Merging upstream version 1.66.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

8 files changed, 310 insertions, 290 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
index b1def1892..02071ed6b 100644
--- a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
@@ -56,7 +56,7 @@ impl<'tcx> UniverseInfo<'tcx> {
     ) {
         match self.0 {
             UniverseInfoInner::RelateTys { expected, found } => {
-                let err = mbcx.infcx.report_mismatched_types(
+                let err = mbcx.infcx.err_ctxt().report_mismatched_types(
                     &cause,
                     expected,
                     found,
@@ -238,20 +238,11 @@ impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
-        mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
-            cause.span,
-            &self.canonical_query,
-            |ref infcx, key, _| {
-                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-                type_op_prove_predicate_with_cause(infcx, &mut *fulfill_cx, key, cause);
-                try_extract_error_from_fulfill_cx(
-                    fulfill_cx,
-                    infcx,
-                    placeholder_region,
-                    error_region,
-                )
-            },
-        )
+        let (ref infcx, key, _) =
+            mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
+        let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
+        type_op_prove_predicate_with_cause(infcx, &mut *fulfill_cx, key, cause);
+        try_extract_error_from_fulfill_cx(fulfill_cx, infcx, placeholder_region, error_region)
     }
 }
 
@@ -288,37 +279,24 @@ where
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
-        mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
-            cause.span,
-            &self.canonical_query,
-            |ref infcx, key, _| {
-                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-
-                let mut selcx = SelectionContext::new(infcx);
-
-                // FIXME(lqd): Unify and de-duplicate the following with the actual
-                // `rustc_traits::type_op::type_op_normalize` query to allow the span we need in the
-                // `ObligationCause`. The normalization results are currently different between
-                // `AtExt::normalize` used in the query and `normalize` called below: the former fails
-                // to normalize the `nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs` test. Check
-                // after #85499 lands to see if its fixes have erased this difference.
-                let (param_env, value) = key.into_parts();
-                let Normalized { value: _, obligations } = rustc_trait_selection::traits::normalize(
-                    &mut selcx,
-                    param_env,
-                    cause,
-                    value.value,
-                );
-                fulfill_cx.register_predicate_obligations(infcx, obligations);
-
-                try_extract_error_from_fulfill_cx(
-                    fulfill_cx,
-                    infcx,
-                    placeholder_region,
-                    error_region,
-                )
-            },
-        )
+        let (ref infcx, key, _) =
+            mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
+        let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
+
+        let mut selcx = SelectionContext::new(infcx);
+
+        // FIXME(lqd): Unify and de-duplicate the following with the actual
+        // `rustc_traits::type_op::type_op_normalize` query to allow the span we need in the
+        // `ObligationCause`. The normalization results are currently different between
+        // `AtExt::normalize` used in the query and `normalize` called below: the former fails
+        // to normalize the `nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs` test. Check
+        // after #85499 lands to see if its fixes have erased this difference.
+        let (param_env, value) = key.into_parts();
+        let Normalized { value: _, obligations } =
+            rustc_trait_selection::traits::normalize(&mut selcx, param_env, cause, value.value);
+        fulfill_cx.register_predicate_obligations(infcx, obligations);
+
+        try_extract_error_from_fulfill_cx(fulfill_cx, infcx, placeholder_region, error_region)
     }
 }
 
@@ -349,21 +327,11 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
-        mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
-            cause.span,
-            &self.canonical_query,
-            |ref infcx, key, _| {
-                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-                type_op_ascribe_user_type_with_span(infcx, &mut *fulfill_cx, key, Some(cause.span))
-                    .ok()?;
-                try_extract_error_from_fulfill_cx(
-                    fulfill_cx,
-                    infcx,
-                    placeholder_region,
-                    error_region,
-                )
-            },
-        )
+        let (ref infcx, key, _) =
+            mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
+        let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
+        type_op_ascribe_user_type_with_span(infcx, &mut *fulfill_cx, key, Some(cause.span)).ok()?;
+        try_extract_error_from_fulfill_cx(fulfill_cx, infcx, placeholder_region, error_region)
     }
 }
 
@@ -407,7 +375,7 @@ impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
 #[instrument(skip(fulfill_cx, infcx), level = "debug")]
 fn try_extract_error_from_fulfill_cx<'tcx>(
     mut fulfill_cx: Box<dyn TraitEngine<'tcx> + 'tcx>,
-    infcx: &InferCtxt<'_, 'tcx>,
+    infcx: &InferCtxt<'tcx>,
     placeholder_region: ty::Region<'tcx>,
     error_region: Option<ty::Region<'tcx>>,
 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
@@ -427,7 +395,7 @@ fn try_extract_error_from_fulfill_cx<'tcx>(
 }
 
 fn try_extract_error_from_region_constraints<'tcx>(
-    infcx: &InferCtxt<'_, 'tcx>,
+    infcx: &InferCtxt<'tcx>,
     placeholder_region: ty::Region<'tcx>,
     error_region: Option<ty::Region<'tcx>>,
     region_constraints: &RegionConstraintData<'tcx>,
@@ -449,42 +417,38 @@ fn try_extract_error_from_region_constraints<'tcx>(
         })?;
 
     debug!(?sub_region, "cause = {:#?}", cause);
-    let nice_error = match (error_region, *sub_region) {
-        (Some(error_region), ty::ReVar(vid)) => NiceRegionError::new(
-            infcx,
-            RegionResolutionError::SubSupConflict(
-                vid,
-                region_var_origin(vid),
-                cause.clone(),
-                error_region,
-                cause.clone(),
-                placeholder_region,
-                vec![],
-            ),
-        ),
-        (Some(error_region), _) => NiceRegionError::new(
-            infcx,
-            RegionResolutionError::ConcreteFailure(cause.clone(), error_region, placeholder_region),
+    let error = match (error_region, *sub_region) {
+        (Some(error_region), ty::ReVar(vid)) => RegionResolutionError::SubSupConflict(
+            vid,
+            region_var_origin(vid),
+            cause.clone(),
+            error_region,
+            cause.clone(),
+            placeholder_region,
+            vec![],
         ),
+        (Some(error_region), _) => {
+            RegionResolutionError::ConcreteFailure(cause.clone(), error_region, placeholder_region)
+        }
         // Note universe here is wrong...
-        (None, ty::ReVar(vid)) => NiceRegionError::new(
-            infcx,
-            RegionResolutionError::UpperBoundUniverseConflict(
-                vid,
-                region_var_origin(vid),
-                universe_of_region(vid),
-                cause.clone(),
-                placeholder_region,
-            ),
-        ),
-        (None, _) => NiceRegionError::new(
-            infcx,
-            RegionResolutionError::ConcreteFailure(cause.clone(), sub_region, placeholder_region),
+        (None, ty::ReVar(vid)) => RegionResolutionError::UpperBoundUniverseConflict(
+            vid,
+            region_var_origin(vid),
+            universe_of_region(vid),
+            cause.clone(),
+            placeholder_region,
         ),
+        (None, _) => {
+            RegionResolutionError::ConcreteFailure(cause.clone(), sub_region, placeholder_region)
+        }
     };
-    nice_error.try_report_from_nll().or_else(|| {
+    NiceRegionError::new(&infcx.err_ctxt(), error).try_report_from_nll().or_else(|| {
         if let SubregionOrigin::Subtype(trace) = cause {
-            Some(infcx.report_and_explain_type_error(*trace, TypeError::RegionsPlaceholderMismatch))
+            Some(
+                infcx
+                    .err_ctxt()
+                    .report_and_explain_type_error(*trace, TypeError::RegionsPlaceholderMismatch),
+            )
         } else {
             None
         }
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index f2204c242..583bc2e28 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -16,7 +16,7 @@ use rustc_middle::mir::{
     FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef,
     ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, VarBindingForm,
 };
-use rustc_middle::ty::{self, subst::Subst, suggest_constraining_type_params, PredicateKind, Ty};
+use rustc_middle::ty::{self, suggest_constraining_type_params, PredicateKind, Ty};
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::hygiene::DesugaringKind;
@@ -198,7 +198,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     move_span,
                     move_spans,
                     *moved_place,
-                    Some(used_place),
                     partially_str,
                     loop_message,
                     move_msg,
@@ -369,6 +368,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let mut visitor = ConditionVisitor { spans: &spans, name: &name, errors: vec![] };
         visitor.visit_body(&body);
 
+        let mut show_assign_sugg = false;
         let isnt_initialized = if let InitializationRequiringAction::PartialAssignment
         | InitializationRequiringAction::Assignment = desired_action
         {
@@ -396,6 +396,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             .count()
             == 0
         {
+            show_assign_sugg = true;
             "isn't initialized"
         } else {
             "is possibly-uninitialized"
@@ -446,10 +447,84 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 }
             }
         }
+
         err.span_label(decl_span, "binding declared here but left uninitialized");
+        if show_assign_sugg {
+            struct LetVisitor {
+                decl_span: Span,
+                sugg_span: Option<Span>,
+            }
+
+            impl<'v> Visitor<'v> for LetVisitor {
+                fn visit_stmt(&mut self, ex: &'v hir::Stmt<'v>) {
+                    if self.sugg_span.is_some() {
+                        return;
+                    }
+                    if let hir::StmtKind::Local(hir::Local {
+                            span, ty, init: None, ..
+                        }) = &ex.kind && span.contains(self.decl_span) {
+                            self.sugg_span = ty.map_or(Some(self.decl_span), |ty| Some(ty.span));
+                    }
+                    hir::intravisit::walk_stmt(self, ex);
+                }
+            }
+
+            let mut visitor = LetVisitor { decl_span, sugg_span: None };
+            visitor.visit_body(&body);
+            if let Some(span) = visitor.sugg_span {
+                self.suggest_assign_value(&mut err, moved_place, span);
+            }
+        }
         err
     }
 
+    fn suggest_assign_value(
+        &self,
+        err: &mut Diagnostic,
+        moved_place: PlaceRef<'tcx>,
+        sugg_span: Span,
+    ) {
+        let ty = moved_place.ty(self.body, self.infcx.tcx).ty;
+        debug!("ty: {:?}, kind: {:?}", ty, ty.kind());
+
+        let tcx = self.infcx.tcx;
+        let implements_default = |ty, param_env| {
+            let Some(default_trait) = tcx.get_diagnostic_item(sym::Default) else {
+                return false;
+            };
+            // Regions are already solved, so we must use a fresh InferCtxt,
+            // but the type has region variables, so erase those.
+            tcx.infer_ctxt()
+                .build()
+                .type_implements_trait(
+                    default_trait,
+                    tcx.erase_regions(ty),
+                    ty::List::empty(),
+                    param_env,
+                )
+                .must_apply_modulo_regions()
+        };
+
+        let assign_value = match ty.kind() {
+            ty::Bool => "false",
+            ty::Float(_) => "0.0",
+            ty::Int(_) | ty::Uint(_) => "0",
+            ty::Never | ty::Error(_) => "",
+            ty::Adt(def, _) if Some(def.did()) == tcx.get_diagnostic_item(sym::Vec) => "vec![]",
+            ty::Adt(_, _) if implements_default(ty, self.param_env) => "Default::default()",
+            _ => "todo!()",
+        };
+
+        if !assign_value.is_empty() {
+            err.span_suggestion_verbose(
+                sugg_span.shrink_to_hi(),
+                format!("consider assigning a value"),
+                format!(" = {}", assign_value),
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
+
     fn suggest_borrow_fn_like(
         &self,
         err: &mut Diagnostic,
@@ -537,41 +612,40 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             .and_then(|def_id| tcx.hir().get_generics(def_id))
         else { return; };
         // Try to find predicates on *generic params* that would allow copying `ty`
-        let predicates: Result<Vec<_>, _> = tcx.infer_ctxt().enter(|infcx| {
-            let mut fulfill_cx = <dyn rustc_infer::traits::TraitEngine<'_>>::new(infcx.tcx);
+        let infcx = tcx.infer_ctxt().build();
+        let mut fulfill_cx = <dyn rustc_infer::traits::TraitEngine<'_>>::new(infcx.tcx);
 
-            let copy_did = infcx.tcx.lang_items().copy_trait().unwrap();
-            let cause = ObligationCause::new(
-                span,
-                self.mir_hir_id(),
-                rustc_infer::traits::ObligationCauseCode::MiscObligation,
-            );
-            fulfill_cx.register_bound(
-                &infcx,
-                self.param_env,
-                // Erase any region vids from the type, which may not be resolved
-                infcx.tcx.erase_regions(ty),
-                copy_did,
-                cause,
-            );
-            // Select all, including ambiguous predicates
-            let errors = fulfill_cx.select_all_or_error(&infcx);
-
-            // Only emit suggestion if all required predicates are on generic
-            errors
-                .into_iter()
-                .map(|err| match err.obligation.predicate.kind().skip_binder() {
-                    PredicateKind::Trait(predicate) => match predicate.self_ty().kind() {
-                        ty::Param(param_ty) => Ok((
-                            generics.type_param(param_ty, tcx),
-                            predicate.trait_ref.print_only_trait_path().to_string(),
-                        )),
-                        _ => Err(()),
-                    },
+        let copy_did = infcx.tcx.lang_items().copy_trait().unwrap();
+        let cause = ObligationCause::new(
+            span,
+            self.mir_hir_id(),
+            rustc_infer::traits::ObligationCauseCode::MiscObligation,
+        );
+        fulfill_cx.register_bound(
+            &infcx,
+            self.param_env,
+            // Erase any region vids from the type, which may not be resolved
+            infcx.tcx.erase_regions(ty),
+            copy_did,
+            cause,
+        );
+        // Select all, including ambiguous predicates
+        let errors = fulfill_cx.select_all_or_error(&infcx);
+
+        // Only emit suggestion if all required predicates are on generic
+        let predicates: Result<Vec<_>, _> = errors
+            .into_iter()
+            .map(|err| match err.obligation.predicate.kind().skip_binder() {
+                PredicateKind::Trait(predicate) => match predicate.self_ty().kind() {
+                    ty::Param(param_ty) => Ok((
+                        generics.type_param(param_ty, tcx),
+                        predicate.trait_ref.print_only_trait_path().to_string(),
+                    )),
                     _ => Err(()),
-                })
-                .collect()
-        });
+                },
+                _ => Err(()),
+            })
+            .collect();
 
         if let Ok(predicates) = predicates {
             suggest_constraining_type_params(
@@ -2146,7 +2220,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             }
                             StorageDeadOrDrop::Destructor(_) => kind,
                         },
-                        ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => {
+                        ProjectionElem::OpaqueCast { .. }
+                        | ProjectionElem::Field(..)
+                        | ProjectionElem::Downcast(..) => {
                             match place_ty.ty.kind() {
                                 ty::Adt(def, _) if def.has_dtor(tcx) => {
                                     // Report the outermost adt with a destructor
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 1c01e78ab..582d683dd 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -1,8 +1,5 @@
 //! Print diagnostics to explain why values are borrowed.
 
-use std::collections::VecDeque;
-
-use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{Applicability, Diagnostic};
 use rustc_index::vec::IndexVec;
 use rustc_infer::infer::NllRegionVariableOrigin;
@@ -359,19 +356,37 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let borrow_region_vid = borrow.region;
         debug!(?borrow_region_vid);
 
-        let region_sub = self.regioncx.find_sub_region_live_at(borrow_region_vid, location);
+        let mut region_sub = self.regioncx.find_sub_region_live_at(borrow_region_vid, location);
         debug!(?region_sub);
 
-        match find_use::find(body, regioncx, tcx, region_sub, location) {
+        let mut use_location = location;
+        let mut use_in_later_iteration_of_loop = false;
+
+        if region_sub == borrow_region_vid {
+            // When `region_sub` is the same as `borrow_region_vid` (the location where the borrow is
+            // issued is the same location that invalidates the reference), this is likely a loop iteration
+            // - in this case, try using the loop terminator location in `find_sub_region_live_at`.
+            if let Some(loop_terminator_location) =
+                regioncx.find_loop_terminator_location(borrow.region, body)
+            {
+                region_sub = self
+                    .regioncx
+                    .find_sub_region_live_at(borrow_region_vid, loop_terminator_location);
+                debug!("explain_why_borrow_contains_point: region_sub in loop={:?}", region_sub);
+                use_location = loop_terminator_location;
+                use_in_later_iteration_of_loop = true;
+            }
+        }
+
+        match find_use::find(body, regioncx, tcx, region_sub, use_location) {
             Some(Cause::LiveVar(local, location)) => {
                 let span = body.source_info(location).span;
                 let spans = self
                     .move_spans(Place::from(local).as_ref(), location)
                     .or_else(|| self.borrow_spans(span, location));
 
-                let borrow_location = location;
-                if self.is_use_in_later_iteration_of_loop(borrow_location, location) {
-                    let later_use = self.later_use_kind(borrow, spans, location);
+                if use_in_later_iteration_of_loop {
+                    let later_use = self.later_use_kind(borrow, spans, use_location);
                     BorrowExplanation::UsedLaterInLoop(later_use.0, later_use.1, later_use.2)
                 } else {
                     // Check if the location represents a `FakeRead`, and adapt the error
@@ -425,131 +440,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }
     }
 
-    /// true if `borrow_location` can reach `use_location` by going through a loop and
-    /// `use_location` is also inside of that loop
-    fn is_use_in_later_iteration_of_loop(
-        &self,
-        borrow_location: Location,
-        use_location: Location,
-    ) -> bool {
-        let back_edge = self.reach_through_backedge(borrow_location, use_location);
-        back_edge.map_or(false, |back_edge| self.can_reach_head_of_loop(use_location, back_edge))
-    }
-
-    /// Returns the outmost back edge if `from` location can reach `to` location passing through
-    /// that back edge
-    fn reach_through_backedge(&self, from: Location, to: Location) -> Option<Location> {
-        let mut visited_locations = FxHashSet::default();
-        let mut pending_locations = VecDeque::new();
-        visited_locations.insert(from);
-        pending_locations.push_back(from);
-        debug!("reach_through_backedge: from={:?} to={:?}", from, to,);
-
-        let mut outmost_back_edge = None;
-        while let Some(location) = pending_locations.pop_front() {
-            debug!(
-                "reach_through_backedge: location={:?} outmost_back_edge={:?}
-                   pending_locations={:?} visited_locations={:?}",
-                location, outmost_back_edge, pending_locations, visited_locations
-            );
-
-            if location == to && outmost_back_edge.is_some() {
-                // We've managed to reach the use location
-                debug!("reach_through_backedge: found!");
-                return outmost_back_edge;
-            }
-
-            let block = &self.body.basic_blocks[location.block];
-
-            if location.statement_index < block.statements.len() {
-                let successor = location.successor_within_block();
-                if visited_locations.insert(successor) {
-                    pending_locations.push_back(successor);
-                }
-            } else {
-                pending_locations.extend(
-                    block
-                        .terminator()
-                        .successors()
-                        .map(|bb| Location { statement_index: 0, block: bb })
-                        .filter(|s| visited_locations.insert(*s))
-                        .map(|s| {
-                            if self.is_back_edge(location, s) {
-                                match outmost_back_edge {
-                                    None => {
-                                        outmost_back_edge = Some(location);
-                                    }
-
-                                    Some(back_edge)
-                                        if location.dominates(back_edge, &self.dominators) =>
-                                    {
-                                        outmost_back_edge = Some(location);
-                                    }
-
-                                    Some(_) => {}
-                                }
-                            }
-
-                            s
-                        }),
-                );
-            }
-        }
-
-        None
-    }
-
-    /// true if `from` location can reach `loop_head` location and `loop_head` dominates all the
-    /// intermediate nodes
-    fn can_reach_head_of_loop(&self, from: Location, loop_head: Location) -> bool {
-        self.find_loop_head_dfs(from, loop_head, &mut FxHashSet::default())
-    }
-
-    fn find_loop_head_dfs(
-        &self,
-        from: Location,
-        loop_head: Location,
-        visited_locations: &mut FxHashSet<Location>,
-    ) -> bool {
-        visited_locations.insert(from);
-
-        if from == loop_head {
-            return true;
-        }
-
-        if loop_head.dominates(from, &self.dominators) {
-            let block = &self.body.basic_blocks[from.block];
-
-            if from.statement_index < block.statements.len() {
-                let successor = from.successor_within_block();
-
-                if !visited_locations.contains(&successor)
-                    && self.find_loop_head_dfs(successor, loop_head, visited_locations)
-                {
-                    return true;
-                }
-            } else {
-                for bb in block.terminator().successors() {
-                    let successor = Location { statement_index: 0, block: bb };
-
-                    if !visited_locations.contains(&successor)
-                        && self.find_loop_head_dfs(successor, loop_head, visited_locations)
-                    {
-                        return true;
-                    }
-                }
-            }
-        }
-
-        false
-    }
-
-    /// True if an edge `source -> target` is a backedge -- in other words, if the target
-    /// dominates the source.
-    fn is_back_edge(&self, source: Location, target: Location) -> bool {
-        target.dominates(source, &self.dominators)
-    }
-
     /// Determine how the borrow was later used.
     /// First span returned points to the location of the conflicting use
     /// Second span if `Some` is returned in the case of closures and points
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 683084cf0..534d9ecae 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -237,6 +237,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 }
                 ProjectionElem::Downcast(..) if opt.including_downcast => return None,
                 ProjectionElem::Downcast(..) => (),
+                ProjectionElem::OpaqueCast(..) => (),
                 ProjectionElem::Field(field, _ty) => {
                     // FIXME(project-rfc_2229#36): print capture precisely here.
                     if let Some(field) = self.is_upvar_field_projection(PlaceRef {
@@ -317,6 +318,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
                 }
                 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
+                ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty),
                 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
             },
         };
@@ -970,7 +972,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         move_span: Span,
         move_spans: UseSpans<'tcx>,
         moved_place: Place<'tcx>,
-        used_place: Option<PlaceRef<'tcx>>,
         partially_str: &str,
         loop_message: &str,
         move_msg: &str,
@@ -1024,7 +1025,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
                         let ty = moved_place.ty(self.body, self.infcx.tcx).ty;
                         let suggest = match self.infcx.tcx.get_diagnostic_item(sym::IntoIterator) {
-                            Some(def_id) => self.infcx.tcx.infer_ctxt().enter(|infcx| {
+                            Some(def_id) => {
+                                let infcx = self.infcx.tcx.infer_ctxt().build();
                                 type_known_to_meet_bound_modulo_regions(
                                     &infcx,
                                     self.param_env,
@@ -1035,7 +1037,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                     def_id,
                                     DUMMY_SP,
                                 )
-                            }),
+                            }
                             _ => false,
                         };
                         if suggest {
@@ -1058,9 +1060,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 place_name, partially_str, loop_message
                             ),
                         );
-                        // If we have a `&mut` ref, we need to reborrow.
-                        if let Some(ty::Ref(_, _, hir::Mutability::Mut)) = used_place
-                            .map(|used_place| used_place.ty(self.body, self.infcx.tcx).ty.kind())
+                        // If the moved place was a `&mut` ref, then we can
+                        // suggest to reborrow it where it was moved, so it
+                        // will still be valid by the time we get to the usage.
+                        if let ty::Ref(_, _, hir::Mutability::Mut) =
+                            moved_place.ty(self.body, self.infcx.tcx).ty.kind()
                         {
                             // If we are in a loop this will be suggested later.
                             if !is_loop_move {
diff --git a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
index 8d4c38d3a..5a47f4567 100644
--- a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -401,7 +401,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         };
         if let Some(use_spans) = use_spans {
             self.explain_captures(
-                &mut err, span, span, use_spans, move_place, None, "", "", "", false, true,
+                &mut err, span, span, use_spans, move_place, "", "", "", false, true,
             );
         }
         err
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 6b5014fa9..8ad40c0aa 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -169,6 +169,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         ..,
                         ProjectionElem::Index(_)
                         | ProjectionElem::ConstantIndex { .. }
+                        | ProjectionElem::OpaqueCast { .. }
                         | ProjectionElem::Subslice { .. }
                         | ProjectionElem::Downcast(..),
                     ],
@@ -931,7 +932,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 let opt_suggestions = self
                     .infcx
                     .tcx
-                    .typeck(path_segment.hir_id.owner)
+                    .typeck(path_segment.hir_id.owner.def_id)
                     .type_dependent_def_id(*hir_id)
                     .and_then(|def_id| self.infcx.tcx.impl_of_method(def_id))
                     .map(|def_id| self.infcx.tcx.associated_items(def_id))
@@ -1031,7 +1032,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         if look_at_return && hir.get_return_block(closure_id).is_some() {
             // ...otherwise we are probably in the tail expression of the function, point at the
             // return type.
-            match hir.get_by_def_id(hir.get_parent_item(fn_call_id)) {
+            match hir.get_by_def_id(hir.get_parent_item(fn_call_id).def_id) {
                 hir::Node::Item(hir::Item { ident, kind: hir::ItemKind::Fn(sig, ..), .. })
                 | hir::Node::TraitItem(hir::TraitItem {
                     ident,
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 34be2874f..15230718d 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -186,7 +186,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     if let Some(lower_bound_region) = lower_bound_region {
                         let generic_ty = type_test.generic_kind.to_ty(self.infcx.tcx);
                         let origin = RelateParamBound(type_test_span, generic_ty, None);
-                        self.buffer_error(self.infcx.construct_generic_bound_failure(
+                        self.buffer_error(self.infcx.err_ctxt().construct_generic_bound_failure(
                             self.body.source.def_id().expect_local(),
                             type_test_span,
                             Some(origin),
@@ -281,7 +281,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         let tcx = self.infcx.tcx;
         match tcx.hir().get_if_local(def_id) {
             Some(Node::ImplItem(impl_item)) => {
-                match tcx.hir().find_by_def_id(tcx.hir().get_parent_item(impl_item.hir_id())) {
+                match tcx.hir().find_by_def_id(tcx.hir().get_parent_item(impl_item.hir_id()).def_id)
+                {
                     Some(Node::Item(Item {
                         kind: ItemKind::Impl(hir::Impl { self_ty, .. }),
                         ..
@@ -291,7 +292,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             }
             Some(Node::TraitItem(trait_item)) => {
                 let trait_did = tcx.hir().get_parent_item(trait_item.hir_id());
-                match tcx.hir().find_by_def_id(trait_did) {
+                match tcx.hir().find_by_def_id(trait_did.def_id) {
                     Some(Node::Item(Item { kind: ItemKind::Trait(..), .. })) => {
                         // The method being called is defined in the `trait`, but the `'static`
                         // obligation comes from the `impl`. Find that `impl` so that we can point
@@ -340,7 +341,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     /// Report an error because the universal region `fr` was required to outlive
     /// `outlived_fr` but it is not known to do so. For example:
     ///
-    /// ```compile_fail,E0312
+    /// ```compile_fail
     /// fn foo<'a, 'b>(x: &'a u32) -> &'b u32 { x }
     /// ```
     ///
@@ -364,7 +365,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
         // Check if we can use one of the "nice region errors".
         if let (Some(f), Some(o)) = (self.to_error_region(fr), self.to_error_region(outlived_fr)) {
-            let nice = NiceRegionError::new_from_span(self.infcx, cause.span, o, f);
+            let infer_err = self.infcx.err_ctxt();
+            let nice = NiceRegionError::new_from_span(&infer_err, cause.span, o, f);
             if let Some(diag) = nice.try_report_from_nll() {
                 self.buffer_error(diag);
                 return;
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index 6c1eaa809..c044dbaba 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -251,7 +251,8 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
             .or_else(|| self.give_name_if_anonymous_region_appears_in_upvars(fr))
             .or_else(|| self.give_name_if_anonymous_region_appears_in_output(fr))
             .or_else(|| self.give_name_if_anonymous_region_appears_in_yield_ty(fr))
-            .or_else(|| self.give_name_if_anonymous_region_appears_in_impl_signature(fr));
+            .or_else(|| self.give_name_if_anonymous_region_appears_in_impl_signature(fr))
+            .or_else(|| self.give_name_if_anonymous_region_appears_in_arg_position_impl_trait(fr));
 
         if let Some(ref value) = value {
             self.region_names.try_borrow_mut().unwrap().insert(fr, value.clone());
@@ -707,7 +708,8 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                         hir::AsyncGeneratorKind::Block => " of async block",
                         hir::AsyncGeneratorKind::Closure => " of async closure",
                         hir::AsyncGeneratorKind::Fn => {
-                            let parent_item = hir.get_by_def_id(hir.get_parent_item(mir_hir_id));
+                            let parent_item =
+                                hir.get_by_def_id(hir.get_parent_item(mir_hir_id).def_id);
                             let output = &parent_item
                                 .fn_decl()
                                 .expect("generator lowered from async fn should be in fn")
@@ -863,20 +865,13 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         };
 
         let tcx = self.infcx.tcx;
-        let body_parent_did = tcx.opt_parent(self.mir_def_id().to_def_id())?;
-        if tcx.parent(region.def_id) != body_parent_did
-            || tcx.def_kind(body_parent_did) != DefKind::Impl
-        {
+        let region_parent = tcx.parent(region.def_id);
+        if tcx.def_kind(region_parent) != DefKind::Impl {
             return None;
         }
 
-        let mut found = false;
-        tcx.fold_regions(tcx.type_of(body_parent_did), |r: ty::Region<'tcx>, _| {
-            if *r == ty::ReEarlyBound(region) {
-                found = true;
-            }
-            r
-        });
+        let found = tcx
+            .any_free_region_meets(&tcx.type_of(region_parent), |r| *r == ty::ReEarlyBound(region));
 
         Some(RegionName {
             name: self.synthesize_region_name(),
@@ -889,4 +884,92 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
             ),
         })
     }
+
+    fn give_name_if_anonymous_region_appears_in_arg_position_impl_trait(
+        &self,
+        fr: RegionVid,
+    ) -> Option<RegionName> {
+        let ty::ReEarlyBound(region) = *self.to_error_region(fr)? else {
+            return None;
+        };
+        if region.has_name() {
+            return None;
+        };
+
+        let predicates = self
+            .infcx
+            .tcx
+            .predicates_of(self.body.source.def_id())
+            .instantiate_identity(self.infcx.tcx)
+            .predicates;
+
+        if let Some(upvar_index) = self
+            .regioncx
+            .universal_regions()
+            .defining_ty
+            .upvar_tys()
+            .position(|ty| self.any_param_predicate_mentions(&predicates, ty, region))
+        {
+            let (upvar_name, upvar_span) = self.regioncx.get_upvar_name_and_span_for_region(
+                self.infcx.tcx,
+                &self.upvars,
+                upvar_index,
+            );
+            let region_name = self.synthesize_region_name();
+
+            Some(RegionName {
+                name: region_name,
+                source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name),
+            })
+        } else if let Some(arg_index) = self
+            .regioncx
+            .universal_regions()
+            .unnormalized_input_tys
+            .iter()
+            .position(|ty| self.any_param_predicate_mentions(&predicates, *ty, region))
+        {
+            let (arg_name, arg_span) = self.regioncx.get_argument_name_and_span_for_region(
+                self.body,
+                &self.local_names,
+                arg_index,
+            );
+            let region_name = self.synthesize_region_name();
+
+            Some(RegionName {
+                name: region_name,
+                source: RegionNameSource::AnonRegionFromArgument(
+                    RegionNameHighlight::CannotMatchHirTy(arg_span, arg_name?.to_string()),
+                ),
+            })
+        } else {
+            None
+        }
+    }
+
+    fn any_param_predicate_mentions(
+        &self,
+        predicates: &[ty::Predicate<'tcx>],
+        ty: Ty<'tcx>,
+        region: ty::EarlyBoundRegion,
+    ) -> bool {
+        let tcx = self.infcx.tcx;
+        ty.walk().any(|arg| {
+            if let ty::GenericArgKind::Type(ty) = arg.unpack()
+                && let ty::Param(_) = ty.kind()
+            {
+                predicates.iter().any(|pred| {
+                    match pred.kind().skip_binder() {
+                        ty::PredicateKind::Trait(data) if data.self_ty() == ty => {}
+                        ty::PredicateKind::Projection(data) if data.projection_ty.self_ty() == ty => {}
+                        _ => return false,
+                    }
+                    tcx.any_free_region_meets(pred, |r| {
+                        *r == ty::ReEarlyBound(region)
+                    })
+                })
+            } else {
+                false
+            }
+        })
+    }
 }