Auto merge of #126623 - oli-obk:do_not_count_errors, r=davidtwco

Replace all `&DiagCtxt` with a `DiagCtxtHandle<'_>` wrapper type

r? `@davidtwco`

This paves the way for tracking more state (e.g. error tainting) in the diagnostic context handle

Basically I will add a field to the `DiagCtxtHandle` that refers back to the `InferCtxt`'s (and others) `Option<ErrorHandled>`, allowing us to immediately taint these contexts when emitting an error and not needing manual tainting anymore (which is easy to forget and we don't do in general anyway)

118 files changed, 773 insertions, 915 deletions

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index f18ceb62e0b..da8682d3d09 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -50,7 +50,7 @@ use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::Lrc;
-use rustc_errors::{DiagArgFromDisplay, DiagCtxt, StashKey};
+use rustc_errors::{DiagArgFromDisplay, DiagCtxtHandle, StashKey};
 use rustc_hir::def::{DefKind, LifetimeRes, Namespace, PartialRes, PerNS, Res};
 use rustc_hir::def_id::{LocalDefId, LocalDefIdMap, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::{self as hir};
@@ -188,7 +188,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    pub(crate) fn dcx(&self) -> &'hir DiagCtxt {
+    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'hir> {
         self.tcx.dcx()
     }
 }
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 93abe36a2db..b274a9b9114 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -12,6 +12,7 @@ use rustc_ast::visit::{walk_list, AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor}
 use rustc_ast::*;
 use rustc_ast_pretty::pprust::{self, State};
 use rustc_data_structures::fx::FxIndexMap;
+use rustc_errors::DiagCtxtHandle;
 use rustc_feature::Features;
 use rustc_parse::validate_attr;
 use rustc_session::lint::builtin::{
@@ -269,7 +270,7 @@ impl<'a> AstValidator<'a> {
         }
     }
 
-    fn dcx(&self) -> &rustc_errors::DiagCtxt {
+    fn dcx(&self) -> DiagCtxtHandle<'a> {
         self.session.dcx()
     }
 
@@ -809,11 +810,7 @@ impl<'a> AstValidator<'a> {
 
 /// Checks that generic parameters are in the correct order,
 /// which is lifetimes, then types and then consts. (`<'a, T, const N: usize>`)
-fn validate_generic_param_order(
-    dcx: &rustc_errors::DiagCtxt,
-    generics: &[GenericParam],
-    span: Span,
-) {
+fn validate_generic_param_order(dcx: DiagCtxtHandle<'_>, generics: &[GenericParam], span: Span) {
     let mut max_param: Option<ParamKindOrd> = None;
     let mut out_of_order = FxIndexMap::default();
     let mut param_idents = Vec::with_capacity(generics.len());
diff --git a/compiler/rustc_ast_passes/src/show_span.rs b/compiler/rustc_ast_passes/src/show_span.rs
index 10590074282..e7ba2e7fc30 100644
--- a/compiler/rustc_ast_passes/src/show_span.rs
+++ b/compiler/rustc_ast_passes/src/show_span.rs
@@ -8,6 +8,7 @@ use std::str::FromStr;
 use rustc_ast as ast;
 use rustc_ast::visit;
 use rustc_ast::visit::Visitor;
+use rustc_errors::DiagCtxtHandle;
 
 use crate::errors;
 
@@ -31,7 +32,7 @@ impl FromStr for Mode {
 }
 
 struct ShowSpanVisitor<'a> {
-    dcx: &'a rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     mode: Mode,
 }
 
@@ -58,7 +59,7 @@ impl<'a> Visitor<'a> for ShowSpanVisitor<'a> {
     }
 }
 
-pub fn run(dcx: &rustc_errors::DiagCtxt, mode: &str, krate: &ast::Crate) {
+pub fn run(dcx: DiagCtxtHandle<'_>, mode: &str, krate: &ast::Crate) {
     let Ok(mode) = mode.parse() else {
         return;
     };
diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index 5113c5adc8f..34c24a26f7b 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -596,7 +596,7 @@ pub fn eval_condition(
     features: Option<&Features>,
     eval: &mut impl FnMut(Condition) -> bool,
 ) -> bool {
-    let dcx = &sess.psess.dcx;
+    let dcx = sess.dcx();
     match &cfg.kind {
         ast::MetaItemKind::List(mis) if cfg.name_or_empty() == sym::version => {
             try_gate_cfg(sym::version, cfg.span, sess, features);
diff --git a/compiler/rustc_attr/src/session_diagnostics.rs b/compiler/rustc_attr/src/session_diagnostics.rs
index 303909de343..0cffeed0a75 100644
--- a/compiler/rustc_attr/src/session_diagnostics.rs
+++ b/compiler/rustc_attr/src/session_diagnostics.rs
@@ -1,7 +1,8 @@
 use std::num::IntErrorKind;
 
 use rustc_ast as ast;
-use rustc_errors::{codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
+use rustc_errors::DiagCtxtHandle;
+use rustc_errors::{codes::*, Applicability, Diag, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 
@@ -49,7 +50,7 @@ pub(crate) struct UnknownMetaItem<'a> {
 
 // Manual implementation to be able to format `expected` items correctly.
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnknownMetaItem<'_> {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let expected = self.expected.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
         Diag::new(dcx, level, fluent::attr_unknown_meta_item)
             .with_span(self.span)
@@ -202,7 +203,7 @@ pub(crate) struct UnsupportedLiteral {
 }
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnsupportedLiteral {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let mut diag = Diag::new(
             dcx,
             level,
diff --git a/compiler/rustc_borrowck/src/borrowck_errors.rs b/compiler/rustc_borrowck/src/borrowck_errors.rs
index 622feb4e4c7..c1f75328272 100644
--- a/compiler/rustc_borrowck/src/borrowck_errors.rs
+++ b/compiler/rustc_borrowck/src/borrowck_errors.rs
@@ -1,13 +1,13 @@
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::untranslatable_diagnostic)]
 
-use rustc_errors::{codes::*, struct_span_code_err, Diag, DiagCtxt};
+use rustc_errors::{codes::*, struct_span_code_err, Diag, DiagCtxtHandle};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
 
 impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
-    pub fn dcx(&self) -> &'tcx DiagCtxt {
+    pub fn dcx(&self) -> DiagCtxtHandle<'tcx> {
         self.infcx.dcx()
     }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 6bc340e44f5..197da3eb641 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -228,7 +228,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 seen_spans.insert(move_span);
             }
 
-            use_spans.var_path_only_subdiag(self.dcx(), &mut err, desired_action);
+            use_spans.var_path_only_subdiag(&mut err, desired_action);
 
             if !is_loop_move {
                 err.span_label(
@@ -303,24 +303,18 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             if needs_note {
                 if let Some(local) = place.as_local() {
                     let span = self.body.local_decls[local].source_info.span;
-                    err.subdiagnostic(
-                        self.dcx(),
-                        crate::session_diagnostics::TypeNoCopy::Label {
-                            is_partial_move,
-                            ty,
-                            place: &note_msg,
-                            span,
-                        },
-                    );
+                    err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
+                        is_partial_move,
+                        ty,
+                        place: &note_msg,
+                        span,
+                    });
                 } else {
-                    err.subdiagnostic(
-                        self.dcx(),
-                        crate::session_diagnostics::TypeNoCopy::Note {
-                            is_partial_move,
-                            ty,
-                            place: &note_msg,
-                        },
-                    );
+                    err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Note {
+                        is_partial_move,
+                        ty,
+                        place: &note_msg,
+                    });
                 };
             }
 
@@ -597,7 +591,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             E0381,
             "{used} binding {desc}{isnt_initialized}"
         );
-        use_spans.var_path_only_subdiag(self.dcx(), &mut err, desired_action);
+        use_spans.var_path_only_subdiag(&mut err, desired_action);
 
         if let InitializationRequiringAction::PartialAssignment
         | InitializationRequiringAction::Assignment = desired_action
@@ -996,7 +990,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         err: &mut Diag<'_>,
         ty: Ty<'tcx>,
-        expr: &'cx hir::Expr<'cx>,
+        expr: &hir::Expr<'_>,
     ) {
         let typeck_results = self.infcx.tcx.typeck(self.mir_def_id());
         let hir::ExprKind::Struct(struct_qpath, fields, Some(base)) = expr.kind else { return };
@@ -1084,8 +1078,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         &self,
         err: &mut Diag<'_>,
         ty: Ty<'tcx>,
-        mut expr: &'cx hir::Expr<'cx>,
-        mut other_expr: Option<&'cx hir::Expr<'cx>>,
+        mut expr: &'tcx hir::Expr<'tcx>,
+        mut other_expr: Option<&'tcx hir::Expr<'tcx>>,
         use_spans: Option<UseSpans<'tcx>>,
     ) {
         if let hir::ExprKind::Struct(_, _, Some(_)) = expr.kind {
@@ -1410,13 +1404,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             &value_msg,
         );
 
-        borrow_spans.var_path_only_subdiag(
-            self.dcx(),
-            &mut err,
-            crate::InitializationRequiringAction::Borrow,
-        );
+        borrow_spans.var_path_only_subdiag(&mut err, crate::InitializationRequiringAction::Borrow);
 
-        move_spans.var_subdiag(self.dcx(), &mut err, None, |kind, var_span| {
+        move_spans.var_subdiag(&mut err, None, |kind, var_span| {
             use crate::session_diagnostics::CaptureVarCause::*;
             match kind {
                 hir::ClosureKind::Coroutine(_) => MoveUseInCoroutine { var_span },
@@ -1468,7 +1458,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             borrow_span,
             &self.describe_any_place(borrow.borrowed_place.as_ref()),
         );
-        borrow_spans.var_subdiag(self.dcx(), &mut err, Some(borrow.kind), |kind, var_span| {
+        borrow_spans.var_subdiag(&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());
@@ -1633,7 +1623,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         "mutably borrow",
                     );
                     borrow_spans.var_subdiag(
-                        self.dcx(),
                         &mut err,
                         Some(BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture }),
                         |kind, var_span| {
@@ -1730,64 +1719,45 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         };
 
         if issued_spans == borrow_spans {
-            borrow_spans.var_subdiag(
-                self.dcx(),
-                &mut err,
-                Some(gen_borrow_kind),
-                |kind, var_span| {
-                    use crate::session_diagnostics::CaptureVarCause::*;
-                    match kind {
-                        hir::ClosureKind::Coroutine(_) => BorrowUsePlaceCoroutine {
-                            place: desc_place,
-                            var_span,
-                            is_single_var: false,
-                        },
-                        hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
-                            BorrowUsePlaceClosure {
-                                place: desc_place,
-                                var_span,
-                                is_single_var: false,
-                            }
-                        }
+            borrow_spans.var_subdiag(&mut err, Some(gen_borrow_kind), |kind, var_span| {
+                use crate::session_diagnostics::CaptureVarCause::*;
+                match kind {
+                    hir::ClosureKind::Coroutine(_) => BorrowUsePlaceCoroutine {
+                        place: desc_place,
+                        var_span,
+                        is_single_var: false,
+                    },
+                    hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
+                        BorrowUsePlaceClosure { place: desc_place, var_span, is_single_var: false }
                     }
-                },
-            );
+                }
+            });
         } else {
-            issued_spans.var_subdiag(
-                self.dcx(),
-                &mut err,
-                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 {
-                        hir::ClosureKind::Coroutine(_) => {
-                            FirstBorrowUsePlaceCoroutine { place: borrow_place_desc, var_span }
-                        }
-                        hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
-                            FirstBorrowUsePlaceClosure { place: borrow_place_desc, var_span }
-                        }
+            issued_spans.var_subdiag(&mut err, 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 {
+                    hir::ClosureKind::Coroutine(_) => {
+                        FirstBorrowUsePlaceCoroutine { place: borrow_place_desc, var_span }
                     }
-                },
-            );
+                    hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
+                        FirstBorrowUsePlaceClosure { place: borrow_place_desc, var_span }
+                    }
+                }
+            });
 
-            borrow_spans.var_subdiag(
-                self.dcx(),
-                &mut err,
-                Some(gen_borrow_kind),
-                |kind, var_span| {
-                    use crate::session_diagnostics::CaptureVarCause::*;
-                    match kind {
-                        hir::ClosureKind::Coroutine(_) => {
-                            SecondBorrowUsePlaceCoroutine { place: desc_place, var_span }
-                        }
-                        hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
-                            SecondBorrowUsePlaceClosure { place: desc_place, var_span }
-                        }
+            borrow_spans.var_subdiag(&mut err, Some(gen_borrow_kind), |kind, var_span| {
+                use crate::session_diagnostics::CaptureVarCause::*;
+                match kind {
+                    hir::ClosureKind::Coroutine(_) => {
+                        SecondBorrowUsePlaceCoroutine { place: desc_place, var_span }
                     }
-                },
-            );
+                    hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
+                        SecondBorrowUsePlaceClosure { place: desc_place, var_span }
+                    }
+                }
+            });
         }
 
         if union_type_name != "" {
@@ -2016,7 +1986,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         );
     }
 
-    pub(crate) fn find_expr(&self, span: Span) -> Option<&hir::Expr<'_>> {
+    pub(crate) fn find_expr(&self, span: Span) -> Option<&'tcx hir::Expr<'tcx>> {
         let tcx = self.infcx.tcx;
         let body_id = tcx.hir_node(self.mir_hir_id()).body_id()?;
         let mut expr_finder = FindExprBySpan::new(span, tcx);
@@ -2961,7 +2931,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             err.span_label(borrow_span, "borrowed value does not live long enough");
             err.span_label(drop_span, format!("`{name}` dropped here while still borrowed"));
 
-            borrow_spans.args_subdiag(self.dcx(), &mut err, |args_span| {
+            borrow_spans.args_subdiag(&mut err, |args_span| {
                 crate::session_diagnostics::CaptureArgLabel::Capture {
                     is_within: borrow_spans.for_coroutine(),
                     args_span,
@@ -3219,7 +3189,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             None,
         );
 
-        borrow_spans.args_subdiag(self.dcx(), &mut err, |args_span| {
+        borrow_spans.args_subdiag(&mut err, |args_span| {
             crate::session_diagnostics::CaptureArgLabel::Capture {
                 is_within: borrow_spans.for_coroutine(),
                 args_span,
@@ -3680,7 +3650,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     "assign",
                 );
 
-                loan_spans.var_subdiag(self.dcx(), &mut err, Some(loan.kind), |kind, var_span| {
+                loan_spans.var_subdiag(&mut err, Some(loan.kind), |kind, var_span| {
                     use crate::session_diagnostics::CaptureVarCause::*;
                     match kind {
                         hir::ClosureKind::Coroutine(_) => BorrowUseInCoroutine { var_span },
@@ -3698,7 +3668,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
         let mut err = self.cannot_assign_to_borrowed(span, loan_span, &descr_place);
 
-        loan_spans.var_subdiag(self.dcx(), &mut err, Some(loan.kind), |kind, var_span| {
+        loan_spans.var_subdiag(&mut err, Some(loan.kind), |kind, var_span| {
             use crate::session_diagnostics::CaptureVarCause::*;
             match kind {
                 hir::ClosureKind::Coroutine(_) => BorrowUseInCoroutine { var_span },
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index abb0b5afbd8..5b4269caccb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -4,8 +4,8 @@ use crate::session_diagnostics::{
     CaptureArgLabel, CaptureReasonLabel, CaptureReasonNote, CaptureReasonSuggest, CaptureVarCause,
     CaptureVarKind, CaptureVarPathUseCause, OnClosureNote,
 };
+use rustc_errors::MultiSpan;
 use rustc_errors::{Applicability, Diag};
-use rustc_errors::{DiagCtxt, MultiSpan};
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::CoroutineKind;
 use rustc_hir::{self as hir, LangItem};
@@ -130,16 +130,13 @@ 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.subdiagnostic(
-                                self.dcx(),
-                                OnClosureNote::InvokedTwice {
-                                    place_name: &ty::place_to_string_for_capture(
-                                        self.infcx.tcx,
-                                        hir_place,
-                                    ),
-                                    span: *span,
-                                },
-                            );
+                            diag.subdiagnostic(OnClosureNote::InvokedTwice {
+                                place_name: &ty::place_to_string_for_capture(
+                                    self.infcx.tcx,
+                                    hir_place,
+                                ),
+                                span: *span,
+                            });
                             return true;
                         }
                     }
@@ -152,13 +149,10 @@ 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.subdiagnostic(
-                        self.dcx(),
-                        OnClosureNote::MovedTwice {
-                            place_name: &ty::place_to_string_for_capture(self.infcx.tcx, hir_place),
-                            span: *span,
-                        },
-                    );
+                    diag.subdiagnostic(OnClosureNote::MovedTwice {
+                        place_name: &ty::place_to_string_for_capture(self.infcx.tcx, hir_place),
+                        span: *span,
+                    });
                     return true;
                 }
             }
@@ -591,14 +585,9 @@ impl UseSpans<'_> {
 
     /// Add a span label to the arguments of the closure, if it exists.
     #[allow(rustc::diagnostic_outside_of_impl)]
-    pub(super) fn args_subdiag(
-        self,
-        dcx: &DiagCtxt,
-        err: &mut Diag<'_>,
-        f: impl FnOnce(Span) -> CaptureArgLabel,
-    ) {
+    pub(super) fn args_subdiag(self, err: &mut Diag<'_>, f: impl FnOnce(Span) -> CaptureArgLabel) {
         if let UseSpans::ClosureUse { args_span, .. } = self {
-            err.subdiagnostic(dcx, f(args_span));
+            err.subdiagnostic(f(args_span));
         }
     }
 
@@ -607,7 +596,6 @@ impl UseSpans<'_> {
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub(super) fn var_path_only_subdiag(
         self,
-        dcx: &DiagCtxt,
         err: &mut Diag<'_>,
         action: crate::InitializationRequiringAction,
     ) {
@@ -616,26 +604,20 @@ impl UseSpans<'_> {
         if let UseSpans::ClosureUse { closure_kind, path_span, .. } = self {
             match closure_kind {
                 hir::ClosureKind::Coroutine(_) => {
-                    err.subdiagnostic(
-                        dcx,
-                        match action {
-                            Borrow => BorrowInCoroutine { path_span },
-                            MatchOn | Use => UseInCoroutine { path_span },
-                            Assignment => AssignInCoroutine { path_span },
-                            PartialAssignment => AssignPartInCoroutine { path_span },
-                        },
-                    );
+                    err.subdiagnostic(match action {
+                        Borrow => BorrowInCoroutine { path_span },
+                        MatchOn | Use => UseInCoroutine { path_span },
+                        Assignment => AssignInCoroutine { path_span },
+                        PartialAssignment => AssignPartInCoroutine { path_span },
+                    });
                 }
                 hir::ClosureKind::Closure | hir::ClosureKind::CoroutineClosure(_) => {
-                    err.subdiagnostic(
-                        dcx,
-                        match action {
-                            Borrow => BorrowInClosure { path_span },
-                            MatchOn | Use => UseInClosure { path_span },
-                            Assignment => AssignInClosure { path_span },
-                            PartialAssignment => AssignPartInClosure { path_span },
-                        },
-                    );
+                    err.subdiagnostic(match action {
+                        Borrow => BorrowInClosure { path_span },
+                        MatchOn | Use => UseInClosure { path_span },
+                        Assignment => AssignInClosure { path_span },
+                        PartialAssignment => AssignPartInClosure { path_span },
+                    });
                 }
             }
         }
@@ -645,32 +627,28 @@ impl UseSpans<'_> {
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub(super) fn var_subdiag(
         self,
-        dcx: &DiagCtxt,
         err: &mut Diag<'_>,
         kind: Option<rustc_middle::mir::BorrowKind>,
         f: impl FnOnce(hir::ClosureKind, Span) -> CaptureVarCause,
     ) {
         if let UseSpans::ClosureUse { closure_kind, capture_kind_span, path_span, .. } = self {
             if capture_kind_span != path_span {
-                err.subdiagnostic(
-                    dcx,
-                    match kind {
-                        Some(kd) => match kd {
-                            rustc_middle::mir::BorrowKind::Shared
-                            | rustc_middle::mir::BorrowKind::Fake(_) => {
-                                CaptureVarKind::Immut { kind_span: capture_kind_span }
-                            }
+                err.subdiagnostic(match kind {
+                    Some(kd) => match kd {
+                        rustc_middle::mir::BorrowKind::Shared
+                        | rustc_middle::mir::BorrowKind::Fake(_) => {
+                            CaptureVarKind::Immut { kind_span: capture_kind_span }
+                        }
 
-                            rustc_middle::mir::BorrowKind::Mut { .. } => {
-                                CaptureVarKind::Mut { kind_span: capture_kind_span }
-                            }
-                        },
-                        None => CaptureVarKind::Move { kind_span: capture_kind_span },
+                        rustc_middle::mir::BorrowKind::Mut { .. } => {
+                            CaptureVarKind::Mut { kind_span: capture_kind_span }
+                        }
                     },
-                );
+                    None => CaptureVarKind::Move { kind_span: capture_kind_span },
+                });
             };
             let diag = f(closure_kind, path_span);
-            err.subdiagnostic(dcx, diag);
+            err.subdiagnostic(diag);
         }
     }
 
@@ -1042,15 +1020,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 CallKind::FnCall { fn_trait_id, self_ty }
                     if self.infcx.tcx.is_lang_item(fn_trait_id, LangItem::FnOnce) =>
                 {
-                    err.subdiagnostic(
-                        self.dcx(),
-                        CaptureReasonLabel::Call {
-                            fn_call_span,
-                            place_name: &place_name,
-                            is_partial,
-                            is_loop_message,
-                        },
-                    );
+                    err.subdiagnostic(CaptureReasonLabel::Call {
+                        fn_call_span,
+                        place_name: &place_name,
+                        is_partial,
+                        is_loop_message,
+                    });
                     // Check if the move occurs on a value because of a call on a closure that comes
                     // from a type parameter `F: FnOnce()`. If so, we provide a targeted `note`:
                     // ```
@@ -1119,27 +1094,20 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         );
                         err.span_note(span, fluent::borrowck_moved_a_fn_once_in_call_call);
                     } else {
-                        err.subdiagnostic(
-                            self.dcx(),
-                            CaptureReasonNote::FnOnceMoveInCall { var_span },
-                        );
+                        err.subdiagnostic(CaptureReasonNote::FnOnceMoveInCall { var_span });
                     }
                 }
                 CallKind::Operator { self_arg, trait_id, .. } => {
                     let self_arg = self_arg.unwrap();
-                    err.subdiagnostic(
-                        self.dcx(),
-                        CaptureReasonLabel::OperatorUse {
-                            fn_call_span,
-                            place_name: &place_name,
-                            is_partial,
-                            is_loop_message,
-                        },
-                    );
+                    err.subdiagnostic(CaptureReasonLabel::OperatorUse {
+                        fn_call_span,
+                        place_name: &place_name,
+                        is_partial,
+                        is_loop_message,
+                    });
                     if self.fn_self_span_reported.insert(fn_span) {
                         let lang = self.infcx.tcx.lang_items();
                         err.subdiagnostic(
-                            self.dcx(),
                             if [lang.not_trait(), lang.deref_trait(), lang.neg_trait()]
                                 .contains(&Some(trait_id))
                             {
@@ -1164,14 +1132,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         );
 
                         let func = tcx.def_path_str(method_did);
-                        err.subdiagnostic(
-                            self.dcx(),
-                            CaptureReasonNote::FuncTakeSelf {
-                                func,
-                                place_name: place_name.clone(),
-                                span: self_arg.span,
-                            },
-                        );
+                        err.subdiagnostic(CaptureReasonNote::FuncTakeSelf {
+                            func,
+                            place_name: place_name.clone(),
+                            span: self_arg.span,
+                        });
                     }
                     let parent_did = tcx.parent(method_did);
                     let parent_self_ty =
@@ -1185,10 +1150,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
                     });
                     if is_option_or_result && maybe_reinitialized_locations_is_empty {
-                        err.subdiagnostic(
-                            self.dcx(),
-                            CaptureReasonLabel::BorrowContent { var_span },
-                        );
+                        err.subdiagnostic(CaptureReasonLabel::BorrowContent { var_span });
                     }
                     if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
                         let ty = moved_place.ty(self.body, tcx).ty;
@@ -1202,24 +1164,18 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             _ => false,
                         };
                         if suggest {
-                            err.subdiagnostic(
-                                self.dcx(),
-                                CaptureReasonSuggest::IterateSlice {
-                                    ty,
-                                    span: move_span.shrink_to_lo(),
-                                },
-                            );
+                            err.subdiagnostic(CaptureReasonSuggest::IterateSlice {
+                                ty,
+                                span: move_span.shrink_to_lo(),
+                            });
                         }
 
-                        err.subdiagnostic(
-                            self.dcx(),
-                            CaptureReasonLabel::ImplicitCall {
-                                fn_call_span,
-                                place_name: &place_name,
-                                is_partial,
-                                is_loop_message,
-                            },
-                        );
+                        err.subdiagnostic(CaptureReasonLabel::ImplicitCall {
+                            fn_call_span,
+                            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.
@@ -1243,25 +1199,19 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         }
                     } else {
                         if let Some((CallDesugaringKind::Await, _)) = desugaring {
-                            err.subdiagnostic(
-                                self.dcx(),
-                                CaptureReasonLabel::Await {
-                                    fn_call_span,
-                                    place_name: &place_name,
-                                    is_partial,
-                                    is_loop_message,
-                                },
-                            );
+                            err.subdiagnostic(CaptureReasonLabel::Await {
+                                fn_call_span,
+                                place_name: &place_name,
+                                is_partial,
+                                is_loop_message,
+                            });
                         } else {
-                            err.subdiagnostic(
-                                self.dcx(),
-                                CaptureReasonLabel::MethodCall {
-                                    fn_call_span,
-                                    place_name: &place_name,
-                                    is_partial,
-                                    is_loop_message,
-                                },
-                            );
+                            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 = moved_place.ty(self.body, tcx).ty;
@@ -1276,12 +1226,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             )
                             && self.infcx.can_eq(self.param_env, ty, self_ty)
                         {
-                            err.subdiagnostic(
-                                self.dcx(),
-                                CaptureReasonSuggest::FreshReborrow {
-                                    span: move_span.shrink_to_hi(),
-                                },
-                            );
+                            err.subdiagnostic(CaptureReasonSuggest::FreshReborrow {
+                                span: move_span.shrink_to_hi(),
+                            });
                             has_sugg = true;
                         }
                         if let Some(clone_trait) = tcx.lang_items().clone_trait() {
@@ -1368,20 +1315,17 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             }
         } else {
             if move_span != span || is_loop_message {
-                err.subdiagnostic(
-                    self.dcx(),
-                    CaptureReasonLabel::MovedHere {
-                        move_span,
-                        is_partial,
-                        is_move_msg,
-                        is_loop_message,
-                    },
-                );
+                err.subdiagnostic(CaptureReasonLabel::MovedHere {
+                    move_span,
+                    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 !is_loop_message {
-                move_spans.var_subdiag(self.dcx(), err, None, |kind, var_span| match kind {
+                move_spans.var_subdiag(err, None, |kind, var_span| match kind {
                     hir::ClosureKind::Coroutine(_) => {
                         CaptureVarCause::PartialMoveUseInCoroutine { 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 1d844c3d6a2..5a7bca9ab03 100644
--- a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -579,15 +579,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         self.suggest_cloning(err, place_ty, expr, self.find_expr(other_span), None);
                     }
 
-                    err.subdiagnostic(
-                        self.dcx(),
-                        crate::session_diagnostics::TypeNoCopy::Label {
-                            is_partial_move: false,
-                            ty: place_ty,
-                            place: &place_desc,
-                            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();
@@ -620,17 +617,14 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     );
                 }
 
-                err.subdiagnostic(
-                    self.dcx(),
-                    crate::session_diagnostics::TypeNoCopy::Label {
-                        is_partial_move: false,
-                        ty: place_ty,
-                        place: &place_desc,
-                        span: use_span,
-                    },
-                );
+                err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
+                    is_partial_move: false,
+                    ty: place_ty,
+                    place: &place_desc,
+                    span: use_span,
+                });
 
-                use_spans.args_subdiag(self.dcx(), err, |args_span| {
+                use_spans.args_subdiag(err, |args_span| {
                     crate::session_diagnostics::CaptureArgLabel::MoveOutPlace {
                         place: place_desc,
                         args_span,
@@ -733,15 +727,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     self.suggest_cloning(err, bind_to.ty, expr, None, None);
                 }
 
-                err.subdiagnostic(
-                    self.dcx(),
-                    crate::session_diagnostics::TypeNoCopy::Label {
-                        is_partial_move: false,
-                        ty: bind_to.ty,
-                        place: place_desc,
-                        span: binding_span,
-                    },
-                );
+                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 9fd23bc94cf..e0b18536dd5 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -230,7 +230,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 }
                 if suggest {
                     borrow_spans.var_subdiag(
-                        self.dcx(),
                         &mut err,
                         Some(mir::BorrowKind::Mut { kind: mir::MutBorrowKind::Default }),
                         |_kind, var_span| {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 15a8764aab3..67c11ff4a5b 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -631,13 +631,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 let upvars_map = self.infcx.tcx.upvars_mentioned(def_id).unwrap();
                 let upvar_def_span = self.infcx.tcx.hir().span(def_hir);
                 let upvar_span = upvars_map.get(&def_hir).unwrap().span;
-                diag.subdiagnostic(self.dcx(), VarHereDenote::Defined { span: upvar_def_span });
-                diag.subdiagnostic(self.dcx(), VarHereDenote::Captured { span: upvar_span });
+                diag.subdiagnostic(VarHereDenote::Defined { span: upvar_def_span });
+                diag.subdiagnostic(VarHereDenote::Captured { span: upvar_span });
             }
         }
 
         if let Some(fr_span) = self.give_region_a_name(*outlived_fr).unwrap().span() {
-            diag.subdiagnostic(self.dcx(), VarHereDenote::FnMutInferred { span: fr_span });
+            diag.subdiagnostic(VarHereDenote::FnMutInferred { span: fr_span });
         }
 
         self.suggest_move_on_borrowing_closure(&mut diag);
@@ -810,7 +810,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             },
         };
 
-        diag.subdiagnostic(self.dcx(), err_category);
+        diag.subdiagnostic(err_category);
 
         self.add_static_impl_trait_suggestion(&mut diag, *fr, fr_name, *outlived_fr);
         self.suggest_adding_lifetime_params(&mut diag, *fr, *outlived_fr);
@@ -1008,7 +1008,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     ident.span,
                     "calling this method introduces the `impl`'s `'static` requirement",
                 );
-                err.subdiagnostic(self.dcx(), RequireStaticErr::UsedImpl { multi_span });
+                err.subdiagnostic(RequireStaticErr::UsedImpl { multi_span });
                 err.span_suggestion_verbose(
                     span.shrink_to_hi(),
                     "consider relaxing the implicit `'static` requirement",
diff --git a/compiler/rustc_builtin_macros/src/asm.rs b/compiler/rustc_builtin_macros/src/asm.rs
index 1a7961bf70c..64238e81b26 100644
--- a/compiler/rustc_builtin_macros/src/asm.rs
+++ b/compiler/rustc_builtin_macros/src/asm.rs
@@ -46,7 +46,7 @@ pub fn parse_asm_args<'a>(
     sp: Span,
     is_global_asm: bool,
 ) -> PResult<'a, AsmArgs> {
-    let dcx = &p.psess.dcx;
+    let dcx = p.dcx();
 
     if p.token == token::Eof {
         return Err(dcx.create_err(errors::AsmRequiresTemplate { span: sp }));
@@ -307,7 +307,7 @@ pub fn parse_asm_args<'a>(
 fn err_duplicate_option(p: &Parser<'_>, symbol: Symbol, span: Span) {
     // Tool-only output
     let full_span = if p.token.kind == token::Comma { span.to(p.token.span) } else { span };
-    p.psess.dcx.emit_err(errors::AsmOptAlreadyprovided { span, symbol, full_span });
+    p.dcx().emit_err(errors::AsmOptAlreadyprovided { span, symbol, full_span });
 }
 
 /// Try to set the provided option in the provided `AsmArgs`.
@@ -379,7 +379,7 @@ fn parse_clobber_abi<'a>(p: &mut Parser<'a>, args: &mut AsmArgs) -> PResult<'a,
     p.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
 
     if p.eat(&token::CloseDelim(Delimiter::Parenthesis)) {
-        return Err(p.psess.dcx.create_err(errors::NonABI { span: p.token.span }));
+        return Err(p.dcx().create_err(errors::NonABI { span: p.token.span }));
     }
 
     let mut new_abis = Vec::new();
@@ -390,7 +390,7 @@ fn parse_clobber_abi<'a>(p: &mut Parser<'a>, args: &mut AsmArgs) -> PResult<'a,
             }
             Err(opt_lit) => {
                 let span = opt_lit.map_or(p.token.span, |lit| lit.span);
-                let mut err = p.psess.dcx.struct_span_err(span, "expected string literal");
+                let mut err = p.dcx().struct_span_err(span, "expected string literal");
                 err.span_label(span, "not a string literal");
                 return Err(err);
             }
diff --git a/compiler/rustc_builtin_macros/src/cmdline_attrs.rs b/compiler/rustc_builtin_macros/src/cmdline_attrs.rs
index 16184ec7511..58928815e89 100644
--- a/compiler/rustc_builtin_macros/src/cmdline_attrs.rs
+++ b/compiler/rustc_builtin_macros/src/cmdline_attrs.rs
@@ -26,7 +26,7 @@ pub fn inject(krate: &mut ast::Crate, psess: &ParseSess, attrs: &[String]) {
         };
         let end_span = parser.token.span;
         if parser.token != token::Eof {
-            psess.dcx.emit_err(errors::InvalidCrateAttr { span: start_span.to(end_span) });
+            psess.dcx().emit_err(errors::InvalidCrateAttr { span: start_span.to(end_span) });
             continue;
         }
 
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index b14eb2b5ee6..ed2f98f2a39 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -1,5 +1,5 @@
 use rustc_errors::{
-    codes::*, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level, MultiSpan,
+    codes::*, Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level, MultiSpan,
     SingleLabelManySpans, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
@@ -434,7 +434,7 @@ pub(crate) struct EnvNotDefinedWithUserMessage {
 // Hand-written implementation to support custom user messages.
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for EnvNotDefinedWithUserMessage {
     #[track_caller]
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         #[expect(
             rustc::untranslatable_diagnostic,
             reason = "cannot translate user-provided messages"
@@ -801,7 +801,7 @@ pub(crate) struct AsmClobberNoReg {
 }
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AsmClobberNoReg {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         // eager translation as `span_labels` takes `AsRef<str>`
         let lbl1 = dcx.eagerly_translate_to_string(
             crate::fluent_generated::builtin_macros_asm_clobber_abi,
diff --git a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
index 477e5c8bec5..99d0191958d 100644
--- a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
+++ b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
@@ -3,6 +3,7 @@ use rustc_ast::ptr::P;
 use rustc_ast::visit::{self, Visitor};
 use rustc_ast::{self as ast, attr, NodeId};
 use rustc_ast_pretty::pprust;
+use rustc_errors::DiagCtxtHandle;
 use rustc_expand::base::{parse_macro_name_and_helper_attrs, ExtCtxt, ResolverExpand};
 use rustc_expand::expand::{AstFragment, ExpansionConfig};
 use rustc_feature::Features;
@@ -38,7 +39,7 @@ enum ProcMacro {
 struct CollectProcMacros<'a> {
     macros: Vec<ProcMacro>,
     in_root: bool,
-    dcx: &'a rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     source_map: &'a SourceMap,
     is_proc_macro_crate: bool,
     is_test_crate: bool,
@@ -52,7 +53,7 @@ pub fn inject(
     is_proc_macro_crate: bool,
     has_proc_macro_decls: bool,
     is_test_crate: bool,
-    dcx: &rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
 ) {
     let ecfg = ExpansionConfig::default("proc_macro".to_string(), features);
     let mut cx = ExtCtxt::new(sess, ecfg, resolver, None);
diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
index ba4e5cfd130..9d032eb190a 100644
--- a/compiler/rustc_builtin_macros/src/test_harness.rs
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -6,6 +6,7 @@ use rustc_ast::mut_visit::*;
 use rustc_ast::ptr::P;
 use rustc_ast::visit::{walk_item, Visitor};
 use rustc_ast::{attr, ModKind};
+use rustc_errors::DiagCtxtHandle;
 use rustc_expand::base::{ExtCtxt, ResolverExpand};
 use rustc_expand::expand::{AstFragment, ExpansionConfig};
 use rustc_feature::Features;
@@ -391,7 +392,7 @@ fn get_test_name(i: &ast::Item) -> Option<Symbol> {
     attr::first_attr_value_str_by_name(&i.attrs, sym::rustc_test_marker)
 }
 
-fn get_test_runner(dcx: &rustc_errors::DiagCtxt, krate: &ast::Crate) -> Option<ast::Path> {
+fn get_test_runner(dcx: DiagCtxtHandle<'_>, krate: &ast::Crate) -> Option<ast::Path> {
     let test_attr = attr::find_by_name(&krate.attrs, sym::test_runner)?;
     let meta_list = test_attr.meta_item_list()?;
     let span = test_attr.span;
diff --git a/compiler/rustc_codegen_cranelift/src/concurrency_limiter.rs b/compiler/rustc_codegen_cranelift/src/concurrency_limiter.rs
index a73860cf18b..2093b49ff31 100644
--- a/compiler/rustc_codegen_cranelift/src/concurrency_limiter.rs
+++ b/compiler/rustc_codegen_cranelift/src/concurrency_limiter.rs
@@ -1,6 +1,7 @@
 use std::sync::{Arc, Condvar, Mutex};
 
 use jobserver::HelperThread;
+use rustc_errors::DiagCtxtHandle;
 use rustc_session::Session;
 
 // FIXME don't panic when a worker thread panics
@@ -46,7 +47,7 @@ impl ConcurrencyLimiter {
         }
     }
 
-    pub(super) fn acquire(&self, dcx: &rustc_errors::DiagCtxt) -> ConcurrencyLimiterToken {
+    pub(super) fn acquire(&self, dcx: DiagCtxtHandle<'_>) -> ConcurrencyLimiterToken {
         let mut state = self.state.lock().unwrap();
         loop {
             state.assert_invariants();
diff --git a/compiler/rustc_codegen_gcc/src/back/lto.rs b/compiler/rustc_codegen_gcc/src/back/lto.rs
index 61e0f203ee0..ec70fbdddb0 100644
--- a/compiler/rustc_codegen_gcc/src/back/lto.rs
+++ b/compiler/rustc_codegen_gcc/src/back/lto.rs
@@ -28,7 +28,7 @@ use rustc_codegen_ssa::back::write::{CodegenContext, FatLtoInput};
 use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::{looks_like_rust_object_file, ModuleCodegen, ModuleKind};
 use rustc_data_structures::memmap::Mmap;
-use rustc_errors::{DiagCtxt, FatalError};
+use rustc_errors::{DiagCtxtHandle, FatalError};
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::dep_graph::WorkProduct;
 use rustc_middle::middle::exported_symbols::{SymbolExportInfo, SymbolExportLevel};
@@ -59,7 +59,7 @@ struct LtoData {
 
 fn prepare_lto(
     cgcx: &CodegenContext<GccCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
 ) -> Result<LtoData, FatalError> {
     let export_threshold = match cgcx.lto {
         // We're just doing LTO for our one crate
@@ -179,12 +179,13 @@ pub(crate) fn run_fat(
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<LtoModuleCodegen<GccCodegenBackend>, FatalError> {
     let dcx = cgcx.create_dcx();
-    let lto_data = prepare_lto(cgcx, &dcx)?;
+    let dcx = dcx.handle();
+    let lto_data = prepare_lto(cgcx, dcx)?;
     /*let symbols_below_threshold =
     lto_data.symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();*/
     fat_lto(
         cgcx,
-        &dcx,
+        dcx,
         modules,
         cached_modules,
         lto_data.upstream_modules,
@@ -195,7 +196,7 @@ pub(crate) fn run_fat(
 
 fn fat_lto(
     cgcx: &CodegenContext<GccCodegenBackend>,
-    _dcx: &DiagCtxt,
+    _dcx: DiagCtxtHandle<'_>,
     modules: Vec<FatLtoInput<GccCodegenBackend>>,
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
     mut serialized_modules: Vec<(SerializedModule<ModuleBuffer>, CString)>,
diff --git a/compiler/rustc_codegen_gcc/src/back/write.rs b/compiler/rustc_codegen_gcc/src/back/write.rs
index 3ea5be1ee56..b9c7f72d0b7 100644
--- a/compiler/rustc_codegen_gcc/src/back/write.rs
+++ b/compiler/rustc_codegen_gcc/src/back/write.rs
@@ -4,7 +4,7 @@ use gccjit::OutputKind;
 use rustc_codegen_ssa::back::link::ensure_removed;
 use rustc_codegen_ssa::back::write::{BitcodeSection, CodegenContext, EmitObj, ModuleConfig};
 use rustc_codegen_ssa::{CompiledModule, ModuleCodegen};
-use rustc_errors::DiagCtxt;
+use rustc_errors::DiagCtxtHandle;
 use rustc_fs_util::link_or_copy;
 use rustc_session::config::OutputType;
 use rustc_span::fatal_error::FatalError;
@@ -15,7 +15,7 @@ use crate::{GccCodegenBackend, GccContext};
 
 pub(crate) unsafe fn codegen(
     cgcx: &CodegenContext<GccCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     module: ModuleCodegen<GccContext>,
     config: &ModuleConfig,
 ) -> Result<CompiledModule, FatalError> {
@@ -166,7 +166,7 @@ pub(crate) unsafe fn codegen(
 
 pub(crate) fn link(
     _cgcx: &CodegenContext<GccCodegenBackend>,
-    _dcx: &DiagCtxt,
+    _dcx: DiagCtxtHandle<'_>,
     mut _modules: Vec<ModuleCodegen<GccContext>>,
 ) -> Result<ModuleCodegen<GccContext>, FatalError> {
     unimplemented!();
diff --git a/compiler/rustc_codegen_gcc/src/errors.rs b/compiler/rustc_codegen_gcc/src/errors.rs
index aee2b077dba..6bada3d334c 100644
--- a/compiler/rustc_codegen_gcc/src/errors.rs
+++ b/compiler/rustc_codegen_gcc/src/errors.rs
@@ -1,4 +1,4 @@
-use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
+use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
 
@@ -90,13 +90,13 @@ pub(crate) struct TargetFeatureDisableOrEnable<'a> {
 pub(crate) struct MissingFeatures;
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::codegen_gcc_target_feature_disable_or_enable);
         if let Some(span) = self.span {
             diag.span(span);
         };
         if let Some(missing_features) = self.missing_features {
-            diag.subdiagnostic(dcx, missing_features);
+            diag.subdiagnostic(missing_features);
         }
         diag.arg("features", self.features.join(", "));
         diag
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index b1785e150ad..24856506c46 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -16,13 +16,7 @@
 #![allow(internal_features)]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
-#![feature(
-    rustc_private,
-    decl_macro,
-    never_type,
-    trusted_len,
-    hash_raw_entry
-)]
+#![feature(rustc_private, decl_macro, never_type, trusted_len, hash_raw_entry)]
 #![allow(broken_intra_doc_links)]
 #![recursion_limit = "256"]
 #![warn(rust_2018_idioms)]
@@ -104,7 +98,7 @@ use rustc_codegen_ssa::traits::{
 use rustc_codegen_ssa::{CodegenResults, CompiledModule, ModuleCodegen};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync::IntoDynSyncSend;
-use rustc_errors::{DiagCtxt, ErrorGuaranteed};
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
 use rustc_metadata::EncodedMetadata;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
 use rustc_middle::ty::TyCtxt;
@@ -386,7 +380,7 @@ impl WriteBackendMethods for GccCodegenBackend {
 
     unsafe fn optimize(
         _cgcx: &CodegenContext<Self>,
-        _dcx: &DiagCtxt,
+        _dcx: DiagCtxtHandle<'_>,
         module: &ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> Result<(), FatalError> {
@@ -411,14 +405,17 @@ impl WriteBackendMethods for GccCodegenBackend {
 
     unsafe fn codegen(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         module: ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> Result<CompiledModule, FatalError> {
         back::write::codegen(cgcx, dcx, module, config)
     }
 
-    fn prepare_thin(_module: ModuleCodegen<Self::Module>, _emit_summary: bool) -> (String, Self::ThinBuffer) {
+    fn prepare_thin(
+        _module: ModuleCodegen<Self::Module>,
+        _emit_summary: bool,
+    ) -> (String, Self::ThinBuffer) {
         unimplemented!();
     }
 
@@ -428,7 +425,7 @@ impl WriteBackendMethods for GccCodegenBackend {
 
     fn run_link(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         modules: Vec<ModuleCodegen<Self::Module>>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
         back::write::link(cgcx, dcx, modules)
diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index bb7c8fe2ea7..aff3e3d7076 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -14,7 +14,7 @@ use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::{looks_like_rust_object_file, ModuleCodegen, ModuleKind};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::memmap::Mmap;
-use rustc_errors::{DiagCtxt, FatalError};
+use rustc_errors::{DiagCtxtHandle, FatalError};
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::WorkProduct;
@@ -49,7 +49,7 @@ pub fn crate_type_allows_lto(crate_type: CrateType) -> bool {
 
 fn prepare_lto(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
 ) -> Result<(Vec<CString>, Vec<(SerializedModule<ModuleBuffer>, CString)>), FatalError> {
     let export_threshold = match cgcx.lto {
         // We're just doing LTO for our one crate
@@ -203,10 +203,11 @@ pub(crate) fn run_fat(
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<LtoModuleCodegen<LlvmCodegenBackend>, FatalError> {
     let dcx = cgcx.create_dcx();
-    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, &dcx)?;
+    let dcx = dcx.handle();
+    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, dcx)?;
     let symbols_below_threshold =
         symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();
-    fat_lto(cgcx, &dcx, modules, cached_modules, upstream_modules, &symbols_below_threshold)
+    fat_lto(cgcx, dcx, modules, cached_modules, upstream_modules, &symbols_below_threshold)
 }
 
 /// Performs thin LTO by performing necessary global analysis and returning two
@@ -218,7 +219,8 @@ pub(crate) fn run_thin(
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<(Vec<LtoModuleCodegen<LlvmCodegenBackend>>, Vec<WorkProduct>), FatalError> {
     let dcx = cgcx.create_dcx();
-    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, &dcx)?;
+    let dcx = dcx.handle();
+    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, dcx)?;
     let symbols_below_threshold =
         symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();
     if cgcx.opts.cg.linker_plugin_lto.enabled() {
@@ -227,7 +229,7 @@ pub(crate) fn run_thin(
                       is deferred to the linker"
         );
     }
-    thin_lto(cgcx, &dcx, modules, upstream_modules, cached_modules, &symbols_below_threshold)
+    thin_lto(cgcx, dcx, modules, upstream_modules, cached_modules, &symbols_below_threshold)
 }
 
 pub(crate) fn prepare_thin(
@@ -241,7 +243,7 @@ pub(crate) fn prepare_thin(
 
 fn fat_lto(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     modules: Vec<FatLtoInput<LlvmCodegenBackend>>,
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
     mut serialized_modules: Vec<(SerializedModule<ModuleBuffer>, CString)>,
@@ -436,7 +438,7 @@ impl Drop for Linker<'_> {
 /// they all go out of scope.
 fn thin_lto(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     modules: Vec<(String, ThinBuffer)>,
     serialized_modules: Vec<(SerializedModule<ModuleBuffer>, CString)>,
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
@@ -593,7 +595,7 @@ fn thin_lto(
 
 pub(crate) fn run_pass_manager(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     module: &mut ModuleCodegen<ModuleLlvm>,
     thin: bool,
 ) -> Result<(), FatalError> {
@@ -714,10 +716,11 @@ pub unsafe fn optimize_thin_module(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
 ) -> Result<ModuleCodegen<ModuleLlvm>, FatalError> {
     let dcx = cgcx.create_dcx();
+    let dcx = dcx.handle();
 
     let module_name = &thin_module.shared.module_names[thin_module.idx];
     let tm_factory_config = TargetMachineFactoryConfig::new(cgcx, module_name.to_str().unwrap());
-    let tm = (cgcx.tm_factory)(tm_factory_config).map_err(|e| write::llvm_err(&dcx, e))?;
+    let tm = (cgcx.tm_factory)(tm_factory_config).map_err(|e| write::llvm_err(dcx, e))?;
 
     // Right now the implementation we've got only works over serialized
     // modules, so we create a fresh new LLVM context and parse the module
@@ -725,7 +728,7 @@ pub unsafe fn optimize_thin_module(
     // crates but for locally codegened modules we may be able to reuse
     // that LLVM Context and Module.
     let llcx = llvm::LLVMRustContextCreate(cgcx.fewer_names);
-    let llmod_raw = parse_module(llcx, module_name, thin_module.data(), &dcx)? as *const _;
+    let llmod_raw = parse_module(llcx, module_name, thin_module.data(), dcx)? as *const _;
     let mut module = ModuleCodegen {
         module_llvm: ModuleLlvm { llmod_raw, llcx, tm: ManuallyDrop::new(tm) },
         name: thin_module.name().to_string(),
@@ -748,7 +751,7 @@ pub unsafe fn optimize_thin_module(
             let _timer =
                 cgcx.prof.generic_activity_with_arg("LLVM_thin_lto_rename", thin_module.name());
             if !llvm::LLVMRustPrepareThinLTORename(thin_module.shared.data.0, llmod, target) {
-                return Err(write::llvm_err(&dcx, LlvmError::PrepareThinLtoModule));
+                return Err(write::llvm_err(dcx, LlvmError::PrepareThinLtoModule));
             }
             save_temp_bitcode(cgcx, &module, "thin-lto-after-rename");
         }
@@ -758,7 +761,7 @@ pub unsafe fn optimize_thin_module(
                 .prof
                 .generic_activity_with_arg("LLVM_thin_lto_resolve_weak", thin_module.name());
             if !llvm::LLVMRustPrepareThinLTOResolveWeak(thin_module.shared.data.0, llmod) {
-                return Err(write::llvm_err(&dcx, LlvmError::PrepareThinLtoModule));
+                return Err(write::llvm_err(dcx, LlvmError::PrepareThinLtoModule));
             }
             save_temp_bitcode(cgcx, &module, "thin-lto-after-resolve");
         }
@@ -768,7 +771,7 @@ pub unsafe fn optimize_thin_module(
                 .prof
                 .generic_activity_with_arg("LLVM_thin_lto_internalize", thin_module.name());
             if !llvm::LLVMRustPrepareThinLTOInternalize(thin_module.shared.data.0, llmod) {
-                return Err(write::llvm_err(&dcx, LlvmError::PrepareThinLtoModule));
+                return Err(write::llvm_err(dcx, LlvmError::PrepareThinLtoModule));
             }
             save_temp_bitcode(cgcx, &module, "thin-lto-after-internalize");
         }
@@ -777,7 +780,7 @@ pub unsafe fn optimize_thin_module(
             let _timer =
                 cgcx.prof.generic_activity_with_arg("LLVM_thin_lto_import", thin_module.name());
             if !llvm::LLVMRustPrepareThinLTOImport(thin_module.shared.data.0, llmod, target) {
-                return Err(write::llvm_err(&dcx, LlvmError::PrepareThinLtoModule));
+                return Err(write::llvm_err(dcx, LlvmError::PrepareThinLtoModule));
             }
             save_temp_bitcode(cgcx, &module, "thin-lto-after-import");
         }
@@ -789,7 +792,7 @@ pub unsafe fn optimize_thin_module(
         // little differently.
         {
             info!("running thin lto passes over {}", module.name);
-            run_pass_manager(cgcx, &dcx, &mut module, true)?;
+            run_pass_manager(cgcx, dcx, &mut module, true)?;
             save_temp_bitcode(cgcx, &module, "thin-lto-after-pm");
         }
     }
@@ -859,7 +862,7 @@ pub fn parse_module<'a>(
     cx: &'a llvm::Context,
     name: &CStr,
     data: &[u8],
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
 ) -> Result<&'a llvm::Module, FatalError> {
     unsafe {
         llvm::LLVMRustParseBitcodeForLTO(cx, data.as_ptr(), data.len(), name.as_ptr())
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 02e3bb06dda..bbfc697407b 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -26,7 +26,7 @@ use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::{CompiledModule, ModuleCodegen};
 use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_data_structures::small_c_str::SmallCStr;
-use rustc_errors::{DiagCtxt, FatalError, Level};
+use rustc_errors::{DiagCtxtHandle, FatalError, Level};
 use rustc_fs_util::{link_or_copy, path_to_c_string};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{self, Lto, OutputType, Passes};
@@ -47,7 +47,7 @@ use std::slice;
 use std::str;
 use std::sync::Arc;
 
-pub fn llvm_err<'a>(dcx: &rustc_errors::DiagCtxt, err: LlvmError<'a>) -> FatalError {
+pub fn llvm_err<'a>(dcx: DiagCtxtHandle<'_>, err: LlvmError<'a>) -> FatalError {
     match llvm::last_error() {
         Some(llvm_err) => dcx.emit_almost_fatal(WithLlvmError(err, llvm_err)),
         None => dcx.emit_almost_fatal(err),
@@ -55,7 +55,7 @@ pub fn llvm_err<'a>(dcx: &rustc_errors::DiagCtxt, err: LlvmError<'a>) -> FatalEr
 }
 
 pub fn write_output_file<'ll>(
-    dcx: &rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     target: &'ll llvm::TargetMachine,
     pm: &llvm::PassManager<'ll>,
     m: &'ll llvm::Module,
@@ -331,7 +331,7 @@ pub enum CodegenDiagnosticsStage {
 }
 
 pub struct DiagnosticHandlers<'a> {
-    data: *mut (&'a CodegenContext<LlvmCodegenBackend>, &'a DiagCtxt),
+    data: *mut (&'a CodegenContext<LlvmCodegenBackend>, DiagCtxtHandle<'a>),
     llcx: &'a llvm::Context,
     old_handler: Option<&'a llvm::DiagnosticHandler>,
 }
@@ -339,7 +339,7 @@ pub struct DiagnosticHandlers<'a> {
 impl<'a> DiagnosticHandlers<'a> {
     pub fn new(
         cgcx: &'a CodegenContext<LlvmCodegenBackend>,
-        dcx: &'a DiagCtxt,
+        dcx: DiagCtxtHandle<'a>,
         llcx: &'a llvm::Context,
         module: &ModuleCodegen<ModuleLlvm>,
         stage: CodegenDiagnosticsStage,
@@ -428,7 +428,7 @@ unsafe extern "C" fn diagnostic_handler(info: &DiagnosticInfo, user: *mut c_void
     if user.is_null() {
         return;
     }
-    let (cgcx, dcx) = *(user as *const (&CodegenContext<LlvmCodegenBackend>, &DiagCtxt));
+    let (cgcx, dcx) = *(user as *const (&CodegenContext<LlvmCodegenBackend>, DiagCtxtHandle<'_>));
 
     match llvm::diagnostic::Diagnostic::unpack(info) {
         llvm::diagnostic::InlineAsm(inline) => {
@@ -506,7 +506,7 @@ fn get_instr_profile_output_path(config: &ModuleConfig) -> Option<CString> {
 
 pub(crate) unsafe fn llvm_optimize(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     module: &ModuleCodegen<ModuleLlvm>,
     config: &ModuleConfig,
     opt_level: config::OptLevel,
@@ -604,7 +604,7 @@ pub(crate) unsafe fn llvm_optimize(
 // Unsafe due to LLVM calls.
 pub(crate) unsafe fn optimize(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     module: &ModuleCodegen<ModuleLlvm>,
     config: &ModuleConfig,
 ) -> Result<(), FatalError> {
@@ -637,7 +637,7 @@ pub(crate) unsafe fn optimize(
 
 pub(crate) fn link(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     mut modules: Vec<ModuleCodegen<ModuleLlvm>>,
 ) -> Result<ModuleCodegen<ModuleLlvm>, FatalError> {
     use super::lto::{Linker, ModuleBuffer};
@@ -660,7 +660,7 @@ pub(crate) fn link(
 
 pub(crate) unsafe fn codegen(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     module: ModuleCodegen<ModuleLlvm>,
     config: &ModuleConfig,
 ) -> Result<CompiledModule, FatalError> {
diff --git a/compiler/rustc_codegen_llvm/src/errors.rs b/compiler/rustc_codegen_llvm/src/errors.rs
index 9d83dc81163..40ac2f9c8ba 100644
--- a/compiler/rustc_codegen_llvm/src/errors.rs
+++ b/compiler/rustc_codegen_llvm/src/errors.rs
@@ -4,7 +4,7 @@ use std::path::Path;
 
 use crate::fluent_generated as fluent;
 use rustc_data_structures::small_c_str::SmallCStr;
-use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
+use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
 
@@ -100,7 +100,7 @@ pub(crate) struct DynamicLinkingWithLTO;
 pub(crate) struct ParseTargetMachineConfig<'a>(pub LlvmError<'a>);
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for ParseTargetMachineConfig<'_> {
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let diag: Diag<'_, G> = self.0.into_diag(dcx, level);
         let (message, _) = diag.messages.first().expect("`LlvmError` with no message");
         let message = dcx.eagerly_translate_to_string(message.clone(), diag.args.iter());
@@ -120,13 +120,13 @@ pub(crate) struct TargetFeatureDisableOrEnable<'a> {
 pub(crate) struct MissingFeatures;
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::codegen_llvm_target_feature_disable_or_enable);
         if let Some(span) = self.span {
             diag.span(span);
         };
         if let Some(missing_features) = self.missing_features {
-            diag.subdiagnostic(dcx, missing_features);
+            diag.subdiagnostic(missing_features);
         }
         diag.arg("features", self.features.join(", "));
         diag
@@ -180,7 +180,7 @@ pub enum LlvmError<'a> {
 pub(crate) struct WithLlvmError<'a>(pub LlvmError<'a>, pub String);
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for WithLlvmError<'_> {
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         use LlvmError::*;
         let msg_with_llvm_err = match &self.0 {
             WriteOutput { .. } => fluent::codegen_llvm_write_output_with_llvm_err,
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index bb76d388393..4b7a2643007 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -31,7 +31,7 @@ use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::ModuleCodegen;
 use rustc_codegen_ssa::{CodegenResults, CompiledModule};
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_errors::{DiagCtxt, ErrorGuaranteed, FatalError};
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, FatalError};
 use rustc_metadata::EncodedMetadata;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
 use rustc_middle::ty::TyCtxt;
@@ -191,7 +191,7 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     }
     fn run_link(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         modules: Vec<ModuleCodegen<Self::Module>>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
         back::write::link(cgcx, dcx, modules)
@@ -212,7 +212,7 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     }
     unsafe fn optimize(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         module: &ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> Result<(), FatalError> {
@@ -223,7 +223,8 @@ impl WriteBackendMethods for LlvmCodegenBackend {
         module: &mut ModuleCodegen<Self::Module>,
     ) -> Result<(), FatalError> {
         let dcx = cgcx.create_dcx();
-        back::lto::run_pass_manager(cgcx, &dcx, module, false)
+        let dcx = dcx.handle();
+        back::lto::run_pass_manager(cgcx, dcx, module, false)
     }
     unsafe fn optimize_thin(
         cgcx: &CodegenContext<Self>,
@@ -233,7 +234,7 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     }
     unsafe fn codegen(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         module: ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> Result<CompiledModule, FatalError> {
@@ -441,7 +442,7 @@ impl ModuleLlvm {
         cgcx: &CodegenContext<LlvmCodegenBackend>,
         name: &CStr,
         buffer: &[u8],
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
     ) -> Result<Self, FatalError> {
         unsafe {
             let llcx = llvm::LLVMRustContextCreate(cgcx.fewer_names);
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index bdb808b1d4f..c352100b01b 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -3,7 +3,7 @@ use rustc_ast::CRATE_NODE_ID;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::temp_dir::MaybeTempDir;
-use rustc_errors::{DiagCtxt, ErrorGuaranteed, FatalError};
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, FatalError};
 use rustc_fs_util::{fix_windows_verbatim_for_gcc, try_canonicalize};
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_metadata::find_native_static_library;
@@ -54,7 +54,7 @@ use std::process::{ExitStatus, Output, Stdio};
 use std::{env, fmt, fs, io, mem, str};
 use tracing::{debug, info, warn};
 
-pub fn ensure_removed(dcx: &DiagCtxt, path: &Path) {
+pub fn ensure_removed(dcx: DiagCtxtHandle<'_>, path: &Path) {
     if let Err(e) = fs::remove_file(path) {
         if e.kind() != io::ErrorKind::NotFound {
             dcx.err(format!("failed to remove {}: {}", path.display(), e));
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index dec87db0fc5..064be4988bd 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -891,9 +891,10 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
     module_config: &ModuleConfig,
 ) -> Result<WorkItemResult<B>, FatalError> {
     let dcx = cgcx.create_dcx();
+    let dcx = dcx.handle();
 
     unsafe {
-        B::optimize(cgcx, &dcx, &module, module_config)?;
+        B::optimize(cgcx, dcx, &module, module_config)?;
     }
 
     // After we've done the initial round of optimizations we need to
@@ -954,7 +955,11 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
         match link_or_copy(&source_file, &output_path) {
             Ok(_) => Some(output_path),
             Err(error) => {
-                cgcx.create_dcx().emit_err(errors::CopyPathBuf { source_file, output_path, error });
+                cgcx.create_dcx().handle().emit_err(errors::CopyPathBuf {
+                    source_file,
+                    output_path,
+                    error,
+                });
                 None
             }
         }
@@ -987,7 +992,7 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
     let bytecode = load_from_incr_cache(module_config.emit_bc, OutputType::Bitcode);
     let object = load_from_incr_cache(should_emit_obj, OutputType::Object);
     if should_emit_obj && object.is_none() {
-        cgcx.create_dcx().emit_fatal(errors::NoSavedObjectFile { cgu_name: &module.name })
+        cgcx.create_dcx().handle().emit_fatal(errors::NoSavedObjectFile { cgu_name: &module.name })
     }
 
     WorkItemResult::Finished(CompiledModule {
@@ -1016,12 +1021,13 @@ fn finish_intra_module_work<B: ExtraBackendMethods>(
     module_config: &ModuleConfig,
 ) -> Result<WorkItemResult<B>, FatalError> {
     let dcx = cgcx.create_dcx();
+    let dcx = dcx.handle();
 
     if !cgcx.opts.unstable_opts.combine_cgu
         || module.kind == ModuleKind::Metadata
         || module.kind == ModuleKind::Allocator
     {
-        let module = unsafe { B::codegen(cgcx, &dcx, module, module_config)? };
+        let module = unsafe { B::codegen(cgcx, dcx, module, module_config)? };
         Ok(WorkItemResult::Finished(module))
     } else {
         Ok(WorkItemResult::NeedsLink(module))
@@ -1692,9 +1698,10 @@ fn start_executing_work<B: ExtraBackendMethods>(
         if !needs_link.is_empty() {
             assert!(compiled_modules.is_empty());
             let dcx = cgcx.create_dcx();
-            let module = B::run_link(&cgcx, &dcx, needs_link).map_err(|_| ())?;
+            let dcx = dcx.handle();
+            let module = B::run_link(&cgcx, dcx, needs_link).map_err(|_| ())?;
             let module = unsafe {
-                B::codegen(&cgcx, &dcx, module, cgcx.config(ModuleKind::Regular)).map_err(|_| ())?
+                B::codegen(&cgcx, dcx, module, cgcx.config(ModuleKind::Regular)).map_err(|_| ())?
             };
             compiled_modules.push(module);
         }
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index 3641e7842cf..e6ba31c5165 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -4,7 +4,7 @@ use crate::assert_module_sources::CguReuse;
 use crate::back::command::Command;
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    codes::*, Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
+    codes::*, Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
 };
 use rustc_macros::Diagnostic;
 use rustc_middle::ty::layout::LayoutError;
@@ -215,7 +215,7 @@ pub enum LinkRlibError {
 pub struct ThorinErrorWrapper(pub thorin::Error);
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for ThorinErrorWrapper {
-    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let build = |msg| Diag::new(dcx, level, msg);
         match self.0 {
             thorin::Error::ReadInput(_) => build(fluent::codegen_ssa_thorin_read_input_failure),
@@ -348,7 +348,7 @@ pub struct LinkingFailed<'a> {
 }
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
-    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::codegen_ssa_linking_failed);
         diag.arg("linker_path", format!("{}", self.linker_path.display()));
         diag.arg("exit_status", format!("{}", self.exit_status));
diff --git a/compiler/rustc_codegen_ssa/src/traits/write.rs b/compiler/rustc_codegen_ssa/src/traits/write.rs
index f83e34ab01b..f4b1421a532 100644
--- a/compiler/rustc_codegen_ssa/src/traits/write.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/write.rs
@@ -2,7 +2,7 @@ use crate::back::lto::{LtoModuleCodegen, SerializedModule, ThinModule};
 use crate::back::write::{CodegenContext, FatLtoInput, ModuleConfig};
 use crate::{CompiledModule, ModuleCodegen};
 
-use rustc_errors::{DiagCtxt, FatalError};
+use rustc_errors::{DiagCtxtHandle, FatalError};
 use rustc_middle::dep_graph::WorkProduct;
 
 pub trait WriteBackendMethods: 'static + Sized + Clone {
@@ -16,7 +16,7 @@ pub trait WriteBackendMethods: 'static + Sized + Clone {
     /// Merge all modules into main_module and returning it
     fn run_link(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         modules: Vec<ModuleCodegen<Self::Module>>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError>;
     /// Performs fat LTO by merging all modules into a single one and returning it
@@ -38,7 +38,7 @@ pub trait WriteBackendMethods: 'static + Sized + Clone {
     fn print_statistics(&self);
     unsafe fn optimize(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         module: &ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> Result<(), FatalError>;
@@ -52,7 +52,7 @@ pub trait WriteBackendMethods: 'static + Sized + Clone {
     ) -> Result<ModuleCodegen<Self::Module>, FatalError>;
     unsafe fn codegen(
         cgcx: &CodegenContext<Self>,
-        dcx: &DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         module: ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> Result<CompiledModule, FatalError>;
diff --git a/compiler/rustc_const_eval/src/check_consts/mod.rs b/compiler/rustc_const_eval/src/check_consts/mod.rs
index 308b90cd470..ac8f0d842ee 100644
--- a/compiler/rustc_const_eval/src/check_consts/mod.rs
+++ b/compiler/rustc_const_eval/src/check_consts/mod.rs
@@ -5,7 +5,7 @@
 //! it finds operations that are invalid in a certain context.
 
 use rustc_attr as attr;
-use rustc_errors::DiagCtxt;
+use rustc_errors::DiagCtxtHandle;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::bug;
@@ -46,7 +46,7 @@ impl<'mir, 'tcx> ConstCx<'mir, 'tcx> {
         ConstCx { body, tcx, param_env, const_kind }
     }
 
-    pub(crate) fn dcx(&self) -> &'tcx DiagCtxt {
+    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'tcx> {
         self.tcx.dcx()
     }
 
diff --git a/compiler/rustc_const_eval/src/check_consts/ops.rs b/compiler/rustc_const_eval/src/check_consts/ops.rs
index eb9a83fb9cf..55432e63ef9 100644
--- a/compiler/rustc_const_eval/src/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/check_consts/ops.rs
@@ -138,7 +138,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                         // FIXME(effects) revisit this
                         if !tcx.is_const_trait_impl_raw(data.impl_def_id) {
                             let span = tcx.def_span(data.impl_def_id);
-                            err.subdiagnostic(tcx.dcx(), errors::NonConstImplNote { span });
+                            err.subdiagnostic(errors::NonConstImplNote { span });
                         }
                     }
                 }
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index 91d17fdd895..5fa48a59794 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -2,7 +2,7 @@ use std::borrow::Cow;
 
 use either::Either;
 use rustc_errors::{
-    codes::*, Diag, DiagArgValue, DiagCtxt, DiagMessage, Diagnostic, EmissionGuarantee, Level,
+    codes::*, Diag, DiagArgValue, DiagCtxtHandle, DiagMessage, Diagnostic, EmissionGuarantee, Level,
 };
 use rustc_hir::ConstContext;
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
@@ -453,7 +453,7 @@ pub trait ReportErrorExt {
     }
 }
 
-fn bad_pointer_message(msg: CheckInAllocMsg, dcx: &DiagCtxt) -> String {
+fn bad_pointer_message(msg: CheckInAllocMsg, dcx: DiagCtxtHandle<'_>) -> String {
     use crate::fluent_generated::*;
 
     let msg = match msg {
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs
index 86325c5ae24..f602d989e08 100644
--- a/compiler/rustc_const_eval/src/interpret/eval_context.rs
+++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs
@@ -4,7 +4,7 @@ use std::{fmt, mem};
 use either::{Either, Left, Right};
 use tracing::{debug, info, info_span, instrument, trace};
 
-use rustc_errors::DiagCtxt;
+use rustc_errors::DiagCtxtHandle;
 use rustc_hir::{self as hir, def_id::DefId, definitions::DefPathData};
 use rustc_index::IndexVec;
 use rustc_middle::mir;
@@ -474,7 +474,7 @@ pub(super) fn from_known_layout<'tcx>(
 ///
 /// This is NOT the preferred way to render an error; use `report` from `const_eval` instead.
 /// However, this is useful when error messages appear in ICEs.
-pub fn format_interp_error<'tcx>(dcx: &DiagCtxt, e: InterpErrorInfo<'tcx>) -> String {
+pub fn format_interp_error<'tcx>(dcx: DiagCtxtHandle<'_>, e: InterpErrorInfo<'tcx>) -> String {
     let (e, backtrace) = e.into_parts();
     backtrace.print_backtrace();
     // FIXME(fee1-dead), HACK: we want to use the error as title therefore we can just extract the
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 9acff4a0a26..5ffa3a6099c 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -1444,6 +1444,7 @@ fn report_ice(
         fallback_bundle,
     ));
     let dcx = rustc_errors::DiagCtxt::new(emitter);
+    let dcx = dcx.handle();
 
     // a .span_bug or .bug call has already printed what
     // it wants to print.
@@ -1509,7 +1510,7 @@ fn report_ice(
 
     let num_frames = if backtrace { None } else { Some(2) };
 
-    interface::try_print_query_stack(&dcx, num_frames, file);
+    interface::try_print_query_stack(dcx, num_frames, file);
 
     // We don't trust this callback not to panic itself, so run it at the end after we're sure we've
     // printed all the relevant info.
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 34b569c4206..e580910af77 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -1,7 +1,7 @@
 use crate::snippet::Style;
 use crate::{
-    CodeSuggestion, DiagCtxt, DiagMessage, ErrCode, ErrorGuaranteed, ExplicitBug, Level, MultiSpan,
-    StashKey, SubdiagMessage, Substitution, SubstitutionPart, SuggestionStyle,
+    CodeSuggestion, DiagCtxtHandle, DiagMessage, ErrCode, ErrorGuaranteed, ExplicitBug, Level,
+    MultiSpan, StashKey, SubdiagMessage, Substitution, SubstitutionPart, SuggestionStyle,
 };
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_error_messages::fluent_value_from_str_list_sep_by_and;
@@ -133,7 +133,7 @@ impl EmissionGuarantee for rustc_span::fatal_error::FatalError {
 pub trait Diagnostic<'a, G: EmissionGuarantee = ErrorGuaranteed> {
     /// Write out as a diagnostic out of `DiagCtxt`.
     #[must_use]
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G>;
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G>;
 }
 
 impl<'a, T, G> Diagnostic<'a, G> for Spanned<T>
@@ -141,7 +141,7 @@ where
     T: Diagnostic<'a, G>,
     G: EmissionGuarantee,
 {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         self.node.into_diag(dcx, level).with_span(self.span)
     }
 }
@@ -490,7 +490,7 @@ pub struct Subdiag {
 /// the methods of `Diag` here, consider extending `DiagCtxtFlags`.
 #[must_use]
 pub struct Diag<'a, G: EmissionGuarantee = ErrorGuaranteed> {
-    pub dcx: &'a DiagCtxt,
+    pub dcx: DiagCtxtHandle<'a>,
 
     /// Why the `Option`? It is always `Some` until the `Diag` is consumed via
     /// `emit`, `cancel`, etc. At that point it is consumed and replaced with
@@ -578,13 +578,13 @@ macro_rules! with_fn {
 impl<'a, G: EmissionGuarantee> Diag<'a, G> {
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn new(dcx: &'a DiagCtxt, level: Level, message: impl Into<DiagMessage>) -> Self {
+    pub fn new(dcx: DiagCtxtHandle<'a>, level: Level, message: impl Into<DiagMessage>) -> Self {
         Self::new_diagnostic(dcx, DiagInner::new(level, message))
     }
 
     /// Creates a new `Diag` with an already constructed diagnostic.
     #[track_caller]
-    pub(crate) fn new_diagnostic(dcx: &'a DiagCtxt, diag: DiagInner) -> Self {
+    pub(crate) fn new_diagnostic(dcx: DiagCtxtHandle<'a>, diag: DiagInner) -> Self {
         debug!("Created new diagnostic");
         Self { dcx, diag: Some(Box::new(diag)), _marker: PhantomData }
     }
@@ -1192,11 +1192,8 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
     /// used in the subdiagnostic, so suitable for use with repeated messages (i.e. re-use of
     /// interpolated variables).
     #[rustc_lint_diagnostics]
-    pub fn subdiagnostic(
-        &mut self,
-        dcx: &crate::DiagCtxt,
-        subdiagnostic: impl Subdiagnostic,
-    ) -> &mut Self {
+    pub fn subdiagnostic(&mut self, subdiagnostic: impl Subdiagnostic) -> &mut Self {
+        let dcx = self.dcx;
         subdiagnostic.add_to_diag_with(self, &|diag, msg| {
             let args = diag.args.iter();
             let msg = diag.subdiagnostic_message_to_diagnostic_message(msg);
@@ -1341,7 +1338,8 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
 
     /// See `DiagCtxt::stash_diagnostic` for details.
     pub fn stash(mut self, span: Span, key: StashKey) -> Option<ErrorGuaranteed> {
-        self.dcx.stash_diagnostic(span, key, self.take_diag())
+        let diag = self.take_diag();
+        self.dcx.stash_diagnostic(span, key, diag)
     }
 
     /// Delay emission of this diagnostic as a bug.
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index ee6df8e15db..0af80bc5c67 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -1,7 +1,7 @@
 use crate::diagnostic::DiagLocation;
-use crate::{fluent_generated as fluent, Subdiagnostic};
+use crate::{fluent_generated as fluent, DiagCtxtHandle, Subdiagnostic};
 use crate::{
-    Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, ErrCode, IntoDiagArg, Level,
+    Diag, DiagArgValue, Diagnostic, EmissionGuarantee, ErrCode, IntoDiagArg, Level,
     SubdiagMessageOp,
 };
 use rustc_ast as ast;
@@ -315,7 +315,7 @@ impl IntoDiagArg for DiagSymbolList {
 }
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetDataLayoutErrors<'_> {
-    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         match self {
             TargetDataLayoutErrors::InvalidAddressSpace { addr_space, err, cause } => {
                 Diag::new(dcx, level, fluent::errors_target_invalid_address_space)
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 5d4d2555100..245deda50d5 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -567,7 +567,7 @@ impl Emitter for SilentEmitter {
             if let Some(fatal_note) = &self.fatal_note {
                 diag.sub(Level::Note, fatal_note.clone(), MultiSpan::new());
             }
-            self.fatal_dcx.emit_diagnostic(diag);
+            self.fatal_dcx.handle().emit_diagnostic(diag);
         }
     }
 }
diff --git a/compiler/rustc_errors/src/json/tests.rs b/compiler/rustc_errors/src/json/tests.rs
index 80b4d2bf75c..e4b29fc9103 100644
--- a/compiler/rustc_errors/src/json/tests.rs
+++ b/compiler/rustc_errors/src/json/tests.rs
@@ -55,8 +55,7 @@ fn test_positions(code: &str, span: (u32, u32), expected_output: SpanTestData) {
         );
 
         let span = Span::with_root_ctxt(BytePos(span.0), BytePos(span.1));
-        let dcx = DiagCtxt::new(Box::new(je));
-        dcx.span_err(span, "foo");
+        DiagCtxt::new(Box::new(je)).handle().span_err(span, "foo");
 
         let bytes = output.lock().unwrap();
         let actual_output = str::from_utf8(&bytes).unwrap();
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 4dc5d84b318..83d5bbff0b0 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -414,6 +414,19 @@ pub struct DiagCtxt {
     inner: Lock<DiagCtxtInner>,
 }
 
+#[derive(Copy, Clone)]
+pub struct DiagCtxtHandle<'a> {
+    dcx: &'a DiagCtxt,
+}
+
+impl<'a> std::ops::Deref for DiagCtxtHandle<'a> {
+    type Target = &'a DiagCtxt;
+
+    fn deref(&self) -> &Self::Target {
+        &self.dcx
+    }
+}
+
 /// This inner struct exists to keep it all behind a single lock;
 /// this is done to prevent possible deadlocks in a multi-threaded compiler,
 /// as well as inconsistent state observation.
@@ -608,7 +621,7 @@ impl DiagCtxt {
     }
 
     pub fn make_silent(
-        &mut self,
+        &self,
         fallback_bundle: LazyFallbackBundle,
         fatal_note: Option<String>,
         emit_fatal_diagnostic: bool,
@@ -623,7 +636,7 @@ impl DiagCtxt {
         });
     }
 
-    fn wrap_emitter<F>(&mut self, f: F)
+    fn wrap_emitter<F>(&self, f: F)
     where
         F: FnOnce(DiagCtxtInner) -> Box<DynEmitter>,
     {
@@ -738,6 +751,12 @@ impl DiagCtxt {
         *fulfilled_expectations = Default::default();
     }
 
+    pub fn handle<'a>(&'a self) -> DiagCtxtHandle<'a> {
+        DiagCtxtHandle { dcx: self }
+    }
+}
+
+impl<'a> DiagCtxtHandle<'a> {
     /// Stashes a diagnostic for possible later improvement in a different,
     /// later stage of the compiler. Possible actions depend on the diagnostic
     /// level:
@@ -745,8 +764,8 @@ impl DiagCtxt {
     /// - Level::Error: immediately counted as an error that has occurred, because it
     ///   is guaranteed to be emitted eventually. Can be later accessed with the
     ///   provided `span` and `key` through
-    ///   [`DiagCtxt::try_steal_modify_and_emit_err`] or
-    ///   [`DiagCtxt::try_steal_replace_and_emit_err`]. These do not allow
+    ///   [`DiagCtxtHandle::try_steal_modify_and_emit_err`] or
+    ///   [`DiagCtxtHandle::try_steal_replace_and_emit_err`]. These do not allow
     ///   cancellation or downgrading of the error. Returns
     ///   `Some(ErrorGuaranteed)`.
     /// - Level::DelayedBug: this does happen occasionally with errors that are
@@ -757,7 +776,7 @@ impl DiagCtxt {
     ///   user-facing error. Returns `Some(ErrorGuaranteed)` as is normal for
     ///   delayed bugs.
     /// - Level::Warning and lower (i.e. !is_error()): can be accessed with the
-    ///   provided `span` and `key` through [`DiagCtxt::steal_non_err()`]. This
+    ///   provided `span` and `key` through [`DiagCtxtHandle::steal_non_err()`]. This
     ///   allows cancelling and downgrading of the diagnostic. Returns `None`.
     pub fn stash_diagnostic(
         &self,
@@ -793,7 +812,7 @@ impl DiagCtxt {
     /// Steal a previously stashed non-error diagnostic with the given `Span`
     /// and [`StashKey`] as the key. Panics if the found diagnostic is an
     /// error.
-    pub fn steal_non_err(&self, span: Span, key: StashKey) -> Option<Diag<'_, ()>> {
+    pub fn steal_non_err(self, span: Span, key: StashKey) -> Option<Diag<'a, ()>> {
         let key = (span.with_parent(None), key);
         // FIXME(#120456) - is `swap_remove` correct?
         let (diag, guar) = self.inner.borrow_mut().stashed_diagnostics.swap_remove(&key)?;
@@ -807,7 +826,7 @@ impl DiagCtxt {
     /// no matching diagnostic is found. Panics if the found diagnostic's level
     /// isn't `Level::Error`.
     pub fn try_steal_modify_and_emit_err<F>(
-        &self,
+        self,
         span: Span,
         key: StashKey,
         mut modify_err: F,
@@ -833,7 +852,7 @@ impl DiagCtxt {
     /// [`StashKey`] as the key, cancels it if found, and emits `new_err`.
     /// Panics if the found diagnostic's level isn't `Level::Error`.
     pub fn try_steal_replace_and_emit_err(
-        &self,
+        self,
         span: Span,
         key: StashKey,
         new_err: Diag<'_>,
@@ -1106,18 +1125,18 @@ impl DiagCtxt {
 //
 // Functions beginning with `struct_`/`create_` create a diagnostic. Other
 // functions create and emit a diagnostic all in one go.
-impl DiagCtxt {
+impl<'a> DiagCtxtHandle<'a> {
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn struct_bug(&self, msg: impl Into<Cow<'static, str>>) -> Diag<'_, BugAbort> {
+    pub fn struct_bug(self, msg: impl Into<Cow<'static, str>>) -> Diag<'a, BugAbort> {
         Diag::new(self, Bug, msg.into())
     }
 
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn bug(&self, msg: impl Into<Cow<'static, str>>) -> ! {
+    pub fn bug(self, msg: impl Into<Cow<'static, str>>) -> ! {
         self.struct_bug(msg).emit()
     }
 
@@ -1125,111 +1144,108 @@ impl DiagCtxt {
     // user-facing.
     #[track_caller]
     pub fn struct_span_bug(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<Cow<'static, str>>,
-    ) -> Diag<'_, BugAbort> {
+    ) -> Diag<'a, BugAbort> {
         self.struct_bug(msg).with_span(span)
     }
 
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn span_bug(&self, span: impl Into<MultiSpan>, msg: impl Into<Cow<'static, str>>) -> ! {
+    pub fn span_bug(self, span: impl Into<MultiSpan>, msg: impl Into<Cow<'static, str>>) -> ! {
         self.struct_span_bug(span, msg.into()).emit()
     }
 
     #[track_caller]
-    pub fn create_bug<'a>(&'a self, bug: impl Diagnostic<'a, BugAbort>) -> Diag<'a, BugAbort> {
+    pub fn create_bug(self, bug: impl Diagnostic<'a, BugAbort>) -> Diag<'a, BugAbort> {
         bug.into_diag(self, Bug)
     }
 
     #[track_caller]
-    pub fn emit_bug<'a>(&'a self, bug: impl Diagnostic<'a, BugAbort>) -> ! {
+    pub fn emit_bug(self, bug: impl Diagnostic<'a, BugAbort>) -> ! {
         self.create_bug(bug).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_fatal(&self, msg: impl Into<DiagMessage>) -> Diag<'_, FatalAbort> {
+    pub fn struct_fatal(self, msg: impl Into<DiagMessage>) -> Diag<'a, FatalAbort> {
         Diag::new(self, Fatal, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn fatal(&self, msg: impl Into<DiagMessage>) -> ! {
+    pub fn fatal(self, msg: impl Into<DiagMessage>) -> ! {
         self.struct_fatal(msg).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_fatal(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_, FatalAbort> {
+    ) -> Diag<'a, FatalAbort> {
         self.struct_fatal(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn span_fatal(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) -> ! {
+    pub fn span_fatal(self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) -> ! {
         self.struct_span_fatal(span, msg).emit()
     }
 
     #[track_caller]
-    pub fn create_fatal<'a>(
-        &'a self,
-        fatal: impl Diagnostic<'a, FatalAbort>,
-    ) -> Diag<'a, FatalAbort> {
+    pub fn create_fatal(self, fatal: impl Diagnostic<'a, FatalAbort>) -> Diag<'a, FatalAbort> {
         fatal.into_diag(self, Fatal)
     }
 
     #[track_caller]
-    pub fn emit_fatal<'a>(&'a self, fatal: impl Diagnostic<'a, FatalAbort>) -> ! {
+    pub fn emit_fatal(self, fatal: impl Diagnostic<'a, FatalAbort>) -> ! {
         self.create_fatal(fatal).emit()
     }
 
     #[track_caller]
-    pub fn create_almost_fatal<'a>(
-        &'a self,
+    pub fn create_almost_fatal(
+        self,
         fatal: impl Diagnostic<'a, FatalError>,
     ) -> Diag<'a, FatalError> {
         fatal.into_diag(self, Fatal)
     }
 
     #[track_caller]
-    pub fn emit_almost_fatal<'a>(&'a self, fatal: impl Diagnostic<'a, FatalError>) -> FatalError {
+    pub fn emit_almost_fatal(self, fatal: impl Diagnostic<'a, FatalError>) -> FatalError {
         self.create_almost_fatal(fatal).emit()
     }
 
     // FIXME: This method should be removed (every error should have an associated error code).
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_err(&self, msg: impl Into<DiagMessage>) -> Diag<'_> {
+    pub fn struct_err(self, msg: impl Into<DiagMessage>) -> Diag<'a> {
         Diag::new(self, Error, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn err(&self, msg: impl Into<DiagMessage>) -> ErrorGuaranteed {
+    pub fn err(self, msg: impl Into<DiagMessage>) -> ErrorGuaranteed {
         self.struct_err(msg).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_err(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_> {
+    ) -> Diag<'a> {
         self.struct_err(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn span_err(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
     ) -> ErrorGuaranteed {
@@ -1237,12 +1253,12 @@ impl DiagCtxt {
     }
 
     #[track_caller]
-    pub fn create_err<'a>(&'a self, err: impl Diagnostic<'a>) -> Diag<'a> {
+    pub fn create_err(self, err: impl Diagnostic<'a>) -> Diag<'a> {
         err.into_diag(self, Error)
     }
 
     #[track_caller]
-    pub fn emit_err<'a>(&'a self, err: impl Diagnostic<'a>) -> ErrorGuaranteed {
+    pub fn emit_err(self, err: impl Diagnostic<'a>) -> ErrorGuaranteed {
         self.create_err(err).emit()
     }
 
@@ -1251,7 +1267,7 @@ impl DiagCtxt {
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn delayed_bug(&self, msg: impl Into<Cow<'static, str>>) -> ErrorGuaranteed {
+    pub fn delayed_bug(self, msg: impl Into<Cow<'static, str>>) -> ErrorGuaranteed {
         Diag::<ErrorGuaranteed>::new(self, DelayedBug, msg.into()).emit()
     }
 
@@ -1264,7 +1280,7 @@ impl DiagCtxt {
     // user-facing.
     #[track_caller]
     pub fn span_delayed_bug(
-        &self,
+        self,
         sp: impl Into<MultiSpan>,
         msg: impl Into<Cow<'static, str>>,
     ) -> ErrorGuaranteed {
@@ -1273,45 +1289,45 @@ impl DiagCtxt {
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_warn(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_warn(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Warning, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn warn(&self, msg: impl Into<DiagMessage>) {
+    pub fn warn(self, msg: impl Into<DiagMessage>) {
         self.struct_warn(msg).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_warn(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_, ()> {
+    ) -> Diag<'a, ()> {
         self.struct_warn(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn span_warn(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
+    pub fn span_warn(self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
         self.struct_span_warn(span, msg).emit()
     }
 
     #[track_caller]
-    pub fn create_warn<'a>(&'a self, warning: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
+    pub fn create_warn(self, warning: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
         warning.into_diag(self, Warning)
     }
 
     #[track_caller]
-    pub fn emit_warn<'a>(&'a self, warning: impl Diagnostic<'a, ()>) {
+    pub fn emit_warn(self, warning: impl Diagnostic<'a, ()>) {
         self.create_warn(warning).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_note(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_note(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Note, msg)
     }
 
@@ -1324,54 +1340,50 @@ impl DiagCtxt {
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_note(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_, ()> {
+    ) -> Diag<'a, ()> {
         self.struct_note(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn span_note(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
+    pub fn span_note(self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
         self.struct_span_note(span, msg).emit()
     }
 
     #[track_caller]
-    pub fn create_note<'a>(&'a self, note: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
+    pub fn create_note(self, note: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
         note.into_diag(self, Note)
     }
 
     #[track_caller]
-    pub fn emit_note<'a>(&'a self, note: impl Diagnostic<'a, ()>) {
+    pub fn emit_note(self, note: impl Diagnostic<'a, ()>) {
         self.create_note(note).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_help(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_help(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Help, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_failure_note(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_failure_note(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, FailureNote, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_allow(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_allow(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Allow, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_expect(
-        &self,
-        msg: impl Into<DiagMessage>,
-        id: LintExpectationId,
-    ) -> Diag<'_, ()> {
+    pub fn struct_expect(self, msg: impl Into<DiagMessage>, id: LintExpectationId) -> Diag<'a, ()> {
         Diag::new(self, Expect(id), msg)
     }
 }
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index b3f6a35f3a4..ddc6490ac0c 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -12,7 +12,7 @@ use rustc_ast::{self as ast, AttrVec, Attribute, HasAttrs, Item, NodeId, PatKind
 use rustc_attr::{self as attr, Deprecation, Stability};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync::{self, Lrc};
-use rustc_errors::{DiagCtxt, ErrorGuaranteed, PResult};
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, PResult};
 use rustc_feature::Features;
 use rustc_lint_defs::{BufferedEarlyLint, RegisteredTools};
 use rustc_parse::{parser::Parser, MACRO_ARGUMENTS};
@@ -1135,7 +1135,7 @@ impl<'a> ExtCtxt<'a> {
         }
     }
 
-    pub fn dcx(&self) -> &'a DiagCtxt {
+    pub fn dcx(&self) -> DiagCtxtHandle<'a> {
         self.sess.dcx()
     }
 
@@ -1256,7 +1256,7 @@ pub fn resolve_path(sess: &Session, path: impl Into<PathBuf>, span: Span) -> PRe
 }
 
 pub fn parse_macro_name_and_helper_attrs(
-    dcx: &rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     attr: &Attribute,
     macro_type: &str,
 ) -> Option<(Symbol, Vec<Symbol>)> {
@@ -1358,7 +1358,7 @@ fn pretty_printing_compatibility_hack(item: &Item, sess: &Session) {
         if crate_matches {
             // FIXME: make this translatable
             #[allow(rustc::untranslatable_diagnostic)]
-            sess.psess.dcx.emit_fatal(errors::ProcMacroBackCompat {
+            sess.dcx().emit_fatal(errors::ProcMacroBackCompat {
                 crate_name: "rental".to_string(),
                 fixed_version: "0.5.6".to_string(),
             });
diff --git a/compiler/rustc_expand/src/mbe/diagnostics.rs b/compiler/rustc_expand/src/mbe/diagnostics.rs
index 442fd654b6a..bf475c1dc96 100644
--- a/compiler/rustc_expand/src/mbe/diagnostics.rs
+++ b/compiler/rustc_expand/src/mbe/diagnostics.rs
@@ -7,7 +7,7 @@ use crate::mbe::{
 use rustc_ast::token::{self, Token, TokenKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast_pretty::pprust;
-use rustc_errors::{Applicability, Diag, DiagCtxt, DiagMessage};
+use rustc_errors::{Applicability, Diag, DiagMessage};
 use rustc_macros::Subdiagnostic;
 use rustc_parse::parser::{Parser, Recovery};
 use rustc_span::source_map::SourceMap;
@@ -61,7 +61,7 @@ pub(super) fn failed_to_match_macro<'cx>(
         err.span_label(cx.source_map().guess_head_span(def_span), "when calling this macro");
     }
 
-    annotate_doc_comment(cx.sess.dcx(), &mut err, psess.source_map(), span);
+    annotate_doc_comment(&mut err, psess.source_map(), span);
 
     if let Some(span) = remaining_matcher.span() {
         err.span_note(span, format!("while trying to match {remaining_matcher}"));
@@ -324,12 +324,12 @@ enum ExplainDocComment {
     },
 }
 
-pub(super) fn annotate_doc_comment(dcx: &DiagCtxt, err: &mut Diag<'_>, sm: &SourceMap, span: Span) {
+pub(super) fn annotate_doc_comment(err: &mut Diag<'_>, sm: &SourceMap, span: Span) {
     if let Ok(src) = sm.span_to_snippet(span) {
         if src.starts_with("///") || src.starts_with("/**") {
-            err.subdiagnostic(dcx, ExplainDocComment::Outer { span });
+            err.subdiagnostic(ExplainDocComment::Outer { span });
         } else if src.starts_with("//!") || src.starts_with("/*!") {
-            err.subdiagnostic(dcx, ExplainDocComment::Inner { span });
+            err.subdiagnostic(ExplainDocComment::Inner { span });
         }
     }
 }
diff --git a/compiler/rustc_expand/src/mbe/macro_check.rs b/compiler/rustc_expand/src/mbe/macro_check.rs
index 72dbbde54b3..d9a945a3215 100644
--- a/compiler/rustc_expand/src/mbe/macro_check.rs
+++ b/compiler/rustc_expand/src/mbe/macro_check.rs
@@ -206,7 +206,7 @@ pub(super) fn check_meta_variables(
     rhses: &[TokenTree],
 ) -> Result<(), ErrorGuaranteed> {
     if lhses.len() != rhses.len() {
-        psess.dcx.span_bug(span, "length mismatch between LHSes and RHSes")
+        psess.dcx().span_bug(span, "length mismatch between LHSes and RHSes")
     }
     let mut guar = None;
     for (lhs, rhs) in iter::zip(lhses, rhses) {
@@ -245,7 +245,7 @@ fn check_binders(
         // MetaVar(fragment) and not as MetaVarDecl(y, fragment).
         TokenTree::MetaVar(span, name) => {
             if macros.is_empty() {
-                psess.dcx.span_bug(span, "unexpected MetaVar in lhs");
+                psess.dcx().span_bug(span, "unexpected MetaVar in lhs");
             }
             let name = MacroRulesNormalizedIdent::new(name);
             // There are 3 possibilities:
@@ -276,7 +276,7 @@ fn check_binders(
                 );
             }
             if !macros.is_empty() {
-                psess.dcx.span_bug(span, "unexpected MetaVarDecl in nested lhs");
+                psess.dcx().span_bug(span, "unexpected MetaVarDecl in nested lhs");
             }
             let name = MacroRulesNormalizedIdent::new(name);
             if let Some(prev_info) = get_binder_info(macros, binders, name) {
@@ -284,7 +284,7 @@ fn check_binders(
                 // for nested macro definitions.
                 *guar = Some(
                     psess
-                        .dcx
+                        .dcx()
                         .emit_err(errors::DuplicateMatcherBinding { span, prev: prev_info.span }),
                 );
             } else {
@@ -344,7 +344,7 @@ fn check_occurrences(
     match *rhs {
         TokenTree::Token(..) => {}
         TokenTree::MetaVarDecl(span, _name, _kind) => {
-            psess.dcx.span_bug(span, "unexpected MetaVarDecl in rhs")
+            psess.dcx().span_bug(span, "unexpected MetaVarDecl in rhs")
         }
         TokenTree::MetaVar(span, name) => {
             let name = MacroRulesNormalizedIdent::new(name);
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index 5d3ba5d3223..49b1f5ce0e3 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -383,7 +383,7 @@ pub fn compile_declarative_macro(
     };
     let dummy_syn_ext = |guar| (mk_syn_ext(Box::new(DummyExpander(guar))), Vec::new());
 
-    let dcx = &sess.psess.dcx;
+    let dcx = sess.dcx();
     let lhs_nm = Ident::new(sym::lhs, def.span);
     let rhs_nm = Ident::new(sym::rhs, def.span);
     let tt_spec = Some(NonterminalKind::TT);
@@ -463,7 +463,7 @@ pub fn compile_declarative_macro(
                 let sp = token.span.substitute_dummy(def.span);
                 let mut err = sess.dcx().struct_span_err(sp, s);
                 err.span_label(sp, msg);
-                annotate_doc_comment(sess.dcx(), &mut err, sess.source_map(), sp);
+                annotate_doc_comment(&mut err, sess.source_map(), sp);
                 let guar = err.emit();
                 return dummy_syn_ext(guar);
             }
diff --git a/compiler/rustc_expand/src/mbe/metavar_expr.rs b/compiler/rustc_expand/src/mbe/metavar_expr.rs
index 3295a91029e..25958e03028 100644
--- a/compiler/rustc_expand/src/mbe/metavar_expr.rs
+++ b/compiler/rustc_expand/src/mbe/metavar_expr.rs
@@ -42,7 +42,7 @@ impl MetaVarExpr {
         let ident = parse_ident(&mut tts, psess, outer_span)?;
         let Some(TokenTree::Delimited(.., Delimiter::Parenthesis, args)) = tts.next() else {
             let msg = "meta-variable expression parameter must be wrapped in parentheses";
-            return Err(psess.dcx.struct_span_err(ident.span, msg));
+            return Err(psess.dcx().struct_span_err(ident.span, msg));
         };
         check_trailing_token(&mut tts, psess)?;
         let mut iter = args.trees();
@@ -62,12 +62,12 @@ impl MetaVarExpr {
                         break;
                     }
                     if !try_eat_comma(&mut iter) {
-                        return Err(psess.dcx.struct_span_err(outer_span, "expected comma"));
+                        return Err(psess.dcx().struct_span_err(outer_span, "expected comma"));
                     }
                 }
                 if result.len() < 2 {
                     return Err(psess
-                        .dcx
+                        .dcx()
                         .struct_span_err(ident.span, "`concat` must have at least two elements"));
                 }
                 MetaVarExpr::Concat(result.into())
@@ -81,7 +81,7 @@ impl MetaVarExpr {
             "len" => MetaVarExpr::Len(parse_depth(&mut iter, psess, ident.span)?),
             _ => {
                 let err_msg = "unrecognized meta-variable expression";
-                let mut err = psess.dcx.struct_span_err(ident.span, err_msg);
+                let mut err = psess.dcx().struct_span_err(ident.span, err_msg);
                 err.span_suggestion(
                     ident.span,
                     "supported expressions are count, ignore, index and len",
@@ -120,7 +120,7 @@ fn check_trailing_token<'psess>(
 ) -> PResult<'psess, ()> {
     if let Some(tt) = iter.next() {
         let mut diag = psess
-            .dcx
+            .dcx()
             .struct_span_err(tt.span(), format!("unexpected token: {}", pprust::tt_to_string(tt)));
         diag.span_note(tt.span(), "meta-variable expression must not have trailing tokens");
         Err(diag)
@@ -139,7 +139,7 @@ fn parse_count<'psess>(
     let ident = parse_ident(iter, psess, span)?;
     let depth = if try_eat_comma(iter) {
         if iter.look_ahead(0).is_none() {
-            return Err(psess.dcx.struct_span_err(
+            return Err(psess.dcx().struct_span_err(
                 span,
                 "`count` followed by a comma must have an associated index indicating its depth",
             ));
@@ -160,7 +160,7 @@ fn parse_depth<'psess>(
     let Some(tt) = iter.next() else { return Ok(0) };
     let TokenTree::Token(token::Token { kind: token::TokenKind::Literal(lit), .. }, _) = tt else {
         return Err(psess
-            .dcx
+            .dcx()
             .struct_span_err(span, "meta-variable expression depth must be a literal"));
     };
     if let Ok(lit_kind) = LitKind::from_token_lit(*lit)
@@ -170,7 +170,7 @@ fn parse_depth<'psess>(
         Ok(n_usize)
     } else {
         let msg = "only unsuffixes integer literals are supported in meta-variable expressions";
-        Err(psess.dcx.struct_span_err(span, msg))
+        Err(psess.dcx().struct_span_err(span, msg))
     }
 }
 
@@ -181,20 +181,21 @@ fn parse_ident<'psess>(
     fallback_span: Span,
 ) -> PResult<'psess, Ident> {
     let Some(tt) = iter.next() else {
-        return Err(psess.dcx.struct_span_err(fallback_span, "expected identifier"));
+        return Err(psess.dcx().struct_span_err(fallback_span, "expected identifier"));
     };
     let TokenTree::Token(token, _) = tt else {
-        return Err(psess.dcx.struct_span_err(tt.span(), "expected identifier"));
+        return Err(psess.dcx().struct_span_err(tt.span(), "expected identifier"));
     };
     if let Some((elem, is_raw)) = token.ident() {
         if let IdentIsRaw::Yes = is_raw {
-            return Err(psess.dcx.struct_span_err(elem.span, RAW_IDENT_ERR));
+            return Err(psess.dcx().struct_span_err(elem.span, RAW_IDENT_ERR));
         }
         return Ok(elem);
     }
     let token_str = pprust::token_to_string(token);
-    let mut err =
-        psess.dcx.struct_span_err(token.span, format!("expected identifier, found `{token_str}`"));
+    let mut err = psess
+        .dcx()
+        .struct_span_err(token.span, format!("expected identifier, found `{token_str}`"));
     err.span_suggestion(
         token.span,
         format!("try removing `{token_str}`"),
@@ -236,7 +237,7 @@ fn eat_dollar<'psess>(
         let _ = iter.next();
         return Ok(());
     }
-    Err(psess.dcx.struct_span_err(
+    Err(psess.dcx().struct_span_err(
         span,
         "meta-variables within meta-variable expressions must be referenced using a dollar sign",
     ))
diff --git a/compiler/rustc_expand/src/mbe/transcribe.rs b/compiler/rustc_expand/src/mbe/transcribe.rs
index 914bd03675a..f935f1b77e0 100644
--- a/compiler/rustc_expand/src/mbe/transcribe.rs
+++ b/compiler/rustc_expand/src/mbe/transcribe.rs
@@ -10,7 +10,7 @@ use rustc_ast::token::IdentIsRaw;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{pluralize, Diag, DiagCtxt, PResult};
+use rustc_errors::{pluralize, Diag, DiagCtxtHandle, PResult};
 use rustc_parse::parser::ParseNtResult;
 use rustc_session::parse::ParseSess;
 use rustc_span::hygiene::{LocalExpnId, Transparency};
@@ -141,7 +141,7 @@ pub(super) fn transcribe<'a>(
     let mut result_stack = Vec::new();
     let mut marker = Marker(expand_id, transparency, Default::default());
 
-    let dcx = &psess.dcx;
+    let dcx = psess.dcx();
     loop {
         // Look at the last frame on the stack.
         // If it still has a TokenTree we have not looked at yet, use that tree.
@@ -571,7 +571,7 @@ fn lockstep_iter_size(
 /// * `[ $( ${count(foo, 1)} ),* ]` will return an error because `${count(foo, 1)}` is
 ///   declared inside a single repetition and the index `1` implies two nested repetitions.
 fn count_repetitions<'a>(
-    dcx: &'a DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     depth_user: usize,
     mut matched: &NamedMatch,
     repeats: &[(usize, usize)],
@@ -632,7 +632,7 @@ fn count_repetitions<'a>(
 
 /// Returns a `NamedMatch` item declared on the LHS given an arbitrary [Ident]
 fn matched_from_ident<'ctx, 'interp, 'rslt>(
-    dcx: &'ctx DiagCtxt,
+    dcx: DiagCtxtHandle<'ctx>,
     ident: Ident,
     interp: &'interp FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
 ) -> PResult<'ctx, &'rslt NamedMatch>
@@ -646,7 +646,7 @@ where
 
 /// Used by meta-variable expressions when an user input is out of the actual declared bounds. For
 /// example, index(999999) in an repetition of only three elements.
-fn out_of_bounds_err<'a>(dcx: &'a DiagCtxt, max: usize, span: Span, ty: &str) -> Diag<'a> {
+fn out_of_bounds_err<'a>(dcx: DiagCtxtHandle<'a>, max: usize, span: Span, ty: &str) -> Diag<'a> {
     let msg = if max == 0 {
         format!(
             "meta-variable expression `{ty}` with depth parameter \
@@ -662,7 +662,7 @@ fn out_of_bounds_err<'a>(dcx: &'a DiagCtxt, max: usize, span: Span, ty: &str) ->
 }
 
 fn transcribe_metavar_expr<'a>(
-    dcx: &'a DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     expr: &MetaVarExpr,
     interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
     marker: &mut Marker,
@@ -730,7 +730,7 @@ fn transcribe_metavar_expr<'a>(
 
 /// Extracts an identifier that can be originated from a `$var:ident` variable or from a token tree.
 fn extract_ident<'a>(
-    dcx: &'a DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     ident: Ident,
     interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
 ) -> PResult<'a, String> {
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index 93f8682090d..5508358f53b 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -522,7 +522,7 @@ impl server::FreeFunctions for Rustc<'_, '_> {
     fn emit_diagnostic(&mut self, diagnostic: Diagnostic<Self::Span>) {
         let message = rustc_errors::DiagMessage::from(diagnostic.message);
         let mut diag: Diag<'_, ()> =
-            Diag::new(&self.psess().dcx, diagnostic.level.to_internal(), message);
+            Diag::new(self.psess().dcx(), diagnostic.level.to_internal(), message);
         diag.span(MultiSpan::from_spans(diagnostic.spans));
         for child in diagnostic.children {
             // This message comes from another diagnostic, and we are just reconstructing the
diff --git a/compiler/rustc_hir_analysis/src/check/errs.rs b/compiler/rustc_hir_analysis/src/check/errs.rs
index 2cdcc06f53c..17cb20df754 100644
--- a/compiler/rustc_hir_analysis/src/check/errs.rs
+++ b/compiler/rustc_hir_analysis/src/check/errs.rs
@@ -63,7 +63,7 @@ fn handle_static_mut_ref(
         } else {
             (errors::StaticMutRefSugg::Shared { span, var }, "shared")
         };
-        tcx.sess.psess.dcx.emit_err(errors::StaticMutRef { span, sugg, shared });
+        tcx.dcx().emit_err(errors::StaticMutRef { span, sugg, shared });
     } else {
         let (sugg, shared) = if mutable == Mutability::Mut {
             (errors::RefOfMutStaticSugg::Mut { span, var }, "mutable")
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index 61ac4af0151..9421269e51e 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -403,74 +403,56 @@ fn emit_orphan_check_error<'tcx>(
                 match *ty.kind() {
                     ty::Slice(_) => {
                         if is_foreign {
-                            diag.subdiagnostic(
-                                tcx.dcx(),
-                                errors::OnlyCurrentTraitsForeign { span },
-                            );
+                            diag.subdiagnostic(errors::OnlyCurrentTraitsForeign { span });
                         } else {
-                            diag.subdiagnostic(
-                                tcx.dcx(),
-                                errors::OnlyCurrentTraitsName { span, name: "slices" },
-                            );
+                            diag.subdiagnostic(errors::OnlyCurrentTraitsName {
+                                span,
+                                name: "slices",
+                            });
                         }
                     }
                     ty::Array(..) => {
                         if is_foreign {
-                            diag.subdiagnostic(
-                                tcx.dcx(),
-                                errors::OnlyCurrentTraitsForeign { span },
-                            );
+                            diag.subdiagnostic(errors::OnlyCurrentTraitsForeign { span });
                         } else {
-                            diag.subdiagnostic(
-                                tcx.dcx(),
-                                errors::OnlyCurrentTraitsName { span, name: "arrays" },
-                            );
+                            diag.subdiagnostic(errors::OnlyCurrentTraitsName {
+                                span,
+                                name: "arrays",
+                            });
                         }
                     }
                     ty::Tuple(..) => {
                         if is_foreign {
-                            diag.subdiagnostic(
-                                tcx.dcx(),
-                                errors::OnlyCurrentTraitsForeign { span },
-                            );
+                            diag.subdiagnostic(errors::OnlyCurrentTraitsForeign { span });
                         } else {
-                            diag.subdiagnostic(
-                                tcx.dcx(),
-                                errors::OnlyCurrentTraitsName { span, name: "tuples" },
-                            );
+                            diag.subdiagnostic(errors::OnlyCurrentTraitsName {
+                                span,
+                                name: "tuples",
+                            });
                         }
                     }
                     ty::Alias(ty::Opaque, ..) => {
-                        diag.subdiagnostic(tcx.dcx(), errors::OnlyCurrentTraitsOpaque { span });
+                        diag.subdiagnostic(errors::OnlyCurrentTraitsOpaque { span });
                     }
                     ty::RawPtr(ptr_ty, mutbl) => {
                         if !trait_ref.self_ty().has_param() {
-                            diag.subdiagnostic(
-                                tcx.dcx(),
-                                errors::OnlyCurrentTraitsPointerSugg {
-                                    wrapper_span: impl_.self_ty.span,
-                                    struct_span: item.span.shrink_to_lo(),
-                                    mut_key: mutbl.prefix_str(),
-                                    ptr_ty,
-                                },
-                            );
+                            diag.subdiagnostic(errors::OnlyCurrentTraitsPointerSugg {
+                                wrapper_span: impl_.self_ty.span,
+                                struct_span: item.span.shrink_to_lo(),
+                                mut_key: mutbl.prefix_str(),
+                                ptr_ty,
+                            });
                         }
-                        diag.subdiagnostic(
-                            tcx.dcx(),
-                            errors::OnlyCurrentTraitsPointer { span, pointer: ty },
-                        );
+                        diag.subdiagnostic(errors::OnlyCurrentTraitsPointer { span, pointer: ty });
                     }
                     ty::Adt(adt_def, _) => {
-                        diag.subdiagnostic(
-                            tcx.dcx(),
-                            errors::OnlyCurrentTraitsAdt {
-                                span,
-                                name: tcx.def_path_str(adt_def.did()),
-                            },
-                        );
+                        diag.subdiagnostic(errors::OnlyCurrentTraitsAdt {
+                            span,
+                            name: tcx.def_path_str(adt_def.did()),
+                        });
                     }
                     _ => {
-                        diag.subdiagnostic(tcx.dcx(), errors::OnlyCurrentTraitsTy { span, ty });
+                        diag.subdiagnostic(errors::OnlyCurrentTraitsTy { span, ty });
                     }
                 }
             }
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 41dceea2e32..cff8d5a5ea5 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -2,7 +2,7 @@
 
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level, MultiSpan,
+    codes::*, Applicability, Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level, MultiSpan,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
@@ -424,7 +424,7 @@ pub struct MissingTypeParams {
 // Manual implementation of `Diagnostic` to be able to call `span_to_snippet`.
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for MissingTypeParams {
     #[track_caller]
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let mut err = Diag::new(dcx, level, fluent::hir_analysis_missing_type_params);
         err.span(self.span);
         err.code(E0393);
diff --git a/compiler/rustc_hir_typeck/src/_match.rs b/compiler/rustc_hir_typeck/src/_match.rs
index 281af80bff5..4e2104ff561 100644
--- a/compiler/rustc_hir_typeck/src/_match.rs
+++ b/compiler/rustc_hir_typeck/src/_match.rs
@@ -246,7 +246,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let semi = expr.span.shrink_to_hi().with_hi(semi_span.hi());
         let sugg = crate::errors::RemoveSemiForCoerce { expr: expr.span, ret, semi };
-        diag.subdiagnostic(self.dcx(), sugg);
+        diag.subdiagnostic(sugg);
     }
 
     /// When the previously checked expression (the scrutinee) diverges,
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index 9e9a1f678ed..58708510282 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -1005,25 +1005,19 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             if let Some((deref_ty, _)) = derefed {
                 // Give a note about what the expr derefs to.
                 if deref_ty != self.expr_ty.peel_refs() {
-                    err.subdiagnostic(
-                        fcx.dcx(),
-                        errors::DerefImplsIsEmpty {
-                            span: self.expr_span,
-                            deref_ty: fcx.ty_to_string(deref_ty),
-                        },
-                    );
+                    err.subdiagnostic(errors::DerefImplsIsEmpty {
+                        span: self.expr_span,
+                        deref_ty: fcx.ty_to_string(deref_ty),
+                    });
                 }
 
                 // Create a multipart suggestion: add `!` and `.is_empty()` in
                 // place of the cast.
-                err.subdiagnostic(
-                    fcx.dcx(),
-                    errors::UseIsEmpty {
-                        lo: self.expr_span.shrink_to_lo(),
-                        hi: self.span.with_lo(self.expr_span.hi()),
-                        expr_ty: fcx.ty_to_string(self.expr_ty),
-                    },
-                );
+                err.subdiagnostic(errors::UseIsEmpty {
+                    lo: self.expr_span.shrink_to_lo(),
+                    hi: self.span.with_lo(self.expr_span.hi()),
+                    expr_ty: fcx.ty_to_string(self.expr_ty),
+                });
             }
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index fcd22b74676..31f85e21d71 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -1782,20 +1782,14 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
         }
 
         let rpid_def_span = fcx.tcx.def_span(rpit_def_id);
-        err.subdiagnostic(
-            fcx.tcx.dcx(),
-            SuggestBoxingForReturnImplTrait::ChangeReturnType {
-                start_sp: rpid_def_span.with_hi(rpid_def_span.lo() + BytePos(4)),
-                end_sp: rpid_def_span.shrink_to_hi(),
-            },
-        );
+        err.subdiagnostic(SuggestBoxingForReturnImplTrait::ChangeReturnType {
+            start_sp: rpid_def_span.with_hi(rpid_def_span.lo() + BytePos(4)),
+            end_sp: rpid_def_span.shrink_to_hi(),
+        });
 
         let (starts, ends) =
             arm_spans.map(|span| (span.shrink_to_lo(), span.shrink_to_hi())).unzip();
-        err.subdiagnostic(
-            fcx.tcx.dcx(),
-            SuggestBoxingForReturnImplTrait::BoxReturnExpr { starts, ends },
-        );
+        err.subdiagnostic(SuggestBoxingForReturnImplTrait::BoxReturnExpr { starts, ends });
     }
 
     fn report_return_mismatched_types<'a>(
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index fe497498c4b..233dc2afa9b 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -384,7 +384,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         if let Some(sp) =
                             tcx.sess.psess.ambiguous_block_expr_parse.borrow().get(&sp)
                         {
-                            err.subdiagnostic(self.dcx(), ExprParenthesesNeeded::surrounding(*sp));
+                            err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
                         }
                         oprnd_t = Ty::new_error(tcx, err.emit());
                     }
@@ -2018,10 +2018,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .shrink_to_hi()
                 .to(range_end.span);
 
-            err.subdiagnostic(
-                self.dcx(),
-                TypeMismatchFruTypo { expr_span: range_start.span, fru_span, expr },
-            );
+            err.subdiagnostic(TypeMismatchFruTypo { expr_span: range_start.span, fru_span, expr });
 
             // Suppress any range expr type mismatches
             self.dcx().try_steal_replace_and_emit_err(
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 10d9e07db6f..1138642c56d 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -1435,7 +1435,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         {
             // The user provided `ptr::null()`, but the function expects
             // `ptr::null_mut()`.
-            err.subdiagnostic(self.dcx(), SuggestPtrNullMut { span: arg.span });
+            err.subdiagnostic(SuggestPtrNullMut { span: arg.span });
         }
     }
 
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index 2ef27e6a0ba..1713d75092e 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -5,14 +5,13 @@ mod checks;
 mod inspect_obligations;
 mod suggestions;
 
-use rustc_errors::ErrorGuaranteed;
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
 
 use crate::coercion::DynamicCoerceMany;
 use crate::fallback::DivergingFallbackBehavior;
 use crate::fn_ctxt::checks::DivergingBlockBehavior;
 use crate::{CoroutineTypes, Diverges, EnclosingBreakables, TypeckRootCtxt};
 use hir::def_id::CRATE_DEF_ID;
-use rustc_errors::DiagCtxt;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir_analysis::hir_ty_lowering::{HirTyLowerer, RegionInferReason};
@@ -145,8 +144,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub(crate) fn dcx(&self) -> &'tcx DiagCtxt {
-        self.tcx.dcx()
+    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'tcx> {
+        self.infcx.dcx()
     }
 
     pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index 9743dc7c69f..337a92c0d01 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -460,16 +460,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // but those checks need to be a bit more delicate and the benefit is diminishing.
             if self.can_eq(self.param_env, found_ty_inner, peeled) && error_tys_equate_as_ref {
                 let sugg = prefix_wrap(".as_ref()");
-                err.subdiagnostic(
-                    self.dcx(),
-                    errors::SuggestConvertViaMethod {
-                        span: expr.span.shrink_to_hi(),
-                        sugg,
-                        expected,
-                        found,
-                        borrow_removal_span,
-                    },
-                );
+                err.subdiagnostic(errors::SuggestConvertViaMethod {
+                    span: expr.span.shrink_to_hi(),
+                    sugg,
+                    expected,
+                    found,
+                    borrow_removal_span,
+                });
                 return true;
             } else if let Some((deref_ty, _)) =
                 self.autoderef(expr.span, found_ty_inner).silence_errors().nth(1)
@@ -477,16 +474,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && error_tys_equate_as_ref
             {
                 let sugg = prefix_wrap(".as_deref()");
-                err.subdiagnostic(
-                    self.dcx(),
-                    errors::SuggestConvertViaMethod {
-                        span: expr.span.shrink_to_hi(),
-                        sugg,
-                        expected,
-                        found,
-                        borrow_removal_span,
-                    },
-                );
+                err.subdiagnostic(errors::SuggestConvertViaMethod {
+                    span: expr.span.shrink_to_hi(),
+                    sugg,
+                    expected,
+                    found,
+                    borrow_removal_span,
+                });
                 return true;
             } else if let ty::Adt(adt, _) = found_ty_inner.peel_refs().kind()
                 && self.tcx.is_lang_item(adt.did(), LangItem::String)
@@ -573,7 +567,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     end: span.shrink_to_hi(),
                 },
             };
-            err.subdiagnostic(self.dcx(), suggest_boxing);
+            err.subdiagnostic(suggest_boxing);
 
             true
         } else {
@@ -814,28 +808,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         match &fn_decl.output {
             &hir::FnRetTy::DefaultReturn(span) if expected.is_unit() && !can_suggest => {
                 // `fn main()` must return `()`, do not suggest changing return type
-                err.subdiagnostic(self.dcx(), errors::ExpectedReturnTypeLabel::Unit { span });
+                err.subdiagnostic(errors::ExpectedReturnTypeLabel::Unit { span });
                 return true;
             }
             &hir::FnRetTy::DefaultReturn(span) if expected.is_unit() => {
                 if let Some(found) = found.make_suggestable(self.tcx, false, None) {
-                    err.subdiagnostic(
-                        self.dcx(),
-                        errors::AddReturnTypeSuggestion::Add { span, found: found.to_string() },
-                    );
+                    err.subdiagnostic(errors::AddReturnTypeSuggestion::Add {
+                        span,
+                        found: found.to_string(),
+                    });
                     return true;
                 } else if let Some(sugg) = suggest_impl_trait(self, self.param_env, found) {
-                    err.subdiagnostic(
-                        self.dcx(),
-                        errors::AddReturnTypeSuggestion::Add { span, found: sugg },
-                    );
+                    err.subdiagnostic(errors::AddReturnTypeSuggestion::Add { span, found: sugg });
                     return true;
                 } else {
                     // FIXME: if `found` could be `impl Iterator` we should suggest that.
-                    err.subdiagnostic(
-                        self.dcx(),
-                        errors::AddReturnTypeSuggestion::MissingHere { span },
-                    );
+                    err.subdiagnostic(errors::AddReturnTypeSuggestion::MissingHere { span });
                     return true;
                 }
             }
@@ -856,19 +844,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     debug!(?found);
                     if found.is_suggestable(self.tcx, false) {
                         if ty.span.is_empty() {
-                            err.subdiagnostic(
-                                self.dcx(),
-                                errors::AddReturnTypeSuggestion::Add {
-                                    span: ty.span,
-                                    found: found.to_string(),
-                                },
-                            );
+                            err.subdiagnostic(errors::AddReturnTypeSuggestion::Add {
+                                span: ty.span,
+                                found: found.to_string(),
+                            });
                             return true;
                         } else {
-                            err.subdiagnostic(
-                                self.dcx(),
-                                errors::ExpectedReturnTypeLabel::Other { span: ty.span, expected },
-                            );
+                            err.subdiagnostic(errors::ExpectedReturnTypeLabel::Other {
+                                span: ty.span,
+                                expected,
+                            });
                         }
                     }
                 } else {
@@ -883,10 +868,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let ty = self.normalize(hir_ty.span, ty);
                     let ty = self.tcx.instantiate_bound_regions_with_erased(ty);
                     if self.can_coerce(expected, ty) {
-                        err.subdiagnostic(
-                            self.dcx(),
-                            errors::ExpectedReturnTypeLabel::Other { span: hir_ty.span, expected },
-                        );
+                        err.subdiagnostic(errors::ExpectedReturnTypeLabel::Other {
+                            span: hir_ty.span,
+                            expected,
+                        });
                         self.try_suggest_return_impl_trait(err, expected, found, fn_id);
                         self.note_caller_chooses_ty_for_ty_param(err, expected, found);
                         return true;
@@ -905,13 +890,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         found: Ty<'tcx>,
     ) {
         if let ty::Param(expected_ty_as_param) = expected.kind() {
-            diag.subdiagnostic(
-                self.dcx(),
-                errors::NoteCallerChoosesTyForTyParam {
-                    ty_param_name: expected_ty_as_param.name,
-                    found_ty: found,
-                },
-            );
+            diag.subdiagnostic(errors::NoteCallerChoosesTyForTyParam {
+                ty_param_name: expected_ty_as_param.name,
+                found_ty: found,
+            });
         }
     }
 
@@ -1136,7 +1118,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let sp = self.tcx.sess.source_map().start_point(expr.span).with_parent(None);
         if let Some(sp) = self.tcx.sess.psess.ambiguous_block_expr_parse.borrow().get(&sp) {
             // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }`
-            err.subdiagnostic(self.dcx(), ExprParenthesesNeeded::surrounding(*sp));
+            err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
             true
         } else {
             false
@@ -1250,7 +1232,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 } else {
                     return false;
                 };
-                diag.subdiagnostic(self.dcx(), subdiag);
+                diag.subdiagnostic(subdiag);
                 return true;
             }
         }
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index abbfe452f5f..6a44d2afc15 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -3729,22 +3729,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     if impls_trait(trait_info.def_id) {
                         self.suggest_valid_traits(err, item_name, vec![trait_info.def_id], false);
                     } else {
-                        err.subdiagnostic(
-                            self.dcx(),
-                            CandidateTraitNote {
-                                span: self.tcx.def_span(trait_info.def_id),
-                                trait_name: self.tcx.def_path_str(trait_info.def_id),
-                                item_name,
-                                action_or_ty: if trait_missing_method {
-                                    "NONE".to_string()
-                                } else {
-                                    param_type.map_or_else(
-                                        || "implement".to_string(), // FIXME: it might only need to be imported into scope, not implemented.
-                                        |p| p.to_string(),
-                                    )
-                                },
+                        err.subdiagnostic(CandidateTraitNote {
+                            span: self.tcx.def_span(trait_info.def_id),
+                            trait_name: self.tcx.def_path_str(trait_info.def_id),
+                            item_name,
+                            action_or_ty: if trait_missing_method {
+                                "NONE".to_string()
+                            } else {
+                                param_type.map_or_else(
+                                    || "implement".to_string(), // FIXME: it might only need to be imported into scope, not implemented.
+                                    |p| p.to_string(),
+                                )
                             },
-                        );
+                        });
                     }
                 }
                 trait_infos => {
diff --git a/compiler/rustc_hir_typeck/src/op.rs b/compiler/rustc_hir_typeck/src/op.rs
index d774ae2146a..5a11cb7096f 100644
--- a/compiler/rustc_hir_typeck/src/op.rs
+++ b/compiler/rustc_hir_typeck/src/op.rs
@@ -820,7 +820,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // If the previous expression was a block expression, suggest parentheses
                         // (turning this into a binary subtraction operation instead.)
                         // for example, `{2} - 2` -> `({2}) - 2` (see src\test\ui\parser\expr-as-stmt.rs)
-                        err.subdiagnostic(self.dcx(), ExprParenthesesNeeded::surrounding(*sp));
+                        err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
                     } else {
                         match actual.kind() {
                             Uint(_) if op == hir::UnOp::Neg => {
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index e15866f3f0f..227691d0994 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -61,8 +61,8 @@ use crate::traits::{
 use crate::infer::relate::{self, RelateResult, TypeRelation};
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{
-    codes::*, pluralize, struct_span_code_err, Applicability, Diag, DiagCtxt, DiagStyledString,
-    ErrorGuaranteed, IntoDiagArg, StringPart,
+    codes::*, pluralize, struct_span_code_err, Applicability, Diag, DiagCtxtHandle,
+    DiagStyledString, ErrorGuaranteed, IntoDiagArg, StringPart,
 };
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -139,8 +139,8 @@ pub struct TypeErrCtxt<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
-    pub fn dcx(&self) -> &'tcx DiagCtxt {
-        self.infcx.tcx.dcx()
+    pub fn dcx(&self) -> DiagCtxtHandle<'tcx> {
+        self.infcx.dcx()
     }
 
     /// This is just to avoid a potential footgun of accidentally
@@ -892,7 +892,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         arm_ty,
                         arm_span,
                     ) {
-                        err.subdiagnostic(self.dcx(), subdiag);
+                        err.subdiagnostic(subdiag);
                     }
                 }
             },
@@ -918,7 +918,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     else_ty,
                     else_span,
                 ) {
-                    err.subdiagnostic(self.dcx(), subdiag);
+                    err.subdiagnostic(subdiag);
                 }
             }
             ObligationCauseCode::LetElse => {
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note.rs b/compiler/rustc_infer/src/infer/error_reporting/note.rs
index acb74f8a82c..8fd19563c30 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note.rs
@@ -369,7 +369,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 trait_predicates: trait_predicates.join(", "),
             }
         };
-        err.subdiagnostic(self.dcx(), suggestion);
+        err.subdiagnostic(suggestion);
     }
 
     pub(super) fn report_placeholder_failure(
diff --git a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
index 17fb760295a..74c65e93616 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
@@ -121,7 +121,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             span_low: cause.span.shrink_to_lo(),
                             span_high: cause.span.shrink_to_hi(),
                         };
-                        diag.subdiagnostic(self.dcx(), sugg);
+                        diag.subdiagnostic(sugg);
                     }
                     _ => {
                         // More than one matching variant.
@@ -130,7 +130,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             cause_span: cause.span,
                             compatible_variants,
                         };
-                        diag.subdiagnostic(self.dcx(), sugg);
+                        diag.subdiagnostic(sugg);
                     }
                 }
             }
@@ -202,10 +202,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             },
             (_, Some(ty)) if self.same_type_modulo_infer(exp_found.expected, ty) => {
                 // FIXME: Seems like we can't have a suggestion and a note with different spans in a single subdiagnostic
-                diag.subdiagnostic(
-                    self.dcx(),
-                    ConsiderAddingAwait::FutureSugg { span: exp_span.shrink_to_hi() },
-                );
+                diag.subdiagnostic(ConsiderAddingAwait::FutureSugg {
+                    span: exp_span.shrink_to_hi(),
+                });
                 Some(ConsiderAddingAwait::FutureSuggNote { span: exp_span })
             }
             (Some(ty), _) if self.same_type_modulo_infer(ty, exp_found.found) => match cause.code()
@@ -233,7 +232,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             _ => None,
         };
         if let Some(subdiag) = subdiag {
-            diag.subdiagnostic(self.dcx(), subdiag);
+            diag.subdiagnostic(subdiag);
         }
     }
 
@@ -269,7 +268,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         } else {
                             return;
                         };
-                        diag.subdiagnostic(self.dcx(), suggestion);
+                        diag.subdiagnostic(suggestion);
                     }
                 }
             }
@@ -401,15 +400,15 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     (true, false) => FunctionPointerSuggestion::UseRef { span, fn_name },
                     (false, true) => FunctionPointerSuggestion::RemoveRef { span, fn_name },
                     (true, true) => {
-                        diag.subdiagnostic(self.dcx(), FnItemsAreDistinct);
+                        diag.subdiagnostic(FnItemsAreDistinct);
                         FunctionPointerSuggestion::CastRef { span, fn_name, sig: *sig }
                     }
                     (false, false) => {
-                        diag.subdiagnostic(self.dcx(), FnItemsAreDistinct);
+                        diag.subdiagnostic(FnItemsAreDistinct);
                         FunctionPointerSuggestion::Cast { span, fn_name, sig: *sig }
                     }
                 };
-                diag.subdiagnostic(self.dcx(), sugg);
+                diag.subdiagnostic(sugg);
             }
             (ty::FnDef(did1, args1), ty::FnDef(did2, args2)) => {
                 let expected_sig =
@@ -418,7 +417,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     &(self.normalize_fn_sig)(self.tcx.fn_sig(*did2).instantiate(self.tcx, args2));
 
                 if self.same_type_modulo_infer(*expected_sig, *found_sig) {
-                    diag.subdiagnostic(self.dcx(), FnUniqTypes);
+                    diag.subdiagnostic(FnUniqTypes);
                 }
 
                 if !self.same_type_modulo_infer(*found_sig, *expected_sig)
@@ -447,7 +446,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     }
                 };
 
-                diag.subdiagnostic(self.dcx(), sug);
+                diag.subdiagnostic(sug);
             }
             (ty::FnDef(did, args), ty::FnPtr(sig)) => {
                 let expected_sig =
@@ -466,7 +465,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     format!("{fn_name} as {found_sig}")
                 };
 
-                diag.subdiagnostic(self.dcx(), FnConsiderCasting { casting });
+                diag.subdiagnostic(FnConsiderCasting { casting });
             }
             _ => {
                 return;
@@ -889,7 +888,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let diag = self.consider_returning_binding_diag(blk, expected_ty);
         match diag {
             Some(diag) => {
-                err.subdiagnostic(self.dcx(), diag);
+                err.subdiagnostic(diag);
                 true
             }
             None => false,
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 8412912b9f3..c908faec756 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -4,6 +4,7 @@ pub use lexical_region_resolve::RegionResolutionError;
 pub use relate::combine::CombineFields;
 pub use relate::combine::PredicateEmittingRelation;
 pub use relate::StructurallyRelateAliases;
+use rustc_errors::DiagCtxtHandle;
 pub use rustc_macros::{TypeFoldable, TypeVisitable};
 pub use rustc_middle::ty::IntVarValue;
 pub use BoundRegionConversionTime::*;
@@ -23,7 +24,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::undo_log::Rollback;
 use rustc_data_structures::unify as ut;
-use rustc_errors::{Diag, DiagCtxt, ErrorGuaranteed};
+use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_macros::extension;
 use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
@@ -826,7 +827,7 @@ impl<'tcx> InferOk<'tcx, ()> {
 }
 
 impl<'tcx> InferCtxt<'tcx> {
-    pub fn dcx(&self) -> &'tcx DiagCtxt {
+    pub fn dcx(&self) -> DiagCtxtHandle<'tcx> {
         self.tcx.dcx()
     }
 
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index c95a10f4e8d..41c8b941717 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -9,7 +9,7 @@ use rustc_data_structures::jobserver;
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::registry::Registry;
-use rustc_errors::{DiagCtxt, ErrorGuaranteed};
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
 use rustc_lint::LintStore;
 use rustc_middle::ty;
 use rustc_middle::ty::CurrentGcx;
@@ -46,7 +46,7 @@ pub struct Compiler {
 }
 
 /// Converts strings provided as `--cfg [cfgspec]` into a `Cfg`.
-pub(crate) fn parse_cfg(dcx: &DiagCtxt, cfgs: Vec<String>) -> Cfg {
+pub(crate) fn parse_cfg(dcx: DiagCtxtHandle<'_>, cfgs: Vec<String>) -> Cfg {
     cfgs.into_iter()
         .map(|s| {
             let psess = ParseSess::with_silent_emitter(
@@ -105,7 +105,7 @@ pub(crate) fn parse_cfg(dcx: &DiagCtxt, cfgs: Vec<String>) -> Cfg {
 }
 
 /// Converts strings provided as `--check-cfg [specs]` into a `CheckCfg`.
-pub(crate) fn parse_check_cfg(dcx: &DiagCtxt, specs: Vec<String>) -> CheckCfg {
+pub(crate) fn parse_check_cfg(dcx: DiagCtxtHandle<'_>, specs: Vec<String>) -> CheckCfg {
     // If any --check-cfg is passed then exhaustive_values and exhaustive_names
     // are enabled by default.
     let exhaustive_names = !specs.is_empty();
@@ -451,12 +451,12 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
 
             codegen_backend.init(&sess);
 
-            let cfg = parse_cfg(&sess.dcx(), config.crate_cfg);
+            let cfg = parse_cfg(sess.dcx(), config.crate_cfg);
             let mut cfg = config::build_configuration(&sess, cfg);
             util::add_configuration(&mut cfg, &mut sess, &*codegen_backend);
             sess.psess.config = cfg;
 
-            let mut check_cfg = parse_check_cfg(&sess.dcx(), config.crate_check_cfg);
+            let mut check_cfg = parse_check_cfg(sess.dcx(), config.crate_check_cfg);
             check_cfg.fill_well_known(&sess.target);
             sess.psess.check_config = check_cfg;
 
@@ -529,7 +529,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
 }
 
 pub fn try_print_query_stack(
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     num_frames: Option<usize>,
     file: Option<std::fs::File>,
 ) {
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index fa3e44e7744..2909f8adfb0 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -70,7 +70,7 @@ where
             Arc::default(),
             Default::default(),
         );
-        let cfg = parse_cfg(&sess.dcx(), matches.opt_strs("cfg"));
+        let cfg = parse_cfg(sess.dcx(), matches.opt_strs("cfg"));
         let cfg = build_configuration(&sess, cfg);
         f(sess, cfg)
     });
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index f60f8f7c6b7..4ad31ccc280 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1405,7 +1405,7 @@ impl<'a> LintDiagnostic<'a, ()> for NonLocalDefinitionsDiag {
                     diag.note(fluent::lint_macro_to_change);
                 }
                 if let Some(cargo_update) = cargo_update {
-                    diag.subdiagnostic(&diag.dcx, cargo_update);
+                    diag.subdiagnostic(cargo_update);
                 }
 
                 if has_trait {
@@ -1471,7 +1471,7 @@ impl<'a> LintDiagnostic<'a, ()> for NonLocalDefinitionsDiag {
                 diag.note(fluent::lint_non_local_definitions_deprecation);
 
                 if let Some(cargo_update) = cargo_update {
-                    diag.subdiagnostic(&diag.dcx, cargo_update);
+                    diag.subdiagnostic(cargo_update);
                 }
             }
         }
@@ -1957,7 +1957,7 @@ impl<'a> LintDiagnostic<'a, ()> for UnusedDef<'_, '_> {
             diag.note(note.to_string());
         }
         if let Some(sugg) = self.suggestion {
-            diag.subdiagnostic(diag.dcx, sugg);
+            diag.subdiagnostic(sugg);
         }
     }
 }
diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic.rs b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
index ef6005283d6..a3abbdcf18c 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
@@ -78,7 +78,7 @@ impl<'a> DiagnosticDerive<'a> {
                 #[track_caller]
                 fn into_diag(
                     self,
-                    dcx: &'_sess rustc_errors::DiagCtxt,
+                    dcx: rustc_errors::DiagCtxtHandle<'_sess>,
                     level: rustc_errors::Level
                 ) -> rustc_errors::Diag<'_sess, G> {
                     #implementation
diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
index 38d4a5ee61c..46bd80c2df6 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
@@ -335,7 +335,7 @@ impl DiagnosticDeriveVariantBuilder {
                 }
             }
             (Meta::Path(_), "subdiagnostic") => {
-                return Ok(quote! { diag.subdiagnostic(diag.dcx, #binding); });
+                return Ok(quote! { diag.subdiagnostic(#binding); });
             }
             _ => (),
         }
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index ad283117d7e..749495bc2ef 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -10,7 +10,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::owned_slice::OwnedSlice;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{self, FreezeReadGuard, FreezeWriteGuard};
-use rustc_errors::DiagCtxt;
+use rustc_errors::DiagCtxtHandle;
 use rustc_expand::base::SyntaxExtension;
 use rustc_fs_util::try_canonicalize;
 use rustc_hir::def_id::{CrateNum, LocalDefId, StableCrateId, LOCAL_CRATE};
@@ -91,8 +91,8 @@ impl<'a, 'tcx> std::ops::Deref for CrateLoader<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
-    fn dcx(&self) -> &'tcx DiagCtxt {
-        &self.tcx.dcx()
+    fn dcx(&self) -> DiagCtxtHandle<'tcx> {
+        self.tcx.dcx()
     }
 }
 
diff --git a/compiler/rustc_metadata/src/errors.rs b/compiler/rustc_metadata/src/errors.rs
index 47d183a0440..b0d82a0e3b7 100644
--- a/compiler/rustc_metadata/src/errors.rs
+++ b/compiler/rustc_metadata/src/errors.rs
@@ -3,7 +3,7 @@ use std::{
     path::{Path, PathBuf},
 };
 
-use rustc_errors::{codes::*, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
+use rustc_errors::{codes::*, Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{sym, Span, Symbol};
 use rustc_target::spec::{PanicStrategy, TargetTriple};
@@ -503,7 +503,7 @@ pub(crate) struct MultipleCandidates {
 }
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for MultipleCandidates {
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::metadata_multiple_candidates);
         diag.arg("crate_name", self.crate_name);
         diag.arg("flavor", self.flavor);
@@ -602,7 +602,7 @@ pub struct InvalidMetadataFiles {
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for InvalidMetadataFiles {
     #[track_caller]
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::metadata_invalid_meta_files);
         diag.arg("crate_name", self.crate_name);
         diag.arg("add_info", self.add_info);
@@ -631,7 +631,7 @@ pub struct CannotFindCrate {
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for CannotFindCrate {
     #[track_caller]
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::metadata_cannot_find_crate);
         diag.arg("crate_name", self.crate_name);
         diag.arg("current_crate", self.current_crate);
diff --git a/compiler/rustc_middle/src/macros.rs b/compiler/rustc_middle/src/macros.rs
index 817ac594627..fcea1ea81a7 100644
--- a/compiler/rustc_middle/src/macros.rs
+++ b/compiler/rustc_middle/src/macros.rs
@@ -4,10 +4,10 @@
 ///
 /// If you have a span available, you should use [`span_bug`] instead.
 ///
-/// If the bug should only be emitted when compilation didn't fail, [`DiagCtxt::span_delayed_bug`]
+/// If the bug should only be emitted when compilation didn't fail, [`DiagCtxtHandle::span_delayed_bug`]
 /// may be useful.
 ///
-/// [`DiagCtxt::span_delayed_bug`]: rustc_errors::DiagCtxt::span_delayed_bug
+/// [`DiagCtxtHandle::span_delayed_bug`]: rustc_errors::DiagCtxtHandle::span_delayed_bug
 /// [`span_bug`]: crate::span_bug
 #[macro_export]
 macro_rules! bug {
@@ -30,10 +30,10 @@ macro_rules! bug {
 /// at the code the compiler was compiling when it ICEd. This is the preferred way to trigger
 /// ICEs.
 ///
-/// If the bug should only be emitted when compilation didn't fail, [`DiagCtxt::span_delayed_bug`]
+/// If the bug should only be emitted when compilation didn't fail, [`DiagCtxtHandle::span_delayed_bug`]
 /// may be useful.
 ///
-/// [`DiagCtxt::span_delayed_bug`]: rustc_errors::DiagCtxt::span_delayed_bug
+/// [`DiagCtxtHandle::span_delayed_bug`]: rustc_errors::DiagCtxtHandle::span_delayed_bug
 #[macro_export]
 macro_rules! span_bug {
     ($span:expr, $msg:expr) => (
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 8cf1bedf0da..d1ccd158cf9 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -176,7 +176,7 @@ impl<'a, G: EmissionGuarantee> rustc_errors::LintDiagnostic<'a, G> for Deprecate
             diag.arg("has_note", false);
         }
         if let Some(sub) = self.sub {
-            diag.subdiagnostic(diag.dcx, sub);
+            diag.subdiagnostic(sub);
         }
     }
 }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index e2f15dac019..7a804c23638 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -47,7 +47,9 @@ use rustc_data_structures::sync::{self, FreezeReadGuard, Lock, Lrc, RwLock, Work
 #[cfg(parallel_compiler)]
 use rustc_data_structures::sync::{DynSend, DynSync};
 use rustc_data_structures::unord::UnordSet;
-use rustc_errors::{Applicability, Diag, DiagCtxt, ErrorGuaranteed, LintDiagnostic, MultiSpan};
+use rustc_errors::{
+    Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, LintDiagnostic, MultiSpan,
+};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
@@ -1415,7 +1417,7 @@ impl<'tcx> TyCtxt<'tcx> {
         )
     }
 
-    pub fn dcx(self) -> &'tcx DiagCtxt {
+    pub fn dcx(self) -> DiagCtxtHandle<'tcx> {
         self.sess.dcx()
     }
 }
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index cf7610bb4f6..3d397b6b37e 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -5,7 +5,7 @@ use crate::ty::normalize_erasing_regions::NormalizationError;
 use crate::ty::{self, CoroutineArgsExt, Ty, TyCtxt, TypeVisitableExt};
 use rustc_error_messages::DiagMessage;
 use rustc_errors::{
-    Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
+    Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
 };
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
@@ -1256,7 +1256,7 @@ pub enum FnAbiError<'tcx> {
 }
 
 impl<'a, 'b, G: EmissionGuarantee> Diagnostic<'a, G> for FnAbiError<'b> {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         match self {
             Self::Layout(e) => e.into_diagnostic().into_diag(dcx, level),
             Self::AdjustForForeignAbi(call::AdjustForForeignAbiError::Unsupported {
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 3bd2e47976b..7c73d8a6d47 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -1,9 +1,9 @@
 use crate::fluent_generated as fluent;
-use rustc_errors::DiagArgValue;
 use rustc_errors::{
-    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level, MultiSpan,
+    codes::*, Applicability, Diag, Diagnostic, EmissionGuarantee, Level, MultiSpan,
     SubdiagMessageOp, Subdiagnostic,
 };
+use rustc_errors::{DiagArgValue, DiagCtxtHandle};
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::{self, Ty};
 use rustc_pattern_analysis::{errors::Uncovered, rustc::RustcPatCtxt};
@@ -492,7 +492,7 @@ pub(crate) struct NonExhaustivePatternsTypeNotEmpty<'p, 'tcx, 'm> {
 }
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for NonExhaustivePatternsTypeNotEmpty<'_, '_, '_> {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'_, G> {
         let mut diag =
             Diag::new(dcx, level, fluent::mir_build_non_exhaustive_patterns_type_not_empty);
         diag.span(self.scrut_span);
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 30f57c8c622..70065b5a2c3 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -1137,7 +1137,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
 
     let all_arms_have_guards = arms.iter().all(|arm_id| thir[*arm_id].guard.is_some());
     if !is_empty_match && all_arms_have_guards {
-        err.subdiagnostic(cx.tcx.dcx(), NonExhaustiveMatchAllArmsGuarded);
+        err.subdiagnostic(NonExhaustiveMatchAllArmsGuarded);
     }
     if let Some((span, sugg)) = suggestion {
         err.span_suggestion_verbose(span, msg, sugg, Applicability::HasPlaceholders);
diff --git a/compiler/rustc_mir_transform/src/errors.rs b/compiler/rustc_mir_transform/src/errors.rs
index b28dcb38cb6..dc7648d27b5 100644
--- a/compiler/rustc_mir_transform/src/errors.rs
+++ b/compiler/rustc_mir_transform/src/errors.rs
@@ -104,7 +104,7 @@ impl<'a> LintDiagnostic<'a, ()> for MustNotSupend<'_, '_> {
         diag.primary_message(fluent::mir_transform_must_not_suspend);
         diag.span_label(self.yield_sp, fluent::_subdiag::label);
         if let Some(reason) = self.reason {
-            diag.subdiagnostic(diag.dcx, reason);
+            diag.subdiagnostic(reason);
         }
         diag.span_help(self.src_sp, fluent::_subdiag::help);
         diag.arg("pre", self.pre);
diff --git a/compiler/rustc_monomorphize/src/errors.rs b/compiler/rustc_monomorphize/src/errors.rs
index 35fc78f2045..c0d1efd96c5 100644
--- a/compiler/rustc_monomorphize/src/errors.rs
+++ b/compiler/rustc_monomorphize/src/errors.rs
@@ -1,7 +1,7 @@
 use std::path::PathBuf;
 
 use crate::fluent_generated as fluent;
-use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
+use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, LintDiagnostic};
 use rustc_span::{Span, Symbol};
 
@@ -48,7 +48,7 @@ pub struct UnusedGenericParamsHint {
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for UnusedGenericParamsHint {
     #[track_caller]
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::monomorphize_unused_generic_params);
         diag.span(self.span);
         for (span, name) in self.param_spans.into_iter().zip(self.param_names) {
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 6c1fcbe06fc..7566a4d5066 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -3,7 +3,7 @@ use std::borrow::Cow;
 use rustc_ast::token::Token;
 use rustc_ast::{Path, Visibility};
 use rustc_errors::{
-    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
+    codes::*, Applicability, Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level,
     SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
@@ -1052,7 +1052,7 @@ pub(crate) struct ExpectedIdentifier {
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for ExpectedIdentifier {
     #[track_caller]
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let token_descr = TokenDescription::from_token(&self.token);
 
         let mut diag = Diag::new(
@@ -1112,7 +1112,7 @@ pub(crate) struct ExpectedSemi {
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for ExpectedSemi {
     #[track_caller]
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let token_descr = TokenDescription::from_token(&self.token);
 
         let mut diag = Diag::new(
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 43f4963b27a..511805cf8d6 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -7,7 +7,7 @@ use rustc_ast::ast::{self, AttrStyle};
 use rustc_ast::token::{self, CommentKind, Delimiter, IdentIsRaw, Token, TokenKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::util::unicode::contains_text_flow_control_chars;
-use rustc_errors::{codes::*, Applicability, Diag, DiagCtxt, StashKey};
+use rustc_errors::{codes::*, Applicability, Diag, DiagCtxtHandle, StashKey};
 use rustc_lexer::unescape::{self, EscapeError, Mode};
 use rustc_lexer::{Base, DocStyle, RawStrError};
 use rustc_lexer::{Cursor, LiteralKind};
@@ -113,8 +113,8 @@ struct StringReader<'psess, 'src> {
 }
 
 impl<'psess, 'src> StringReader<'psess, 'src> {
-    fn dcx(&self) -> &'psess DiagCtxt {
-        &self.psess.dcx
+    fn dcx(&self) -> DiagCtxtHandle<'psess> {
+        self.psess.dcx()
     }
 
     fn mk_sp(&self, lo: BytePos, hi: BytePos) -> Span {
@@ -248,8 +248,8 @@ impl<'psess, 'src> StringReader<'psess, 'src> {
                     let suffix = if suffix_start < self.pos {
                         let string = self.str_from(suffix_start);
                         if string == "_" {
-                            self.psess
-                                .dcx
+                            self
+                                .dcx()
                                 .emit_err(errors::UnderscoreLiteralSuffix { span: self.mk_sp(suffix_start, self.pos) });
                             None
                         } else {
@@ -597,8 +597,7 @@ impl<'psess, 'src> StringReader<'psess, 'src> {
     }
 
     fn report_non_started_raw_string(&self, start: BytePos, bad_char: char) -> ! {
-        self.psess
-            .dcx
+        self.dcx()
             .struct_span_fatal(
                 self.mk_sp(start, self.pos),
                 format!(
diff --git a/compiler/rustc_parse/src/lexer/tokentrees.rs b/compiler/rustc_parse/src/lexer/tokentrees.rs
index f7645446081..8e543454691 100644
--- a/compiler/rustc_parse/src/lexer/tokentrees.rs
+++ b/compiler/rustc_parse/src/lexer/tokentrees.rs
@@ -71,7 +71,7 @@ impl<'psess, 'src> TokenTreesReader<'psess, 'src> {
 
     fn eof_err(&mut self) -> PErr<'psess> {
         let msg = "this file contains an unclosed delimiter";
-        let mut err = self.string_reader.psess.dcx.struct_span_err(self.token.span, msg);
+        let mut err = self.string_reader.dcx().struct_span_err(self.token.span, msg);
         for &(_, sp) in &self.diag_info.open_braces {
             err.span_label(sp, "unclosed delimiter");
             self.diag_info.unmatched_delims.push(UnmatchedDelim {
@@ -290,7 +290,7 @@ impl<'psess, 'src> TokenTreesReader<'psess, 'src> {
         // An unexpected closing delimiter (i.e., there is no matching opening delimiter).
         let token_str = token_to_string(&self.token);
         let msg = format!("unexpected closing delimiter: `{token_str}`");
-        let mut err = self.string_reader.psess.dcx.struct_span_err(self.token.span, msg);
+        let mut err = self.string_reader.dcx().struct_span_err(self.token.span, msg);
 
         report_suspicious_mismatch_block(
             &mut err,
diff --git a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
index cad25c66827..b7a790fcf83 100644
--- a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
+++ b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
@@ -3,7 +3,7 @@
 use std::iter::once;
 use std::ops::Range;
 
-use rustc_errors::{Applicability, DiagCtxt, ErrorGuaranteed};
+use rustc_errors::{Applicability, DiagCtxtHandle, ErrorGuaranteed};
 use rustc_lexer::unescape::{EscapeError, Mode};
 use rustc_span::{BytePos, Span};
 use tracing::debug;
@@ -11,7 +11,7 @@ use tracing::debug;
 use crate::errors::{MoreThanOneCharNote, MoreThanOneCharSugg, NoBraceUnicodeSub, UnescapeError};
 
 pub(crate) fn emit_unescape_error(
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     // interior part of the literal, between quotes
     lit: &str,
     // full span of the literal, including quotes and any prefix
diff --git a/compiler/rustc_parse/src/lexer/unicode_chars.rs b/compiler/rustc_parse/src/lexer/unicode_chars.rs
index 8eb299108d1..0a82ede3b75 100644
--- a/compiler/rustc_parse/src/lexer/unicode_chars.rs
+++ b/compiler/rustc_parse/src/lexer/unicode_chars.rs
@@ -351,7 +351,7 @@ pub(super) fn check_for_substitution(
 
     let Some((_, ascii_name, token)) = ASCII_ARRAY.iter().find(|&&(s, _, _)| s == ascii_str) else {
         let msg = format!("substitution character not found for '{ch}'");
-        reader.psess.dcx.span_bug(span, msg);
+        reader.dcx().span_bug(span, msg);
     };
 
     // special help suggestion for "directed" double quotes
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index 25cab7252a3..5522127be83 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -73,7 +73,7 @@ pub fn new_parser_from_file<'a>(
 ) -> Result<Parser<'a>, Vec<Diag<'a>>> {
     let source_file = psess.source_map().load_file(path).unwrap_or_else(|e| {
         let msg = format!("couldn't read {}: {}", path.display(), e);
-        let mut err = psess.dcx.struct_fatal(msg);
+        let mut err = psess.dcx().struct_fatal(msg);
         if let Some(sp) = sp {
             err.span(sp);
         }
@@ -115,7 +115,7 @@ fn source_file_to_stream<'psess>(
     override_span: Option<Span>,
 ) -> Result<TokenStream, Vec<Diag<'psess>>> {
     let src = source_file.src.as_ref().unwrap_or_else(|| {
-        psess.dcx.bug(format!(
+        psess.dcx().bug(format!(
             "cannot lex `source_file` without source: {}",
             psess.source_map().filename_for_diagnostics(&source_file.name)
         ));
@@ -179,7 +179,7 @@ pub fn parse_cfg_attr(
             }
         }
         _ => {
-            psess.dcx.emit_err(errors::MalformedCfgAttr {
+            psess.dcx().emit_err(errors::MalformedCfgAttr {
                 span: attr.span,
                 sugg: CFG_ATTR_GRAMMAR_HELP,
             });
diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs
index 62c8f9f5dac..f5c931034fd 100644
--- a/compiler/rustc_parse/src/parser/attr_wrapper.rs
+++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs
@@ -41,7 +41,7 @@ impl AttrWrapper {
     }
 
     pub(crate) fn take_for_recovery(self, psess: &ParseSess) -> AttrVec {
-        psess.dcx.span_delayed_bug(
+        psess.dcx().span_delayed_bug(
             self.attrs.get(0).map(|attr| attr.span).unwrap_or(DUMMY_SP),
             "AttrVec is taken for recovery but no error is produced",
         );
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 0c326c8eca2..c1aac84bcae 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -34,7 +34,7 @@ use rustc_ast::{
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{
-    pluralize, Applicability, Diag, DiagCtxt, ErrorGuaranteed, FatalError, PErr, PResult,
+    pluralize, Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, FatalError, PErr, PResult,
     Subdiagnostic,
 };
 use rustc_session::errors::ExprParenthesesNeeded;
@@ -240,8 +240,8 @@ impl<'a> DerefMut for SnapshotParser<'a> {
 }
 
 impl<'a> Parser<'a> {
-    pub fn dcx(&self) -> &'a DiagCtxt {
-        &self.psess.dcx
+    pub fn dcx(&self) -> DiagCtxtHandle<'a> {
+        self.psess.dcx()
     }
 
     /// Replace `self` with `snapshot.parser`.
@@ -666,7 +666,7 @@ impl<'a> Parser<'a> {
         {
             err.note("you may be trying to write a c-string literal");
             err.note("c-string literals require Rust 2021 or later");
-            err.subdiagnostic(self.dcx(), HelpUseLatestEdition::new());
+            err.subdiagnostic(HelpUseLatestEdition::new());
         }
 
         // `pub` may be used for an item or `pub(crate)`
@@ -2357,7 +2357,7 @@ impl<'a> Parser<'a> {
         let mut err = self.dcx().struct_span_err(span, msg);
         let sp = self.psess.source_map().start_point(self.token.span);
         if let Some(sp) = self.psess.ambiguous_block_expr_parse.borrow().get(&sp) {
-            err.subdiagnostic(self.dcx(), ExprParenthesesNeeded::surrounding(*sp));
+            err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
         }
         err.span_label(span, "expected expression");
 
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 8916c5de63d..5decfc142da 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1461,7 +1461,7 @@ impl<'a> Parser<'a> {
                     // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
                     // then suggest parens around the lhs.
                     if let Some(sp) = this.psess.ambiguous_block_expr_parse.borrow().get(&lo) {
-                        err.subdiagnostic(this.dcx(), ExprParenthesesNeeded::surrounding(*sp));
+                        err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
                     }
                     err
                 })
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 3d2eee247b8..42f8c6e38b9 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1966,7 +1966,7 @@ impl<'a> Parser<'a> {
         if self.token.kind == token::Not {
             if let Err(mut err) = self.unexpected() {
                 // Encounter the macro invocation
-                err.subdiagnostic(self.dcx(), MacroExpandsToAdtField { adt_ty });
+                err.subdiagnostic(MacroExpandsToAdtField { adt_ty });
                 return Err(err);
             }
         }
@@ -2382,13 +2382,10 @@ impl<'a> Parser<'a> {
                             .into_iter()
                             .any(|s| self.prev_token.is_ident_named(s));
 
-                        err.subdiagnostic(
-                            self.dcx(),
-                            errors::FnTraitMissingParen {
-                                span: self.prev_token.span,
-                                machine_applicable,
-                            },
-                        );
+                        err.subdiagnostic(errors::FnTraitMissingParen {
+                            span: self.prev_token.span,
+                            machine_applicable,
+                        });
                     }
                     return Err(err);
                 }
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 604959b1cda..6dee913c141 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1596,7 +1596,7 @@ pub(crate) fn make_unclosed_delims_error(
     if let Some(sp) = unmatched.unclosed_span {
         spans.push(sp);
     };
-    let err = psess.dcx.create_err(MismatchedClosingDelimiter {
+    let err = psess.dcx().create_err(MismatchedClosingDelimiter {
         spans,
         delimiter: pprust::token_kind_to_string(&token::CloseDelim(found_delim)).to_string(),
         unmatched: unmatched.found_span,
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 8af415f7c9d..f7f06ab7cbd 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -851,7 +851,7 @@ impl<'a> Parser<'a> {
 
         let sp = self.psess.source_map().start_point(self.token.span);
         if let Some(sp) = self.psess.ambiguous_block_expr_parse.borrow().get(&sp) {
-            err.subdiagnostic(self.dcx(), ExprParenthesesNeeded::surrounding(*sp));
+            err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
         }
 
         Err(err)
diff --git a/compiler/rustc_parse/src/parser/tests.rs b/compiler/rustc_parse/src/parser/tests.rs
index 79a6cf1b541..3a4690670af 100644
--- a/compiler/rustc_parse/src/parser/tests.rs
+++ b/compiler/rustc_parse/src/parser/tests.rs
@@ -61,7 +61,7 @@ where
 {
     let mut p = string_to_parser(&psess, s);
     let x = f(&mut p).unwrap();
-    p.psess.dcx.abort_if_errors();
+    p.dcx().abort_if_errors();
     x
 }
 
@@ -193,7 +193,7 @@ impl<T: Write> Write for Shared<T> {
 #[allow(rustc::untranslatable_diagnostic)] // no translation needed for tests
 fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &str) {
     create_default_session_globals_then(|| {
-        let (handler, source_map, output) = create_test_handler();
+        let (dcx, source_map, output) = create_test_handler();
         source_map.new_source_file(Path::new("test.rs").to_owned().into(), file_text.to_owned());
 
         let primary_span = make_span(&file_text, &span_labels[0].start, &span_labels[0].end);
@@ -205,7 +205,7 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
             println!("text: {:?}", source_map.span_to_snippet(span));
         }
 
-        handler.span_err(msp, "foo");
+        dcx.handle().span_err(msp, "foo");
 
         assert!(
             expected_output.chars().next() == Some('\n'),
diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index 19d6f512572..4ca52146039 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -65,7 +65,7 @@ pub fn parse_meta<'a>(psess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Met
                     let res = match res {
                         Ok(lit) => {
                             if token_lit.suffix.is_some() {
-                                let mut err = psess.dcx.struct_span_err(
+                                let mut err = psess.dcx().struct_span_err(
                                     expr.span,
                                     "suffixed literals are not allowed in attributes",
                                 );
@@ -98,7 +98,7 @@ pub fn parse_meta<'a>(psess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Met
                     //   the error because an earlier error will have already
                     //   been reported.
                     let msg = "attribute value must be a literal";
-                    let mut err = psess.dcx.struct_span_err(expr.span, msg);
+                    let mut err = psess.dcx().struct_span_err(expr.span, msg);
                     if let ast::ExprKind::Err(_) = expr.kind {
                         err.downgrade_to_delayed_bug();
                     }
@@ -114,7 +114,7 @@ fn check_meta_bad_delim(psess: &ParseSess, span: DelimSpan, delim: Delimiter) {
     if let Delimiter::Parenthesis = delim {
         return;
     }
-    psess.dcx.emit_err(errors::MetaBadDelim {
+    psess.dcx().emit_err(errors::MetaBadDelim {
         span: span.entire(),
         sugg: errors::MetaBadDelimSugg { open: span.open, close: span.close },
     });
@@ -124,7 +124,7 @@ pub(super) fn check_cfg_attr_bad_delim(psess: &ParseSess, span: DelimSpan, delim
     if let Delimiter::Parenthesis = delim {
         return;
     }
-    psess.dcx.emit_err(errors::CfgAttrBadDelim {
+    psess.dcx().emit_err(errors::CfgAttrBadDelim {
         span: span.entire(),
         sugg: errors::MetaBadDelimSugg { open: span.open, close: span.close },
     });
@@ -191,7 +191,7 @@ fn emit_malformed_attribute(
     } else {
         suggestions.sort();
         psess
-            .dcx
+            .dcx()
             .struct_span_err(span, error_msg)
             .with_span_suggestions(
                 span,
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 6ce7c41acc8..a0b3470df6d 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -8,8 +8,8 @@ use crate::{errors, fluent_generated as fluent};
 use rustc_ast::{ast, AttrKind, AttrStyle, Attribute, LitKind};
 use rustc_ast::{MetaItemKind, MetaItemLit, NestedMetaItem};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::StashKey;
-use rustc_errors::{Applicability, DiagCtxt, IntoDiagArg, MultiSpan};
+use rustc_errors::{Applicability, IntoDiagArg, MultiSpan};
+use rustc_errors::{DiagCtxtHandle, StashKey};
 use rustc_feature::{
     is_unsafe_attr, AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP,
 };
@@ -99,7 +99,7 @@ struct CheckAttrVisitor<'tcx> {
 }
 
 impl<'tcx> CheckAttrVisitor<'tcx> {
-    fn dcx(&self) -> &'tcx DiagCtxt {
+    fn dcx(&self) -> DiagCtxtHandle<'tcx> {
         self.tcx.dcx()
     }
 
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index a935f1ad7d3..25df80d5a92 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -6,8 +6,8 @@ use std::{
 use crate::fluent_generated as fluent;
 use rustc_ast::{ast, Label};
 use rustc_errors::{
-    codes::*, Applicability, Diag, DiagCtxt, DiagSymbolList, Diagnostic, EmissionGuarantee, Level,
-    MultiSpan, SubdiagMessageOp, Subdiagnostic,
+    codes::*, Applicability, Diag, DiagCtxtHandle, DiagSymbolList, Diagnostic, EmissionGuarantee,
+    Level, MultiSpan, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_hir::{self as hir, ExprKind, Target};
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
@@ -880,7 +880,7 @@ pub struct ItemFollowingInnerAttr {
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for InvalidAttrAtCrateLevel {
     #[track_caller]
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::passes_invalid_attr_at_crate_level);
         diag.span(self.span);
         diag.arg("name", self.name);
@@ -1030,7 +1030,7 @@ pub struct BreakNonLoop<'a> {
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'_, G> for BreakNonLoop<'a> {
     #[track_caller]
-    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::passes_break_non_loop);
         diag.span(self.span);
         diag.code(E0571);
@@ -1176,7 +1176,7 @@ pub struct NakedFunctionsAsmBlock {
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for NakedFunctionsAsmBlock {
     #[track_caller]
-    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::passes_naked_functions_asm_block);
         diag.span(self.span);
         diag.code(E0787);
@@ -1264,7 +1264,7 @@ pub struct NoMainErr {
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for NoMainErr {
     #[track_caller]
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let mut diag = Diag::new(dcx, level, fluent::passes_no_main_function);
         diag.span(DUMMY_SP);
         diag.code(E0601);
@@ -1322,7 +1322,7 @@ pub struct DuplicateLangItem {
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for DuplicateLangItem {
     #[track_caller]
-    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(
             dcx,
             level,
diff --git a/compiler/rustc_query_system/src/query/job.rs b/compiler/rustc_query_system/src/query/job.rs
index 248a741af90..3f44b11850e 100644
--- a/compiler/rustc_query_system/src/query/job.rs
+++ b/compiler/rustc_query_system/src/query/job.rs
@@ -4,7 +4,7 @@ use crate::query::plumbing::CycleError;
 use crate::query::DepKind;
 use crate::query::{QueryContext, QueryStackFrame};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{Diag, DiagCtxt};
+use rustc_errors::{Diag, DiagCtxtHandle};
 use rustc_hir::def::DefKind;
 use rustc_session::Session;
 use rustc_span::Span;
@@ -600,7 +600,7 @@ pub fn report_cycle<'a>(
 pub fn print_query_stack<Qcx: QueryContext>(
     qcx: Qcx,
     mut current_query: Option<QueryJobId>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     num_frames: Option<usize>,
     mut file: Option<std::fs::File>,
 ) -> usize {
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 8d470c6c61e..263daa11ec3 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -6,7 +6,7 @@ use rustc_ast::{MetaItemKind, NestedMetaItem};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{
-    codes::*, report_ambiguity_error, struct_span_code_err, Applicability, Diag, DiagCtxt,
+    codes::*, report_ambiguity_error, struct_span_code_err, Applicability, Diag, DiagCtxtHandle,
     ErrorGuaranteed, MultiSpan, SuggestionStyle,
 };
 use rustc_feature::BUILTIN_ATTRIBUTES;
@@ -120,7 +120,7 @@ fn reduce_impl_span_to_impl_keyword(sm: &SourceMap, impl_span: Span) -> Span {
 }
 
 impl<'a, 'tcx> Resolver<'a, 'tcx> {
-    pub(crate) fn dcx(&self) -> &'tcx DiagCtxt {
+    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'tcx> {
         self.tcx.dcx()
     }
 
@@ -334,12 +334,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             Some((import, _, true)) if should_remove_import && !import.is_glob() => {
                 // Simple case - remove the entire import. Due to the above match arm, this can
                 // only be a single use so just remove it entirely.
-                err.subdiagnostic(
-                    self.tcx.dcx(),
-                    errors::ToolOnlyRemoveUnnecessaryImport {
-                        span: import.use_span_with_attributes,
-                    },
-                );
+                err.subdiagnostic(errors::ToolOnlyRemoveUnnecessaryImport {
+                    span: import.use_span_with_attributes,
+                });
             }
             Some((import, span, _)) => {
                 self.add_suggestion_for_rename_of_use(&mut err, name, import, span);
@@ -405,12 +402,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         }
 
         if let Some(suggestion) = suggestion {
-            err.subdiagnostic(
-                self.dcx(),
-                ChangeImportBindingSuggestion { span: binding_span, suggestion },
-            );
+            err.subdiagnostic(ChangeImportBindingSuggestion { span: binding_span, suggestion });
         } else {
-            err.subdiagnostic(self.dcx(), ChangeImportBinding { span: binding_span });
+            err.subdiagnostic(ChangeImportBinding { span: binding_span });
         }
     }
 
@@ -458,20 +452,19 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         // previous imports.
         if found_closing_brace {
             if let Some(span) = extend_span_to_previous_binding(self.tcx.sess, span) {
-                err.subdiagnostic(self.dcx(), errors::ToolOnlyRemoveUnnecessaryImport { span });
+                err.subdiagnostic(errors::ToolOnlyRemoveUnnecessaryImport { span });
             } else {
                 // Remove the entire line if we cannot extend the span back, this indicates an
                 // `issue_52891::{self}` case.
-                err.subdiagnostic(
-                    self.dcx(),
-                    errors::RemoveUnnecessaryImport { span: import.use_span_with_attributes },
-                );
+                err.subdiagnostic(errors::RemoveUnnecessaryImport {
+                    span: import.use_span_with_attributes,
+                });
             }
 
             return;
         }
 
-        err.subdiagnostic(self.dcx(), errors::RemoveUnnecessaryImport { span });
+        err.subdiagnostic(errors::RemoveUnnecessaryImport { span });
     }
 
     pub(crate) fn lint_if_path_starts_with_module(
@@ -682,10 +675,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     .dcx()
                     .create_err(errors::VariableIsNotBoundInAllPatterns { multispan: msp, name });
                 for sp in target_sp {
-                    err.subdiagnostic(self.dcx(), errors::PatternDoesntBindName { span: sp, name });
+                    err.subdiagnostic(errors::PatternDoesntBindName { span: sp, name });
                 }
                 for sp in origin_sp {
-                    err.subdiagnostic(self.dcx(), errors::VariableNotInAllPatterns { span: sp });
+                    err.subdiagnostic(errors::VariableNotInAllPatterns { span: sp });
                 }
                 if could_be_path {
                     let import_suggestions = self.lookup_import_candidates(
@@ -1446,12 +1439,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         );
 
         if macro_kind == MacroKind::Bang && ident.name == sym::macro_rules {
-            err.subdiagnostic(self.dcx(), MaybeMissingMacroRulesName { span: ident.span });
+            err.subdiagnostic(MaybeMissingMacroRulesName { span: ident.span });
             return;
         }
 
         if macro_kind == MacroKind::Derive && (ident.name == sym::Send || ident.name == sym::Sync) {
-            err.subdiagnostic(self.dcx(), ExplicitUnsafeTraits { span: ident.span, ident });
+            err.subdiagnostic(ExplicitUnsafeTraits { span: ident.span, ident });
             return;
         }
 
@@ -1467,14 +1460,14 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             let scope = self.local_macro_def_scopes[&def_id];
             let parent_nearest = parent_scope.module.nearest_parent_mod();
             if Some(parent_nearest) == scope.opt_def_id() {
-                err.subdiagnostic(self.dcx(), MacroDefinedLater { span: unused_ident.span });
-                err.subdiagnostic(self.dcx(), MacroSuggMovePosition { span: ident.span, ident });
+                err.subdiagnostic(MacroDefinedLater { span: unused_ident.span });
+                err.subdiagnostic(MacroSuggMovePosition { span: ident.span, ident });
                 return;
             }
         }
 
         if self.macro_names.contains(&ident.normalize_to_macros_2_0()) {
-            err.subdiagnostic(self.dcx(), AddedMacroUse);
+            err.subdiagnostic(AddedMacroUse);
             return;
         }
 
@@ -1484,13 +1477,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             let span = self.def_span(def_id);
             let source_map = self.tcx.sess.source_map();
             let head_span = source_map.guess_head_span(span);
-            err.subdiagnostic(
-                self.dcx(),
-                ConsiderAddingADerive {
-                    span: head_span.shrink_to_lo(),
-                    suggestion: "#[derive(Default)]\n".to_string(),
-                },
-            );
+            err.subdiagnostic(ConsiderAddingADerive {
+                span: head_span.shrink_to_lo(),
+                suggestion: "#[derive(Default)]\n".to_string(),
+            });
         }
         for ns in [Namespace::MacroNS, Namespace::TypeNS, Namespace::ValueNS] {
             if let Ok(binding) = self.early_resolve_ident_in_lexical_scope(
@@ -1533,7 +1523,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             imported_ident: ident,
                             imported_ident_desc: &desc,
                         };
-                        err.subdiagnostic(self.tcx.dcx(), note);
+                        err.subdiagnostic(note);
                         // Silence the 'unused import' warning we might get,
                         // since this diagnostic already covers that import.
                         self.record_use(ident, binding, Used::Other);
@@ -1544,7 +1534,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     imported_ident: ident,
                     imported_ident_desc: &desc,
                 };
-                err.subdiagnostic(self.tcx.dcx(), note);
+                err.subdiagnostic(note);
                 return;
             }
         }
@@ -1599,7 +1589,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 }
             };
             did_label_def_span = true;
-            err.subdiagnostic(self.tcx.dcx(), label);
+            err.subdiagnostic(label);
         }
 
         let (span, msg, sugg) = if let SuggestionTarget::SimilarlyNamed = suggestion.target
@@ -1790,7 +1780,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     outer_ident_descr: this_res.descr(),
                     outer_ident,
                 };
-                err.subdiagnostic(self.tcx.dcx(), label);
+                err.subdiagnostic(label);
             }
         }
 
@@ -1805,14 +1795,14 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             non_exhaustive = Some(attr.span);
         } else if let Some(span) = ctor_fields_span {
             let label = errors::ConstructorPrivateIfAnyFieldPrivate { span };
-            err.subdiagnostic(self.tcx.dcx(), label);
+            err.subdiagnostic(label);
             if let Res::Def(_, d) = res
                 && let Some(fields) = self.field_visibility_spans.get(&d)
             {
                 let spans = fields.iter().map(|span| *span).collect();
                 let sugg =
                     errors::ConsiderMakingTheFieldPublic { spans, number_of_fields: fields.len() };
-                err.subdiagnostic(self.tcx.dcx(), sugg);
+                err.subdiagnostic(sugg);
             }
         }
 
@@ -1921,7 +1911,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 first,
                 dots: next_binding.is_some(),
             };
-            err.subdiagnostic(self.tcx.dcx(), note);
+            err.subdiagnostic(note);
         }
         // We prioritize shorter paths, non-core imports and direct imports over the alternatives.
         sugg_paths.sort_by_key(|(p, reexport)| (p.len(), p[0] == "core", *reexport));
@@ -1940,7 +1930,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             } else {
                 errors::ImportIdent::Directly { span: dedup_span, ident, path }
             };
-            err.subdiagnostic(self.tcx.dcx(), sugg);
+            err.subdiagnostic(sugg);
             break;
         }
 
@@ -2521,14 +2511,14 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             }
 
             let note = errors::FoundItemConfigureOut { span: name.span };
-            err.subdiagnostic(self.tcx.dcx(), note);
+            err.subdiagnostic(note);
 
             if let MetaItemKind::List(nested) = &cfg.kind
                 && let NestedMetaItem::MetaItem(meta_item) = &nested[0]
                 && let MetaItemKind::NameValue(feature_name) = &meta_item.kind
             {
                 let note = errors::ItemWasBehindFeature { feature: feature_name.symbol };
-                err.subdiagnostic(self.tcx.dcx(), note);
+                err.subdiagnostic(note);
             }
         }
     }
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 6c7afb305ba..96a4647b942 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -1294,12 +1294,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             // exclude decl_macro
                             if self.get_macro_by_def_id(def_id).macro_rules =>
                         {
-                            err.subdiagnostic(self.dcx(), ConsiderAddingMacroExport {
+                            err.subdiagnostic( ConsiderAddingMacroExport {
                                 span: binding.span,
                             });
                         }
                         _ => {
-                            err.subdiagnostic(self.dcx(), ConsiderMarkingAsPub {
+                            err.subdiagnostic( ConsiderMarkingAsPub {
                                 span: import.span,
                                 ident,
                             });
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 75a1aff4fc5..764cc350182 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1109,14 +1109,11 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                 Side::Start => (segment.ident.span.between(range.span), " @ ".into()),
                 Side::End => (range.span.to(segment.ident.span), format!("{} @ ..", segment.ident)),
             };
-            err.subdiagnostic(
-                self.r.dcx(),
-                errors::UnexpectedResUseAtOpInSlicePatWithRangeSugg {
-                    span,
-                    ident: segment.ident,
-                    snippet,
-                },
-            );
+            err.subdiagnostic(errors::UnexpectedResUseAtOpInSlicePatWithRangeSugg {
+                span,
+                ident: segment.ident,
+                snippet,
+            });
         }
 
         enum Side {
@@ -1208,13 +1205,10 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
         });
 
         if let Some(param) = param {
-            err.subdiagnostic(
-                self.r.dcx(),
-                errors::UnexpectedResChangeTyToConstParamSugg {
-                    span: param.shrink_to_lo(),
-                    applicability,
-                },
-            );
+            err.subdiagnostic(errors::UnexpectedResChangeTyToConstParamSugg {
+                span: param.shrink_to_lo(),
+                applicability,
+            });
         }
     }
 
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index dce56382a53..4cbc1b57022 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -3,8 +3,8 @@ use std::num::NonZero;
 use rustc_ast::token;
 use rustc_ast::util::literal::LitError;
 use rustc_errors::{
-    codes::*, Diag, DiagCtxt, DiagMessage, Diagnostic, EmissionGuarantee, ErrorGuaranteed, Level,
-    MultiSpan,
+    codes::*, Diag, DiagCtxtHandle, DiagMessage, Diagnostic, EmissionGuarantee, ErrorGuaranteed,
+    Level, MultiSpan,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
@@ -19,7 +19,7 @@ pub(crate) struct FeatureGateError {
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for FeatureGateError {
     #[track_caller]
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         Diag::new(dcx, level, self.explain).with_span(self.span).with_code(E0658)
     }
 }
@@ -401,7 +401,7 @@ pub fn report_lit_error(
         valid.then(|| format!("0{}{}", base_char.to_ascii_lowercase(), &suffix[1..]))
     }
 
-    let dcx = &psess.dcx;
+    let dcx = psess.dcx();
     match err {
         LitError::InvalidSuffix(suffix) => {
             dcx.emit_err(InvalidLiteralSuffix { span, kind: lit.kind.descr(), suffix })
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index df07f81bc45..200505aaea2 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -15,8 +15,8 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
 use rustc_data_structures::sync::{AppendOnlyVec, Lock, Lrc};
 use rustc_errors::emitter::{stderr_destination, HumanEmitter, SilentEmitter};
 use rustc_errors::{
-    fallback_fluent_bundle, ColorConfig, Diag, DiagCtxt, DiagMessage, EmissionGuarantee, MultiSpan,
-    StashKey,
+    fallback_fluent_bundle, ColorConfig, Diag, DiagCtxt, DiagCtxtHandle, DiagMessage,
+    EmissionGuarantee, MultiSpan, StashKey,
 };
 use rustc_feature::{find_feature_issue, GateIssue, UnstableFeatures};
 use rustc_span::edition::Edition;
@@ -106,12 +106,12 @@ pub fn feature_err_issue(
 
     // Cancel an earlier warning for this same error, if it exists.
     if let Some(span) = span.primary_span() {
-        if let Some(err) = sess.psess.dcx.steal_non_err(span, StashKey::EarlySyntaxWarning) {
+        if let Some(err) = sess.dcx().steal_non_err(span, StashKey::EarlySyntaxWarning) {
             err.cancel()
         }
     }
 
-    let mut err = sess.psess.dcx.create_err(FeatureGateError { span, explain: explain.into() });
+    let mut err = sess.dcx().create_err(FeatureGateError { span, explain: explain.into() });
     add_feature_diagnostics_for_issue(&mut err, sess, feature, issue, false, None);
     err
 }
@@ -140,7 +140,7 @@ pub fn feature_warn_issue(
     issue: GateIssue,
     explain: &'static str,
 ) {
-    let mut err = sess.psess.dcx.struct_span_warn(span, explain);
+    let mut err = sess.dcx().struct_span_warn(span, explain);
     add_feature_diagnostics_for_issue(&mut err, sess, feature, issue, false, None);
 
     // Decorate this as a future-incompatibility lint as in rustc_middle::lint::lint_level
@@ -178,30 +178,30 @@ pub fn add_feature_diagnostics_for_issue<G: EmissionGuarantee>(
     inject_span: Option<Span>,
 ) {
     if let Some(n) = find_feature_issue(feature, issue) {
-        err.subdiagnostic(sess.dcx(), FeatureDiagnosticForIssue { n });
+        err.subdiagnostic(FeatureDiagnosticForIssue { n });
     }
 
     // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
     if sess.psess.unstable_features.is_nightly_build() {
         if feature_from_cli {
-            err.subdiagnostic(sess.dcx(), CliFeatureDiagnosticHelp { feature });
+            err.subdiagnostic(CliFeatureDiagnosticHelp { feature });
         } else if let Some(span) = inject_span {
-            err.subdiagnostic(sess.dcx(), FeatureDiagnosticSuggestion { feature, span });
+            err.subdiagnostic(FeatureDiagnosticSuggestion { feature, span });
         } else {
-            err.subdiagnostic(sess.dcx(), FeatureDiagnosticHelp { feature });
+            err.subdiagnostic(FeatureDiagnosticHelp { feature });
         }
 
         if sess.opts.unstable_opts.ui_testing {
-            err.subdiagnostic(sess.dcx(), SuggestUpgradeCompiler::ui_testing());
+            err.subdiagnostic(SuggestUpgradeCompiler::ui_testing());
         } else if let Some(suggestion) = SuggestUpgradeCompiler::new() {
-            err.subdiagnostic(sess.dcx(), suggestion);
+            err.subdiagnostic(suggestion);
         }
     }
 }
 
 /// Info about a parsing session.
 pub struct ParseSess {
-    pub dcx: DiagCtxt,
+    dcx: DiagCtxt,
     pub unstable_features: UnstableFeatures,
     pub config: Cfg,
     pub check_config: CheckCfg,
@@ -326,4 +326,8 @@ impl ParseSess {
         // AppendOnlyVec, so we resort to this scheme.
         self.proc_macro_quoted_spans.iter_enumerated()
     }
+
+    pub fn dcx(&self) -> DiagCtxtHandle<'_> {
+        self.dcx.handle()
+    }
 }
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 20e50ef1b4a..89d029fa6e0 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -22,8 +22,8 @@ use rustc_errors::emitter::{stderr_destination, DynEmitter, HumanEmitter, HumanR
 use rustc_errors::json::JsonEmitter;
 use rustc_errors::registry::Registry;
 use rustc_errors::{
-    codes::*, fallback_fluent_bundle, Diag, DiagCtxt, DiagMessage, Diagnostic, ErrorGuaranteed,
-    FatalAbort, FluentBundle, LazyFallbackBundle, TerminalUrl,
+    codes::*, fallback_fluent_bundle, Diag, DiagCtxt, DiagCtxtHandle, DiagMessage, Diagnostic,
+    ErrorGuaranteed, FatalAbort, FluentBundle, LazyFallbackBundle, TerminalUrl,
 };
 use rustc_macros::HashStable_Generic;
 pub use rustc_span::def_id::StableCrateId;
@@ -328,8 +328,8 @@ impl Session {
     }
 
     #[inline]
-    pub fn dcx(&self) -> &DiagCtxt {
-        &self.psess.dcx
+    pub fn dcx(&self) -> DiagCtxtHandle<'_> {
+        self.psess.dcx()
     }
 
     #[inline]
@@ -1070,7 +1070,7 @@ pub fn build_session(
         match profiler {
             Ok(profiler) => Some(Arc::new(profiler)),
             Err(e) => {
-                dcx.emit_warn(errors::FailedToCreateProfiler { err: e.to_string() });
+                dcx.handle().emit_warn(errors::FailedToCreateProfiler { err: e.to_string() });
                 None
             }
         }
@@ -1371,7 +1371,7 @@ impl EarlyDiagCtxt {
     /// format. Any errors prior to that will cause an abort and all stashed diagnostics of the
     /// previous dcx will be emitted.
     pub fn abort_if_error_and_set_error_format(&mut self, output: ErrorOutputType) {
-        self.dcx.abort_if_errors();
+        self.dcx.handle().abort_if_errors();
 
         let emitter = mk_emitter(output);
         self.dcx = DiagCtxt::new(emitter);
@@ -1380,44 +1380,44 @@ impl EarlyDiagCtxt {
     #[allow(rustc::untranslatable_diagnostic)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub fn early_note(&self, msg: impl Into<DiagMessage>) {
-        self.dcx.note(msg)
+        self.dcx.handle().note(msg)
     }
 
     #[allow(rustc::untranslatable_diagnostic)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub fn early_help(&self, msg: impl Into<DiagMessage>) {
-        self.dcx.struct_help(msg).emit()
+        self.dcx.handle().struct_help(msg).emit()
     }
 
     #[allow(rustc::untranslatable_diagnostic)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     #[must_use = "ErrorGuaranteed must be returned from `run_compiler` in order to exit with a non-zero status code"]
     pub fn early_err(&self, msg: impl Into<DiagMessage>) -> ErrorGuaranteed {
-        self.dcx.err(msg)
+        self.dcx.handle().err(msg)
     }
 
     #[allow(rustc::untranslatable_diagnostic)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub fn early_fatal(&self, msg: impl Into<DiagMessage>) -> ! {
-        self.dcx.fatal(msg)
+        self.dcx.handle().fatal(msg)
     }
 
     #[allow(rustc::untranslatable_diagnostic)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub fn early_struct_fatal(&self, msg: impl Into<DiagMessage>) -> Diag<'_, FatalAbort> {
-        self.dcx.struct_fatal(msg)
+        self.dcx.handle().struct_fatal(msg)
     }
 
     #[allow(rustc::untranslatable_diagnostic)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub fn early_warn(&self, msg: impl Into<DiagMessage>) {
-        self.dcx.warn(msg)
+        self.dcx.handle().warn(msg)
     }
 
     #[allow(rustc::untranslatable_diagnostic)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     pub fn early_struct_warn(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
-        self.dcx.struct_warn(msg)
+        self.dcx.handle().struct_warn(msg)
     }
 }
 
diff --git a/compiler/rustc_symbol_mangling/src/errors.rs b/compiler/rustc_symbol_mangling/src/errors.rs
index b5721ee489d..9b87a1419fa 100644
--- a/compiler/rustc_symbol_mangling/src/errors.rs
+++ b/compiler/rustc_symbol_mangling/src/errors.rs
@@ -1,6 +1,6 @@
 //! Errors emitted by symbol_mangling.
 
-use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
+use rustc_errors::{Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
 use rustc_span::Span;
 use std::fmt;
 
@@ -14,7 +14,7 @@ pub struct TestOutput {
 // natural language, and (b) it's only used in tests. So we construct it
 // manually and avoid the fluent machinery.
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for TestOutput {
-    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let TestOutput { span, kind, content } = self;
 
         #[allow(rustc::untranslatable_diagnostic)]
diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index b442446f79b..a46cba35b2d 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -1,6 +1,6 @@
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
+    codes::*, Applicability, Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level,
     SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
@@ -59,7 +59,7 @@ pub struct NegativePositiveConflict<'tcx> {
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for NegativePositiveConflict<'_> {
     #[track_caller]
-    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::trait_selection_negative_positive_conflict);
         diag.arg("trait_desc", self.trait_desc.print_only_trait_path().to_string());
         diag.arg("self_desc", self.self_ty.map_or_else(|| "none".to_string(), |ty| ty.to_string()));
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index f632f1ad4f2..038f11c60b8 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -4705,14 +4705,11 @@ fn hint_missing_borrow<'tcx>(
     }
 
     if !to_borrow.is_empty() {
-        err.subdiagnostic(infcx.dcx(), errors::AdjustSignatureBorrow::Borrow { to_borrow });
+        err.subdiagnostic(errors::AdjustSignatureBorrow::Borrow { to_borrow });
     }
 
     if !remove_borrow.is_empty() {
-        err.subdiagnostic(
-            infcx.dcx(),
-            errors::AdjustSignatureBorrow::RemoveBorrow { remove_borrow },
-        );
+        err.subdiagnostic(errors::AdjustSignatureBorrow::RemoveBorrow { remove_borrow });
     }
 }
 
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 78d4129f642..45bd1616e83 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -8,6 +8,7 @@ use std::path::PathBuf;
 use std::str::FromStr;
 
 use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::DiagCtxtHandle;
 use rustc_session::config::{
     self, parse_crate_types_from_list, parse_externs, parse_target_triple, CrateType,
 };
@@ -383,9 +384,10 @@ impl Options {
         };
 
         let dcx = new_dcx(error_format, None, diagnostic_width, &unstable_opts);
+        let dcx = dcx.handle();
 
         // check for deprecated options
-        check_deprecated_options(matches, &dcx);
+        check_deprecated_options(matches, dcx);
 
         if matches.opt_strs("passes") == ["list"] {
             println!("Available passes for running rustdoc:");
@@ -458,7 +460,7 @@ impl Options {
             println!("rustdoc: [check-theme] Starting tests! (Ignoring all other arguments)");
             for theme_file in to_check.iter() {
                 print!(" - Checking \"{theme_file}\"...");
-                let (success, differences) = theme::test_theme_against(theme_file, &paths, &dcx);
+                let (success, differences) = theme::test_theme_against(theme_file, &paths, dcx);
                 if !differences.is_empty() || !success {
                     println!(" FAILED");
                     errors += 1;
@@ -603,7 +605,7 @@ impl Options {
                         .with_help("arguments to --theme must have a .css extension")
                         .emit();
                 }
-                let (success, ret) = theme::test_theme_against(&theme_file, &paths, &dcx);
+                let (success, ret) = theme::test_theme_against(&theme_file, &paths, dcx);
                 if !success {
                     dcx.fatal(format!("error loading theme file: \"{theme_s}\""));
                 } else if !ret.is_empty() {
@@ -630,7 +632,7 @@ impl Options {
             &matches.opt_strs("markdown-before-content"),
             &matches.opt_strs("markdown-after-content"),
             nightly_options::match_is_nightly_build(matches),
-            &dcx,
+            dcx,
             &mut id_map,
             edition,
             &None,
@@ -741,9 +743,9 @@ impl Options {
             );
         }
 
-        let scrape_examples_options = ScrapeExamplesOptions::new(matches, &dcx);
+        let scrape_examples_options = ScrapeExamplesOptions::new(matches, dcx);
         let with_examples = matches.opt_strs("with-examples");
-        let call_locations = crate::scrape_examples::load_call_locations(with_examples, &dcx);
+        let call_locations = crate::scrape_examples::load_call_locations(with_examples, dcx);
 
         let unstable_features =
             rustc_feature::UnstableFeatures::from_environment(crate_name.as_deref());
@@ -847,7 +849,7 @@ fn parse_remap_path_prefix(
 }
 
 /// Prints deprecation warnings for deprecated options
-fn check_deprecated_options(matches: &getopts::Matches, dcx: &rustc_errors::DiagCtxt) {
+fn check_deprecated_options(matches: &getopts::Matches, dcx: DiagCtxtHandle<'_>) {
     let deprecated_flags = [];
 
     for &flag in deprecated_flags.iter() {
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index ce098a1bcfb..5d8e61f9fa0 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -3,7 +3,7 @@ use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::emitter::{stderr_destination, DynEmitter, HumanEmitter};
 use rustc_errors::json::JsonEmitter;
-use rustc_errors::{codes::*, ErrorGuaranteed, TerminalUrl};
+use rustc_errors::{codes::*, DiagCtxtHandle, ErrorGuaranteed, TerminalUrl};
 use rustc_feature::UnstableFeatures;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, LocalDefId};
@@ -379,7 +379,7 @@ pub(crate) fn run_global_ctxt(
         );
     }
 
-    fn report_deprecated_attr(name: &str, dcx: &rustc_errors::DiagCtxt, sp: Span) {
+    fn report_deprecated_attr(name: &str, dcx: DiagCtxtHandle<'_>, sp: Span) {
         let mut msg =
             dcx.struct_span_warn(sp, format!("the `#![doc({name})]` attribute is deprecated"));
         msg.note(
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 81a7463deca..40cc4a9d441 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -7,7 +7,7 @@ pub(crate) use markdown::test as test_markdown;
 
 use rustc_ast as ast;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_errors::{ColorConfig, ErrorGuaranteed, FatalError};
+use rustc_errors::{ColorConfig, DiagCtxtHandle, ErrorGuaranteed, FatalError};
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_hir::CRATE_HIR_ID;
 use rustc_interface::interface;
@@ -90,10 +90,7 @@ fn get_doctest_dir() -> io::Result<TempDir> {
     TempFileBuilder::new().prefix("rustdoctest").tempdir()
 }
 
-pub(crate) fn run(
-    dcx: &rustc_errors::DiagCtxt,
-    options: RustdocOptions,
-) -> Result<(), ErrorGuaranteed> {
+pub(crate) fn run(dcx: DiagCtxtHandle<'_>, options: RustdocOptions) -> Result<(), ErrorGuaranteed> {
     let invalid_codeblock_attributes_name = crate::lint::INVALID_CODEBLOCK_ATTRIBUTES.name;
 
     // See core::create_config for what's going on here.
diff --git a/src/librustdoc/doctest/make.rs b/src/librustdoc/doctest/make.rs
index 599611407ed..74833c11362 100644
--- a/src/librustdoc/doctest/make.rs
+++ b/src/librustdoc/doctest/make.rs
@@ -229,7 +229,7 @@ fn check_for_main_and_extern_crate(
             // dcx. Any errors in the tests will be reported when the test file is compiled,
             // Note that we still need to cancel the errors above otherwise `Diag` will panic on
             // drop.
-            psess.dcx.reset_err_count();
+            psess.dcx().reset_err_count();
 
             (found_main, found_extern_crate, found_macro)
         })
diff --git a/src/librustdoc/externalfiles.rs b/src/librustdoc/externalfiles.rs
index 03ee042aa8d..62cdc0bd5a6 100644
--- a/src/librustdoc/externalfiles.rs
+++ b/src/librustdoc/externalfiles.rs
@@ -1,4 +1,5 @@
 use crate::html::markdown::{ErrorCodes, HeadingOffset, IdMap, Markdown, Playground};
+use rustc_errors::DiagCtxtHandle;
 use rustc_span::edition::Edition;
 use std::fs;
 use std::path::Path;
@@ -27,7 +28,7 @@ impl ExternalHtml {
         md_before_content: &[String],
         md_after_content: &[String],
         nightly_build: bool,
-        dcx: &rustc_errors::DiagCtxt,
+        dcx: DiagCtxtHandle<'_>,
         id_map: &mut IdMap,
         edition: Edition,
         playground: &Option<Playground>,
@@ -75,7 +76,7 @@ pub(crate) enum LoadStringError {
 
 pub(crate) fn load_string<P: AsRef<Path>>(
     file_path: P,
-    dcx: &rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
 ) -> Result<String, LoadStringError> {
     let file_path = file_path.as_ref();
     let contents = match fs::read(file_path) {
@@ -98,7 +99,7 @@ pub(crate) fn load_string<P: AsRef<Path>>(
     }
 }
 
-fn load_external_files(names: &[String], dcx: &rustc_errors::DiagCtxt) -> Option<String> {
+fn load_external_files(names: &[String], dcx: DiagCtxtHandle<'_>) -> Option<String> {
     let mut out = String::new();
     for name in names {
         let Ok(s) = load_string(name, dcx) else { return None };
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index d6e715d48ea..fb4cd218b84 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -77,7 +77,7 @@ use std::io::{self, IsTerminal};
 use std::process;
 use std::sync::{atomic::AtomicBool, Arc};
 
-use rustc_errors::{ErrorGuaranteed, FatalError};
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, FatalError};
 use rustc_interface::interface;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{make_crate_type_option, ErrorOutputType, RustcOptGroup};
@@ -670,7 +670,7 @@ fn usage(argv0: &str) {
 /// A result type used by several functions under `main()`.
 type MainResult = Result<(), ErrorGuaranteed>;
 
-pub(crate) fn wrap_return(dcx: &rustc_errors::DiagCtxt, res: Result<(), String>) -> MainResult {
+pub(crate) fn wrap_return(dcx: DiagCtxtHandle<'_>, res: Result<(), String>) -> MainResult {
     match res {
         Ok(()) => dcx.has_errors().map_or(Ok(()), Err),
         Err(err) => Err(dcx.err(err)),
@@ -732,12 +732,13 @@ fn main_args(
         None => return Ok(()),
     };
 
-    let diag =
+    let dcx =
         core::new_dcx(options.error_format, None, options.diagnostic_width, &options.unstable_opts);
+    let dcx = dcx.handle();
 
     match (options.should_test, options.markdown_input()) {
-        (true, Some(_)) => return wrap_return(&diag, doctest::test_markdown(options)),
-        (true, None) => return doctest::run(&diag, options),
+        (true, Some(_)) => return wrap_return(dcx, doctest::test_markdown(options)),
+        (true, None) => return doctest::run(dcx, options),
         (false, Some(input)) => {
             let input = input.to_owned();
             let edition = options.edition;
@@ -747,7 +748,7 @@ fn main_args(
             // requires session globals and a thread pool, so we use
             // `run_compiler`.
             return wrap_return(
-                &diag,
+                dcx,
                 interface::run_compiler(config, |_compiler| {
                     markdown::render(&input, render_options, edition)
                 }),
diff --git a/src/librustdoc/scrape_examples.rs b/src/librustdoc/scrape_examples.rs
index e9b380fdeac..5a595e03953 100644
--- a/src/librustdoc/scrape_examples.rs
+++ b/src/librustdoc/scrape_examples.rs
@@ -7,6 +7,7 @@ use crate::formats::renderer::FormatRenderer;
 use crate::html::render::Context;
 
 use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::DiagCtxtHandle;
 use rustc_hir::{
     self as hir,
     intravisit::{self, Visitor},
@@ -38,7 +39,7 @@ pub(crate) struct ScrapeExamplesOptions {
 }
 
 impl ScrapeExamplesOptions {
-    pub(crate) fn new(matches: &getopts::Matches, dcx: &rustc_errors::DiagCtxt) -> Option<Self> {
+    pub(crate) fn new(matches: &getopts::Matches, dcx: DiagCtxtHandle<'_>) -> Option<Self> {
         let output_path = matches.opt_str("scrape-examples-output-path");
         let target_crates = matches.opt_strs("scrape-examples-target-crate");
         let scrape_tests = matches.opt_present("scrape-tests");
@@ -336,7 +337,7 @@ pub(crate) fn run(
 // options.
 pub(crate) fn load_call_locations(
     with_examples: Vec<String>,
-    dcx: &rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
 ) -> AllCallLocations {
     let mut all_calls: AllCallLocations = FxHashMap::default();
     for path in with_examples {
diff --git a/src/librustdoc/theme.rs b/src/librustdoc/theme.rs
index 31d32e23f8e..2fa54a9cd81 100644
--- a/src/librustdoc/theme.rs
+++ b/src/librustdoc/theme.rs
@@ -5,7 +5,7 @@ use std::iter::Peekable;
 use std::path::Path;
 use std::str::Chars;
 
-use rustc_errors::DiagCtxt;
+use rustc_errors::DiagCtxtHandle;
 
 #[cfg(test)]
 mod tests;
@@ -236,7 +236,7 @@ pub(crate) fn get_differences(
 pub(crate) fn test_theme_against<P: AsRef<Path>>(
     f: &P,
     origin: &FxHashMap<String, CssPath>,
-    dcx: &DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
 ) -> (bool, Vec<String>) {
     let against = match fs::read_to_string(f)
         .map_err(|e| e.to_string())
diff --git a/src/tools/clippy/src/driver.rs b/src/tools/clippy/src/driver.rs
index f79da26964f..6117e76897f 100644
--- a/src/tools/clippy/src/driver.rs
+++ b/src/tools/clippy/src/driver.rs
@@ -180,12 +180,12 @@ pub fn main() {
 
     rustc_driver::init_rustc_env_logger(&early_dcx);
 
-    let using_internal_features = rustc_driver::install_ice_hook(BUG_REPORT_URL, |handler| {
+    let using_internal_features = rustc_driver::install_ice_hook(BUG_REPORT_URL, |dcx| {
         // FIXME: this macro calls unwrap internally but is called in a panicking context!  It's not
         // as simple as moving the call from the hook to main, because `install_ice_hook` doesn't
         // accept a generic closure.
         let version_info = rustc_tools_util::get_version_info!();
-        handler.note(format!("Clippy version: {version_info}"));
+        dcx.handle().note(format!("Clippy version: {version_info}"));
     });
 
     exit(rustc_driver::catch_with_exit_code(move || {
diff --git a/src/tools/miri/src/diagnostics.rs b/src/tools/miri/src/diagnostics.rs
index 14e29aa423d..12fb76f3972 100644
--- a/src/tools/miri/src/diagnostics.rs
+++ b/src/tools/miri/src/diagnostics.rs
@@ -566,7 +566,7 @@ pub fn report_msg<'tcx>(
         let is_local = machine.is_local(frame_info);
         // No span for non-local frames and the first frame (which is the error site).
         if is_local && idx > 0 {
-            err.subdiagnostic(err.dcx, frame_info.as_note(machine.tcx));
+            err.subdiagnostic(frame_info.as_note(machine.tcx));
         } else {
             let sm = sess.source_map();
             let span = sm.span_to_embeddable_string(frame_info.span);
diff --git a/src/tools/rustfmt/src/parse/macros/cfg_if.rs b/src/tools/rustfmt/src/parse/macros/cfg_if.rs
index 5fc988e4319..b91d203d531 100644
--- a/src/tools/rustfmt/src/parse/macros/cfg_if.rs
+++ b/src/tools/rustfmt/src/parse/macros/cfg_if.rs
@@ -67,7 +67,7 @@ fn parse_cfg_if_inner<'a>(
                 Ok(None) => continue,
                 Err(err) => {
                     err.cancel();
-                    parser.psess.dcx.reset_err_count();
+                    parser.psess.dcx().reset_err_count();
                     return Err(
                         "Expected item inside cfg_if block, but failed to parse it as an item",
                     );
diff --git a/src/tools/rustfmt/src/parse/macros/lazy_static.rs b/src/tools/rustfmt/src/parse/macros/lazy_static.rs
index badd9569950..7026935294a 100644
--- a/src/tools/rustfmt/src/parse/macros/lazy_static.rs
+++ b/src/tools/rustfmt/src/parse/macros/lazy_static.rs
@@ -16,8 +16,8 @@ pub(crate) fn parse_lazy_static(
         ($method:ident $(,)* $($arg:expr),* $(,)*) => {
             match parser.$method($($arg,)*) {
                 Ok(val) => {
-                    if parser.psess.dcx.has_errors().is_some() {
-                        parser.psess.dcx.reset_err_count();
+                    if parser.psess.dcx().has_errors().is_some() {
+                        parser.psess.dcx().reset_err_count();
                         return None;
                     } else {
                         val
@@ -25,7 +25,7 @@ pub(crate) fn parse_lazy_static(
                 }
                 Err(err) => {
                     err.cancel();
-                    parser.psess.dcx.reset_err_count();
+                    parser.psess.dcx().reset_err_count();
                     return None;
                 }
             }
diff --git a/src/tools/rustfmt/src/parse/macros/mod.rs b/src/tools/rustfmt/src/parse/macros/mod.rs
index cbcc0b2d636..89169e10715 100644
--- a/src/tools/rustfmt/src/parse/macros/mod.rs
+++ b/src/tools/rustfmt/src/parse/macros/mod.rs
@@ -29,8 +29,8 @@ fn parse_macro_arg<'a, 'b: 'a>(parser: &'a mut Parser<'b>) -> Option<MacroArg> {
             if Parser::nonterminal_may_begin_with($nt_kind, &cloned_parser.token) {
                 match $try_parse(&mut cloned_parser) {
                     Ok(x) => {
-                        if parser.psess.dcx.has_errors().is_some() {
-                            parser.psess.dcx.reset_err_count();
+                        if parser.psess.dcx().has_errors().is_some() {
+                            parser.psess.dcx().reset_err_count();
                         } else {
                             // Parsing succeeded.
                             *parser = cloned_parser;
@@ -39,7 +39,7 @@ fn parse_macro_arg<'a, 'b: 'a>(parser: &'a mut Parser<'b>) -> Option<MacroArg> {
                     }
                     Err(e) => {
                         e.cancel();
-                        parser.psess.dcx.reset_err_count();
+                        parser.psess.dcx().reset_err_count();
                     }
                 }
             }
diff --git a/src/tools/rustfmt/src/parse/session.rs b/src/tools/rustfmt/src/parse/session.rs
index 1a39d212386..f4fbabaf6c9 100644
--- a/src/tools/rustfmt/src/parse/session.rs
+++ b/src/tools/rustfmt/src/parse/session.rs
@@ -210,7 +210,9 @@ impl ParseSess {
             rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(),
             false,
         );
-        self.raw_psess.dcx.make_silent(fallback_bundle, None, false);
+        self.raw_psess
+            .dcx()
+            .make_silent(fallback_bundle, None, false);
     }
 
     pub(crate) fn span_to_filename(&self, span: Span) -> FileName {
@@ -286,11 +288,11 @@ impl ParseSess {
     }
 
     pub(super) fn has_errors(&self) -> bool {
-        self.raw_psess.dcx.has_errors().is_some()
+        self.raw_psess.dcx().has_errors().is_some()
     }
 
     pub(super) fn reset_errors(&self) {
-        self.raw_psess.dcx.reset_err_count();
+        self.raw_psess.dcx().reset_err_count();
     }
 }
 
diff --git a/tests/ui-fulldeps/internal-lints/diagnostics.rs b/tests/ui-fulldeps/internal-lints/diagnostics.rs
index 7c3a2c97474..5fcff74064a 100644
--- a/tests/ui-fulldeps/internal-lints/diagnostics.rs
+++ b/tests/ui-fulldeps/internal-lints/diagnostics.rs
@@ -14,8 +14,8 @@ extern crate rustc_session;
 extern crate rustc_span;
 
 use rustc_errors::{
-    Diag, DiagCtxt, DiagInner, DiagMessage, Diagnostic, EmissionGuarantee, Level, LintDiagnostic,
-    SubdiagMessageOp, SubdiagMessage, Subdiagnostic,
+    Diag, DiagCtxtHandle, DiagInner, DiagMessage, Diagnostic, EmissionGuarantee, Level,
+    LintDiagnostic, SubdiagMessage, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
@@ -39,7 +39,7 @@ struct Note {
 pub struct UntranslatableInDiagnostic;
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UntranslatableInDiagnostic {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         Diag::new(dcx, level, "untranslatable diagnostic")
         //~^ ERROR diagnostics should be created using translatable messages
     }
@@ -48,7 +48,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UntranslatableInDiagnostic
 pub struct TranslatableInDiagnostic;
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for TranslatableInDiagnostic {
-    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         Diag::new(dcx, level, crate::fluent_generated::no_crate_example)
     }
 }
@@ -81,7 +81,7 @@ impl Subdiagnostic for TranslatableInAddtoDiag {
 pub struct UntranslatableInLintDiagnostic;
 
 impl<'a> LintDiagnostic<'a, ()> for UntranslatableInLintDiagnostic {
-    fn decorate_lint<'b, >(self, diag: &'b mut Diag<'a, ()>) {
+    fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.note("untranslatable diagnostic");
         //~^ ERROR diagnostics should be created using translatable messages
     }
@@ -95,7 +95,7 @@ impl<'a> LintDiagnostic<'a, ()> for TranslatableInLintDiagnostic {
     }
 }
 
-pub fn make_diagnostics<'a>(dcx: &'a DiagCtxt) {
+pub fn make_diagnostics<'a>(dcx: DiagCtxtHandle<'a>) {
     let _diag = dcx.struct_err(crate::fluent_generated::no_crate_example);
     //~^ ERROR diagnostics should only be created in `Diagnostic`/`Subdiagnostic`/`LintDiagnostic` impls
 
@@ -107,7 +107,7 @@ pub fn make_diagnostics<'a>(dcx: &'a DiagCtxt) {
 // Check that `rustc_lint_diagnostics`-annotated functions aren't themselves linted for
 // `diagnostic_outside_of_impl`.
 #[rustc_lint_diagnostics]
-pub fn skipped_because_of_annotation<'a>(dcx: &'a DiagCtxt) {
+pub fn skipped_because_of_annotation<'a>(dcx: DiagCtxtHandle<'a>) {
     #[allow(rustc::untranslatable_diagnostic)]
     let _diag = dcx.struct_err("untranslatable diagnostic"); // okay!
 }