Merging upstream version 1.71.1+dfsg1.

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

10 files changed, 783 insertions, 622 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
index 84f75caa6..f41795d60 100644
--- a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
@@ -128,7 +128,7 @@ impl<'tcx> ToUniverseInfo<'tcx>
     }
 }
 
-impl<'tcx, F, G> ToUniverseInfo<'tcx> for Canonical<'tcx, type_op::custom::CustomTypeOp<F, G>> {
+impl<'tcx, F> ToUniverseInfo<'tcx> for Canonical<'tcx, type_op::custom::CustomTypeOp<F>> {
     fn to_universe_info(self, _base_universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {
         // We can't rerun custom type ops.
         UniverseInfo::other()
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 75a3dd0c0..15d73ed73 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -1,5 +1,6 @@
+use std::iter;
+
 use either::Either;
-use rustc_const_eval::util::CallKind;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{
@@ -9,8 +10,8 @@ use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
 use rustc_hir::{AsyncGeneratorKind, GeneratorKind, LangItem};
-use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::ObligationCause;
+use rustc_middle::hir::nested_filter::OnlyBodies;
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
     self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory,
@@ -18,20 +19,19 @@ use rustc_middle::mir::{
     ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, VarBindingForm,
 };
 use rustc_middle::ty::{self, suggest_constraining_type_params, PredicateKind, Ty};
+use rustc_middle::util::CallKind;
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::hygiene::DesugaringKind;
-use rustc_span::symbol::{kw, sym};
+use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::ObligationCtxt;
 
 use crate::borrow_set::TwoPhaseActivation;
 use crate::borrowck_errors;
-
 use crate::diagnostics::conflict_errors::StorageDeadOrDrop::LocalStorageDead;
-use crate::diagnostics::find_all_local_uses;
-use crate::diagnostics::mutability_errors::mut_borrow_of_mutable_ref;
+use crate::diagnostics::{find_all_local_uses, CapturedMessageOpt};
 use crate::{
     borrow_set::BorrowData, diagnostics::Instance, prefixes::IsPrefixOf,
     InitializationRequiringAction, MirBorrowckCtxt, PrefixSet, WriteKind,
@@ -158,7 +158,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             } else if reinits > 1 {
                 err.span_note(
                     MultiSpan::from_spans(reinit_spans),
-                    &if reinits <= 3 {
+                    if reinits <= 3 {
                         format!("these {reinits} reinitializations might get skipped")
                     } else {
                         format!(
@@ -183,13 +183,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 let move_spans = self.move_spans(moved_place.as_ref(), move_out.source);
                 let move_span = move_spans.args_or_use();
 
-                let move_msg = if move_spans.for_closure() { " into closure" } else { "" };
+                let is_move_msg = move_spans.for_closure();
 
-                let loop_message = if location == move_out.source || move_site.traversed_back_edge {
-                    ", in previous iteration of loop"
-                } else {
-                    ""
-                };
+                let is_loop_message = location == move_out.source || move_site.traversed_back_edge;
 
                 if location == move_out.source {
                     is_loop_move = true;
@@ -206,17 +202,21 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         );
                     }
 
+                    let msg_opt = CapturedMessageOpt {
+                        is_partial_move,
+                        is_loop_message,
+                        is_move_msg,
+                        is_loop_move,
+                        maybe_reinitialized_locations_is_empty: maybe_reinitialized_locations
+                            .is_empty(),
+                    };
                     self.explain_captures(
                         &mut err,
                         span,
                         move_span,
                         move_spans,
                         *moved_place,
-                        partially_str,
-                        loop_message,
-                        move_msg,
-                        is_loop_move,
-                        maybe_reinitialized_locations.is_empty(),
+                        msg_opt,
                     );
                 }
                 seen_spans.insert(move_span);
@@ -253,7 +253,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     // We have a `&mut` ref, we need to reborrow on each iteration (#62112).
                     err.span_suggestion_verbose(
                         span.shrink_to_lo(),
-                        &format!(
+                        format!(
                             "consider creating a fresh reborrow of {} here",
                             self.describe_place(moved_place)
                                 .map(|n| format!("`{n}`"))
@@ -282,12 +282,21 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
 
             if needs_note {
-                let span = if let Some(local) = place.as_local() {
-                    Some(self.body.local_decls[local].source_info.span)
+                if let Some(local) = place.as_local() {
+                    let span = self.body.local_decls[local].source_info.span;
+                    err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
+                        is_partial_move,
+                        ty,
+                        place: &note_msg,
+                        span,
+                    });
                 } else {
-                    None
+                    err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Note {
+                        is_partial_move,
+                        ty,
+                        place: &note_msg,
+                    });
                 };
-                self.note_type_does_not_implement_copy(&mut err, &note_msg, ty, span, partial_str);
             }
 
             if let UseSpans::FnSelfUse {
@@ -295,7 +304,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 ..
             } = use_spans
             {
-                err.note(&format!(
+                err.note(format!(
                     "{} occurs due to deref coercion to `{deref_target_ty}`",
                     desired_action.as_noun(),
                 ));
@@ -577,7 +586,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 //     _ => {} // We don't want to point to this.
                 // };
                 // ```
-                err.span_label(sp, &label);
+                err.span_label(sp, label);
                 shown = true;
             }
         }
@@ -633,11 +642,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             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)], param_env)
+            self.infcx
+                .type_implements_trait(default_trait, [ty], param_env)
                 .must_apply_modulo_regions()
         };
 
@@ -696,7 +702,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 .copied()
                 .find_map(find_fn_kind_from_did),
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => tcx
-                .bound_explicit_item_bounds(def_id)
+                .explicit_item_bounds(def_id)
                 .subst_iter_copied(tcx, substs)
                 .find_map(find_fn_kind_from_did),
             ty::Closure(_, substs) => match substs.as_closure().kind() {
@@ -730,13 +736,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     fn suggest_cloning(&self, err: &mut Diagnostic, ty: Ty<'tcx>, span: Span) {
         let tcx = self.infcx.tcx;
         // Try to find predicates on *generic params* that would allow copying `ty`
-        let infcx = tcx.infer_ctxt().build();
-
         if let Some(clone_trait_def) = tcx.lang_items().clone_trait()
-            && infcx
+            && self.infcx
                 .type_implements_trait(
                     clone_trait_def,
-                    [tcx.erase_regions(ty)],
+                    [ty],
                     self.param_env,
                 )
                 .must_apply_modulo_regions()
@@ -760,12 +764,11 @@ 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 infcx = tcx.infer_ctxt().build();
-        let ocx = ObligationCtxt::new(&infcx);
+        let ocx = ObligationCtxt::new(&self.infcx);
         let copy_did = tcx.require_lang_item(LangItem::Copy, Some(span));
         let cause = ObligationCause::misc(span, self.mir_def_id());
 
-        ocx.register_bound(cause, self.param_env, infcx.tcx.erase_regions(ty), copy_did);
+        ocx.register_bound(cause, self.param_env, ty, copy_did);
         let errors = ocx.select_all_or_error();
 
         // Only emit suggestion if all required predicates are on generic
@@ -827,11 +830,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         borrow_spans.var_path_only_subdiag(&mut err, crate::InitializationRequiringAction::Borrow);
 
-        move_spans.var_span_label(
-            &mut err,
-            format!("move occurs due to use{}", move_spans.describe()),
-            "moved",
-        );
+        move_spans.var_subdiag(None, &mut err, None, |kind, var_span| {
+            use crate::session_diagnostics::CaptureVarCause::*;
+            match kind {
+                Some(_) => MoveUseInGenerator { var_span },
+                None => MoveUseInClosure { var_span },
+            }
+        });
 
         self.explain_why_borrow_contains_point(location, borrow, None)
             .add_explanation_to_diagnostic(
@@ -868,13 +873,15 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             borrow_span,
             &self.describe_any_place(borrow.borrowed_place.as_ref()),
         );
-        borrow_spans.var_subdiag(&mut err, Some(borrow.kind), |kind, var_span| {
+        borrow_spans.var_subdiag(None, &mut err, Some(borrow.kind), |kind, var_span| {
             use crate::session_diagnostics::CaptureVarCause::*;
             let place = &borrow.borrowed_place;
             let desc_place = self.describe_any_place(place.as_ref());
             match kind {
-                Some(_) => BorrowUsePlaceGenerator { place: desc_place, var_span },
-                None => BorrowUsePlaceClosure { place: desc_place, var_span },
+                Some(_) => {
+                    BorrowUsePlaceGenerator { place: desc_place, var_span, is_single_var: true }
+                }
+                None => BorrowUsePlaceClosure { place: desc_place, var_span, is_single_var: true },
             }
         });
 
@@ -946,7 +953,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     &msg_borrow,
                     None,
                 );
-                self.suggest_binding_for_closure_capture_self(
+                self.suggest_binding_for_closure_capture_self(&mut err, &issued_spans);
+                self.suggest_using_closure_argument_instead_of_capture(
                     &mut err,
                     issued_borrow.borrowed_place,
                     &issued_spans,
@@ -969,6 +977,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     place,
                     issued_borrow.borrowed_place,
                 );
+                self.suggest_using_closure_argument_instead_of_capture(
+                    &mut err,
+                    issued_borrow.borrowed_place,
+                    &issued_spans,
+                );
                 err
             }
 
@@ -988,16 +1001,26 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         immutable_section_description,
                         "mutably borrow",
                     );
-                    borrow_spans.var_span_label(
+                    borrow_spans.var_subdiag(
+                        None,
                         &mut err,
-                        format!(
-                            "borrow occurs due to use of {}{}",
-                            desc_place,
-                            borrow_spans.describe(),
-                        ),
-                        "immutable",
+                        Some(BorrowKind::Unique),
+                        |kind, var_span| {
+                            use crate::session_diagnostics::CaptureVarCause::*;
+                            match kind {
+                                Some(_) => BorrowUsePlaceGenerator {
+                                    place: desc_place,
+                                    var_span,
+                                    is_single_var: true,
+                                },
+                                None => BorrowUsePlaceClosure {
+                                    place: desc_place,
+                                    var_span,
+                                    is_single_var: true,
+                                },
+                            }
+                        },
                     );
-
                     return err;
                 } else {
                     first_borrow_desc = "immutable ";
@@ -1070,37 +1093,53 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         };
 
         if issued_spans == borrow_spans {
-            borrow_spans.var_span_label(
-                &mut err,
-                format!("borrows occur due to use of {}{}", desc_place, borrow_spans.describe(),),
-                gen_borrow_kind.describe_mutability(),
-            );
+            borrow_spans.var_subdiag(None, &mut err, Some(gen_borrow_kind), |kind, var_span| {
+                use crate::session_diagnostics::CaptureVarCause::*;
+                match kind {
+                    Some(_) => BorrowUsePlaceGenerator {
+                        place: desc_place,
+                        var_span,
+                        is_single_var: false,
+                    },
+                    None => {
+                        BorrowUsePlaceClosure { place: desc_place, var_span, is_single_var: false }
+                    }
+                }
+            });
         } else {
-            let borrow_place = &issued_borrow.borrowed_place;
-            let borrow_place_desc = self.describe_any_place(borrow_place.as_ref());
-            issued_spans.var_span_label(
+            issued_spans.var_subdiag(
+                Some(&self.infcx.tcx.sess.parse_sess.span_diagnostic),
                 &mut err,
-                format!(
-                    "first borrow occurs due to use of {}{}",
-                    borrow_place_desc,
-                    issued_spans.describe(),
-                ),
-                issued_borrow.kind.describe_mutability(),
+                Some(issued_borrow.kind),
+                |kind, var_span| {
+                    use crate::session_diagnostics::CaptureVarCause::*;
+                    let borrow_place = &issued_borrow.borrowed_place;
+                    let borrow_place_desc = self.describe_any_place(borrow_place.as_ref());
+                    match kind {
+                        Some(_) => {
+                            FirstBorrowUsePlaceGenerator { place: borrow_place_desc, var_span }
+                        }
+                        None => FirstBorrowUsePlaceClosure { place: borrow_place_desc, var_span },
+                    }
+                },
             );
 
-            borrow_spans.var_span_label(
+            borrow_spans.var_subdiag(
+                Some(&self.infcx.tcx.sess.parse_sess.span_diagnostic),
                 &mut err,
-                format!(
-                    "second borrow occurs due to use of {}{}",
-                    desc_place,
-                    borrow_spans.describe(),
-                ),
-                gen_borrow_kind.describe_mutability(),
+                Some(gen_borrow_kind),
+                |kind, var_span| {
+                    use crate::session_diagnostics::CaptureVarCause::*;
+                    match kind {
+                        Some(_) => SecondBorrowUsePlaceGenerator { place: desc_place, var_span },
+                        None => SecondBorrowUsePlaceClosure { place: desc_place, var_span },
+                    }
+                },
             );
         }
 
         if union_type_name != "" {
-            err.note(&format!(
+            err.note(format!(
                 "{} is a field of the union `{}`, so it overlaps the field {}",
                 msg_place, union_type_name, msg_borrow,
             ));
@@ -1199,14 +1238,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }
         err.span_help(
             inner_call_span,
-            &format!(
+            format!(
                 "try adding a local storing this{}...",
                 if use_span.is_some() { "" } else { " argument" }
             ),
         );
         err.span_help(
             outer_call_span,
-            &format!(
+            format!(
                 "...and then using that local {}",
                 if use_span.is_some() { "here" } else { "as the argument to this call" }
             ),
@@ -1229,22 +1268,160 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }
     }
 
-    fn suggest_binding_for_closure_capture_self(
+    /// Suggest using closure argument instead of capture.
+    ///
+    /// For example:
+    /// ```ignore (illustrative)
+    /// struct S;
+    ///
+    /// impl S {
+    ///     fn call(&mut self, f: impl Fn(&mut Self)) { /* ... */ }
+    ///     fn x(&self) {}
+    /// }
+    ///
+    ///     let mut v = S;
+    ///     v.call(|this: &mut S| v.x());
+    /// //  ^\                    ^-- help: try using the closure argument: `this`
+    /// //    *-- error: cannot borrow `v` as mutable because it is also borrowed as immutable
+    /// ```
+    fn suggest_using_closure_argument_instead_of_capture(
         &self,
         err: &mut Diagnostic,
         borrowed_place: Place<'tcx>,
         issued_spans: &UseSpans<'tcx>,
     ) {
-        let UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return };
-        let hir = self.infcx.tcx.hir();
+        let &UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return };
+        let tcx = self.infcx.tcx;
+        let hir = tcx.hir();
 
-        // check whether the borrowed place is capturing `self` by mut reference
+        // Get the type of the local that we are trying to borrow
         let local = borrowed_place.local;
-        let Some(_) = self
-            .body
-            .local_decls
-            .get(local)
-            .map(|l| mut_borrow_of_mutable_ref(l, self.local_names[local])) else { return };
+        let local_ty = self.body.local_decls[local].ty;
+
+        // Get the body the error happens in
+        let Some(body_id) = hir.get(self.mir_hir_id()).body_id() else { return };
+
+        let body_expr = hir.body(body_id).value;
+
+        struct ClosureFinder<'hir> {
+            hir: rustc_middle::hir::map::Map<'hir>,
+            borrow_span: Span,
+            res: Option<(&'hir hir::Expr<'hir>, &'hir hir::Closure<'hir>)>,
+            /// The path expression with the `borrow_span` span
+            error_path: Option<(&'hir hir::Expr<'hir>, &'hir hir::QPath<'hir>)>,
+        }
+        impl<'hir> Visitor<'hir> for ClosureFinder<'hir> {
+            type NestedFilter = OnlyBodies;
+
+            fn nested_visit_map(&mut self) -> Self::Map {
+                self.hir
+            }
+
+            fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) {
+                if let hir::ExprKind::Path(qpath) = &ex.kind
+                    && ex.span == self.borrow_span
+                {
+                    self.error_path = Some((ex, qpath));
+                }
+
+                if let hir::ExprKind::Closure(closure) = ex.kind
+                    && ex.span.contains(self.borrow_span)
+                    // To support cases like `|| { v.call(|this| v.get()) }`
+                    // FIXME: actually support such cases (need to figure out how to move from the capture place to original local)
+                    && self.res.as_ref().map_or(true, |(prev_res, _)| prev_res.span.contains(ex.span))
+                {
+                    self.res = Some((ex, closure));
+                }
+
+                hir::intravisit::walk_expr(self, ex);
+            }
+        }
+
+        // Find the closure that most tightly wraps `capture_kind_span`
+        let mut finder =
+            ClosureFinder { hir, borrow_span: capture_kind_span, res: None, error_path: None };
+        finder.visit_expr(body_expr);
+        let Some((closure_expr, closure)) = finder.res else { return };
+
+        let typeck_results = tcx.typeck(self.mir_def_id());
+
+        // Check that the parent of the closure is a method call,
+        // with receiver matching with local's type (modulo refs)
+        let parent = hir.parent_id(closure_expr.hir_id);
+        if let hir::Node::Expr(parent) = hir.get(parent) {
+            if let hir::ExprKind::MethodCall(_, recv, ..) = parent.kind {
+                let recv_ty = typeck_results.expr_ty(recv);
+
+                if recv_ty.peel_refs() != local_ty {
+                    return;
+                }
+            }
+        }
+
+        // Get closure's arguments
+        let ty::Closure(_, substs) = typeck_results.expr_ty(closure_expr).kind() else { /* hir::Closure can be a generator too */ return };
+        let sig = substs.as_closure().sig();
+        let tupled_params =
+            tcx.erase_late_bound_regions(sig.inputs().iter().next().unwrap().map_bound(|&b| b));
+        let ty::Tuple(params) = tupled_params.kind() else { return };
+
+        // Find the first argument with a matching type, get its name
+        let Some((_, this_name)) = params
+            .iter()
+            .zip(hir.body_param_names(closure.body))
+            .find(|(param_ty, name)|{
+                // FIXME: also support deref for stuff like `Rc` arguments
+                param_ty.peel_refs() == local_ty && name != &Ident::empty()
+            })
+            else { return };
+
+        let spans;
+        if let Some((_path_expr, qpath)) = finder.error_path
+            && let hir::QPath::Resolved(_, path) = qpath
+            && let hir::def::Res::Local(local_id) = path.res
+        {
+            // Find all references to the problematic variable in this closure body
+
+            struct VariableUseFinder {
+                local_id: hir::HirId,
+                spans: Vec<Span>,
+            }
+            impl<'hir> Visitor<'hir> for VariableUseFinder {
+                fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) {
+                    if let hir::ExprKind::Path(qpath) = &ex.kind
+                        && let hir::QPath::Resolved(_, path) = qpath
+                        && let hir::def::Res::Local(local_id) = path.res
+                        && local_id == self.local_id
+                    {
+                        self.spans.push(ex.span);
+                    }
+
+                    hir::intravisit::walk_expr(self, ex);
+                }
+            }
+
+            let mut finder = VariableUseFinder { local_id, spans: Vec::new() };
+            finder.visit_expr(hir.body(closure.body).value);
+
+            spans = finder.spans;
+        } else {
+            spans = vec![capture_kind_span];
+        }
+
+        err.multipart_suggestion(
+            "try using the closure argument",
+            iter::zip(spans, iter::repeat(this_name.to_string())).collect(),
+            Applicability::MaybeIncorrect,
+        );
+    }
+
+    fn suggest_binding_for_closure_capture_self(
+        &self,
+        err: &mut Diagnostic,
+        issued_spans: &UseSpans<'tcx>,
+    ) {
+        let UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return };
+        let hir = self.infcx.tcx.hir();
 
         struct ExpressionFinder<'hir> {
             capture_span: Span,
@@ -1458,34 +1635,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             })
     }
 
-    /// Reports StorageDeadOrDrop of `place` conflicts with `borrow`.
-    ///
-    /// Depending on the origin of the StorageDeadOrDrop, this may be
-    /// reported as either a drop or an illegal mutation of a borrowed value.
-    /// The latter is preferred when the this is a drop triggered by a
-    /// reassignment, as it's more user friendly to report a problem with the
-    /// explicit assignment than the implicit drop.
-    #[instrument(level = "debug", skip(self))]
-    pub(crate) fn report_storage_dead_or_drop_of_borrowed(
-        &mut self,
-        location: Location,
-        place_span: (Place<'tcx>, Span),
-        borrow: &BorrowData<'tcx>,
-    ) {
-        // It's sufficient to check the last desugaring as Replace is the last
-        // one to be applied.
-        if let Some(DesugaringKind::Replace) = place_span.1.desugaring_kind() {
-            self.report_illegal_mutation_of_borrowed(location, place_span, borrow)
-        } else {
-            self.report_borrowed_value_does_not_live_long_enough(
-                location,
-                borrow,
-                place_span,
-                Some(WriteKind::StorageDeadOrDrop),
-            )
-        }
-    }
-
     /// This means that some data referenced by `borrow` needs to live
     /// past the point where the StorageDeadOrDrop of `place` occurs.
     /// This is usually interpreted as meaning that `place` has too
@@ -1731,9 +1880,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             err.span_label(borrow_span, "borrowed value does not live long enough");
             err.span_label(drop_span, format!("`{}` dropped here while still borrowed", name));
 
-            let within = if borrow_spans.for_generator() { " by generator" } else { "" };
-
-            borrow_spans.args_span_label(&mut err, format!("value captured here{}", within));
+            borrow_spans.args_subdiag(&mut err, |args_span| {
+                crate::session_diagnostics::CaptureArgLabel::Capture {
+                    is_within: borrow_spans.for_generator(),
+                    args_span,
+                }
+            });
 
             explanation.add_explanation_to_diagnostic(
                 self.infcx.tcx,
@@ -1947,9 +2099,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             None,
         );
 
-        let within = if borrow_spans.for_generator() { " by generator" } else { "" };
-
-        borrow_spans.args_span_label(&mut err, format!("value captured here{}", within));
+        borrow_spans.args_subdiag(&mut err, |args_span| {
+            crate::session_diagnostics::CaptureArgLabel::Capture {
+                is_within: borrow_spans.for_generator(),
+                args_span,
+            }
+        });
 
         err
     }
@@ -2029,7 +2184,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             let tcx = self.infcx.tcx;
 
             let return_ty = self.regioncx.universal_regions().unnormalized_output_ty;
-            let return_ty = tcx.erase_regions(return_ty);
 
             // to avoid panics
             if let Some(iter_trait) = tcx.get_diagnostic_item(sym::Iterator)
@@ -2099,7 +2253,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         );
         err.span_suggestion_verbose(
             sugg_span,
-            &format!(
+            format!(
                 "to force the {} to take ownership of {} (and any \
                  other referenced variables), use the `move` keyword",
                 kind, captured_var
@@ -2111,7 +2265,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         match category {
             ConstraintCategory::Return(_) | ConstraintCategory::OpaqueType => {
                 let msg = format!("{} is returned here", kind);
-                err.span_note(constraint_span, &msg);
+                err.span_note(constraint_span, msg);
             }
             ConstraintCategory::CallArgument(_) => {
                 fr_name.highlight_region_name(&mut err);
@@ -2122,7 +2276,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     );
                 } else {
                     let msg = format!("{scope} requires argument type to outlive `{fr_name}`");
-                    err.span_note(constraint_span, &msg);
+                    err.span_note(constraint_span, msg);
                 }
             }
             _ => bug!(
@@ -2382,11 +2536,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     section,
                     "assign",
                 );
-                loan_spans.var_span_label(
-                    &mut err,
-                    format!("borrow occurs due to use{}", loan_spans.describe()),
-                    loan.kind.describe_mutability(),
-                );
+
+                loan_spans.var_subdiag(None, &mut err, Some(loan.kind), |kind, var_span| {
+                    use crate::session_diagnostics::CaptureVarCause::*;
+                    match kind {
+                        Some(_) => BorrowUseInGenerator { var_span },
+                        None => BorrowUseInClosure { var_span },
+                    }
+                });
 
                 self.buffer_error(err);
 
@@ -2396,11 +2553,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         let mut err = self.cannot_assign_to_borrowed(span, loan_span, &descr_place);
 
-        loan_spans.var_span_label(
-            &mut err,
-            format!("borrow occurs due to use{}", loan_spans.describe()),
-            loan.kind.describe_mutability(),
-        );
+        loan_spans.var_subdiag(None, &mut err, Some(loan.kind), |kind, var_span| {
+            use crate::session_diagnostics::CaptureVarCause::*;
+            match kind {
+                Some(_) => BorrowUseInGenerator { var_span },
+                None => BorrowUseInClosure { var_span },
+            }
+        });
 
         self.explain_why_borrow_contains_point(location, loan, None).add_explanation_to_diagnostic(
             self.infcx.tcx,
@@ -2424,7 +2583,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             Some((method_did, method_substs)),
         ) = (
             &self.body[loan.reserve_location.block].terminator,
-            rustc_const_eval::util::find_self_call(
+            rustc_middle::util::find_self_call(
                 tcx,
                 self.body,
                 loan.assigned_place.local,
@@ -2439,7 +2598,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     });
                 if let Some(Ok(instance)) = deref_target {
                     let deref_target_ty = instance.ty(tcx, self.param_env);
-                    err.note(&format!(
+                    err.note(format!(
                         "borrow occurs due to deref coercion to `{}`",
                         deref_target_ty
                     ));
@@ -2993,7 +3152,7 @@ impl<'tcx> AnnotatedBorrowFnSignature<'tcx> {
 
                 diag.span_label(*return_span, format!("also has lifetime `{}`", region_name,));
 
-                diag.help(&format!(
+                diag.help(format!(
                     "use data from the highlighted arguments which match the `{}` lifetime of \
                      the return type",
                     region_name,
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 8860395e7..1d430a93a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -3,7 +3,7 @@
 use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
-use rustc_index::vec::IndexSlice;
+use rustc_index::IndexSlice;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::mir::{
     Body, CastKind, ConstraintCategory, FakeReadCause, Local, LocalInfo, Location, Operand, Place,
@@ -90,7 +90,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
                     {
                         err.span_label(
                             pat.span,
-                            &format!("binding `{ident}` declared here"),
+                            format!("binding `{ident}` declared here"),
                         );
                     }
                 }
@@ -118,7 +118,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
                     let path_span = path_span.unwrap();
                     // path_span is only present in the case of closure capture
                     assert!(matches!(later_use_kind, LaterUseKind::ClosureCapture));
-                    if !borrow_span.map_or(false, |sp| sp.overlaps(var_or_use_span)) {
+                    if !borrow_span.is_some_and(|sp| sp.overlaps(var_or_use_span)) {
                         let path_label = "used here by closure";
                         let capture_kind_label = message;
                         err.span_label(
@@ -224,12 +224,9 @@ impl<'tcx> BorrowExplanation<'tcx> {
                             if info.tail_result_is_ignored {
                                 // #85581: If the first mutable borrow's scope contains
                                 // the second borrow, this suggestion isn't helpful.
-                                if !multiple_borrow_span
-                                    .map(|(old, new)| {
-                                        old.to(info.span.shrink_to_hi()).contains(new)
-                                    })
-                                    .unwrap_or(false)
-                                {
+                                if !multiple_borrow_span.is_some_and(|(old, new)| {
+                                    old.to(info.span.shrink_to_hi()).contains(new)
+                                }) {
                                     err.span_suggestion_verbose(
                                         info.span.shrink_to_hi(),
                                         "consider adding semicolon after the expression so its \
@@ -323,7 +320,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
 
             err.span_suggestion_verbose(
                 span.shrink_to_hi(),
-                &msg,
+                msg,
                 format!(" + {suggestable_name}"),
                 Applicability::Unspecified,
             );
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 110354a20..20370e4c6 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -1,13 +1,16 @@
 //! Borrow checker diagnostics.
 
+use crate::session_diagnostics::{
+    CaptureArgLabel, CaptureReasonLabel, CaptureReasonNote, CaptureReasonSuggest, CaptureVarCause,
+    CaptureVarKind, CaptureVarPathUseCause, OnClosureNote,
+};
 use itertools::Itertools;
-use rustc_const_eval::util::{call_kind, CallDesugaringKind};
 use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::GeneratorKind;
-use rustc_index::vec::IndexSlice;
-use rustc_infer::infer::{LateBoundRegionConversionTime, TyCtxtInferExt};
+use rustc_index::IndexSlice;
+use rustc_infer::infer::LateBoundRegionConversionTime;
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
     AggregateKind, Constant, FakeReadCause, Local, LocalInfo, LocalKind, Location, Operand, Place,
@@ -15,6 +18,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::print::Print;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
+use rustc_middle::util::{call_kind, CallDesugaringKind};
 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
@@ -45,7 +49,7 @@ pub(crate) use mutability_errors::AccessKind;
 pub(crate) use outlives_suggestion::OutlivesSuggestionBuilder;
 pub(crate) use region_errors::{ErrorConstraintInfo, RegionErrorKind, RegionErrors};
 pub(crate) use region_name::{RegionName, RegionNameSource};
-pub(crate) use rustc_const_eval::util::CallKind;
+pub(crate) use rustc_middle::util::CallKind;
 
 pub(super) struct DescribePlaceOpt {
     pub including_downcast: bool,
@@ -117,13 +121,15 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     if let ty::Closure(did, _) = self.body.local_decls[closure].ty.kind() {
                         let did = did.expect_local();
                         if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) {
-                            diag.span_note(
-                                *span,
-                                &format!(
-                                    "closure cannot be invoked more than once because it moves the \
-                                    variable `{}` out of its environment",
-                                    ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
-                                ),
+                            diag.eager_subdiagnostic(
+                                &self.infcx.tcx.sess.parse_sess.span_diagnostic,
+                                OnClosureNote::InvokedTwice {
+                                    place_name: &ty::place_to_string_for_capture(
+                                        self.infcx.tcx,
+                                        hir_place,
+                                    ),
+                                    span: *span,
+                                },
                             );
                             return true;
                         }
@@ -137,13 +143,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             if let ty::Closure(did, _) = self.body.local_decls[target].ty.kind() {
                 let did = did.expect_local();
                 if let Some((span, hir_place)) = self.infcx.tcx.closure_kind_origin(did) {
-                    diag.span_note(
-                        *span,
-                        &format!(
-                            "closure cannot be moved more than once as it is not `Copy` due to \
-                             moving the variable `{}` out of its environment",
-                            ty::place_to_string_for_capture(self.infcx.tcx, hir_place)
-                        ),
+                    diag.eager_subdiagnostic(
+                        &self.infcx.tcx.sess.parse_sess.span_diagnostic,
+                        OnClosureNote::MovedTwice {
+                            place_name: &ty::place_to_string_for_capture(self.infcx.tcx, hir_place),
+                            span: *span,
+                        },
                     );
                     return true;
                 }
@@ -380,25 +385,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }
     }
 
-    /// Add a note that a type does not implement `Copy`
-    pub(super) fn note_type_does_not_implement_copy(
-        &self,
-        err: &mut Diagnostic,
-        place_desc: &str,
-        ty: Ty<'tcx>,
-        span: Option<Span>,
-        move_prefix: &str,
-    ) {
-        let message = format!(
-            "{move_prefix}move occurs because {place_desc} has type `{ty}`, which does not implement the `Copy` trait",
-        );
-        if let Some(span) = span {
-            err.span_label(span, message);
-        } else {
-            err.note(&message);
-        }
-    }
-
     pub(super) fn borrowed_content_source(
         &self,
         deref_base: PlaceRef<'tcx>,
@@ -582,9 +568,13 @@ impl UseSpans<'_> {
     }
 
     /// Add a span label to the arguments of the closure, if it exists.
-    pub(super) fn args_span_label(self, err: &mut Diagnostic, message: impl Into<String>) {
+    pub(super) fn args_subdiag(
+        self,
+        err: &mut Diagnostic,
+        f: impl FnOnce(Span) -> CaptureArgLabel,
+    ) {
         if let UseSpans::ClosureUse { args_span, .. } = self {
-            err.span_label(args_span, message);
+            err.subdiagnostic(f(args_span));
         }
     }
 
@@ -595,8 +585,8 @@ impl UseSpans<'_> {
         err: &mut Diagnostic,
         action: crate::InitializationRequiringAction,
     ) {
-        use crate::session_diagnostics::CaptureVarPathUseCause::*;
         use crate::InitializationRequiringAction::*;
+        use CaptureVarPathUseCause::*;
         if let UseSpans::ClosureUse { generator_kind, path_span, .. } = self {
             match generator_kind {
                 Some(_) => {
@@ -619,34 +609,14 @@ impl UseSpans<'_> {
         }
     }
 
-    /// Add a span label to the use of the captured variable, if it exists.
-    pub(super) fn var_span_label(
-        self,
-        err: &mut Diagnostic,
-        message: impl Into<String>,
-        kind_desc: impl Into<String>,
-    ) {
-        if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
-            if capture_kind_span == path_span {
-                err.span_label(capture_kind_span, message);
-            } else {
-                let capture_kind_label =
-                    format!("capture is {} because of use here", kind_desc.into());
-                let path_label = message;
-                err.span_label(capture_kind_span, capture_kind_label);
-                err.span_label(path_span, path_label);
-            }
-        }
-    }
-
     /// Add a subdiagnostic to the use of the captured variable, if it exists.
     pub(super) fn var_subdiag(
         self,
+        handler: Option<&rustc_errors::Handler>,
         err: &mut Diagnostic,
         kind: Option<rustc_middle::mir::BorrowKind>,
-        f: impl Fn(Option<GeneratorKind>, Span) -> crate::session_diagnostics::CaptureVarCause,
+        f: impl FnOnce(Option<GeneratorKind>, Span) -> CaptureVarCause,
     ) {
-        use crate::session_diagnostics::CaptureVarKind::*;
         if let UseSpans::ClosureUse { generator_kind, capture_kind_span, path_span, .. } = self {
             if capture_kind_span != path_span {
                 err.subdiagnostic(match kind {
@@ -654,17 +624,21 @@ impl UseSpans<'_> {
                         rustc_middle::mir::BorrowKind::Shared
                         | rustc_middle::mir::BorrowKind::Shallow
                         | rustc_middle::mir::BorrowKind::Unique => {
-                            Immute { kind_span: capture_kind_span }
+                            CaptureVarKind::Immut { kind_span: capture_kind_span }
                         }
 
                         rustc_middle::mir::BorrowKind::Mut { .. } => {
-                            Mut { kind_span: capture_kind_span }
+                            CaptureVarKind::Mut { kind_span: capture_kind_span }
                         }
                     },
-                    None => Move { kind_span: capture_kind_span },
+                    None => CaptureVarKind::Move { kind_span: capture_kind_span },
                 });
             };
-            err.subdiagnostic(f(generator_kind, path_span));
+            let diag = f(generator_kind, path_span);
+            match handler {
+                Some(hd) => err.eager_subdiagnostic(hd, diag),
+                None => err.subdiagnostic(diag),
+            };
         }
     }
 
@@ -684,20 +658,6 @@ impl UseSpans<'_> {
         }
     }
 
-    /// Describe the span associated with a use of a place.
-    pub(super) fn describe(&self) -> &str {
-        match *self {
-            UseSpans::ClosureUse { generator_kind, .. } => {
-                if generator_kind.is_some() {
-                    " in generator"
-                } else {
-                    " in closure"
-                }
-            }
-            _ => "",
-        }
-    }
-
     pub(super) fn or_else<F>(self, if_other: F) -> Self
     where
         F: FnOnce() -> Self,
@@ -788,6 +748,15 @@ impl<'tcx> BorrowedContentSource<'tcx> {
     }
 }
 
+///helper struct for explain_captures()
+struct CapturedMessageOpt {
+    is_partial_move: bool,
+    is_loop_message: bool,
+    is_move_msg: bool,
+    is_loop_move: bool,
+    maybe_reinitialized_locations_is_empty: bool,
+}
+
 impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     /// Finds the spans associated to a move or copy of move_place at location.
     pub(super) fn move_spans(
@@ -874,7 +843,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }) = &self.body[location.block].terminator
         {
             let Some((method_did, method_substs)) =
-                rustc_const_eval::util::find_self_call(
+            rustc_middle::util::find_self_call(
                     self.infcx.tcx,
                     &self.body,
                     target_temp,
@@ -1027,12 +996,15 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         move_span: Span,
         move_spans: UseSpans<'tcx>,
         moved_place: Place<'tcx>,
-        partially_str: &str,
-        loop_message: &str,
-        move_msg: &str,
-        is_loop_move: bool,
-        maybe_reinitialized_locations_is_empty: bool,
+        msg_opt: CapturedMessageOpt,
     ) {
+        let CapturedMessageOpt {
+            is_partial_move: is_partial,
+            is_loop_message,
+            is_move_msg,
+            is_loop_move,
+            maybe_reinitialized_locations_is_empty,
+        } = msg_opt;
         if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
             let place_name = self
                 .describe_place(moved_place.as_ref())
@@ -1042,30 +1014,26 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 CallKind::FnCall { fn_trait_id, .. }
                     if Some(fn_trait_id) == self.infcx.tcx.lang_items().fn_once_trait() =>
                 {
-                    err.span_label(
+                    err.subdiagnostic(CaptureReasonLabel::Call {
                         fn_call_span,
-                        &format!(
-                            "{place_name} {partially_str}moved due to this call{loop_message}",
-                        ),
-                    );
-                    err.span_note(
-                        var_span,
-                        "this value implements `FnOnce`, which causes it to be moved when called",
-                    );
+                        place_name: &place_name,
+                        is_partial,
+                        is_loop_message,
+                    });
+                    err.subdiagnostic(CaptureReasonNote::FnOnceMoveInCall { var_span });
                 }
                 CallKind::Operator { self_arg, .. } => {
                     let self_arg = self_arg.unwrap();
-                    err.span_label(
+                    err.subdiagnostic(CaptureReasonLabel::OperatorUse {
                         fn_call_span,
-                        &format!(
-                            "{place_name} {partially_str}moved due to usage in operator{loop_message}",
-                        ),
-                    );
+                        place_name: &place_name,
+                        is_partial,
+                        is_loop_message,
+                    });
                     if self.fn_self_span_reported.insert(fn_span) {
-                        err.span_note(
-                            self_arg.span,
-                            "calling this operator moves the left-hand side",
-                        );
+                        err.subdiagnostic(CaptureReasonNote::LhsMoveByOperator {
+                            span: self_arg.span,
+                        });
                     }
                 }
                 CallKind::Normal { self_arg, desugaring, method_did, method_substs } => {
@@ -1074,35 +1042,27 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
                         let ty = moved_place.ty(self.body, tcx).ty;
                         let suggest = match tcx.get_diagnostic_item(sym::IntoIterator) {
-                            Some(def_id) => {
-                                let infcx = self.infcx.tcx.infer_ctxt().build();
-                                type_known_to_meet_bound_modulo_regions(
-                                    &infcx,
-                                    self.param_env,
-                                    tcx.mk_imm_ref(tcx.lifetimes.re_erased, tcx.erase_regions(ty)),
-                                    def_id,
-                                )
-                            }
+                            Some(def_id) => type_known_to_meet_bound_modulo_regions(
+                                &self.infcx,
+                                self.param_env,
+                                tcx.mk_imm_ref(tcx.lifetimes.re_erased, ty),
+                                def_id,
+                            ),
                             _ => false,
                         };
                         if suggest {
-                            err.span_suggestion_verbose(
-                                move_span.shrink_to_lo(),
-                                &format!(
-                                    "consider iterating over a slice of the `{ty}`'s content to \
-                                     avoid moving into the `for` loop",
-                                ),
-                                "&",
-                                Applicability::MaybeIncorrect,
-                            );
+                            err.subdiagnostic(CaptureReasonSuggest::IterateSlice {
+                                ty,
+                                span: move_span.shrink_to_lo(),
+                            });
                         }
 
-                        err.span_label(
+                        err.subdiagnostic(CaptureReasonLabel::ImplicitCall {
                             fn_call_span,
-                            &format!(
-                                "{place_name} {partially_str}moved due to this implicit call to `.into_iter()`{loop_message}",
-                            ),
-                        );
+                            place_name: &place_name,
+                            is_partial,
+                            is_loop_message,
+                        });
                         // 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.
@@ -1113,7 +1073,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             if !is_loop_move {
                                 err.span_suggestion_verbose(
                                     move_span.shrink_to_lo(),
-                                    &format!(
+                                    format!(
                                         "consider creating a fresh reborrow of {} here",
                                         self.describe_place(moved_place.as_ref())
                                             .map(|n| format!("`{n}`"))
@@ -1125,44 +1085,49 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             }
                         }
                     } else {
-                        err.span_label(
-                            fn_call_span,
-                            &format!(
-                                "{place_name} {partially_str}moved due to this method call{loop_message}",
-                            ),
-                        );
-
-                        let infcx = tcx.infer_ctxt().build();
+                        if let Some((CallDesugaringKind::Await, _)) = desugaring {
+                            err.subdiagnostic(CaptureReasonLabel::Await {
+                                fn_call_span,
+                                place_name: &place_name,
+                                is_partial,
+                                is_loop_message,
+                            });
+                        } else {
+                            err.subdiagnostic(CaptureReasonLabel::MethodCall {
+                                fn_call_span,
+                                place_name: &place_name,
+                                is_partial,
+                                is_loop_message,
+                            });
+                        }
                         // Erase and shadow everything that could be passed to the new infcx.
-                        let ty = tcx.erase_regions(moved_place.ty(self.body, tcx).ty);
-                        let method_substs = tcx.erase_regions(method_substs);
+                        let ty = moved_place.ty(self.body, tcx).ty;
 
                         if let ty::Adt(def, substs) = ty.kind()
                             && Some(def.did()) == tcx.lang_items().pin_type()
                             && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind()
-                            && let self_ty = infcx.instantiate_binder_with_fresh_vars(
+                            && let self_ty = self.infcx.instantiate_binder_with_fresh_vars(
                                 fn_call_span,
                                 LateBoundRegionConversionTime::FnCall,
                                 tcx.fn_sig(method_did).subst(tcx, method_substs).input(0),
                             )
-                            && infcx.can_eq(self.param_env, ty, self_ty)
+                            && self.infcx.can_eq(self.param_env, ty, self_ty)
                         {
-                            err.span_suggestion_verbose(
-                                fn_call_span.shrink_to_lo(),
-                                "consider reborrowing the `Pin` instead of moving it",
-                                "as_mut().".to_string(),
-                                Applicability::MaybeIncorrect,
-                            );
+                            err.eager_subdiagnostic(
+                                &self.infcx.tcx.sess.parse_sess.span_diagnostic,
+                                CaptureReasonSuggest::FreshReborrow {
+                                    span: fn_call_span.shrink_to_lo(),
+                                });
                         }
                         if let Some(clone_trait) = tcx.lang_items().clone_trait()
-                            && let trait_ref = tcx.mk_trait_ref(clone_trait, [ty])
+                            && let trait_ref = ty::TraitRef::new(tcx, clone_trait, [ty])
                             && let o = Obligation::new(
                                 tcx,
                                 ObligationCause::dummy(),
                                 self.param_env,
                                 ty::Binder::dummy(trait_ref),
                             )
-                            && infcx.predicate_must_hold_modulo_regions(&o)
+                            && self.infcx.predicate_must_hold_modulo_regions(&o)
                         {
                             err.span_suggestion_verbose(
                                 fn_call_span.shrink_to_lo(),
@@ -1177,10 +1142,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     // error messages.
                     if span != DUMMY_SP && self.fn_self_span_reported.insert(self_arg.span) {
                         let func = tcx.def_path_str(method_did);
-                        err.span_note(
-                            self_arg.span,
-                            &format!("`{func}` takes ownership of the receiver `self`, which moves {place_name}")
-                        );
+                        err.subdiagnostic(CaptureReasonNote::FuncTakeSelf {
+                            func,
+                            place_name,
+                            span: self_arg.span,
+                        });
                     }
                     let parent_did = tcx.parent(method_did);
                     let parent_self_ty =
@@ -1190,34 +1156,32 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 ty::Adt(def, ..) => Some(def.did()),
                                 _ => None,
                             });
-                    let is_option_or_result = parent_self_ty.map_or(false, |def_id| {
+                    let is_option_or_result = parent_self_ty.is_some_and(|def_id| {
                         matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
                     });
                     if is_option_or_result && maybe_reinitialized_locations_is_empty {
-                        err.span_label(
-                            var_span,
-                            "help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents",
-                        );
+                        err.subdiagnostic(CaptureReasonLabel::BorrowContent { var_span });
                     }
                 }
                 // Other desugarings takes &self, which cannot cause a move
                 _ => {}
             }
         } else {
-            if move_span != span || !loop_message.is_empty() {
-                err.span_label(
+            if move_span != span || is_loop_message {
+                err.subdiagnostic(CaptureReasonLabel::MovedHere {
                     move_span,
-                    format!("value {partially_str}moved{move_msg} here{loop_message}"),
-                );
+                    is_partial,
+                    is_move_msg,
+                    is_loop_message,
+                });
             }
             // If the move error occurs due to a loop, don't show
             // another message for the same span
-            if loop_message.is_empty() {
-                move_spans.var_span_label(
-                    err,
-                    format!("variable {partially_str}moved due to use{}", move_spans.describe()),
-                    "moved",
-                );
+            if !is_loop_message {
+                move_spans.var_subdiag(None, err, None, |kind, var_span| match kind {
+                    Some(_) => CaptureVarCause::PartialMoveUseInGenerator { var_span, is_partial },
+                    None => CaptureVarCause::PartialMoveUseInClosure { var_span, is_partial },
+                })
             }
         }
     }
diff --git a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
index 3662bec0c..8b77477a3 100644
--- a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -6,6 +6,7 @@ use rustc_mir_dataflow::move_paths::{
 };
 use rustc_span::{BytePos, Span};
 
+use crate::diagnostics::CapturedMessageOpt;
 use crate::diagnostics::{DescribePlaceOpt, UseSpans};
 use crate::prefixes::PrefixSet;
 use crate::MirBorrowckCtxt;
@@ -397,10 +398,15 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 }
             }
         };
+        let msg_opt = CapturedMessageOpt {
+            is_partial_move: false,
+            is_loop_message: false,
+            is_move_msg: false,
+            is_loop_move: false,
+            maybe_reinitialized_locations_is_empty: true,
+        };
         if let Some(use_spans) = use_spans {
-            self.explain_captures(
-                &mut err, span, span, use_spans, move_place, "", "", "", false, true,
-            );
+            self.explain_captures(&mut err, span, span, use_spans, move_place, msg_opt);
         }
         err
     }
@@ -416,13 +422,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         None => "value".to_string(),
                     };
 
-                    self.note_type_does_not_implement_copy(
-                        err,
-                        &place_desc,
-                        place_ty,
-                        Some(span),
-                        "",
-                    );
+                    err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
+                        is_partial_move: false,
+                        ty: place_ty,
+                        place: &place_desc,
+                        span,
+                    });
                 } else {
                     binds_to.sort();
                     binds_to.dedup();
@@ -444,9 +449,19 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     Some(desc) => format!("`{desc}`"),
                     None => "value".to_string(),
                 };
-                self.note_type_does_not_implement_copy(err, &place_desc, place_ty, Some(span), "");
+                err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
+                    is_partial_move: false,
+                    ty: place_ty,
+                    place: &place_desc,
+                    span,
+                });
 
-                use_spans.args_span_label(err, format!("{place_desc} is moved here"));
+                use_spans.args_subdiag(err, |args_span| {
+                    crate::session_diagnostics::CaptureArgLabel::MoveOutPlace {
+                        place: place_desc,
+                        args_span,
+                    }
+                });
             }
         }
     }
@@ -518,7 +533,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         suggestions.sort_unstable_by_key(|&(span, _, _)| span);
         suggestions.dedup_by_key(|&mut (span, _, _)| span);
         for (span, msg, suggestion) in suggestions {
-            err.span_suggestion_verbose(span, &msg, suggestion, Applicability::MachineApplicable);
+            err.span_suggestion_verbose(span, msg, suggestion, Applicability::MachineApplicable);
         }
     }
 
@@ -534,13 +549,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             }
 
             if binds_to.len() == 1 {
-                self.note_type_does_not_implement_copy(
-                    err,
-                    &format!("`{}`", self.local_names[*local].unwrap()),
-                    bind_to.ty,
-                    Some(binding_span),
-                    "",
-                );
+                let place_desc = &format!("`{}`", self.local_names[*local].unwrap());
+                err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
+                    is_partial_move: false,
+                    ty: bind_to.ty,
+                    place: &place_desc,
+                    span: binding_span,
+                });
             }
         }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 9d9040096..d0e17bf5a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -1,4 +1,4 @@
-use rustc_errors::{Applicability, Diagnostic};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::Node;
@@ -15,8 +15,8 @@ use rustc_span::{sym, BytePos, Span};
 use rustc_target::abi::FieldIdx;
 
 use crate::diagnostics::BorrowedContentSource;
+use crate::util::FindAssignments;
 use crate::MirBorrowckCtxt;
-use rustc_const_eval::util::collect_writes::FindAssignments;
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub(crate) enum AccessKind {
@@ -231,14 +231,18 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     }
                 }
                 if suggest {
-                    borrow_spans.var_span_label(
-                        &mut err,
-                        format!(
-                            "mutable borrow occurs due to use of {} in closure",
-                            self.describe_any_place(access_place.as_ref()),
-                        ),
-                        "mutable",
-                    );
+                    borrow_spans.var_subdiag(
+                    None,
+                    &mut err,
+                    Some(mir::BorrowKind::Mut { allow_two_phase_borrow: false }),
+                    |_kind, var_span| {
+                        let place = self.describe_any_place(access_place.as_ref());
+                        crate::session_diagnostics::CaptureVarCause::MutableBorrowUsePlaceClosure {
+                            place,
+                            var_span,
+                        }
+                    },
+                );
                 }
                 borrow_span
             }
@@ -285,8 +289,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     .body
                     .local_decls
                     .get(local)
-                    .map(|l| mut_borrow_of_mutable_ref(l, self.local_names[local]))
-                    .unwrap_or(false) =>
+                    .is_some_and(|l| mut_borrow_of_mutable_ref(l, self.local_names[local])) =>
             {
                 let decl = &self.body.local_decls[local];
                 err.span_label(span, format!("cannot {act}"));
@@ -439,7 +442,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     .sess
                     .source_map()
                     .span_to_snippet(span)
-                    .map_or(false, |snippet| snippet.starts_with("&mut ")) =>
+                    .is_ok_and(|snippet| snippet.starts_with("&mut ")) =>
             {
                 err.span_label(span, format!("cannot {act}"));
                 err.span_suggestion(
@@ -474,179 +477,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
                 match self.local_names[local] {
                     Some(name) if !local_decl.from_compiler_desugaring() => {
-                        let label = match *local_decl.local_info() {
-                            LocalInfo::User(mir::BindingForm::ImplicitSelf(_)) => {
-                                let (span, suggestion) =
-                                    suggest_ampmut_self(self.infcx.tcx, local_decl);
-                                Some((true, span, suggestion))
-                            }
-
-                            LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
-                                binding_mode: ty::BindingMode::BindByValue(_),
-                                opt_ty_info,
-                                ..
-                            })) => {
-                                // check if the RHS is from desugaring
-                                let opt_assignment_rhs_span =
-                                    self.body.find_assignments(local).first().map(|&location| {
-                                        if let Some(mir::Statement {
-                                            source_info: _,
-                                            kind:
-                                                mir::StatementKind::Assign(box (
-                                                    _,
-                                                    mir::Rvalue::Use(mir::Operand::Copy(place)),
-                                                )),
-                                        }) = self.body[location.block]
-                                            .statements
-                                            .get(location.statement_index)
-                                        {
-                                            self.body.local_decls[place.local].source_info.span
-                                        } else {
-                                            self.body.source_info(location).span
-                                        }
-                                    });
-                                match opt_assignment_rhs_span.and_then(|s| s.desugaring_kind()) {
-                                    // on for loops, RHS points to the iterator part
-                                    Some(DesugaringKind::ForLoop) => {
-                                        self.suggest_similar_mut_method_for_for_loop(&mut err);
-                                        err.span_label(opt_assignment_rhs_span.unwrap(), format!(
-                                            "this iterator yields `{pointer_sigil}` {pointer_desc}s",
-                                        ));
-                                        None
-                                    }
-                                    // don't create labels for compiler-generated spans
-                                    Some(_) => None,
-                                    None => {
-                                        let label = if name != kw::SelfLower {
-                                            suggest_ampmut(
-                                                self.infcx.tcx,
-                                                local_decl,
-                                                opt_assignment_rhs_span,
-                                                opt_ty_info,
-                                            )
-                                        } else {
-                                            match local_decl.local_info() {
-                                                LocalInfo::User(mir::BindingForm::Var(
-                                                    mir::VarBindingForm {
-                                                        opt_ty_info: None, ..
-                                                    },
-                                                )) => {
-                                                    let (span, sugg) = suggest_ampmut_self(
-                                                        self.infcx.tcx,
-                                                        local_decl,
-                                                    );
-                                                    (true, span, sugg)
-                                                }
-                                                // explicit self (eg `self: &'a Self`)
-                                                _ => suggest_ampmut(
-                                                    self.infcx.tcx,
-                                                    local_decl,
-                                                    opt_assignment_rhs_span,
-                                                    opt_ty_info,
-                                                ),
-                                            }
-                                        };
-                                        Some(label)
-                                    }
-                                }
-                            }
-
-                            LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
-                                binding_mode: ty::BindingMode::BindByReference(_),
-                                ..
-                            })) => {
-                                let pattern_span = local_decl.source_info.span;
-                                suggest_ref_mut(self.infcx.tcx, pattern_span)
-                                    .map(|replacement| (true, pattern_span, replacement))
-                            }
-
-                            _ => unreachable!(),
-                        };
-
-                        match label {
-                            Some((true, err_help_span, suggested_code)) => {
-                                let (is_trait_sig, local_trait) = self.is_error_in_trait(local);
-                                if !is_trait_sig {
-                                    err.span_suggestion_verbose(
-                                        err_help_span,
-                                        &format!(
-                                            "consider changing this to be a mutable {pointer_desc}"
-                                        ),
-                                        suggested_code,
-                                        Applicability::MachineApplicable,
-                                    );
-                                } else if let Some(x) = local_trait {
-                                    err.span_suggestion_verbose(
-                                        x,
-                                        &format!(
-                                            "consider changing that to be a mutable {pointer_desc}"
-                                        ),
-                                        suggested_code,
-                                        Applicability::MachineApplicable,
-                                    );
-                                }
-                            }
-                            Some((false, err_label_span, message)) => {
-                                struct BindingFinder {
-                                    span: Span,
-                                    hir_id: Option<hir::HirId>,
-                                }
-
-                                impl<'tcx> Visitor<'tcx> for BindingFinder {
-                                    fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
-                                        if let hir::StmtKind::Local(local) = s.kind {
-                                            if local.pat.span == self.span {
-                                                self.hir_id = Some(local.hir_id);
-                                            }
-                                        }
-                                        hir::intravisit::walk_stmt(self, s);
-                                    }
-                                }
-                                let hir_map = self.infcx.tcx.hir();
-                                let def_id = self.body.source.def_id();
-                                let hir_id = hir_map.local_def_id_to_hir_id(def_id.expect_local());
-                                let node = hir_map.find(hir_id);
-                                let hir_id = if let Some(hir::Node::Item(item)) = node
-                                    && let hir::ItemKind::Fn(.., body_id) = item.kind
-                                {
-                                    let body = hir_map.body(body_id);
-                                    let mut v = BindingFinder {
-                                        span: err_label_span,
-                                        hir_id: None,
-                                    };
-                                    v.visit_body(body);
-                                    v.hir_id
-                                } else {
-                                    None
-                                };
-                                if let Some(hir_id) = hir_id
-                                    && let Some(hir::Node::Local(local)) = hir_map.find(hir_id)
-                                {
-                                    let (changing, span, sugg) = match local.ty {
-                                        Some(ty) => ("changing", ty.span, message),
-                                        None => (
-                                            "specifying",
-                                            local.pat.span.shrink_to_hi(),
-                                            format!(": {message}"),
-                                        ),
-                                    };
-                                    err.span_suggestion_verbose(
-                                        span,
-                                        &format!("consider {changing} this binding's type"),
-                                        sugg,
-                                        Applicability::HasPlaceholders,
-                                    );
-                                } else {
-                                    err.span_label(
-                                        err_label_span,
-                                        &format!(
-                                            "consider changing this binding's type to be: `{message}`"
-                                        ),
-                                    );
-                                }
-                            }
-                            None => {}
-                        }
                         err.span_label(
                             span,
                             format!(
@@ -654,6 +484,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                                  so the data it refers to cannot be {acted_on}",
                             ),
                         );
+
+                        self.suggest_make_local_mut(&mut err, local, name);
                     }
                     _ => {
                         err.span_label(
@@ -675,13 +507,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
                 match opt_source {
                     Some(BorrowedContentSource::OverloadedDeref(ty)) => {
-                        err.help(&format!(
+                        err.help(format!(
                             "trait `DerefMut` is required to modify through a dereference, \
                              but it is not implemented for `{ty}`",
                         ));
                     }
                     Some(BorrowedContentSource::OverloadedIndex(ty)) => {
-                        err.help(&format!(
+                        err.help(format!(
                             "trait `IndexMut` is required to modify indexed content, \
                              but it is not implemented for `{ty}`",
                         ));
@@ -732,7 +564,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         // val[index] = rv;
                         // ---------- place
                         self.err.multipart_suggestions(
-                            &format!(
+                            format!(
                                 "to modify a `{}`, use `.get_mut()`, `.insert()` or the entry API",
                                 self.ty,
                             ),
@@ -784,7 +616,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     {
                         // val[index].path(args..);
                         self.err.multipart_suggestion(
-                            &format!("to modify a `{}` use `.get_mut()`", self.ty),
+                            format!("to modify a `{}` use `.get_mut()`", self.ty),
                             vec![
                                 (
                                     val.span.shrink_to_hi().with_hi(index.span.lo()),
@@ -809,16 +641,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             let Some(hir::Node::Item(item)) = node else { return; };
             let hir::ItemKind::Fn(.., body_id) = item.kind else { return; };
             let body = self.infcx.tcx.hir().body(body_id);
-            let mut assign_span = span;
-            // Drop desugaring is done at MIR build so it's not in the HIR
-            if let Some(DesugaringKind::Replace) = span.desugaring_kind() {
-                assign_span.remove_mark();
-            }
 
-            let mut v = V { assign_span, err, ty, suggested: false };
+            let mut v = V { assign_span: span, err, ty, suggested: false };
             v.visit_body(body);
             if !v.suggested {
-                err.help(&format!(
+                err.help(format!(
                     "to modify a `{ty}`, use `.get_mut()`, `.insert()` or the entry API",
                 ));
             }
@@ -1127,6 +954,184 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             }
         }
     }
+
+    fn suggest_make_local_mut(
+        &self,
+        err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
+        local: Local,
+        name: Symbol,
+    ) {
+        let local_decl = &self.body.local_decls[local];
+
+        let (pointer_sigil, pointer_desc) =
+            if local_decl.ty.is_ref() { ("&", "reference") } else { ("*const", "pointer") };
+
+        let (is_trait_sig, local_trait) = self.is_error_in_trait(local);
+        if is_trait_sig && local_trait.is_none() {
+            return;
+        }
+
+        let decl_span = match local_trait {
+            Some(span) => span,
+            None => local_decl.source_info.span,
+        };
+
+        let label = match *local_decl.local_info() {
+            LocalInfo::User(mir::BindingForm::ImplicitSelf(_)) => {
+                let suggestion = suggest_ampmut_self(self.infcx.tcx, decl_span);
+                Some((true, decl_span, suggestion))
+            }
+
+            LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
+                binding_mode: ty::BindingMode::BindByValue(_),
+                opt_ty_info,
+                ..
+            })) => {
+                // check if the RHS is from desugaring
+                let opt_assignment_rhs_span =
+                    self.body.find_assignments(local).first().map(|&location| {
+                        if let Some(mir::Statement {
+                            source_info: _,
+                            kind:
+                                mir::StatementKind::Assign(box (
+                                    _,
+                                    mir::Rvalue::Use(mir::Operand::Copy(place)),
+                                )),
+                        }) = self.body[location.block].statements.get(location.statement_index)
+                        {
+                            self.body.local_decls[place.local].source_info.span
+                        } else {
+                            self.body.source_info(location).span
+                        }
+                    });
+                match opt_assignment_rhs_span.and_then(|s| s.desugaring_kind()) {
+                    // on for loops, RHS points to the iterator part
+                    Some(DesugaringKind::ForLoop) => {
+                        self.suggest_similar_mut_method_for_for_loop(err);
+                        err.span_label(
+                            opt_assignment_rhs_span.unwrap(),
+                            format!("this iterator yields `{pointer_sigil}` {pointer_desc}s",),
+                        );
+                        None
+                    }
+                    // don't create labels for compiler-generated spans
+                    Some(_) => None,
+                    None => {
+                        let label = if name != kw::SelfLower {
+                            suggest_ampmut(
+                                self.infcx.tcx,
+                                local_decl.ty,
+                                decl_span,
+                                opt_assignment_rhs_span,
+                                opt_ty_info,
+                            )
+                        } else {
+                            match local_decl.local_info() {
+                                LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
+                                    opt_ty_info: None,
+                                    ..
+                                })) => {
+                                    let sugg = suggest_ampmut_self(self.infcx.tcx, decl_span);
+                                    (true, decl_span, sugg)
+                                }
+                                // explicit self (eg `self: &'a Self`)
+                                _ => suggest_ampmut(
+                                    self.infcx.tcx,
+                                    local_decl.ty,
+                                    decl_span,
+                                    opt_assignment_rhs_span,
+                                    opt_ty_info,
+                                ),
+                            }
+                        };
+                        Some(label)
+                    }
+                }
+            }
+
+            LocalInfo::User(mir::BindingForm::Var(mir::VarBindingForm {
+                binding_mode: ty::BindingMode::BindByReference(_),
+                ..
+            })) => {
+                let pattern_span: Span = local_decl.source_info.span;
+                suggest_ref_mut(self.infcx.tcx, pattern_span)
+                    .map(|span| (true, span, "mut ".to_owned()))
+            }
+
+            _ => unreachable!(),
+        };
+
+        match label {
+            Some((true, err_help_span, suggested_code)) => {
+                err.span_suggestion_verbose(
+                    err_help_span,
+                    format!("consider changing this to be a mutable {pointer_desc}"),
+                    suggested_code,
+                    Applicability::MachineApplicable,
+                );
+            }
+            Some((false, err_label_span, message)) => {
+                struct BindingFinder {
+                    span: Span,
+                    hir_id: Option<hir::HirId>,
+                }
+
+                impl<'tcx> Visitor<'tcx> for BindingFinder {
+                    fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
+                        if let hir::StmtKind::Local(local) = s.kind {
+                            if local.pat.span == self.span {
+                                self.hir_id = Some(local.hir_id);
+                            }
+                        }
+                        hir::intravisit::walk_stmt(self, s);
+                    }
+                }
+                let hir_map = self.infcx.tcx.hir();
+                let def_id = self.body.source.def_id();
+                let hir_id = hir_map.local_def_id_to_hir_id(def_id.expect_local());
+                let node = hir_map.find(hir_id);
+                let hir_id = if let Some(hir::Node::Item(item)) = node
+                && let hir::ItemKind::Fn(.., body_id) = item.kind
+            {
+                let body = hir_map.body(body_id);
+                let mut v = BindingFinder {
+                    span: err_label_span,
+                    hir_id: None,
+                };
+                v.visit_body(body);
+                v.hir_id
+            } else {
+                None
+            };
+                if let Some(hir_id) = hir_id
+                && let Some(hir::Node::Local(local)) = hir_map.find(hir_id)
+            {
+                let (changing, span, sugg) = match local.ty {
+                    Some(ty) => ("changing", ty.span, message),
+                    None => (
+                        "specifying",
+                        local.pat.span.shrink_to_hi(),
+                        format!(": {message}"),
+                    ),
+                };
+                err.span_suggestion_verbose(
+                    span,
+                    format!("consider {changing} this binding's type"),
+                    sugg,
+                    Applicability::HasPlaceholders,
+                );
+            } else {
+                err.span_label(
+                    err_label_span,
+                    format!(
+                        "consider changing this binding's type to be: `{message}`"
+                    ),
+                );
+            }
+            }
+            None => {}
+        }
+    }
 }
 
 pub fn mut_borrow_of_mutable_ref(local_decl: &LocalDecl<'_>, local_name: Option<Symbol>) -> bool {
@@ -1143,7 +1148,7 @@ pub fn mut_borrow_of_mutable_ref(local_decl: &LocalDecl<'_>, local_name: Option<
             // suggest removing the `&mut`.
             //
             // Deliberately fall into this case for all implicit self types,
-            // so that we don't fall in to the next case with them.
+            // so that we don't fall into the next case with them.
             kind == hir::ImplicitSelfKind::MutRef
         }
         _ if Some(kw::SelfLower) == local_name => {
@@ -1156,25 +1161,18 @@ pub fn mut_borrow_of_mutable_ref(local_decl: &LocalDecl<'_>, local_name: Option<
     }
 }
 
-fn suggest_ampmut_self<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    local_decl: &mir::LocalDecl<'tcx>,
-) -> (Span, String) {
-    let sp = local_decl.source_info.span;
-    (
-        sp,
-        match tcx.sess.source_map().span_to_snippet(sp) {
-            Ok(snippet) => {
-                let lt_pos = snippet.find('\'');
-                if let Some(lt_pos) = lt_pos {
-                    format!("&{}mut self", &snippet[lt_pos..snippet.len() - 4])
-                } else {
-                    "&mut self".to_string()
-                }
+fn suggest_ampmut_self<'tcx>(tcx: TyCtxt<'tcx>, span: Span) -> String {
+    match tcx.sess.source_map().span_to_snippet(span) {
+        Ok(snippet) => {
+            let lt_pos = snippet.find('\'');
+            if let Some(lt_pos) = lt_pos {
+                format!("&{}mut self", &snippet[lt_pos..snippet.len() - 4])
+            } else {
+                "&mut self".to_string()
             }
-            _ => "&mut self".to_string(),
-        },
-    )
+        }
+        _ => "&mut self".to_string(),
+    }
 }
 
 // When we want to suggest a user change a local variable to be a `&mut`, there
@@ -1194,72 +1192,89 @@ fn suggest_ampmut_self<'tcx>(
 // by trying (3.), then (2.) and finally falling back on (1.).
 fn suggest_ampmut<'tcx>(
     tcx: TyCtxt<'tcx>,
-    local_decl: &mir::LocalDecl<'tcx>,
+    decl_ty: Ty<'tcx>,
+    decl_span: Span,
     opt_assignment_rhs_span: Option<Span>,
     opt_ty_info: Option<Span>,
 ) -> (bool, Span, String) {
+    // if there is a RHS and it starts with a `&` from it, then check if it is
+    // mutable, and if not, put suggest putting `mut ` to make it mutable.
+    // we don't have to worry about lifetime annotations here because they are
+    // not valid when taking a reference. For example, the following is not valid Rust:
+    //
+    // let x: &i32 = &'a 5;
+    //                ^^ lifetime annotation not allowed
+    //
     if let Some(assignment_rhs_span) = opt_assignment_rhs_span
         && let Ok(src) = tcx.sess.source_map().span_to_snippet(assignment_rhs_span)
+        && let Some(stripped) = src.strip_prefix('&')
     {
-        let is_mutbl = |ty: &str| -> bool {
-            if let Some(rest) = ty.strip_prefix("mut") {
-                match rest.chars().next() {
-                    // e.g. `&mut x`
-                    Some(c) if c.is_whitespace() => true,
-                    // e.g. `&mut(x)`
-                    Some('(') => true,
-                    // e.g. `&mut{x}`
-                    Some('{') => true,
-                    // e.g. `&mutablevar`
-                    _ => false,
-                }
-            } else {
-                false
+        let is_mut = if let Some(rest) = stripped.trim_start().strip_prefix("mut") {
+            match rest.chars().next() {
+                // e.g. `&mut x`
+                Some(c) if c.is_whitespace() => true,
+                // e.g. `&mut(x)`
+                Some('(') => true,
+                // e.g. `&mut{x}`
+                Some('{') => true,
+                // e.g. `&mutablevar`
+                _ => false,
             }
+        } else {
+            false
         };
-        if let (true, Some(ws_pos)) = (src.starts_with("&'"), src.find(char::is_whitespace)) {
-            let lt_name = &src[1..ws_pos];
-            let ty = src[ws_pos..].trim_start();
-            if !is_mutbl(ty) {
-                return (true, assignment_rhs_span, format!("&{lt_name} mut {ty}"));
-            }
-        } else if let Some(stripped) = src.strip_prefix('&') {
-            let stripped = stripped.trim_start();
-            if !is_mutbl(stripped) {
-                return (true, assignment_rhs_span, format!("&mut {stripped}"));
-            }
+        // if the reference is already mutable then there is nothing we can do
+        // here.
+        if !is_mut {
+            let span = assignment_rhs_span;
+            // shrink the span to just after the `&` in `&variable`
+            let span = span.with_lo(span.lo() + BytePos(1)).shrink_to_lo();
+
+            // FIXME(Ezrashaw): returning is bad because we still might want to
+            // update the annotated type, see #106857.
+            return (true, span, "mut ".to_owned());
         }
     }
 
-    let (suggestability, highlight_span) = match opt_ty_info {
+    let (binding_exists, span) = match opt_ty_info {
         // if this is a variable binding with an explicit type,
-        // try to highlight that for the suggestion.
+        // then we will suggest changing it to be mutable.
+        // this is `Applicability::MachineApplicable`.
         Some(ty_span) => (true, ty_span),
 
-        // otherwise, just highlight the span associated with
-        // the (MIR) LocalDecl.
-        None => (false, local_decl.source_info.span),
+        // otherwise, we'll suggest *adding* an annotated type, we'll suggest
+        // the RHS's type for that.
+        // this is `Applicability::HasPlaceholders`.
+        None => (false, decl_span),
     };
 
-    if let Ok(src) = tcx.sess.source_map().span_to_snippet(highlight_span)
-        && let (true, Some(ws_pos)) = (src.starts_with("&'"), src.find(char::is_whitespace))
+    // if the binding already exists and is a reference with a explicit
+    // lifetime, then we can suggest adding ` mut`. this is special-cased from
+    // the path without a explicit lifetime.
+    if let Ok(src) = tcx.sess.source_map().span_to_snippet(span)
+        && src.starts_with("&'")
+        // note that `&     'a T` is invalid so this is correct.
+        && let Some(ws_pos) = src.find(char::is_whitespace)
     {
-        let lt_name = &src[1..ws_pos];
-        let ty = &src[ws_pos..];
-        return (true, highlight_span, format!("&{lt_name} mut{ty}"));
-    }
+        let span = span.with_lo(span.lo() + BytePos(ws_pos as u32)).shrink_to_lo();
+        (true, span, " mut".to_owned())
+    // if there is already a binding, we modify it to be `mut`
+    } else if binding_exists {
+        // shrink the span to just after the `&` in `&variable`
+        let span = span.with_lo(span.lo() + BytePos(1)).shrink_to_lo();
+        (true, span, "mut ".to_owned())
+    } else {
+        // otherwise, suggest that the user annotates the binding; we provide the
+        // type of the local.
+        let ty_mut = decl_ty.builtin_deref(true).unwrap();
+        assert_eq!(ty_mut.mutbl, hir::Mutability::Not);
 
-    let ty_mut = local_decl.ty.builtin_deref(true).unwrap();
-    assert_eq!(ty_mut.mutbl, hir::Mutability::Not);
-    (
-        suggestability,
-        highlight_span,
-        if local_decl.ty.is_ref() {
-            format!("&mut {}", ty_mut.ty)
-        } else {
-            format!("*mut {}", ty_mut.ty)
-        },
-    )
+        (
+            false,
+            span,
+            format!("{}mut {}", if decl_ty.is_ref() {"&"} else {"*"}, ty_mut.ty)
+        )
+    }
 }
 
 fn is_closure_or_generator(ty: Ty<'_>) -> bool {
@@ -1296,11 +1311,13 @@ fn get_mut_span_in_struct_field<'tcx>(
 }
 
 /// If possible, suggest replacing `ref` with `ref mut`.
-fn suggest_ref_mut(tcx: TyCtxt<'_>, binding_span: Span) -> Option<String> {
-    let hi_src = tcx.sess.source_map().span_to_snippet(binding_span).ok()?;
-    if hi_src.starts_with("ref") && hi_src["ref".len()..].starts_with(rustc_lexer::is_whitespace) {
-        let replacement = format!("ref mut{}", &hi_src["ref".len()..]);
-        Some(replacement)
+fn suggest_ref_mut(tcx: TyCtxt<'_>, span: Span) -> Option<Span> {
+    let pattern_str = tcx.sess.source_map().span_to_snippet(span).ok()?;
+    if pattern_str.starts_with("ref")
+        && pattern_str["ref".len()..].starts_with(rustc_lexer::is_whitespace)
+    {
+        let span = span.with_lo(span.lo() + BytePos(4)).shrink_to_lo();
+        Some(span)
     } else {
         None
     }
diff --git a/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs b/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
index d5ece5743..b6eb9ae98 100644
--- a/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/outlives_suggestion.rs
@@ -125,8 +125,7 @@ impl OutlivesSuggestionBuilder {
                     |(r, _)| {
                         self.constraints_to_add
                             .get(r)
-                            .map(|r_outlived| r_outlived.as_slice().contains(fr))
-                            .unwrap_or(false)
+                            .is_some_and(|r_outlived| r_outlived.as_slice().contains(fr))
                     },
                 );
 
@@ -171,7 +170,7 @@ impl OutlivesSuggestionBuilder {
         if let (Some(fr_name), Some(outlived_fr_name)) = (fr_name, outlived_fr_name)
             && !matches!(outlived_fr_name.source, RegionNameSource::Static)
         {
-            diag.help(&format!(
+            diag.help(format!(
                 "consider adding the following bound: `{fr_name}: {outlived_fr_name}`",
             ));
         }
@@ -207,7 +206,7 @@ impl OutlivesSuggestionBuilder {
         // If there is exactly one suggestable constraints, then just suggest it. Otherwise, emit a
         // list of diagnostics.
         let mut diag = if suggested.len() == 1 {
-            mbcx.infcx.tcx.sess.diagnostic().struct_help(&match suggested.last().unwrap() {
+            mbcx.infcx.tcx.sess.diagnostic().struct_help(match suggested.last().unwrap() {
                 SuggestedConstraint::Outlives(a, bs) => {
                     let bs: SmallVec<[String; 2]> = bs.iter().map(|r| r.to_string()).collect();
                     format!("add bound `{a}: {}`", bs.join(" + "))
@@ -232,15 +231,15 @@ impl OutlivesSuggestionBuilder {
                 match constraint {
                     SuggestedConstraint::Outlives(a, bs) => {
                         let bs: SmallVec<[String; 2]> = bs.iter().map(|r| r.to_string()).collect();
-                        diag.help(&format!("add bound `{a}: {}`", bs.join(" + ")));
+                        diag.help(format!("add bound `{a}: {}`", bs.join(" + ")));
                     }
                     SuggestedConstraint::Equal(a, b) => {
-                        diag.help(&format!(
+                        diag.help(format!(
                             "`{a}` and `{b}` must be the same: replace one with the other",
                         ));
                     }
                     SuggestedConstraint::Static(a) => {
-                        diag.help(&format!("replace `{a}` with `'static`"));
+                        diag.help(format!("replace `{a}` with `'static`"));
                     }
                 }
             }
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 9fcebeb0a..8ec872e20 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -533,8 +533,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     }
                     _ => panic!("Unexpected type {ty:?}"),
                 };
-                diag.note(&format!("requirement occurs because of {desc}",));
-                diag.note(&note);
+                diag.note(format!("requirement occurs because of {desc}",));
+                diag.note(note);
                 diag.help("see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance");
             }
         }
@@ -845,7 +845,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 return;
             }
 
-            let Some((alias_tys, alias_span)) = self
+            let Some((alias_tys, alias_span, lt_addition_span)) = self
                 .infcx
                 .tcx
                 .return_type_impl_or_dyn_traits_with_type_alias(suitable_region.def_id) else { return; };
@@ -858,12 +858,22 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     ()
                 }
                 if let TyKind::TraitObject(_, lt, _) = alias_ty.kind {
-                    spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string()));
+                    if lt.ident.name == kw::Empty {
+                        spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string()));
+                    } else {
+                        spans_suggs.push((lt.ident.span, "'a".to_string()));
+                    }
                 }
             }
-            spans_suggs.push((alias_span.shrink_to_hi(), "<'a>".to_string()));
+
+            if let Some(lt_addition_span) = lt_addition_span {
+                spans_suggs.push((lt_addition_span, "'a, ".to_string()));
+            } else {
+                spans_suggs.push((alias_span.shrink_to_hi(), "<'a>".to_string()));
+            }
+
             diag.multipart_suggestion_verbose(
-                &format!(
+                format!(
                     "to declare that the trait object {captures}, you can add a lifetime parameter `'a` in the type alias"
                 ),
                 spans_suggs,
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index f69c4829a..f38e1605f 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -622,7 +622,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                     // programs, so we need to use delay_span_bug here. See #82126.
                     self.infcx.tcx.sess.delay_span_bug(
                         hir_arg.span(),
-                        &format!("unmatched subst and hir arg: found {kind:?} vs {hir_arg:?}"),
+                        format!("unmatched subst and hir arg: found {kind:?} vs {hir_arg:?}"),
                     );
                 }
             }
diff --git a/compiler/rustc_borrowck/src/diagnostics/var_name.rs b/compiler/rustc_borrowck/src/diagnostics/var_name.rs
index 376415e3d..98418e237 100644
--- a/compiler/rustc_borrowck/src/diagnostics/var_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/var_name.rs
@@ -3,7 +3,7 @@
 
 use crate::region_infer::RegionInferenceContext;
 use crate::Upvar;
-use rustc_index::vec::{Idx, IndexSlice};
+use rustc_index::IndexSlice;
 use rustc_middle::mir::{Body, Local};
 use rustc_middle::ty::{RegionVid, TyCtxt};
 use rustc_span::source_map::Span;
@@ -117,7 +117,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         argument_index: usize,
     ) -> (Option<Symbol>, Span) {
         let implicit_inputs = self.universal_regions().defining_ty.implicit_inputs();
-        let argument_local = Local::new(implicit_inputs + argument_index + 1);
+        let argument_local = Local::from_usize(implicit_inputs + argument_index + 1);
         debug!("get_argument_name_and_span_for_region: argument_local={argument_local:?}");
 
         let argument_name = local_names[argument_local];