diff --git a/compiler/rustc_borrowck/src/borrow_set.rs b/compiler/rustc_borrowck/src/borrow_set.rs
index 3e6d0311b2703..0bae1bd07a298 100644
--- a/compiler/rustc_borrowck/src/borrow_set.rs
+++ b/compiler/rustc_borrowck/src/borrow_set.rs
@@ -126,7 +126,7 @@ impl<'tcx> BorrowSet<'tcx> {
     ) -> Self {
         let mut visitor = GatherBorrows {
             tcx,
-            body: body,
+            body,
             location_map: Default::default(),
             activation_map: Default::default(),
             local_map: Default::default(),
diff --git a/compiler/rustc_borrowck/src/borrowck_errors.rs b/compiler/rustc_borrowck/src/borrowck_errors.rs
index c1f753282725a..8a2936c265796 100644
--- a/compiler/rustc_borrowck/src/borrowck_errors.rs
+++ b/compiler/rustc_borrowck/src/borrowck_errors.rs
@@ -213,7 +213,7 @@ impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
             via(msg_old),
         );
 
-        if msg_new == "" {
+        if msg_new.is_empty() {
             // If `msg_new` is empty, then this isn't a borrow of a union field.
             err.span_label(span, format!("{kind_new} borrow occurs here"));
             err.span_label(old_span, format!("{kind_old} borrow occurs here"));
diff --git a/compiler/rustc_borrowck/src/dataflow.rs b/compiler/rustc_borrowck/src/dataflow.rs
index ec7d4582a6013..f2b5ddcd7827c 100644
--- a/compiler/rustc_borrowck/src/dataflow.rs
+++ b/compiler/rustc_borrowck/src/dataflow.rs
@@ -43,9 +43,9 @@ impl<'mir, 'tcx> ResultsVisitable<'tcx> for BorrowckResults<'mir, 'tcx> {
     }
 
     fn reset_to_block_entry(&self, state: &mut Self::FlowState, block: BasicBlock) {
-        state.borrows.clone_from(&self.borrows.entry_set_for_block(block));
-        state.uninits.clone_from(&self.uninits.entry_set_for_block(block));
-        state.ever_inits.clone_from(&self.ever_inits.entry_set_for_block(block));
+        state.borrows.clone_from(self.borrows.entry_set_for_block(block));
+        state.uninits.clone_from(self.uninits.entry_set_for_block(block));
+        state.ever_inits.clone_from(self.ever_inits.entry_set_for_block(block));
     }
 
     fn reconstruct_before_statement_effect(
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 67c11ff4a5bda..c214c52880a94 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -895,7 +895,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             for alias_ty in alias_tys {
                 if alias_ty.span.desugaring_kind().is_some() {
                     // Skip `async` desugaring `impl Future`.
-                    ()
                 }
                 if let TyKind::TraitObject(_, lt, _) = alias_ty.kind {
                     if lt.ident.name == kw::Empty {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index 77fb9fb431518..25a0d40218bbb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -519,7 +519,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                     }
 
                     // Otherwise, let's descend into the referent types.
-                    search_stack.push((*referent_ty, &referent_hir_ty.ty));
+                    search_stack.push((*referent_ty, referent_hir_ty.ty));
                 }
 
                 // Match up something like `Foo<'1>`
@@ -558,7 +558,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                 }
 
                 (ty::RawPtr(mut_ty, _), hir::TyKind::Ptr(mut_hir_ty)) => {
-                    search_stack.push((*mut_ty, &mut_hir_ty.ty));
+                    search_stack.push((*mut_ty, mut_hir_ty.ty));
                 }
 
                 _ => {
@@ -652,7 +652,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         let upvar_index = self.regioncx.get_upvar_index_for_region(self.infcx.tcx, fr)?;
         let (upvar_name, upvar_span) = self.regioncx.get_upvar_name_and_span_for_region(
             self.infcx.tcx,
-            &self.upvars,
+            self.upvars,
             upvar_index,
         );
         let region_name = self.synthesize_region_name();
@@ -717,7 +717,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                             .output;
                         span = output.span();
                         if let hir::FnRetTy::Return(ret) = output {
-                            hir_ty = Some(self.get_future_inner_return_ty(*ret));
+                            hir_ty = Some(self.get_future_inner_return_ty(ret));
                         }
                         " of async function"
                     }
@@ -958,7 +958,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         {
             let (upvar_name, upvar_span) = self.regioncx.get_upvar_name_and_span_for_region(
                 self.infcx.tcx,
-                &self.upvars,
+                self.upvars,
                 upvar_index,
             );
             let region_name = self.synthesize_region_name();
diff --git a/compiler/rustc_borrowck/src/nll.rs b/compiler/rustc_borrowck/src/nll.rs
index 5d7ce548469fb..923cf7e940573 100644
--- a/compiler/rustc_borrowck/src/nll.rs
+++ b/compiler/rustc_borrowck/src/nll.rs
@@ -114,7 +114,6 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
             move_data,
             elements,
             upvars,
-            polonius_input,
         );
 
     // Create the region inference context, taking ownership of the
diff --git a/compiler/rustc_borrowck/src/polonius/mod.rs b/compiler/rustc_borrowck/src/polonius/mod.rs
index 9984f76e6d446..c590104978c2d 100644
--- a/compiler/rustc_borrowck/src/polonius/mod.rs
+++ b/compiler/rustc_borrowck/src/polonius/mod.rs
@@ -43,8 +43,8 @@ pub(crate) fn emit_facts<'tcx>(
     emit_universal_region_facts(
         all_facts,
         borrow_set,
-        &universal_regions,
-        &universal_region_relations,
+        universal_regions,
+        universal_region_relations,
     );
     emit_cfg_and_loan_kills_facts(all_facts, tcx, location_table, body, borrow_set);
     emit_loan_invalidations_facts(all_facts, tcx, location_table, body, borrow_set);
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index bf1c1b1433ea6..c56eaaff076ce 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -344,7 +344,7 @@ fn sccs_info<'tcx>(infcx: &BorrowckInferCtxt<'tcx>, sccs: &ConstraintSccs) {
 
     for (reg_var_idx, scc_idx) in sccs.scc_indices().iter().enumerate() {
         let reg_var = ty::RegionVid::from_usize(reg_var_idx);
-        let origin = var_to_origin.get(&reg_var).unwrap_or_else(|| &RegionCtxt::Unknown);
+        let origin = var_to_origin.get(&reg_var).unwrap_or(&RegionCtxt::Unknown);
         components[scc_idx.as_usize()].insert((reg_var, *origin));
     }
 
@@ -2216,7 +2216,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // #114907 where this happens via liveness and dropck outlives results.
         // Therefore, we return a default value in case that happens, which should at worst emit a
         // suboptimal error, instead of the ICE.
-        self.universe_causes.get(&universe).cloned().unwrap_or_else(|| UniverseInfo::other())
+        self.universe_causes.get(&universe).cloned().unwrap_or_else(UniverseInfo::other)
     }
 
     /// Tries to find the terminator of the loop in which the region 'r' resides.
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index 51c3648d7307d..67e5c8352df0f 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -418,9 +418,7 @@ fn check_opaque_type_parameter_valid<'tcx>(
             let opaque_param = opaque_generics.param_at(i, tcx);
             let kind = opaque_param.kind.descr();
 
-            if let Err(guar) = opaque_env.param_is_error(i) {
-                return Err(guar);
-            }
+            opaque_env.param_is_error(i)?;
 
             return Err(tcx.dcx().emit_err(NonGenericOpaqueTypeParam {
                 ty: arg,
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
index 8b863efad6ca2..b777e01f7a6c2 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
@@ -12,9 +12,7 @@ use rustc_mir_dataflow::ResultsCursor;
 use std::rc::Rc;
 
 use crate::{
-    constraints::OutlivesConstraintSet,
-    facts::{AllFacts, AllFactsExt},
-    region_infer::values::LivenessValues,
+    constraints::OutlivesConstraintSet, region_infer::values::LivenessValues,
     universal_regions::UniversalRegions,
 };
 
@@ -38,7 +36,6 @@ pub(super) fn generate<'mir, 'tcx>(
     elements: &Rc<DenseLocationMap>,
     flow_inits: &mut ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>,
     move_data: &MoveData<'tcx>,
-    use_polonius: bool,
 ) {
     debug!("liveness::generate");
 
@@ -49,11 +46,8 @@ pub(super) fn generate<'mir, 'tcx>(
     );
     let (relevant_live_locals, boring_locals) =
         compute_relevant_live_locals(typeck.tcx(), &free_regions, body);
-    let facts_enabled = use_polonius || AllFacts::enabled(typeck.tcx());
 
-    if facts_enabled {
-        polonius::populate_access_facts(typeck, body, move_data);
-    };
+    polonius::populate_access_facts(typeck, body, move_data);
 
     trace::trace(
         typeck,
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs b/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
index d8f03a07a63ca..a009e28a0ddd0 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
@@ -87,10 +87,10 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
     body: &Body<'tcx>,
     move_data: &MoveData<'tcx>,
 ) {
-    debug!("populate_access_facts()");
-    let location_table = typeck.borrowck_context.location_table;
-
     if let Some(facts) = typeck.borrowck_context.all_facts.as_mut() {
+        debug!("populate_access_facts()");
+        let location_table = typeck.borrowck_context.location_table;
+
         let mut extractor = UseFactsExtractor {
             var_defined_at: &mut facts.var_defined_at,
             var_used_at: &mut facts.var_used_at,
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
index 50843c602cc84..359c4ea0eb1e2 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
@@ -217,35 +217,52 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
     /// Add facts for all locals with free regions, since regions may outlive
     /// the function body only at certain nodes in the CFG.
     fn add_extra_drop_facts(&mut self, relevant_live_locals: &[Local]) -> Option<()> {
-        let drop_used = self
-            .cx
-            .typeck
-            .borrowck_context
-            .all_facts
-            .as_ref()
-            .map(|facts| facts.var_dropped_at.clone())?;
+        // This collect is more necessary than immediately apparent
+        // because these facts go into `add_drop_live_facts_for()`,
+        // which also writes to `all_facts`, and so this is genuinely
+        // a simulatneous overlapping mutable borrow.
+        // FIXME for future hackers: investigate whether this is
+        // actually necessary; these facts come from Polonius
+        // and probably maybe plausibly does not need to go back in.
+        // 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 relevant_live_locals: FxIndexSet<_> =
+                relevant_live_locals.iter().copied().collect();
+
+            drop_used
+                .iter()
+                .filter_map(|(local, location_index)| {
+                    let local_ty = self.cx.body.local_decls[*local].ty;
+                    if relevant_live_locals.contains(local) || !local_ty.has_free_regions() {
+                        return None;
+                    }
 
-        let relevant_live_locals: FxIndexSet<_> = relevant_live_locals.iter().copied().collect();
-
-        let locations = IntervalSet::new(self.cx.elements.num_points());
-
-        for (local, location_index) in drop_used {
-            if !relevant_live_locals.contains(&local) {
-                let local_ty = self.cx.body.local_decls[local].ty;
-                if local_ty.has_free_regions() {
                     let location = match self
                         .cx
                         .typeck
                         .borrowck_context
                         .location_table
-                        .to_location(location_index)
+                        .to_location(*location_index)
                     {
                         RichLocation::Start(l) => l,
                         RichLocation::Mid(l) => l,
                     };
-                    self.cx.add_drop_live_facts_for(local, local_ty, &[location], &locations);
-                }
-            }
+
+                    Some((*local, local_ty, location))
+                })
+                .collect()
+        };
+
+        // FIXME: these locations seem to have a special meaning (e.g. everywhere, at the end, ...), but I don't know which one. Please help me rename it to something descriptive!
+        // Also, if this IntervalSet is used in many places, it maybe should have a newtype'd
+        // name with a description of what it means for future mortals passing by.
+        let locations = IntervalSet::new(self.cx.elements.num_points());
+
+        for (local, local_ty, location) in facts_to_add {
+            self.cx.add_drop_live_facts_for(local, local_ty, &[location], &locations);
         }
         Some(())
     }
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index c7c1b2af6a7bc..81bde14a82f4e 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -133,7 +133,6 @@ pub(crate) fn type_check<'mir, 'tcx>(
     move_data: &MoveData<'tcx>,
     elements: &Rc<DenseLocationMap>,
     upvars: &[&ty::CapturedPlace<'tcx>],
-    use_polonius: bool,
 ) -> MirTypeckResults<'tcx> {
     let implicit_region_bound = ty::Region::new_var(infcx.tcx, universal_regions.fr_fn_body);
     let mut constraints = MirTypeckRegionConstraints {
@@ -189,7 +188,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
     checker.equate_inputs_and_outputs(body, universal_regions, &normalized_inputs_and_output);
     checker.check_signature_annotation(body);
 
-    liveness::generate(&mut checker, body, elements, flow_inits, move_data, use_polonius);
+    liveness::generate(&mut checker, body, elements, flow_inits, move_data);
 
     translate_outlives_facts(&mut checker);
     let opaque_type_values = infcx.take_opaque_types();