Rename `AddToDiagnostic` as `Subdiagnostic`.

To match `derive(Subdiagnostic)`.

Also rename `add_to_diagnostic{,_with}` as `add_to_diag{,_with}`.

28 files changed, 153 insertions, 153 deletions

diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
index 153737db883..6fd980ed3ca 100644
--- a/compiler/rustc_ast_lowering/src/errors.rs
+++ b/compiler/rustc_ast_lowering/src/errors.rs
@@ -1,5 +1,5 @@
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Diag, DiagArgFromDisplay, EmissionGuarantee, SubdiagMessageOp,
+    codes::*, Diag, DiagArgFromDisplay, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{symbol::Ident, Span, Symbol};
@@ -40,8 +40,8 @@ pub struct InvalidAbi {
 
 pub struct InvalidAbiReason(pub &'static str);
 
-impl AddToDiagnostic for InvalidAbiReason {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for InvalidAbiReason {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _: F,
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index e225401ea37..9e8c1d7f5fd 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -2,7 +2,7 @@
 
 use rustc_ast::ParamKindOrd;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, Diag, EmissionGuarantee, SubdiagMessageOp,
+    codes::*, Applicability, Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{symbol::Ident, Span, Symbol};
@@ -373,8 +373,8 @@ pub struct ArgsBeforeConstraint {
 pub struct EmptyLabelManySpans(pub Vec<Span>);
 
 // The derive for `Vec<Span>` does multiple calls to `span_label`, adding commas between each
-impl AddToDiagnostic for EmptyLabelManySpans {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for EmptyLabelManySpans {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _: F,
@@ -742,8 +742,8 @@ pub struct StableFeature {
     pub since: Symbol,
 }
 
-impl AddToDiagnostic for StableFeature {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for StableFeature {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _: F,
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index 768bb105905..377aff8fb6c 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -1,6 +1,6 @@
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level, MultiSpan,
-    SingleLabelManySpans, SubdiagMessageOp,
+    codes::*, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level, MultiSpan,
+    SingleLabelManySpans, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{symbol::Ident, Span, Symbol};
@@ -589,8 +589,8 @@ pub(crate) struct FormatUnusedArg {
 
 // Allow the singular form to be a subdiagnostic of the multiple-unused
 // form of diagnostic.
-impl AddToDiagnostic for FormatUnusedArg {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for FormatUnusedArg {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 5793cb13e67..ccaf8c7a235 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -170,19 +170,19 @@ impl Into<FluentValue<'static>> for DiagArgValue {
 
 /// Trait implemented by error types. This should not be implemented manually. Instead, use
 /// `#[derive(Subdiagnostic)]` -- see [rustc_macros::Subdiagnostic].
-#[rustc_diagnostic_item = "AddToDiagnostic"]
-pub trait AddToDiagnostic
+#[rustc_diagnostic_item = "Subdiagnostic"]
+pub trait Subdiagnostic
 where
     Self: Sized,
 {
     /// Add a subdiagnostic to an existing diagnostic.
-    fn add_to_diagnostic<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        self.add_to_diagnostic_with(diag, |_, m| m);
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
+        self.add_to_diag_with(diag, |_, m| m);
     }
 
     /// Add a subdiagnostic to an existing diagnostic where `f` is invoked on every message used
     /// (to optionally perform eager translation).
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
@@ -1194,9 +1194,9 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
     pub fn subdiagnostic(
         &mut self,
         dcx: &crate::DiagCtxt,
-        subdiagnostic: impl AddToDiagnostic,
+        subdiagnostic: impl Subdiagnostic,
     ) -> &mut Self {
-        subdiagnostic.add_to_diagnostic_with(self, |diag, msg| {
+        subdiagnostic.add_to_diag_with(self, |diag, msg| {
             let args = diag.args.iter();
             let msg = diag.subdiagnostic_message_to_diagnostic_message(msg);
             dcx.eagerly_translate(msg, args)
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index 5f65f35cc30..f90190797ae 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -1,5 +1,5 @@
 use crate::diagnostic::DiagLocation;
-use crate::{fluent_generated as fluent, AddToDiagnostic};
+use crate::{fluent_generated as fluent, Subdiagnostic};
 use crate::{
     Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, ErrCode, IntoDiagArg, Level,
     SubdiagMessageOp,
@@ -297,8 +297,8 @@ pub struct SingleLabelManySpans {
     pub spans: Vec<Span>,
     pub label: &'static str,
 }
-impl AddToDiagnostic for SingleLabelManySpans {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for SingleLabelManySpans {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _: F,
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index b079de1dde1..99c5bb46d2f 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -37,9 +37,9 @@ extern crate self as rustc_errors;
 
 pub use codes::*;
 pub use diagnostic::{
-    AddToDiagnostic, BugAbort, DecorateLint, Diag, DiagArg, DiagArgMap, DiagArgName, DiagArgValue,
-    DiagInner, DiagStyledString, Diagnostic, EmissionGuarantee, FatalAbort, IntoDiagArg,
-    StringPart, Subdiag, SubdiagMessageOp,
+    BugAbort, DecorateLint, Diag, DiagArg, DiagArgMap, DiagArgName, DiagArgValue, DiagInner,
+    DiagStyledString, Diagnostic, EmissionGuarantee, FatalAbort, IntoDiagArg, StringPart, Subdiag,
+    SubdiagMessageOp, Subdiagnostic,
 };
 pub use diagnostic_impls::{
     DiagArgFromDisplay, DiagSymbolList, ExpectedLifetimeParameter, IndicateAnonymousLifetime,
diff --git a/compiler/rustc_hir_typeck/src/errors.rs b/compiler/rustc_hir_typeck/src/errors.rs
index 7e8a229f2a2..df21b84f92e 100644
--- a/compiler/rustc_hir_typeck/src/errors.rs
+++ b/compiler/rustc_hir_typeck/src/errors.rs
@@ -3,8 +3,8 @@ use std::borrow::Cow;
 
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, Diag, DiagArgValue, EmissionGuarantee, IntoDiagArg,
-    MultiSpan, SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagArgValue, EmissionGuarantee, IntoDiagArg, MultiSpan,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
@@ -194,8 +194,8 @@ pub struct TypeMismatchFruTypo {
     pub expr: Option<String>,
 }
 
-impl AddToDiagnostic for TypeMismatchFruTypo {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for TypeMismatchFruTypo {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -373,8 +373,8 @@ pub struct RemoveSemiForCoerce {
     pub semi: Span,
 }
 
-impl AddToDiagnostic for RemoveSemiForCoerce {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for RemoveSemiForCoerce {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -549,8 +549,8 @@ pub enum CastUnknownPointerSub {
     From(Span),
 }
 
-impl rustc_errors::AddToDiagnostic for CastUnknownPointerSub {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl rustc_errors::Subdiagnostic for CastUnknownPointerSub {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index ceaae9cf49f..7e19e577d7d 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -26,8 +26,8 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{
-    codes::*, pluralize, struct_span_code_err, AddToDiagnostic, Applicability, Diag,
-    ErrorGuaranteed, StashKey,
+    codes::*, pluralize, struct_span_code_err, Applicability, Diag, ErrorGuaranteed, StashKey,
+    Subdiagnostic,
 };
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};
@@ -2600,7 +2600,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // We know by construction that `<expr>.await` is either on Rust 2015
             // or results in `ExprKind::Await`. Suggest switching the edition to 2018.
             err.note("to `.await` a `Future`, switch to Rust 2018 or later");
-            HelpUseLatestEdition::new().add_to_diagnostic(&mut err);
+            HelpUseLatestEdition::new().add_to_diag(&mut err);
         }
 
         err.emit()
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index a7d3bb240c8..a3cf0d8e520 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -1,7 +1,7 @@
 use hir::GenericParamKind;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, Diag, DiagMessage, DiagStyledString,
-    EmissionGuarantee, IntoDiagArg, MultiSpan, SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagMessage, DiagStyledString, EmissionGuarantee, IntoDiagArg,
+    MultiSpan, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_hir as hir;
 use rustc_hir::FnRetTy;
@@ -224,8 +224,8 @@ pub enum RegionOriginNote<'a> {
     },
 }
 
-impl AddToDiagnostic for RegionOriginNote<'_> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for RegionOriginNote<'_> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -289,8 +289,8 @@ pub enum LifetimeMismatchLabels {
     },
 }
 
-impl AddToDiagnostic for LifetimeMismatchLabels {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for LifetimeMismatchLabels {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -337,8 +337,8 @@ pub struct AddLifetimeParamsSuggestion<'a> {
     pub add_note: bool,
 }
 
-impl AddToDiagnostic for AddLifetimeParamsSuggestion<'_> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -439,8 +439,8 @@ pub struct IntroducesStaticBecauseUnmetLifetimeReq {
     pub binding_span: Span,
 }
 
-impl AddToDiagnostic for IntroducesStaticBecauseUnmetLifetimeReq {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for IntroducesStaticBecauseUnmetLifetimeReq {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         mut self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -758,8 +758,8 @@ pub struct ConsiderBorrowingParamHelp {
     pub spans: Vec<Span>,
 }
 
-impl AddToDiagnostic for ConsiderBorrowingParamHelp {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for ConsiderBorrowingParamHelp {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
@@ -803,8 +803,8 @@ pub struct DynTraitConstraintSuggestion {
     pub ident: Ident,
 }
 
-impl AddToDiagnostic for DynTraitConstraintSuggestion {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for DynTraitConstraintSuggestion {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
@@ -850,8 +850,8 @@ pub struct ReqIntroducedLocations {
     pub add_label: bool,
 }
 
-impl AddToDiagnostic for ReqIntroducedLocations {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for ReqIntroducedLocations {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         mut self,
         diag: &mut Diag<'_, G>,
         f: F,
@@ -873,8 +873,8 @@ pub struct MoreTargeted {
     pub ident: Symbol,
 }
 
-impl AddToDiagnostic for MoreTargeted {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for MoreTargeted {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -1296,8 +1296,8 @@ pub struct SuggestTuplePatternMany {
     pub compatible_variants: Vec<String>,
 }
 
-impl AddToDiagnostic for SuggestTuplePatternMany {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for SuggestTuplePatternMany {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
diff --git a/compiler/rustc_infer/src/errors/note_and_explain.rs b/compiler/rustc_infer/src/errors/note_and_explain.rs
index c8141f67192..7b962b01408 100644
--- a/compiler/rustc_infer/src/errors/note_and_explain.rs
+++ b/compiler/rustc_infer/src/errors/note_and_explain.rs
@@ -1,6 +1,6 @@
 use crate::fluent_generated as fluent;
 use crate::infer::error_reporting::nice_region_error::find_anon_type;
-use rustc_errors::{AddToDiagnostic, Diag, EmissionGuarantee, IntoDiagArg, SubdiagMessageOp};
+use rustc_errors::{Diag, EmissionGuarantee, IntoDiagArg, SubdiagMessageOp, Subdiagnostic};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::{symbol::kw, Span};
 
@@ -159,8 +159,8 @@ impl RegionExplanation<'_> {
     }
 }
 
-impl AddToDiagnostic for RegionExplanation<'_> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for RegionExplanation<'_> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs
index aa700005a3a..84bfa5b5af7 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs
@@ -11,7 +11,7 @@ use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::SubregionOrigin;
 use crate::infer::TyCtxt;
 
-use rustc_errors::AddToDiagnostic;
+use rustc_errors::Subdiagnostic;
 use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::Ty;
 use rustc_middle::ty::Region;
@@ -145,5 +145,5 @@ pub fn suggest_adding_lifetime_params<'tcx>(
     err: &mut Diag<'_>,
 ) {
     let suggestion = AddLifetimeParamsSuggestion { tcx, sub, ty_sup, ty_sub, add_note: false };
-    suggestion.add_to_diagnostic(err);
+    suggestion.add_to_diag(err);
 }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index adde45f081a..afcb4a182fa 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -9,7 +9,7 @@ use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::{SubregionOrigin, TypeTrace};
 use crate::traits::{ObligationCauseCode, UnifyReceiverContext};
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{AddToDiagnostic, Applicability, Diag, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{Applicability, Diag, ErrorGuaranteed, MultiSpan, Subdiagnostic};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_ty, Visitor};
 use rustc_hir::{
@@ -234,7 +234,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         if let (Some(ident), true) = (override_error_code, fn_returns.is_empty()) {
             // Provide a more targeted error code and description.
             let retarget_subdiag = MoreTargeted { ident };
-            retarget_subdiag.add_to_diagnostic(&mut err);
+            retarget_subdiag.add_to_diag(&mut err);
         }
 
         let arg = match param.param.pat.simple_ident() {
@@ -532,7 +532,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             hir_v.visit_ty(self_ty);
             for &span in &traits {
                 let subdiag = DynTraitConstraintSuggestion { span, ident };
-                subdiag.add_to_diagnostic(err);
+                subdiag.add_to_diag(err);
                 suggested = true;
             }
         }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note.rs b/compiler/rustc_infer/src/infer/error_reporting/note.rs
index 2c369b5ad60..3ae1165d2a4 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note.rs
@@ -5,7 +5,7 @@ use crate::errors::{
 use crate::fluent_generated as fluent;
 use crate::infer::error_reporting::{note_and_explain_region, TypeErrCtxt};
 use crate::infer::{self, SubregionOrigin};
-use rustc_errors::{AddToDiagnostic, Diag};
+use rustc_errors::{Diag, Subdiagnostic};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::error::TypeError;
@@ -22,13 +22,13 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 requirement: ObligationCauseAsDiagArg(trace.cause.clone()),
                 expected_found: self.values_str(trace.values).map(|(e, f, _)| (e, f)),
             }
-            .add_to_diagnostic(err),
+            .add_to_diag(err),
             infer::Reborrow(span) => {
-                RegionOriginNote::Plain { span, msg: fluent::infer_reborrow }.add_to_diagnostic(err)
+                RegionOriginNote::Plain { span, msg: fluent::infer_reborrow }.add_to_diag(err)
             }
             infer::RelateObjectBound(span) => {
                 RegionOriginNote::Plain { span, msg: fluent::infer_relate_object_bound }
-                    .add_to_diagnostic(err);
+                    .add_to_diag(err);
             }
             infer::ReferenceOutlivesReferent(ty, span) => {
                 RegionOriginNote::WithName {
@@ -37,7 +37,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     name: &self.ty_to_string(ty),
                     continues: false,
                 }
-                .add_to_diagnostic(err);
+                .add_to_diag(err);
             }
             infer::RelateParamBound(span, ty, opt_span) => {
                 RegionOriginNote::WithName {
@@ -46,19 +46,19 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     name: &self.ty_to_string(ty),
                     continues: opt_span.is_some(),
                 }
-                .add_to_diagnostic(err);
+                .add_to_diag(err);
                 if let Some(span) = opt_span {
                     RegionOriginNote::Plain { span, msg: fluent::infer_relate_param_bound_2 }
-                        .add_to_diagnostic(err);
+                        .add_to_diag(err);
                 }
             }
             infer::RelateRegionParamBound(span) => {
                 RegionOriginNote::Plain { span, msg: fluent::infer_relate_region_param_bound }
-                    .add_to_diagnostic(err);
+                    .add_to_diag(err);
             }
             infer::CompareImplItemObligation { span, .. } => {
                 RegionOriginNote::Plain { span, msg: fluent::infer_compare_impl_item_obligation }
-                    .add_to_diagnostic(err);
+                    .add_to_diag(err);
             }
             infer::CheckAssociatedTypeBounds { ref parent, .. } => {
                 self.note_region_origin(err, parent);
@@ -68,7 +68,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     span,
                     msg: fluent::infer_ascribe_user_type_prove_predicate,
                 }
-                .add_to_diagnostic(err);
+                .add_to_diag(err);
             }
         }
     }
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index 20b58032331..df1e2b40265 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -186,7 +186,7 @@ lint_deprecated_lint_name =
     .help = change it to {$replace}
 
 lint_diag_out_of_impl =
-    diagnostics should only be created in `Diagnostic`/`AddToDiagnostic` impls
+    diagnostics should only be created in `Diagnostic`/`Subdiagnostic` impls
 
 lint_drop_glue =
     types that do not implement `Drop` can still have drop glue, consider instead using `{$needs_drop}` to detect whether a type is trivially dropped
diff --git a/compiler/rustc_lint/src/errors.rs b/compiler/rustc_lint/src/errors.rs
index d73f9e7a4a1..ee99e824a54 100644
--- a/compiler/rustc_lint/src/errors.rs
+++ b/compiler/rustc_lint/src/errors.rs
@@ -1,5 +1,5 @@
 use crate::fluent_generated as fluent;
-use rustc_errors::{codes::*, AddToDiagnostic, Diag, EmissionGuarantee, SubdiagMessageOp};
+use rustc_errors::{codes::*, Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_session::lint::Level;
 use rustc_span::{Span, Symbol};
@@ -23,8 +23,8 @@ pub enum OverruledAttributeSub {
     CommandLineSource,
 }
 
-impl AddToDiagnostic for OverruledAttributeSub {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for OverruledAttributeSub {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
diff --git a/compiler/rustc_lint/src/internal.rs b/compiler/rustc_lint/src/internal.rs
index bf5646b4651..edbd0bb1923 100644
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@@ -351,7 +351,7 @@ declare_tool_lint! {
 
 declare_tool_lint! {
     /// The `diagnostic_outside_of_impl` lint detects calls to functions annotated with
-    /// `#[rustc_lint_diagnostics]` that are outside an `Diagnostic`, `AddToDiagnostic`, or
+    /// `#[rustc_lint_diagnostics]` that are outside an `Diagnostic`, `Subdiagnostic`, or
     /// `DecorateLint` impl, or a `#[derive(Diagnostic)]`, `#[derive(Subdiagnostic)]`,
     /// `#[derive(DecorateLint)]` expansion.
     ///
@@ -359,7 +359,7 @@ declare_tool_lint! {
     /// [here](https://rustc-dev-guide.rust-lang.org/diagnostics/diagnostic-structs.html).
     pub rustc::DIAGNOSTIC_OUTSIDE_OF_IMPL,
     Deny,
-    "prevent creation of diagnostics outside of `Diagnostic`/`AddToDiagnostic` impls",
+    "prevent creation of diagnostics outside of `Diagnostic`/`Subdiagnostic` impls",
     report_in_external_macro: true
 }
 
@@ -455,7 +455,7 @@ impl LateLintPass<'_> for Diagnostics {
         }
 
         // Calls to `#[rustc_lint_diagnostics]`-marked functions should only occur:
-        // - inside an impl of `Diagnostic`, `AddToDiagnostic`, or `DecorateLint`, or
+        // - inside an impl of `Diagnostic`, `Subdiagnostic`, or `DecorateLint`, or
         // - inside a parent function that is itself marked with `#[rustc_lint_diagnostics]`.
         //
         // Otherwise, emit a `DIAGNOSTIC_OUTSIDE_OF_IMPL` lint.
@@ -467,7 +467,7 @@ impl LateLintPass<'_> for Diagnostics {
                     && let Impl { of_trait: Some(of_trait), .. } = impl_
                     && let Some(def_id) = of_trait.trait_def_id()
                     && let Some(name) = cx.tcx.get_diagnostic_name(def_id)
-                    && matches!(name, sym::Diagnostic | sym::AddToDiagnostic | sym::DecorateLint)
+                    && matches!(name, sym::Diagnostic | sym::Subdiagnostic | sym::DecorateLint)
                 {
                     is_inside_appropriate_impl = true;
                     break;
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 7e0ac1bfff1..1d0b7e45a90 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -5,8 +5,8 @@ use std::num::NonZero;
 use crate::errors::RequestedLevel;
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, DecorateLint, Diag, DiagMessage, DiagStyledString,
-    EmissionGuarantee, SubdiagMessageOp, SuggestionStyle,
+    codes::*, Applicability, DecorateLint, Diag, DiagMessage, DiagStyledString, EmissionGuarantee,
+    SubdiagMessageOp, Subdiagnostic, SuggestionStyle,
 };
 use rustc_hir::def_id::DefId;
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
@@ -270,8 +270,8 @@ pub struct SuggestChangingAssocTypes<'a, 'b> {
     pub ty: &'a rustc_hir::Ty<'b>,
 }
 
-impl<'a, 'b> AddToDiagnostic for SuggestChangingAssocTypes<'a, 'b> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl<'a, 'b> Subdiagnostic for SuggestChangingAssocTypes<'a, 'b> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -326,8 +326,8 @@ pub struct BuiltinTypeAliasGenericBoundsSuggestion {
     pub suggestions: Vec<(Span, String)>,
 }
 
-impl AddToDiagnostic for BuiltinTypeAliasGenericBoundsSuggestion {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for BuiltinTypeAliasGenericBoundsSuggestion {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -434,7 +434,7 @@ impl<'a> DecorateLint<'a, ()> for BuiltinUnpermittedTypeInit<'_> {
                 fluent::lint_builtin_unpermitted_type_init_label_suggestion,
             );
         }
-        self.sub.add_to_diagnostic(diag);
+        self.sub.add_to_diag(diag);
     }
 
     fn msg(&self) -> DiagMessage {
@@ -447,8 +447,8 @@ pub struct BuiltinUnpermittedTypeInitSub {
     pub err: InitError,
 }
 
-impl AddToDiagnostic for BuiltinUnpermittedTypeInitSub {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for BuiltinUnpermittedTypeInitSub {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -502,8 +502,8 @@ pub struct BuiltinClashingExternSub<'a> {
     pub found: Ty<'a>,
 }
 
-impl AddToDiagnostic for BuiltinClashingExternSub<'_> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for BuiltinClashingExternSub<'_> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -784,8 +784,8 @@ pub struct HiddenUnicodeCodepointsDiagLabels {
     pub spans: Vec<(char, Span)>,
 }
 
-impl AddToDiagnostic for HiddenUnicodeCodepointsDiagLabels {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for HiddenUnicodeCodepointsDiagLabels {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -802,8 +802,8 @@ pub enum HiddenUnicodeCodepointsDiagSub {
 }
 
 // Used because of multiple multipart_suggestion and note
-impl AddToDiagnostic for HiddenUnicodeCodepointsDiagSub {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for HiddenUnicodeCodepointsDiagSub {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -950,8 +950,8 @@ pub struct NonBindingLetSub {
     pub is_assign_desugar: bool,
 }
 
-impl AddToDiagnostic for NonBindingLetSub {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for NonBindingLetSub {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -1236,8 +1236,8 @@ pub enum NonSnakeCaseDiagSub {
     SuggestionAndNote { span: Span },
 }
 
-impl AddToDiagnostic for NonSnakeCaseDiagSub {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for NonSnakeCaseDiagSub {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -1478,8 +1478,8 @@ pub enum OverflowingBinHexSign {
     Negative,
 }
 
-impl AddToDiagnostic for OverflowingBinHexSign {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for OverflowingBinHexSign {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
diff --git a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
index ef326106404..cda9de66a55 100644
--- a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
@@ -16,7 +16,7 @@ use synstructure::{BindingInfo, Structure, VariantInfo};
 
 use super::utils::SubdiagnosticVariant;
 
-/// The central struct for constructing the `add_to_diagnostic` method from an annotated struct.
+/// The central struct for constructing the `add_to_diag` method from an annotated struct.
 pub(crate) struct SubdiagnosticDeriveBuilder {
     diag: syn::Ident,
     f: syn::Ident,
@@ -86,8 +86,8 @@ impl SubdiagnosticDeriveBuilder {
         let diag = &self.diag;
         let f = &self.f;
         let ret = structure.gen_impl(quote! {
-            gen impl rustc_errors::AddToDiagnostic for @Self {
-                fn add_to_diagnostic_with<__G, __F>(
+            gen impl rustc_errors::Subdiagnostic for @Self {
+                fn add_to_diag_with<__G, __F>(
                     self,
                     #diag: &mut rustc_errors::Diag<'_, __G>,
                     #f: __F
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index f44aaad8351..2b4c6541857 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -1,8 +1,8 @@
 use crate::fluent_generated as fluent;
 use rustc_errors::DiagArgValue;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
-    MultiSpan, SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level, MultiSpan,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::{self, Ty};
@@ -419,8 +419,8 @@ pub struct UnsafeNotInheritedLintNote {
     pub body_span: Span,
 }
 
-impl AddToDiagnostic for UnsafeNotInheritedLintNote {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for UnsafeNotInheritedLintNote {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
@@ -865,8 +865,8 @@ pub struct Variant {
     pub span: Span,
 }
 
-impl<'tcx> AddToDiagnostic for AdtDefinedHere<'tcx> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl<'tcx> Subdiagnostic for AdtDefinedHere<'tcx> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 394e4106c91..32b56bb7e87 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -3,8 +3,8 @@ use std::borrow::Cow;
 use rustc_ast::token::Token;
 use rustc_ast::{Path, Visibility};
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
-    SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_session::errors::ExprParenthesesNeeded;
@@ -1093,17 +1093,17 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for ExpectedIdentifier {
         diag.arg("token", self.token);
 
         if let Some(sugg) = self.suggest_raw {
-            sugg.add_to_diagnostic(&mut diag);
+            sugg.add_to_diag(&mut diag);
         }
 
-        ExpectedIdentifierFound::new(token_descr, self.span).add_to_diagnostic(&mut diag);
+        ExpectedIdentifierFound::new(token_descr, self.span).add_to_diag(&mut diag);
 
         if let Some(sugg) = self.suggest_remove_comma {
-            sugg.add_to_diagnostic(&mut diag);
+            sugg.add_to_diag(&mut diag);
         }
 
         if let Some(help) = self.help_cannot_start_number {
-            help.add_to_diagnostic(&mut diag);
+            help.add_to_diag(&mut diag);
         }
 
         diag
@@ -1154,7 +1154,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for ExpectedSemi {
             diag.span_label(unexpected_token_label, fluent::parse_label_unexpected_token);
         }
 
-        self.sugg.add_to_diagnostic(&mut diag);
+        self.sugg.add_to_diag(&mut diag);
 
         diag
     }
@@ -1466,8 +1466,8 @@ pub(crate) struct FnTraitMissingParen {
     pub machine_applicable: bool,
 }
 
-impl AddToDiagnostic for FnTraitMissingParen {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for FnTraitMissingParen {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _: F,
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index e56fc3e1129..7038b8bbe47 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -36,8 +36,8 @@ use rustc_ast::{
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{
-    pluralize, AddToDiagnostic, Applicability, Diag, DiagCtxt, ErrorGuaranteed, FatalError, PErr,
-    PResult,
+    pluralize, Applicability, Diag, DiagCtxt, ErrorGuaranteed, FatalError, PErr, PResult,
+    Subdiagnostic,
 };
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::source_map::Spanned;
@@ -1271,7 +1271,7 @@ impl<'a> Parser<'a> {
                 Ok(_) => {
                     if self.token == token::Eq {
                         let sugg = SuggAddMissingLetStmt { span: prev_span };
-                        sugg.add_to_diagnostic(err);
+                        sugg.add_to_diag(err);
                     }
                 }
                 Err(e) => {
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 7a34bc7890c..e27a5f93799 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -27,7 +27,7 @@ use rustc_ast::{Arm, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLim
 use rustc_ast::{ClosureBinder, MetaItemLit, StmtKind};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::stack::ensure_sufficient_stack;
-use rustc_errors::{AddToDiagnostic, Applicability, Diag, PResult, StashKey};
+use rustc_errors::{Applicability, Diag, PResult, StashKey, Subdiagnostic};
 use rustc_lexer::unescape::unescape_char;
 use rustc_macros::Subdiagnostic;
 use rustc_session::errors::{report_lit_error, ExprParenthesesNeeded};
@@ -3451,8 +3451,8 @@ impl<'a> Parser<'a> {
         let in_if_guard = self.restrictions.contains(Restrictions::IN_IF_GUARD);
 
         let async_block_err = |e: &mut Diag<'_>, span: Span| {
-            errors::AsyncBlockIn2015 { span }.add_to_diagnostic(e);
-            errors::HelpUseLatestEdition::new().add_to_diagnostic(e);
+            errors::AsyncBlockIn2015 { span }.add_to_diag(e);
+            errors::HelpUseLatestEdition::new().add_to_diag(e);
         };
 
         while self.token != token::CloseDelim(close_delim) {
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 12b5e0cfe8b..3f26ea4507d 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::Label;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, Diag, DiagCtxt, DiagSymbolList, Diagnostic,
-    EmissionGuarantee, Level, MultiSpan, SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagCtxt, DiagSymbolList, Diagnostic, EmissionGuarantee, Level,
+    MultiSpan, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_hir::{self as hir, ExprKind, Target};
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
@@ -1751,8 +1751,8 @@ pub struct UnusedVariableStringInterp {
     pub hi: Span,
 }
 
-impl AddToDiagnostic for UnusedVariableStringInterp {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for UnusedVariableStringInterp {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
diff --git a/compiler/rustc_pattern_analysis/src/errors.rs b/compiler/rustc_pattern_analysis/src/errors.rs
index e471b8abd73..21a61d46ccb 100644
--- a/compiler/rustc_pattern_analysis/src/errors.rs
+++ b/compiler/rustc_pattern_analysis/src/errors.rs
@@ -1,4 +1,4 @@
-use rustc_errors::{AddToDiagnostic, Diag, EmissionGuarantee, SubdiagMessageOp};
+use rustc_errors::{Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
 use rustc_middle::thir::Pat;
 use rustc_middle::ty::Ty;
@@ -61,8 +61,8 @@ pub struct Overlap<'tcx> {
     pub range: Pat<'tcx>,
 }
 
-impl<'tcx> AddToDiagnostic for Overlap<'tcx> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl<'tcx> Subdiagnostic for Overlap<'tcx> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _: F,
@@ -109,8 +109,8 @@ pub struct GappedRange<'tcx> {
     pub first_range: Pat<'tcx>,
 }
 
-impl<'tcx> AddToDiagnostic for GappedRange<'tcx> {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl<'tcx> Subdiagnostic for GappedRange<'tcx> {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _: F,
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 2a9f1e5fb02..0c8732d3cd0 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -129,7 +129,6 @@ symbols! {
         Abi,
         AcqRel,
         Acquire,
-        AddToDiagnostic,
         Any,
         Arc,
         ArcWeak,
@@ -305,6 +304,7 @@ symbols! {
         String,
         StructuralPartialEq,
         SubdiagMessage,
+        Subdiagnostic,
         Sync,
         T,
         Target,
diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index d9e58b75088..b126062102e 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -1,7 +1,7 @@
 use crate::fluent_generated as fluent;
 use rustc_errors::{
-    codes::*, AddToDiagnostic, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
-    SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::Diagnostic;
 use rustc_middle::ty::{self, ClosureKind, PolyTraitRef, Ty};
@@ -100,8 +100,8 @@ pub enum AdjustSignatureBorrow {
     RemoveBorrow { remove_borrow: Vec<(Span, String)> },
 }
 
-impl AddToDiagnostic for AdjustSignatureBorrow {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for AdjustSignatureBorrow {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         _f: F,
diff --git a/tests/ui-fulldeps/internal-lints/diagnostics.rs b/tests/ui-fulldeps/internal-lints/diagnostics.rs
index e9c5a37bcd7..f9399cb81c8 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::{
-    AddToDiagnostic, DecorateLint, Diag, DiagCtxt, DiagInner, DiagMessage, EmissionGuarantee,
-    Diagnostic, Level, SubdiagMessageOp,
+    DecorateLint, Diag, DiagCtxt, DiagInner, DiagMessage, Diagnostic, EmissionGuarantee, Level,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
@@ -53,10 +53,10 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for TranslatableInDiagnostic {
     }
 }
 
-pub struct UntranslatableInAddToDiagnostic;
+pub struct UntranslatableInAddtoDiag;
 
-impl AddToDiagnostic for UntranslatableInAddToDiagnostic {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for UntranslatableInAddtoDiag {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
@@ -66,10 +66,10 @@ impl AddToDiagnostic for UntranslatableInAddToDiagnostic {
     }
 }
 
-pub struct TranslatableInAddToDiagnostic;
+pub struct TranslatableInAddtoDiag;
 
-impl AddToDiagnostic for TranslatableInAddToDiagnostic {
-    fn add_to_diagnostic_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+impl Subdiagnostic for TranslatableInAddtoDiag {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
         f: F,
@@ -105,10 +105,10 @@ impl<'a> DecorateLint<'a, ()> for TranslatableInDecorateLint {
 
 pub fn make_diagnostics<'a>(dcx: &'a DiagCtxt) {
     let _diag = dcx.struct_err(crate::fluent_generated::no_crate_example);
-    //~^ ERROR diagnostics should only be created in `Diagnostic`/`AddToDiagnostic` impls
+    //~^ ERROR diagnostics should only be created in `Diagnostic`/`Subdiagnostic` impls
 
     let _diag = dcx.struct_err("untranslatable diagnostic");
-    //~^ ERROR diagnostics should only be created in `Diagnostic`/`AddToDiagnostic` impls
+    //~^ ERROR diagnostics should only be created in `Diagnostic`/`Subdiagnostic` impls
     //~^^ ERROR diagnostics should be created using translatable messages
 }
 
diff --git a/tests/ui-fulldeps/internal-lints/diagnostics.stderr b/tests/ui-fulldeps/internal-lints/diagnostics.stderr
index ce6cc18e872..01184d7264b 100644
--- a/tests/ui-fulldeps/internal-lints/diagnostics.stderr
+++ b/tests/ui-fulldeps/internal-lints/diagnostics.stderr
@@ -22,7 +22,7 @@ error: diagnostics should be created using translatable messages
 LL |         diag.note("untranslatable diagnostic");
    |              ^^^^
 
-error: diagnostics should only be created in `Diagnostic`/`AddToDiagnostic` impls
+error: diagnostics should only be created in `Diagnostic`/`Subdiagnostic` impls
   --> $DIR/diagnostics.rs:107:21
    |
 LL |     let _diag = dcx.struct_err(crate::fluent_generated::no_crate_example);
@@ -34,7 +34,7 @@ note: the lint level is defined here
 LL | #![deny(rustc::diagnostic_outside_of_impl)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: diagnostics should only be created in `Diagnostic`/`AddToDiagnostic` impls
+error: diagnostics should only be created in `Diagnostic`/`Subdiagnostic` impls
   --> $DIR/diagnostics.rs:110:21
    |
 LL |     let _diag = dcx.struct_err("untranslatable diagnostic");