the promoted MIR,
         // then add a liveness constraint to the main MIR for this region
@@ -604,11 +592,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         // unordered.
         #[allow(rustc::potential_query_instability)]
         for region in liveness_constraints.live_regions_unordered() {
-            self.cx
-                .borrowck_context
-                .constraints
-                .liveness_constraints
-                .add_location(region, location);
+            self.cx.constraints.liveness_constraints.add_location(region, location);
         }
     }
 
@@ -863,15 +847,11 @@ struct TypeChecker<'a, 'tcx> {
     known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
     implicit_region_bound: ty::Region<'tcx>,
     reported_errors: FxIndexSet<(Ty<'tcx>, Span)>,
-    borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
-}
-
-struct BorrowCheckContext<'a, 'tcx> {
-    pub(crate) universal_regions: &'a UniversalRegions<'tcx>,
+    universal_regions: &'a UniversalRegions<'tcx>,
     location_table: &'a LocationTable,
     all_facts: &'a mut Option<AllFacts>,
     borrow_set: &'a BorrowSet<'tcx>,
-    pub(crate) constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
+    constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
     upvars: &'a [&'a ty::CapturedPlace<'tcx>],
 }
 
@@ -1006,29 +986,6 @@ impl Locations {
 }
 
 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
-    fn new(
-        infcx: &'a BorrowckInferCtxt<'tcx>,
-        body: &'a Body<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-        region_bound_pairs: &'a RegionBoundPairs<'tcx>,
-        known_type_outlives_obligations: &'tcx [ty::PolyTypeOutlivesPredicate<'tcx>],
-        implicit_region_bound: ty::Region<'tcx>,
-        borrowck_context: &'a mut BorrowCheckContext<'a, 'tcx>,
-    ) -> Self {
-        Self {
-            infcx,
-            last_span: body.span,
-            body,
-            user_type_annotations: &body.user_type_annotations,
-            param_env,
-            region_bound_pairs,
-            known_type_outlives_obligations,
-            implicit_region_bound,
-            borrowck_context,
-            reported_errors: Default::default(),
-        }
-    }
-
     fn body(&self) -> &Body<'tcx> {
         self.body
     }
@@ -1067,7 +1024,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
         constraint_conversion::ConstraintConversion::new(
             self.infcx,
-            self.borrowck_context.universal_regions,
+            self.universal_regions,
             self.region_bound_pairs,
             self.implicit_region_bound,
             self.param_env,
@@ -1075,7 +1032,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             locations,
             locations.span(self.body),
             category,
-            self.borrowck_context.constraints,
+            self.constraints,
         )
         .convert_all(data);
     }
@@ -1191,7 +1148,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // though.
                 let category = match place.as_local() {
                     Some(RETURN_PLACE) => {
-                        let defining_ty = &self.borrowck_context.universal_regions.defining_ty;
+                        let defining_ty = &self.universal_regions.defining_ty;
                         if defining_ty.is_const() {
                             if tcx.is_static(defining_ty.def_id()) {
                                 ConstraintCategory::UseAsStatic
@@ -1439,12 +1396,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // output) types in the signature must be live, since
                 // all the inputs that fed into it were live.
                 for &late_bound_region in map.values() {
-                    let region_vid =
-                        self.borrowck_context.universal_regions.to_region_vid(late_bound_region);
-                    self.borrowck_context
-                        .constraints
-                        .liveness_constraints
-                        .add_location(region_vid, term_location);
+                    let region_vid = self.universal_regions.to_region_vid(late_bound_region);
+                    self.constraints.liveness_constraints.add_location(region_vid, term_location);
                 }
 
                 self.check_call_inputs(body, term, func, &sig, args, term_location, call_source);
@@ -1532,18 +1485,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 let dest_ty = self.normalize(dest_ty, term_location);
                 let category = match destination.as_local() {
                     Some(RETURN_PLACE) => {
-                        if let BorrowCheckContext {
-                            universal_regions:
-                                UniversalRegions {
-                                    defining_ty:
-                                        DefiningTy::Const(def_id, _)
-                                        | DefiningTy::InlineConst(def_id, _),
-                                    ..
-                                },
-                            ..
-                        } = self.borrowck_context
+                        if let DefiningTy::Const(def_id, _) | DefiningTy::InlineConst(def_id, _) =
+                            self.universal_regions.defining_ty
                         {
-                            if tcx.is_static(*def_id) {
+                            if tcx.is_static(def_id) {
                                 ConstraintCategory::UseAsStatic
                             } else {
                                 ConstraintCategory::UseAsConst
@@ -2654,8 +2599,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         borrowed_place: &Place<'tcx>,
     ) {
         // These constraints are only meaningful during borrowck:
-        let BorrowCheckContext { borrow_set, location_table, all_facts, constraints, .. } =
-            self.borrowck_context;
+        let Self { borrow_set, location_table, all_facts, constraints, .. } = self;
 
         // In Polonius mode, we also push a `loan_issued_at` fact
         // linking the loan to the region (in some cases, though,
@@ -2685,12 +2629,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         );
 
         let tcx = self.infcx.tcx;
-        let field = path_utils::is_upvar_field_projection(
-            tcx,
-            self.borrowck_context.upvars,
-            borrowed_place.as_ref(),
-            body,
-        );
+        let field =
+            path_utils::is_upvar_field_projection(tcx, self.upvars, borrowed_place.as_ref(), body);
         let category = if let Some(field) = field {
             ConstraintCategory::ClosureUpvar(field)
         } else {
@@ -2844,7 +2784,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         if let Some(closure_requirements) = &tcx.mir_borrowck(def_id).closure_requirements {
             constraint_conversion::ConstraintConversion::new(
                 self.infcx,
-                self.borrowck_context.universal_regions,
+                self.universal_regions,
                 self.region_bound_pairs,
                 self.implicit_region_bound,
                 self.param_env,
@@ -2852,7 +2792,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 locations,
                 self.body.span,             // irrelevant; will be overridden.
                 ConstraintCategory::Boring, // same as above.
-                self.borrowck_context.constraints,
+                self.constraints,
             )
             .apply_closure_requirements(closure_requirements, def_id.to_def_id(), args);
         }

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -240,11 +240,7 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
 
     fn create_next_universe(&mut self) -> ty::UniverseIndex {
         let universe = self.type_checker.infcx.create_next_universe();
-        self.type_checker
-            .borrowck_context
-            .constraints
-            .universe_causes
-            .insert(universe, self.universe_info.clone());
+        self.type_checker.constraints.universe_causes.insert(universe, self.universe_info.clone());
         universe
     }
 
@@ -264,11 +260,8 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
 
     #[instrument(skip(self), level = "debug")]
     fn next_placeholder_region(&mut self, placeholder: ty::PlaceholderRegion) -> ty::Region<'tcx> {
-        let reg = self
-            .type_checker
-            .borrowck_context
-            .constraints
-            .placeholder_region(self.type_checker.infcx, placeholder);
+        let reg =
+            self.type_checker.constraints.placeholder_region(self.type_checker.infcx, placeholder);
 
         let reg_info = match placeholder.bound.kind {
             ty::BoundRegionKind::BrAnon => sym::anon,
@@ -294,19 +287,17 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
         sub: ty::Region<'tcx>,
         info: ty::VarianceDiagInfo<TyCtxt<'tcx>>,
     ) {
-        let sub = self.type_checker.borrowck_context.universal_regions.to_region_vid(sub);
-        let sup = self.type_checker.borrowck_context.universal_regions.to_region_vid(sup);
-        self.type_checker.borrowck_context.constraints.outlives_constraints.push(
-            OutlivesConstraint {
-                sup,
-                sub,
-                locations: self.locations,
-                span: self.locations.span(self.type_checker.body),
-                category: self.category,
-                variance_info: info,
-                from_closure: false,
-            },
-        );
+        let sub = self.type_checker.universal_regions.to_region_vid(sub);
+        let sup = self.type_checker.universal_regions.to_region_vid(sup);
+        self.type_checker.constraints.outlives_constraints.push(OutlivesConstraint {
+            sup,
+            sub,
+            locations: self.locations,
+            span: self.locations.span(self.type_checker.body),
+            category: self.category,
+            variance_info: info,
+            from_closure: false,
+        });
     }
 }