Auto merge of #122132 - nnethercote:diag-renaming3, r=nnethercote

Diagnostic renaming 3

A sequel to https://github.com/rust-lang/rust/pull/121780.

r? `@davidtwco`

78 files changed, 567 insertions, 586 deletions

diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
index 76744ae6264..6fd980ed3ca 100644
--- a/compiler/rustc_ast_lowering/src/errors.rs
+++ b/compiler/rustc_ast_lowering/src/errors.rs
@@ -1,10 +1,10 @@
 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};
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_generic_type_with_parentheses, code = E0214)]
 pub struct GenericTypeWithParentheses {
     #[primary_span]
@@ -14,7 +14,7 @@ pub struct GenericTypeWithParentheses {
     pub sub: Option<UseAngleBrackets>,
 }
 
-#[derive(Clone, Copy, Subdiagnostic)]
+#[derive(Subdiagnostic)]
 #[multipart_suggestion(ast_lowering_use_angle_brackets, applicability = "maybe-incorrect")]
 pub struct UseAngleBrackets {
     #[suggestion_part(code = "<")]
@@ -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,
@@ -63,7 +63,7 @@ pub struct InvalidAbiSuggestion {
     pub suggestion: String,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_assoc_ty_parentheses)]
 pub struct AssocTyParentheses {
     #[primary_span]
@@ -72,7 +72,7 @@ pub struct AssocTyParentheses {
     pub sub: AssocTyParenthesesSub,
 }
 
-#[derive(Clone, Copy, Subdiagnostic)]
+#[derive(Subdiagnostic)]
 pub enum AssocTyParenthesesSub {
     #[multipart_suggestion(ast_lowering_remove_parentheses)]
     Empty {
@@ -106,7 +106,7 @@ pub struct MisplacedAssocTyBinding {
     pub suggestion: Option<Span>,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_underscore_expr_lhs_assign)]
 pub struct UnderscoreExprLhsAssign {
     #[primary_span]
@@ -114,7 +114,7 @@ pub struct UnderscoreExprLhsAssign {
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_base_expression_double_dot, code = E0797)]
 pub struct BaseExpressionDoubleDot {
     #[primary_span]
@@ -122,7 +122,7 @@ pub struct BaseExpressionDoubleDot {
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_await_only_in_async_fn_and_blocks, code = E0728)]
 pub struct AwaitOnlyInAsyncFnAndBlocks {
     #[primary_span]
@@ -132,21 +132,21 @@ pub struct AwaitOnlyInAsyncFnAndBlocks {
     pub item_span: Option<Span>,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_coroutine_too_many_parameters, code = E0628)]
 pub struct CoroutineTooManyParameters {
     #[primary_span]
     pub fn_decl_span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_closure_cannot_be_static, code = E0697)]
 pub struct ClosureCannotBeStatic {
     #[primary_span]
     pub fn_decl_span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_functional_record_update_destructuring_assignment)]
 pub struct FunctionalRecordUpdateDestructuringAssignment {
     #[primary_span]
@@ -154,28 +154,28 @@ pub struct FunctionalRecordUpdateDestructuringAssignment {
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_async_coroutines_not_supported, code = E0727)]
 pub struct AsyncCoroutinesNotSupported {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_inline_asm_unsupported_target, code = E0472)]
 pub struct InlineAsmUnsupportedTarget {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_att_syntax_only_x86)]
 pub struct AttSyntaxOnlyX86 {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_abi_specified_multiple_times)]
 pub struct AbiSpecifiedMultipleTimes {
     #[primary_span]
@@ -187,7 +187,7 @@ pub struct AbiSpecifiedMultipleTimes {
     pub equivalent: Option<()>,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_clobber_abi_not_supported)]
 pub struct ClobberAbiNotSupported {
     #[primary_span]
@@ -203,7 +203,7 @@ pub struct InvalidAbiClobberAbi {
     pub supported_abis: String,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_invalid_register)]
 pub struct InvalidRegister<'a> {
     #[primary_span]
@@ -212,7 +212,7 @@ pub struct InvalidRegister<'a> {
     pub error: &'a str,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_invalid_register_class)]
 pub struct InvalidRegisterClass<'a> {
     #[primary_span]
@@ -241,7 +241,7 @@ pub enum InvalidAsmTemplateModifierRegClassSub {
     DoesNotSupportModifier { class_name: Symbol },
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_invalid_asm_template_modifier_const)]
 pub struct InvalidAsmTemplateModifierConst {
     #[primary_span]
@@ -251,7 +251,7 @@ pub struct InvalidAsmTemplateModifierConst {
     pub op_span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_invalid_asm_template_modifier_sym)]
 pub struct InvalidAsmTemplateModifierSym {
     #[primary_span]
@@ -261,7 +261,7 @@ pub struct InvalidAsmTemplateModifierSym {
     pub op_span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_invalid_asm_template_modifier_label)]
 pub struct InvalidAsmTemplateModifierLabel {
     #[primary_span]
@@ -271,7 +271,7 @@ pub struct InvalidAsmTemplateModifierLabel {
     pub op_span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_register_class_only_clobber)]
 pub struct RegisterClassOnlyClobber {
     #[primary_span]
@@ -279,7 +279,7 @@ pub struct RegisterClassOnlyClobber {
     pub reg_class_name: Symbol,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_register_conflict)]
 pub struct RegisterConflict<'a> {
     #[primary_span]
@@ -293,7 +293,7 @@ pub struct RegisterConflict<'a> {
     pub in_out: Option<Span>,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[help]
 #[diag(ast_lowering_sub_tuple_binding)]
 pub struct SubTupleBinding<'a> {
@@ -311,7 +311,7 @@ pub struct SubTupleBinding<'a> {
     pub ctx: &'a str,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_extra_double_dot)]
 pub struct ExtraDoubleDot<'a> {
     #[primary_span]
@@ -322,7 +322,7 @@ pub struct ExtraDoubleDot<'a> {
     pub ctx: &'a str,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[note]
 #[diag(ast_lowering_misplaced_double_dot)]
 pub struct MisplacedDoubleDot {
@@ -330,7 +330,7 @@ pub struct MisplacedDoubleDot {
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_misplaced_relax_trait_bound)]
 pub struct MisplacedRelaxTraitBound {
     #[primary_span]
@@ -363,14 +363,14 @@ pub struct NeverPatternWithGuard {
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_arbitrary_expression_in_pattern)]
 pub struct ArbitraryExpressionInPattern {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(Diagnostic, Clone, Copy)]
+#[derive(Diagnostic)]
 #[diag(ast_lowering_inclusive_range_with_no_end)]
 pub struct InclusiveRangeWithNoEnd {
     #[primary_span]
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_attr/src/session_diagnostics.rs b/compiler/rustc_attr/src/session_diagnostics.rs
index f489cc87bc7..0ad7bd6e17e 100644
--- a/compiler/rustc_attr/src/session_diagnostics.rs
+++ b/compiler/rustc_attr/src/session_diagnostics.rs
@@ -1,9 +1,7 @@
 use std::num::IntErrorKind;
 
 use rustc_ast as ast;
-use rustc_errors::{
-    codes::*, Applicability, Diag, DiagCtxt, EmissionGuarantee, IntoDiagnostic, Level,
-};
+use rustc_errors::{codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
 
@@ -50,8 +48,8 @@ pub(crate) struct UnknownMetaItem<'a> {
 }
 
 // Manual implementation to be able to format `expected` items correctly.
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for UnknownMetaItem<'_> {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnknownMetaItem<'_> {
+    fn into_diag(self, dcx: &'a DiagCtxt, 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)
@@ -203,8 +201,8 @@ pub(crate) struct UnsupportedLiteral {
     pub start_point_span: Span,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for UnsupportedLiteral {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnsupportedLiteral {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         let mut diag = Diag::new(
             dcx,
             level,
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index f6f33e10c20..08199068020 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -191,9 +191,9 @@ impl Display for RegionName {
     }
 }
 
-impl rustc_errors::IntoDiagnosticArg for RegionName {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl rustc_errors::IntoDiagArg for RegionName {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index 06302ae577a..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, EmissionGuarantee, IntoDiagnostic, 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};
@@ -425,9 +425,9 @@ pub(crate) struct EnvNotDefinedWithUserMessage {
 }
 
 // Hand-written implementation to support custom user messages.
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for EnvNotDefinedWithUserMessage {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for EnvNotDefinedWithUserMessage {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         #[expect(
             rustc::untranslatable_diagnostic,
             reason = "cannot translate user-provided messages"
@@ -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,
@@ -785,8 +785,8 @@ pub(crate) struct AsmClobberNoReg {
     pub(crate) clobbers: Vec<Span>,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for AsmClobberNoReg {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AsmClobberNoReg {
+    fn into_diag(self, dcx: &'a DiagCtxt, 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_codegen_gcc/src/errors.rs b/compiler/rustc_codegen_gcc/src/errors.rs
index f963a153fba..aee2b077dba 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, EmissionGuarantee, IntoDiagnostic, Level};
+use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
 
@@ -89,8 +89,8 @@ pub(crate) struct TargetFeatureDisableOrEnable<'a> {
 #[help(codegen_gcc_missing_features)]
 pub(crate) struct MissingFeatures;
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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);
diff --git a/compiler/rustc_codegen_llvm/src/errors.rs b/compiler/rustc_codegen_llvm/src/errors.rs
index 5bef240340b..e15eda7c66c 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, EmissionGuarantee, IntoDiagnostic, Level};
+use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
 
@@ -99,9 +99,9 @@ pub(crate) struct DynamicLinkingWithLTO;
 
 pub(crate) struct ParseTargetMachineConfig<'a>(pub LlvmError<'a>);
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for ParseTargetMachineConfig<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
-        let diag: Diag<'_, G> = self.0.into_diagnostic(dcx, level);
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for ParseTargetMachineConfig<'_> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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());
         Diag::new(dcx, level, fluent::codegen_llvm_parse_target_machine_config)
@@ -119,8 +119,8 @@ pub(crate) struct TargetFeatureDisableOrEnable<'a> {
 #[help(codegen_llvm_missing_features)]
 pub(crate) struct MissingFeatures;
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetFeatureDisableOrEnable<'_> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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);
@@ -179,8 +179,8 @@ pub enum LlvmError<'a> {
 
 pub(crate) struct WithLlvmError<'a>(pub LlvmError<'a>, pub String);
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for WithLlvmError<'_> {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for WithLlvmError<'_> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
         use LlvmError::*;
         let msg_with_llvm_err = match &self.0 {
             WriteOutput { .. } => fluent::codegen_llvm_write_output_with_llvm_err,
@@ -198,7 +198,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for WithLlvmError<'_> {
             ParseBitcode => fluent::codegen_llvm_parse_bitcode_with_llvm_err,
         };
         self.0
-            .into_diagnostic(dcx, level)
+            .into_diag(dcx, level)
             .with_primary_message(msg_with_llvm_err)
             .with_arg("llvm_err", self.1)
     }
diff --git a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
index 7ecc3864347..e441aea8400 100644
--- a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
+++ b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
@@ -27,7 +27,7 @@ use crate::errors;
 use rustc_ast as ast;
 use rustc_data_structures::unord::UnordMap;
 use rustc_data_structures::unord::UnordSet;
-use rustc_errors::{DiagArgValue, IntoDiagnosticArg};
+use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::mir::mono::CodegenUnitNameBuilder;
 use rustc_middle::ty::TyCtxt;
@@ -205,8 +205,8 @@ impl fmt::Display for CguReuse {
     }
 }
 
-impl IntoDiagnosticArg for CguReuse {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for CguReuse {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.to_string()))
     }
 }
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index 8fae80de064..3572ee301c8 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -4,8 +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, EmissionGuarantee, IntoDiagnostic, IntoDiagnosticArg,
-    Level,
+    codes::*, Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
 };
 use rustc_macros::Diagnostic;
 use rustc_middle::ty::layout::LayoutError;
@@ -152,8 +151,8 @@ impl<'a> CopyPath<'a> {
 
 struct DebugArgPath<'a>(pub &'a Path);
 
-impl IntoDiagnosticArg for DebugArgPath<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for DebugArgPath<'_> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         DiagArgValue::Str(Cow::Owned(format!("{:?}", self.0)))
     }
 }
@@ -215,8 +214,8 @@ pub enum LinkRlibError {
 
 pub struct ThorinErrorWrapper(pub thorin::Error);
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for ThorinErrorWrapper {
-    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for ThorinErrorWrapper {
+    fn into_diag(self, dcx: &DiagCtxt, 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),
@@ -348,8 +347,8 @@ pub struct LinkingFailed<'a> {
     pub escaped_output: String,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for LinkingFailed<'_> {
-    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
+    fn into_diag(self, dcx: &DiagCtxt, 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));
@@ -974,8 +973,8 @@ pub enum ExpectedPointerMutability {
     Not,
 }
 
-impl IntoDiagnosticArg for ExpectedPointerMutability {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for ExpectedPointerMutability {
+    fn into_diag_arg(self) -> DiagArgValue {
         match self {
             ExpectedPointerMutability::Mut => DiagArgValue::Str(Cow::Borrowed("*mut")),
             ExpectedPointerMutability::Not => DiagArgValue::Str(Cow::Borrowed("*_")),
diff --git a/compiler/rustc_const_eval/src/const_eval/error.rs b/compiler/rustc_const_eval/src/const_eval/error.rs
index e5b4fc3a574..b6adee435ba 100644
--- a/compiler/rustc_const_eval/src/const_eval/error.rs
+++ b/compiler/rustc_const_eval/src/const_eval/error.rs
@@ -1,6 +1,6 @@
 use std::mem;
 
-use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, IntoDiagnostic, IntoDiagnosticArg};
+use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, Diagnostic, IntoDiagArg};
 use rustc_hir::CRATE_HIR_ID;
 use rustc_middle::mir::AssertKind;
 use rustc_middle::query::TyCtxtAt;
@@ -40,10 +40,10 @@ impl MachineStopType for ConstEvalErrKind {
             RecursiveStatic | ConstAccessesMutGlobal | ModifiedGlobal => {}
             AssertFailure(kind) => kind.add_args(adder),
             Panic { msg, line, col, file } => {
-                adder("msg".into(), msg.into_diagnostic_arg());
-                adder("file".into(), file.into_diagnostic_arg());
-                adder("line".into(), line.into_diagnostic_arg());
-                adder("col".into(), col.into_diagnostic_arg());
+                adder("msg".into(), msg.into_diag_arg());
+                adder("file".into(), file.into_diag_arg());
+                adder("line".into(), line.into_diag_arg());
+                adder("col".into(), col.into_diag_arg());
             }
         }
     }
@@ -130,7 +130,7 @@ pub(super) fn report<'tcx, C, F, E>(
 where
     C: FnOnce() -> (Span, Vec<FrameNote>),
     F: FnOnce(Span, Vec<FrameNote>) -> E,
-    E: IntoDiagnostic<'tcx>,
+    E: Diagnostic<'tcx>,
 {
     // Special handling for certain errors
     match error {
@@ -168,7 +168,7 @@ pub(super) fn lint<'tcx, 'mir, L>(
     lint: &'static rustc_session::lint::Lint,
     decorator: impl FnOnce(Vec<errors::FrameNote>) -> L,
 ) where
-    L: for<'a> rustc_errors::DecorateLint<'a, ()>,
+    L: for<'a> rustc_errors::LintDiagnostic<'a, ()>,
 {
     let (span, frames) = get_span_and_frames(tcx, machine);
 
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index afabd9689c6..249c02b75f7 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -1,7 +1,7 @@
 use std::borrow::Cow;
 
 use rustc_errors::{
-    codes::*, Diag, DiagArgValue, DiagCtxt, DiagMessage, EmissionGuarantee, IntoDiagnostic, Level,
+    codes::*, Diag, DiagArgValue, DiagCtxt, DiagMessage, Diagnostic, EmissionGuarantee, Level,
 };
 use rustc_hir::ConstContext;
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
@@ -239,7 +239,7 @@ pub(crate) struct NonConstImplNote {
     pub span: Span,
 }
 
-#[derive(Subdiagnostic, PartialEq, Eq, Clone)]
+#[derive(Subdiagnostic, Clone)]
 #[note(const_eval_frame_note)]
 pub struct FrameNote {
     #[primary_span]
@@ -858,8 +858,7 @@ impl<'tcx> ReportErrorExt for InvalidProgramInfo<'tcx> {
             InvalidProgramInfo::Layout(e) => {
                 // The level doesn't matter, `dummy_diag` is consumed without it being used.
                 let dummy_level = Level::Bug;
-                let dummy_diag: Diag<'_, ()> =
-                    e.into_diagnostic().into_diagnostic(diag.dcx, dummy_level);
+                let dummy_diag: Diag<'_, ()> = e.into_diagnostic().into_diag(diag.dcx, dummy_level);
                 for (name, val) in dummy_diag.args.iter() {
                     diag.arg(name.clone(), val.clone());
                 }
@@ -887,8 +886,8 @@ impl ReportErrorExt for ResourceExhaustionInfo {
     fn add_args<G: EmissionGuarantee>(self, _: &mut Diag<'_, G>) {}
 }
 
-impl rustc_errors::IntoDiagnosticArg for InternKind {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl rustc_errors::IntoDiagArg for InternKind {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Borrowed(match self {
             InternKind::Static(Mutability::Not) => "static",
             InternKind::Static(Mutability::Mut) => "static_mut",
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index c186d5b284f..0c3e7fb75b0 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -38,7 +38,7 @@ pub enum DiagArgValue {
     Str(Cow<'static, str>),
     // This gets converted to a `FluentNumber`, which is an `f64`. An `i32`
     // safely fits in an `f64`. Any integers bigger than that will be converted
-    // to strings in `into_diagnostic_arg` and stored using the `Str` variant.
+    // to strings in `into_diag_arg` and stored using the `Str` variant.
     Number(i32),
     StrListSepByAnd(Vec<Cow<'static, str>>),
 }
@@ -112,48 +112,48 @@ impl EmissionGuarantee for rustc_span::fatal_error::FatalError {
 /// When implemented manually, it should be generic over the emission
 /// guarantee, i.e.:
 /// ```ignore (fragment)
-/// impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for Foo { ... }
+/// impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for Foo { ... }
 /// ```
 /// rather than being specific:
 /// ```ignore (fragment)
-/// impl<'a> IntoDiagnostic<'a> for Bar { ... }  // the default type param is `ErrorGuaranteed`
-/// impl<'a> IntoDiagnostic<'a, ()> for Baz { ... }
+/// impl<'a> Diagnostic<'a> for Bar { ... }  // the default type param is `ErrorGuaranteed`
+/// impl<'a> Diagnostic<'a, ()> for Baz { ... }
 /// ```
 /// There are two reasons for this.
 /// - A diagnostic like `Foo` *could* be emitted at any level -- `level` is
-///   passed in to `into_diagnostic` from outside. Even if in practice it is
+///   passed in to `into_diag` from outside. Even if in practice it is
 ///   always emitted at a single level, we let the diagnostic creation/emission
 ///   site determine the level (by using `create_err`, `emit_warn`, etc.)
-///   rather than the `IntoDiagnostic` impl.
+///   rather than the `Diagnostic` impl.
 /// - Derived impls are always generic, and it's good for the hand-written
 ///   impls to be consistent with them.
-#[rustc_diagnostic_item = "IntoDiagnostic"]
-pub trait IntoDiagnostic<'a, G: EmissionGuarantee = ErrorGuaranteed> {
+#[rustc_diagnostic_item = "Diagnostic"]
+pub trait Diagnostic<'a, G: EmissionGuarantee = ErrorGuaranteed> {
     /// Write out as a diagnostic out of `DiagCtxt`.
     #[must_use]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G>;
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G>;
 }
 
-impl<'a, T, G> IntoDiagnostic<'a, G> for Spanned<T>
+impl<'a, T, G> Diagnostic<'a, G> for Spanned<T>
 where
-    T: IntoDiagnostic<'a, G>,
+    T: Diagnostic<'a, G>,
     G: EmissionGuarantee,
 {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
-        self.node.into_diagnostic(dcx, level).with_span(self.span)
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+        self.node.into_diag(dcx, level).with_span(self.span)
     }
 }
 
-/// Converts a value of a type into a `DiagArg` (typically a field of an `IntoDiagnostic` struct).
+/// Converts a value of a type into a `DiagArg` (typically a field of an `Diag` struct).
 /// Implemented as a custom trait rather than `From` so that it is implemented on the type being
 /// converted rather than on `DiagArgValue`, which enables types from other `rustc_*` crates to
 /// implement this.
-pub trait IntoDiagnosticArg {
-    fn into_diagnostic_arg(self) -> DiagArgValue;
+pub trait IntoDiagArg {
+    fn into_diag_arg(self) -> DiagArgValue;
 }
 
-impl IntoDiagnosticArg for DiagArgValue {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for DiagArgValue {
+    fn into_diag_arg(self) -> DiagArgValue {
         self
     }
 }
@@ -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,
@@ -193,8 +193,8 @@ pub trait SubdiagMessageOp<G> = Fn(&mut Diag<'_, G>, SubdiagMessage) -> SubdiagM
 
 /// Trait implemented by lint types. This should not be implemented manually. Instead, use
 /// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].
-#[rustc_diagnostic_item = "DecorateLint"]
-pub trait DecorateLint<'a, G: EmissionGuarantee> {
+#[rustc_diagnostic_item = "LintDiagnostic"]
+pub trait LintDiagnostic<'a, G: EmissionGuarantee> {
     /// Decorate and emit a lint.
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, G>);
 
@@ -419,8 +419,8 @@ impl DiagInner {
         self.children.push(sub);
     }
 
-    pub(crate) fn arg(&mut self, name: impl Into<DiagArgName>, arg: impl IntoDiagnosticArg) {
-        self.args.insert(name.into(), arg.into_diagnostic_arg());
+    pub(crate) fn arg(&mut self, name: impl Into<DiagArgName>, arg: impl IntoDiagArg) {
+        self.args.insert(name.into(), arg.into_diag_arg());
     }
 
     /// Fields used for Hash, and PartialEq trait.
@@ -482,7 +482,7 @@ pub struct Subdiag {
 /// - The `EmissionGuarantee`, which determines the type returned from `emit`.
 ///
 /// Each constructed `Diag` must be consumed by a function such as `emit`,
-/// `cancel`, `delay_as_bug`, or `into_diagnostic`. A panic occurrs if a `Diag`
+/// `cancel`, `delay_as_bug`, or `into_diag`. A panic occurrs if a `Diag`
 /// is dropped without being consumed by one of these functions.
 ///
 /// If there is some state in a downstream crate you would like to access in
@@ -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)
@@ -1243,7 +1243,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
     pub fn arg(
         &mut self,
         name: impl Into<DiagArgName>,
-        arg: impl IntoDiagnosticArg,
+        arg: impl IntoDiagArg,
     ) -> &mut Self {
         self.deref_mut().arg(name, arg);
         self
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index 839bd65e4a6..f90190797ae 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -1,8 +1,8 @@
 use crate::diagnostic::DiagLocation;
-use crate::{fluent_generated as fluent, AddToDiagnostic};
+use crate::{fluent_generated as fluent, Subdiagnostic};
 use crate::{
-    Diag, DiagArgValue, DiagCtxt, EmissionGuarantee, ErrCode, IntoDiagnostic, IntoDiagnosticArg,
-    Level, SubdiagMessageOp,
+    Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, ErrCode, IntoDiagArg, Level,
+    SubdiagMessageOp,
 };
 use rustc_ast as ast;
 use rustc_ast_pretty::pprust;
@@ -22,9 +22,9 @@ use std::process::ExitStatus;
 
 pub struct DiagArgFromDisplay<'a>(pub &'a dyn fmt::Display);
 
-impl IntoDiagnosticArg for DiagArgFromDisplay<'_> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.0.to_string().into_diagnostic_arg()
+impl IntoDiagArg for DiagArgFromDisplay<'_> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.0.to_string().into_diag_arg()
     }
 }
 
@@ -40,34 +40,34 @@ impl<'a, T: fmt::Display> From<&'a T> for DiagArgFromDisplay<'a> {
     }
 }
 
-impl<'a, T: Clone + IntoDiagnosticArg> IntoDiagnosticArg for &'a T {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.clone().into_diagnostic_arg()
+impl<'a, T: Clone + IntoDiagArg> IntoDiagArg for &'a T {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.clone().into_diag_arg()
     }
 }
 
-macro_rules! into_diagnostic_arg_using_display {
+macro_rules! into_diag_arg_using_display {
     ($( $ty:ty ),+ $(,)?) => {
         $(
-            impl IntoDiagnosticArg for $ty {
-                fn into_diagnostic_arg(self) -> DiagArgValue {
-                    self.to_string().into_diagnostic_arg()
+            impl IntoDiagArg for $ty {
+                fn into_diag_arg(self) -> DiagArgValue {
+                    self.to_string().into_diag_arg()
                 }
             }
         )+
     }
 }
 
-macro_rules! into_diagnostic_arg_for_number {
+macro_rules! into_diag_arg_for_number {
     ($( $ty:ty ),+ $(,)?) => {
         $(
-            impl IntoDiagnosticArg for $ty {
-                fn into_diagnostic_arg(self) -> DiagArgValue {
+            impl IntoDiagArg for $ty {
+                fn into_diag_arg(self) -> DiagArgValue {
                     // Convert to a string if it won't fit into `Number`.
                     if let Ok(n) = TryInto::<i32>::try_into(self) {
                         DiagArgValue::Number(n)
                     } else {
-                        self.to_string().into_diagnostic_arg()
+                        self.to_string().into_diag_arg()
                     }
                 }
             }
@@ -75,7 +75,7 @@ macro_rules! into_diagnostic_arg_for_number {
     }
 }
 
-into_diagnostic_arg_using_display!(
+into_diag_arg_using_display!(
     ast::ParamKindOrd,
     std::io::Error,
     Box<dyn std::error::Error>,
@@ -92,10 +92,10 @@ into_diagnostic_arg_using_display!(
     ErrCode,
 );
 
-into_diagnostic_arg_for_number!(i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize, usize);
+into_diag_arg_for_number!(i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize, usize);
 
-impl IntoDiagnosticArg for bool {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for bool {
+    fn into_diag_arg(self) -> DiagArgValue {
         if self {
             DiagArgValue::Str(Cow::Borrowed("true"))
         } else {
@@ -104,64 +104,64 @@ impl IntoDiagnosticArg for bool {
     }
 }
 
-impl IntoDiagnosticArg for char {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for char {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(format!("{self:?}")))
     }
 }
 
-impl IntoDiagnosticArg for Vec<char> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for Vec<char> {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::StrListSepByAnd(
             self.into_iter().map(|c| Cow::Owned(format!("{c:?}"))).collect(),
         )
     }
 }
 
-impl IntoDiagnosticArg for Symbol {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_ident_string().into_diagnostic_arg()
+impl IntoDiagArg for Symbol {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_ident_string().into_diag_arg()
     }
 }
 
-impl<'a> IntoDiagnosticArg for &'a str {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'a> IntoDiagArg for &'a str {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
-impl IntoDiagnosticArg for String {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for String {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self))
     }
 }
 
-impl<'a> IntoDiagnosticArg for Cow<'a, str> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl<'a> IntoDiagArg for Cow<'a, str> {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.into_owned()))
     }
 }
 
-impl<'a> IntoDiagnosticArg for &'a Path {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl<'a> IntoDiagArg for &'a Path {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.display().to_string()))
     }
 }
 
-impl IntoDiagnosticArg for PathBuf {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for PathBuf {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.display().to_string()))
     }
 }
 
-impl IntoDiagnosticArg for PanicStrategy {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for PanicStrategy {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.desc().to_string()))
     }
 }
 
-impl IntoDiagnosticArg for hir::ConstContext {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for hir::ConstContext {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Borrowed(match self {
             hir::ConstContext::ConstFn => "const_fn",
             hir::ConstContext::Static(_) => "static",
@@ -170,58 +170,58 @@ impl IntoDiagnosticArg for hir::ConstContext {
     }
 }
 
-impl IntoDiagnosticArg for ast::Expr {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for ast::Expr {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(pprust::expr_to_string(&self)))
     }
 }
 
-impl IntoDiagnosticArg for ast::Path {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for ast::Path {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))
     }
 }
 
-impl IntoDiagnosticArg for ast::token::Token {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for ast::token::Token {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(pprust::token_to_string(&self))
     }
 }
 
-impl IntoDiagnosticArg for ast::token::TokenKind {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for ast::token::TokenKind {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(pprust::token_kind_to_string(&self))
     }
 }
 
-impl IntoDiagnosticArg for type_ir::FloatTy {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for type_ir::FloatTy {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Borrowed(self.name_str()))
     }
 }
 
-impl IntoDiagnosticArg for std::ffi::CString {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for std::ffi::CString {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
     }
 }
 
-impl IntoDiagnosticArg for rustc_data_structures::small_c_str::SmallCStr {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for rustc_data_structures::small_c_str::SmallCStr {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
     }
 }
 
-impl IntoDiagnosticArg for ast::Visibility {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for ast::Visibility {
+    fn into_diag_arg(self) -> DiagArgValue {
         let s = pprust::vis_to_string(&self);
         let s = s.trim_end().to_string();
         DiagArgValue::Str(Cow::Owned(s))
     }
 }
 
-impl IntoDiagnosticArg for rustc_lint_defs::Level {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for rustc_lint_defs::Level {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Borrowed(self.to_cmd_flag()))
     }
 }
@@ -235,22 +235,22 @@ impl From<Vec<Symbol>> for DiagSymbolList {
     }
 }
 
-impl IntoDiagnosticArg for DiagSymbolList {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for DiagSymbolList {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::StrListSepByAnd(
             self.0.into_iter().map(|sym| Cow::Owned(format!("`{sym}`"))).collect(),
         )
     }
 }
 
-impl<Id> IntoDiagnosticArg for hir::def::Res<Id> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl<Id> IntoDiagArg for hir::def::Res<Id> {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Borrowed(self.descr()))
     }
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TargetDataLayoutErrors<'_> {
-    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetDataLayoutErrors<'_> {
+    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
         match self {
             TargetDataLayoutErrors::InvalidAddressSpace { addr_space, err, cause } => {
                 Diag::new(dcx, level, fluent::errors_target_invalid_address_space)
@@ -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,
@@ -315,20 +315,20 @@ pub struct ExpectedLifetimeParameter {
     pub count: usize,
 }
 
-impl IntoDiagnosticArg for DiagLocation {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for DiagLocation {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::from(self.to_string()))
     }
 }
 
-impl IntoDiagnosticArg for Backtrace {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for Backtrace {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::from(self.to_string()))
     }
 }
 
-impl IntoDiagnosticArg for Level {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for Level {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::from(self.to_string()))
     }
 }
@@ -342,8 +342,8 @@ pub struct IndicateAnonymousLifetime {
     pub suggestion: String,
 }
 
-impl IntoDiagnosticArg for type_ir::ClosureKind {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for type_ir::ClosureKind {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(self.as_str().into())
     }
 }
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 76b44f73f47..bedb677c1e9 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, EmissionGuarantee, FatalAbort, IntoDiagnostic, IntoDiagnosticArg,
-    StringPart, Subdiag, SubdiagMessageOp,
+    BugAbort, Diag, DiagArg, DiagArgMap, DiagArgName, DiagArgValue, DiagInner, DiagStyledString,
+    Diagnostic, EmissionGuarantee, FatalAbort, IntoDiagArg, LintDiagnostic, StringPart, Subdiag,
+    SubdiagMessageOp, Subdiagnostic,
 };
 pub use diagnostic_impls::{
     DiagArgFromDisplay, DiagSymbolList, ExpectedLifetimeParameter, IndicateAnonymousLifetime,
@@ -1134,12 +1134,12 @@ impl DiagCtxt {
     }
 
     #[track_caller]
-    pub fn create_bug<'a>(&'a self, bug: impl IntoDiagnostic<'a, BugAbort>) -> Diag<'a, BugAbort> {
-        bug.into_diagnostic(self, Bug)
+    pub fn create_bug<'a>(&'a 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 IntoDiagnostic<'a, BugAbort>) -> ! {
+    pub fn emit_bug<'a>(&'a self, bug: impl Diagnostic<'a, BugAbort>) -> ! {
         self.create_bug(bug).emit()
     }
 
@@ -1174,29 +1174,26 @@ impl DiagCtxt {
     #[track_caller]
     pub fn create_fatal<'a>(
         &'a self,
-        fatal: impl IntoDiagnostic<'a, FatalAbort>,
+        fatal: impl Diagnostic<'a, FatalAbort>,
     ) -> Diag<'a, FatalAbort> {
-        fatal.into_diagnostic(self, Fatal)
+        fatal.into_diag(self, Fatal)
     }
 
     #[track_caller]
-    pub fn emit_fatal<'a>(&'a self, fatal: impl IntoDiagnostic<'a, FatalAbort>) -> ! {
+    pub fn emit_fatal<'a>(&'a self, fatal: impl Diagnostic<'a, FatalAbort>) -> ! {
         self.create_fatal(fatal).emit()
     }
 
     #[track_caller]
     pub fn create_almost_fatal<'a>(
         &'a self,
-        fatal: impl IntoDiagnostic<'a, FatalError>,
+        fatal: impl Diagnostic<'a, FatalError>,
     ) -> Diag<'a, FatalError> {
-        fatal.into_diagnostic(self, Fatal)
+        fatal.into_diag(self, Fatal)
     }
 
     #[track_caller]
-    pub fn emit_almost_fatal<'a>(
-        &'a self,
-        fatal: impl IntoDiagnostic<'a, FatalError>,
-    ) -> FatalError {
+    pub fn emit_almost_fatal<'a>(&'a self, fatal: impl Diagnostic<'a, FatalError>) -> FatalError {
         self.create_almost_fatal(fatal).emit()
     }
 
@@ -1234,12 +1231,12 @@ impl DiagCtxt {
     }
 
     #[track_caller]
-    pub fn create_err<'a>(&'a self, err: impl IntoDiagnostic<'a>) -> Diag<'a> {
-        err.into_diagnostic(self, Error)
+    pub fn create_err<'a>(&'a self, err: impl Diagnostic<'a>) -> Diag<'a> {
+        err.into_diag(self, Error)
     }
 
     #[track_caller]
-    pub fn emit_err<'a>(&'a self, err: impl IntoDiagnostic<'a>) -> ErrorGuaranteed {
+    pub fn emit_err<'a>(&'a self, err: impl Diagnostic<'a>) -> ErrorGuaranteed {
         self.create_err(err).emit()
     }
 
@@ -1297,12 +1294,12 @@ impl DiagCtxt {
     }
 
     #[track_caller]
-    pub fn create_warn<'a>(&'a self, warning: impl IntoDiagnostic<'a, ()>) -> Diag<'a, ()> {
-        warning.into_diagnostic(self, Warning)
+    pub fn create_warn<'a>(&'a self, warning: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
+        warning.into_diag(self, Warning)
     }
 
     #[track_caller]
-    pub fn emit_warn<'a>(&'a self, warning: impl IntoDiagnostic<'a, ()>) {
+    pub fn emit_warn<'a>(&'a self, warning: impl Diagnostic<'a, ()>) {
         self.create_warn(warning).emit()
     }
 
@@ -1335,12 +1332,12 @@ impl DiagCtxt {
     }
 
     #[track_caller]
-    pub fn create_note<'a>(&'a self, note: impl IntoDiagnostic<'a, ()>) -> Diag<'a, ()> {
-        note.into_diagnostic(self, Note)
+    pub fn create_note<'a>(&'a self, note: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
+        note.into_diag(self, Note)
     }
 
     #[track_caller]
-    pub fn emit_note<'a>(&'a self, note: impl IntoDiagnostic<'a, ()>) {
+    pub fn emit_note<'a>(&'a self, note: impl Diagnostic<'a, ()>) {
         self.create_note(note).emit()
     }
 
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 7d5b4c0f06d..18dabe67dae 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1510,7 +1510,7 @@ impl fmt::Display for ConstContext {
     }
 }
 
-// NOTE: `IntoDiagnosticArg` impl for `ConstContext` lives in `rustc_errors`
+// NOTE: `IntoDiagArg` impl for `ConstContext` lives in `rustc_errors`
 // due to a cyclical dependency between hir that crate.
 
 /// A literal.
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 26349cd1c65..175991b1be2 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, EmissionGuarantee, IntoDiagnostic, Level, MultiSpan,
+    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level, MultiSpan,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
@@ -355,10 +355,10 @@ pub struct MissingTypeParams {
     pub empty_generic_args: bool,
 }
 
-// Manual implementation of `IntoDiagnostic` to be able to call `span_to_snippet`.
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for 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_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: &'a DiagCtxt, 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/errors.rs b/compiler/rustc_hir_typeck/src/errors.rs
index 502b9ba6451..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,
-    IntoDiagnosticArg, MultiSpan, SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagArgValue, EmissionGuarantee, IntoDiagArg, MultiSpan,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
@@ -42,8 +42,8 @@ pub enum ReturnLikeStatementKind {
     Become,
 }
 
-impl IntoDiagnosticArg for ReturnLikeStatementKind {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for ReturnLikeStatementKind {
+    fn into_diag_arg(self) -> DiagArgValue {
         let kind = match self {
             Self::Return => "return",
             Self::Become => "become",
@@ -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 af09ac2de96..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, IntoDiagnosticArg, 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,
@@ -537,11 +537,11 @@ pub enum TyOrSig<'tcx> {
     ClosureSig(Highlighted<'tcx, Binder<'tcx, FnSig<'tcx>>>),
 }
 
-impl IntoDiagnosticArg for TyOrSig<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for TyOrSig<'_> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         match self {
-            TyOrSig::Ty(ty) => ty.into_diagnostic_arg(),
-            TyOrSig::ClosureSig(sig) => sig.into_diagnostic_arg(),
+            TyOrSig::Ty(ty) => ty.into_diag_arg(),
+            TyOrSig::ClosureSig(sig) => sig.into_diag_arg(),
         }
     }
 }
@@ -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 7bb71d47031..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, IntoDiagnosticArg, SubdiagMessageOp};
+use rustc_errors::{Diag, EmissionGuarantee, IntoDiagArg, SubdiagMessageOp, Subdiagnostic};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::{symbol::kw, Span};
 
@@ -107,8 +107,8 @@ pub enum SuffixKind {
     ReqByBinding,
 }
 
-impl IntoDiagnosticArg for PrefixKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for PrefixKind {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         let kind = match self {
             Self::Empty => "empty",
             Self::RefValidFor => "ref_valid_for",
@@ -129,8 +129,8 @@ impl IntoDiagnosticArg for PrefixKind {
     }
 }
 
-impl IntoDiagnosticArg for SuffixKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for SuffixKind {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         let kind = match self {
             Self::Empty => "empty",
             Self::Continues => "continues",
@@ -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/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index ea5c6b8c057..222c0a39542 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -61,7 +61,7 @@ use crate::traits::{
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{
     codes::*, pluralize, struct_span_code_err, Applicability, Diag, DiagCtxt, DiagStyledString,
-    ErrorGuaranteed, IntoDiagnosticArg,
+    ErrorGuaranteed, IntoDiagArg,
 };
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
@@ -2895,11 +2895,11 @@ impl<'tcx> ObligationCause<'tcx> {
     }
 }
 
-/// Newtype to allow implementing IntoDiagnosticArg
+/// Newtype to allow implementing IntoDiagArg
 pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
 
-impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         use crate::traits::ObligationCauseCode::*;
         let kind = match self.0.code() {
             CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index 6c968c488fe..13e2152e45e 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -5,7 +5,7 @@ use crate::errors::{
 use crate::infer::error_reporting::TypeErrCtxt;
 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::InferCtxt;
-use rustc_errors::{codes::*, Diag, IntoDiagnosticArg};
+use rustc_errors::{codes::*, Diag, IntoDiagArg};
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::def::{CtorOf, DefKind, Namespace};
@@ -133,8 +133,8 @@ impl InferenceDiagnosticsParentData {
     }
 }
 
-impl IntoDiagnosticArg for UnderspecifiedArgKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for UnderspecifiedArgKind {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         let kind = match self {
             Self::Type { .. } => "type",
             Self::Const { is_parameter: true } => "const_with_param",
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/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index d6595a0c114..98719e240bd 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -8,7 +8,7 @@ use crate::infer::ValuePairs;
 use crate::infer::{SubregionOrigin, TypeTrace};
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::intern::Interned;
-use rustc_errors::{Diag, IntoDiagnosticArg};
+use rustc_errors::{Diag, IntoDiagArg};
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::error::ExpectedFound;
@@ -26,11 +26,11 @@ pub struct Highlighted<'tcx, T> {
     value: T,
 }
 
-impl<'tcx, T> IntoDiagnosticArg for Highlighted<'tcx, T>
+impl<'tcx, T> IntoDiagArg for Highlighted<'tcx, T>
 where
     T: for<'a> Print<'tcx, FmtPrinter<'a, 'tcx>>,
 {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         rustc_errors::DiagArgValue::Str(self.to_string().into())
     }
 }
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 8bf9d0b9d4a..d938a0ccb39 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 `IntoDiagnostic`/`AddToDiagnostic` impls
+    diagnostics should only be created in `Diagnostic`/`Subdiagnostic`/`LintDiagnostic` 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/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 5f0af6aee6a..595dc08b081 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -44,7 +44,7 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast::visit::{FnCtxt, FnKind};
 use rustc_ast::{self as ast, *};
 use rustc_ast_pretty::pprust::{self, expr_to_string};
-use rustc_errors::{Applicability, DecorateLint, MultiSpan};
+use rustc_errors::{Applicability, LintDiagnostic, MultiSpan};
 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
@@ -327,7 +327,7 @@ impl UnsafeCode {
         &self,
         cx: &EarlyContext<'_>,
         span: Span,
-        decorate: impl for<'a> DecorateLint<'a, ()>,
+        decorate: impl for<'a> LintDiagnostic<'a, ()>,
     ) {
         // This comes from a macro that has `#[allow_internal_unsafe]`.
         if span.allows_unsafe() {
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 89cdde11726..8c0e5b17fd8 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -21,7 +21,7 @@ use crate::passes::{EarlyLintPassObject, LateLintPassObject};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync;
 use rustc_data_structures::unord::UnordMap;
-use rustc_errors::{DecorateLint, Diag, DiagMessage, MultiSpan};
+use rustc_errors::{Diag, DiagMessage, LintDiagnostic, MultiSpan};
 use rustc_feature::Features;
 use rustc_hir as hir;
 use rustc_hir::def::Res;
@@ -563,13 +563,13 @@ pub trait LintContext {
         decorate: impl for<'a, 'b> FnOnce(&'b mut Diag<'a, ()>),
     );
 
-    /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
+    /// Emit a lint at `span` from a lint struct (some type that implements `LintDiagnostic`,
     /// typically generated by `#[derive(LintDiagnostic)]`).
     fn emit_span_lint<S: Into<MultiSpan>>(
         &self,
         lint: &'static Lint,
         span: S,
-        decorator: impl for<'a> DecorateLint<'a, ()>,
+        decorator: impl for<'a> LintDiagnostic<'a, ()>,
     ) {
         self.opt_span_lint(lint, Some(span), decorator.msg(), |diag| {
             decorator.decorate_lint(diag);
@@ -590,9 +590,9 @@ pub trait LintContext {
         self.opt_span_lint(lint, Some(span), msg, decorate);
     }
 
-    /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
+    /// Emit a lint from a lint struct (some type that implements `LintDiagnostic`, typically
     /// generated by `#[derive(LintDiagnostic)]`).
-    fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
+    fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> LintDiagnostic<'a, ()>) {
         self.opt_span_lint(lint, None as Option<Span>, decorator.msg(), |diag| {
             decorator.decorate_lint(diag);
         });
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 e8fcf4132ea..0872a8a2095 100644
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@@ -351,15 +351,14 @@ 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 `IntoDiagnostic`, `AddToDiagnostic`, or
-    /// `DecorateLint` impl, or a `#[derive(Diagnostic)]`, `#[derive(Subdiagnostic)]`,
-    /// `#[derive(DecorateLint)]` expansion.
+    /// `#[rustc_lint_diagnostics]` that are outside an `Diagnostic`, `Subdiagnostic`, or
+    /// `LintDiagnostic` impl (either hand-written or derived).
     ///
     /// More details on diagnostics implementations can be found
     /// [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 `IntoDiagnostic`/`AddToDiagnostic` impls",
+    "prevent diagnostic creation outside of `Diagnostic`/`Subdiagnostic`/`LintDiagnostic` impls",
     report_in_external_macro: true
 }
 
@@ -455,7 +454,7 @@ impl LateLintPass<'_> for Diagnostics {
         }
 
         // Calls to `#[rustc_lint_diagnostics]`-marked functions should only occur:
-        // - inside an impl of `IntoDiagnostic`, `AddToDiagnostic`, or `DecorateLint`, or
+        // - inside an impl of `Diagnostic`, `Subdiagnostic`, or `LintDiagnostic`, or
         // - inside a parent function that is itself marked with `#[rustc_lint_diagnostics]`.
         //
         // Otherwise, emit a `DIAGNOSTIC_OUTSIDE_OF_IMPL` lint.
@@ -467,10 +466,7 @@ 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::IntoDiagnostic | sym::AddToDiagnostic | sym::DecorateLint
-                    )
+                    && matches!(name, sym::Diagnostic | sym::Subdiagnostic | sym::LintDiagnostic)
                 {
                     is_inside_appropriate_impl = true;
                     break;
diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index 2f08cd53b75..e89df1c9840 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -16,7 +16,7 @@ use crate::{
 use rustc_ast as ast;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_errors::{DecorateLint, Diag, DiagMessage, MultiSpan};
+use rustc_errors::{Diag, DiagMessage, LintDiagnostic, MultiSpan};
 use rustc_feature::{Features, GateIssue};
 use rustc_hir as hir;
 use rustc_hir::intravisit::{self, Visitor};
@@ -1119,7 +1119,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         &self,
         lint: &'static Lint,
         span: MultiSpan,
-        decorate: impl for<'a> DecorateLint<'a, ()>,
+        decorate: impl for<'a> LintDiagnostic<'a, ()>,
     ) {
         let (level, src) = self.lint_level(lint);
         lint_level(self.sess, lint, level, src, Some(span), decorate.msg(), |lint| {
@@ -1128,7 +1128,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     }
 
     #[track_caller]
-    pub fn emit_lint(&self, lint: &'static Lint, decorate: impl for<'a> DecorateLint<'a, ()>) {
+    pub fn emit_lint(&self, lint: &'static Lint, decorate: impl for<'a> LintDiagnostic<'a, ()>) {
         let (level, src) = self.lint_level(lint);
         lint_level(self.sess, lint, level, src, None, decorate.msg(), |lint| {
             decorate.decorate_lint(lint);
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 7e0ac1bfff1..1dac2d89c6b 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, Diag, DiagMessage, DiagStyledString, EmissionGuarantee,
+    LintDiagnostic, SubdiagMessageOp, Subdiagnostic, SuggestionStyle,
 };
 use rustc_hir::def_id::DefId;
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
@@ -136,7 +136,7 @@ pub struct BuiltinMissingDebugImpl<'a> {
 }
 
 // Needed for def_path_str
-impl<'a> DecorateLint<'a, ()> for BuiltinMissingDebugImpl<'_> {
+impl<'a> LintDiagnostic<'a, ()> for BuiltinMissingDebugImpl<'_> {
     fn decorate_lint<'b>(self, diag: &'b mut rustc_errors::Diag<'a, ()>) {
         diag.arg("debug", self.tcx.def_path_str(self.def_id));
     }
@@ -241,7 +241,7 @@ pub struct BuiltinUngatedAsyncFnTrackCaller<'a> {
     pub session: &'a Session,
 }
 
-impl<'a> DecorateLint<'a, ()> for BuiltinUngatedAsyncFnTrackCaller<'_> {
+impl<'a> LintDiagnostic<'a, ()> for BuiltinUngatedAsyncFnTrackCaller<'_> {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.span_label(self.label, fluent::lint_label);
         rustc_session::parse::add_feature_diagnostics(
@@ -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,
@@ -423,7 +423,7 @@ pub struct BuiltinUnpermittedTypeInit<'a> {
     pub tcx: TyCtxt<'a>,
 }
 
-impl<'a> DecorateLint<'a, ()> for BuiltinUnpermittedTypeInit<'_> {
+impl<'a> LintDiagnostic<'a, ()> for BuiltinUnpermittedTypeInit<'_> {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.arg("ty", self.ty);
         diag.span_label(self.label, fluent::lint_builtin_unpermitted_type_init_label);
@@ -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,
@@ -1159,7 +1159,7 @@ pub struct NonFmtPanicUnused {
 }
 
 // Used because of two suggestions based on one Option<Span>
-impl<'a> DecorateLint<'a, ()> for NonFmtPanicUnused {
+impl<'a> LintDiagnostic<'a, ()> for NonFmtPanicUnused {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.arg("count", self.count);
         diag.note(fluent::lint_note);
@@ -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,
@@ -1397,7 +1397,7 @@ pub struct DropTraitConstraintsDiag<'a> {
 }
 
 // Needed for def_path_str
-impl<'a> DecorateLint<'a, ()> for DropTraitConstraintsDiag<'_> {
+impl<'a> LintDiagnostic<'a, ()> for DropTraitConstraintsDiag<'_> {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.arg("predicate", self.predicate);
         diag.arg("needs_drop", self.tcx.def_path_str(self.def_id));
@@ -1414,7 +1414,7 @@ pub struct DropGlue<'a> {
 }
 
 // Needed for def_path_str
-impl<'a> DecorateLint<'a, ()> for DropGlue<'_> {
+impl<'a> LintDiagnostic<'a, ()> for DropGlue<'_> {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.arg("needs_drop", self.tcx.def_path_str(self.def_id));
     }
@@ -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,
@@ -1689,7 +1689,7 @@ pub struct ImproperCTypes<'a> {
 }
 
 // Used because of the complexity of Option<DiagMessage>, DiagMessage, and Option<Span>
-impl<'a> DecorateLint<'a, ()> for ImproperCTypes<'_> {
+impl<'a> LintDiagnostic<'a, ()> for ImproperCTypes<'_> {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.arg("ty", self.ty);
         diag.arg("desc", self.desc);
@@ -1832,7 +1832,7 @@ pub enum UnusedDefSuggestion {
 }
 
 // Needed because of def_path_str
-impl<'a> DecorateLint<'a, ()> for UnusedDef<'_, '_> {
+impl<'a> LintDiagnostic<'a, ()> for UnusedDef<'_, '_> {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.arg("pre", self.pre);
         diag.arg("post", self.post);
@@ -1915,7 +1915,7 @@ pub struct AsyncFnInTraitDiag {
     pub sugg: Option<Vec<(Span, String)>>,
 }
 
-impl<'a> DecorateLint<'a, ()> for AsyncFnInTraitDiag {
+impl<'a> LintDiagnostic<'a, ()> for AsyncFnInTraitDiag {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.note(fluent::lint_note);
         if let Some(sugg) = self.sugg {
diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic.rs b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
index a1a7b19642b..9d21d88165e 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
@@ -10,7 +10,7 @@ use quote::quote;
 use syn::spanned::Spanned;
 use synstructure::Structure;
 
-/// The central struct for constructing the `into_diagnostic` method from an annotated struct.
+/// The central struct for constructing the `into_diag` method from an annotated struct.
 pub(crate) struct DiagnosticDerive<'a> {
     structure: Structure<'a>,
 }
@@ -72,14 +72,11 @@ impl<'a> DiagnosticDerive<'a> {
 
         // A lifetime of `'a` causes conflicts, but `_sess` is fine.
         let mut imp = structure.gen_impl(quote! {
-            gen impl<'_sess, G>
-                    rustc_errors::IntoDiagnostic<'_sess, G>
-                    for @Self
+            gen impl<'_sess, G> rustc_errors::Diagnostic<'_sess, G> for @Self
                 where G: rustc_errors::EmissionGuarantee
             {
-
                 #[track_caller]
-                fn into_diagnostic(
+                fn into_diag(
                     self,
                     dcx: &'_sess rustc_errors::DiagCtxt,
                     level: rustc_errors::Level
@@ -156,7 +153,7 @@ impl<'a> LintDiagnosticDerive<'a> {
         });
 
         let mut imp = structure.gen_impl(quote! {
-            gen impl<'__a> rustc_errors::DecorateLint<'__a, ()> for @Self {
+            gen impl<'__a> rustc_errors::LintDiagnostic<'__a, ()> for @Self {
                 #[track_caller]
                 fn decorate_lint<'__b>(
                     self,
diff --git a/compiler/rustc_macros/src/diagnostics/mod.rs b/compiler/rustc_macros/src/diagnostics/mod.rs
index 044bbadf41c..389d88bebc7 100644
--- a/compiler/rustc_macros/src/diagnostics/mod.rs
+++ b/compiler/rustc_macros/src/diagnostics/mod.rs
@@ -6,7 +6,7 @@ mod utils;
 
 use diagnostic::{DiagnosticDerive, LintDiagnosticDerive};
 use proc_macro2::TokenStream;
-use subdiagnostic::SubdiagnosticDeriveBuilder;
+use subdiagnostic::SubdiagnosticDerive;
 use synstructure::Structure;
 
 /// Implements `#[derive(Diagnostic)]`, which allows for errors to be specified as a struct,
@@ -55,7 +55,7 @@ use synstructure::Structure;
 ///
 /// See rustc dev guide for more examples on using the `#[derive(Diagnostic)]`:
 /// <https://rustc-dev-guide.rust-lang.org/diagnostics/diagnostic-structs.html>
-pub fn session_diagnostic_derive(mut s: Structure<'_>) -> TokenStream {
+pub fn diagnostic_derive(mut s: Structure<'_>) -> TokenStream {
     s.underscore_const(true);
     DiagnosticDerive::new(s).into_tokens()
 }
@@ -153,7 +153,7 @@ pub fn lint_diagnostic_derive(mut s: Structure<'_>) -> TokenStream {
 ///
 /// diag.subdiagnostic(RawIdentifierSuggestion { span, applicability, ident });
 /// ```
-pub fn session_subdiagnostic_derive(mut s: Structure<'_>) -> TokenStream {
+pub fn subdiagnostic_derive(mut s: Structure<'_>) -> TokenStream {
     s.underscore_const(true);
-    SubdiagnosticDeriveBuilder::new().into_tokens(s)
+    SubdiagnosticDerive::new().into_tokens(s)
 }
diff --git a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
index ef326106404..ced782cdbc0 100644
--- a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
@@ -16,13 +16,13 @@ use synstructure::{BindingInfo, Structure, VariantInfo};
 
 use super::utils::SubdiagnosticVariant;
 
-/// The central struct for constructing the `add_to_diagnostic` method from an annotated struct.
-pub(crate) struct SubdiagnosticDeriveBuilder {
+/// The central struct for constructing the `add_to_diag` method from an annotated struct.
+pub(crate) struct SubdiagnosticDerive {
     diag: syn::Ident,
     f: syn::Ident,
 }
 
-impl SubdiagnosticDeriveBuilder {
+impl SubdiagnosticDerive {
     pub(crate) fn new() -> Self {
         let diag = format_ident!("diag");
         let f = format_ident!("f");
@@ -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
@@ -109,7 +109,7 @@ impl SubdiagnosticDeriveBuilder {
 /// double mut borrow later on.
 struct SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
     /// The identifier to use for the generated `Diag` instance.
-    parent: &'parent SubdiagnosticDeriveBuilder,
+    parent: &'parent SubdiagnosticDerive,
 
     /// Info for the current variant (or the type if not an enum).
     variant: &'a VariantInfo<'a>,
diff --git a/compiler/rustc_macros/src/lib.rs b/compiler/rustc_macros/src/lib.rs
index 14e6a06839e..eedc508fb14 100644
--- a/compiler/rustc_macros/src/lib.rs
+++ b/compiler/rustc_macros/src/lib.rs
@@ -118,7 +118,7 @@ decl_derive!(
         suggestion,
         suggestion_short,
         suggestion_hidden,
-        suggestion_verbose)] => diagnostics::session_diagnostic_derive
+        suggestion_verbose)] => diagnostics::diagnostic_derive
 );
 decl_derive!(
     [LintDiagnostic, attributes(
@@ -156,5 +156,5 @@ decl_derive!(
         skip_arg,
         primary_span,
         suggestion_part,
-        applicability)] => diagnostics::session_subdiagnostic_derive
+        applicability)] => diagnostics::subdiagnostic_derive
 );
diff --git a/compiler/rustc_metadata/src/errors.rs b/compiler/rustc_metadata/src/errors.rs
index b18ec85ca11..8bf6b665de8 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, EmissionGuarantee, IntoDiagnostic, Level};
+use rustc_errors::{codes::*, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::Diagnostic;
 use rustc_session::config;
 use rustc_span::{sym, Span, Symbol};
@@ -495,8 +495,8 @@ pub(crate) struct MultipleCandidates {
     pub candidates: Vec<PathBuf>,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for MultipleCandidates {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for MultipleCandidates {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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);
@@ -593,9 +593,9 @@ pub struct InvalidMetadataFiles {
     pub crate_rejections: Vec<String>,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for InvalidMetadataFiles {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for InvalidMetadataFiles {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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);
@@ -622,9 +622,9 @@ pub struct CannotFindCrate {
     pub is_ui_testing: bool,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for CannotFindCrate {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for CannotFindCrate {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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_metadata/src/locator.rs b/compiler/rustc_metadata/src/locator.rs
index 10bbebb3871..7de03be6da6 100644
--- a/compiler/rustc_metadata/src/locator.rs
+++ b/compiler/rustc_metadata/src/locator.rs
@@ -220,7 +220,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::owned_slice::slice_owned;
 use rustc_data_structures::svh::Svh;
-use rustc_errors::{DiagArgValue, IntoDiagnosticArg};
+use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_fs_util::try_canonicalize;
 use rustc_session::config;
 use rustc_session::cstore::CrateSource;
@@ -290,8 +290,8 @@ impl fmt::Display for CrateFlavor {
     }
 }
 
-impl IntoDiagnosticArg for CrateFlavor {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for CrateFlavor {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         match self {
             CrateFlavor::Rlib => DiagArgValue::Str(Cow::Borrowed("rlib")),
             CrateFlavor::Rmeta => DiagArgValue::Str(Cow::Borrowed("rmeta")),
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index aea88c4588b..751d6de83f9 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -6,7 +6,7 @@ use crate::ty::{layout, tls, Ty, TyCtxt, ValTree};
 
 use rustc_ast_ir::Mutability;
 use rustc_data_structures::sync::Lock;
-use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagnosticArg};
+use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagArg};
 use rustc_macros::HashStable;
 use rustc_session::CtfeBacktrace;
 use rustc_span::{def_id::DefId, Span, DUMMY_SP};
@@ -234,8 +234,8 @@ pub enum InvalidMetaKind {
     TooBig,
 }
 
-impl IntoDiagnosticArg for InvalidMetaKind {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for InvalidMetaKind {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Borrowed(match self {
             InvalidMetaKind::SliceTooBig => "slice_too_big",
             InvalidMetaKind::TooBig => "too_big",
@@ -266,10 +266,10 @@ pub struct Misalignment {
     pub required: Align,
 }
 
-macro_rules! impl_into_diagnostic_arg_through_debug {
+macro_rules! impl_into_diag_arg_through_debug {
     ($($ty:ty),*$(,)?) => {$(
-        impl IntoDiagnosticArg for $ty {
-            fn into_diagnostic_arg(self) -> DiagArgValue {
+        impl IntoDiagArg for $ty {
+            fn into_diag_arg(self) -> DiagArgValue {
                 DiagArgValue::Str(Cow::Owned(format!("{self:?}")))
             }
         }
@@ -277,7 +277,7 @@ macro_rules! impl_into_diagnostic_arg_through_debug {
 }
 
 // These types have nice `Debug` output so we can just use them in diagnostics.
-impl_into_diagnostic_arg_through_debug! {
+impl_into_diag_arg_through_debug! {
     AllocId,
     Pointer<AllocId>,
     AllocRange,
@@ -370,8 +370,8 @@ pub enum PointerKind {
     Box,
 }
 
-impl IntoDiagnosticArg for PointerKind {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for PointerKind {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(
             match self {
                 Self::Ref(_) => "ref",
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index 5be09b06d9e..94b9afa1dee 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -100,7 +100,7 @@ macro_rules! err_ub_custom {
                 msg: || $msg,
                 add_args: Box::new(move |mut set_arg| {
                     $($(
-                        set_arg(stringify!($name).into(), rustc_errors::IntoDiagnosticArg::into_diagnostic_arg($name));
+                        set_arg(stringify!($name).into(), rustc_errors::IntoDiagArg::into_diag_arg($name));
                     )*)?
                 })
             }
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 0221bc6c363..4b5a08d6af3 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -14,7 +14,7 @@ use crate::ty::{AdtDef, InstanceDef, UserTypeAnnotationIndex};
 use crate::ty::{GenericArg, GenericArgsRef};
 
 use rustc_data_structures::captures::Captures;
-use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagnosticArg};
+use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagArg};
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::def_id::{DefId, CRATE_DEF_ID};
 use rustc_hir::{self, CoroutineDesugaring, CoroutineKind, ImplicitSelfKind};
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index a4a4df55c48..94f8cba6fb5 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -311,7 +311,7 @@ impl<O> AssertKind<O> {
 
         macro_rules! add {
             ($name: expr, $value: expr) => {
-                adder($name.into(), $value.into_diagnostic_arg());
+                adder($name.into(), $value.into_diag_arg());
             };
         }
 
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 913d0072c29..74b47d8b04e 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -9,7 +9,7 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/thir.html
 
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
-use rustc_errors::{DiagArgValue, IntoDiagnosticArg};
+use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::RangeEnd;
@@ -676,9 +676,9 @@ impl<'tcx> Pat<'tcx> {
     }
 }
 
-impl<'tcx> IntoDiagnosticArg for Pat<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        format!("{self}").into_diagnostic_arg()
+impl<'tcx> IntoDiagArg for Pat<'tcx> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        format!("{self}").into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index 221a9ceee1a..a70e01645f4 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -1,6 +1,6 @@
 use rustc_apfloat::ieee::{Double, Single};
 use rustc_apfloat::Float;
-use rustc_errors::{DiagArgValue, IntoDiagnosticArg};
+use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_target::abi::Size;
 use std::fmt;
@@ -114,10 +114,10 @@ impl std::fmt::Debug for ConstInt {
     }
 }
 
-impl IntoDiagnosticArg for ConstInt {
+impl IntoDiagArg for ConstInt {
     // FIXME this simply uses the Debug impl, but we could probably do better by converting both
     // to an inherent method that returns `Cow`.
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(format!("{self:?}").into())
     }
 }
diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index b35682df2c8..705987d92fe 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -14,9 +14,9 @@ pub struct UnevaluatedConst<'tcx> {
     pub args: GenericArgsRef<'tcx>,
 }
 
-impl rustc_errors::IntoDiagnosticArg for UnevaluatedConst<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
-        format!("{self:?}").into_diagnostic_arg()
+impl rustc_errors::IntoDiagArg for UnevaluatedConst<'_> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
+        format!("{self:?}").into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 0855f6c53fc..b08e5df30ef 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -43,7 +43,7 @@ use rustc_data_structures::sync::{self, FreezeReadGuard, Lock, Lrc, WorkerLocal}
 #[cfg(parallel_compiler)]
 use rustc_data_structures::sync::{DynSend, DynSync};
 use rustc_data_structures::unord::UnordSet;
-use rustc_errors::{DecorateLint, Diag, DiagCtxt, DiagMessage, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{Diag, DiagCtxt, DiagMessage, ErrorGuaranteed, LintDiagnostic, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
@@ -2129,7 +2129,7 @@ impl<'tcx> TyCtxt<'tcx> {
         T::collect_and_apply(iter, |xs| self.mk_bound_variable_kinds(xs))
     }
 
-    /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
+    /// Emit a lint at `span` from a lint struct (some type that implements `LintDiagnostic`,
     /// typically generated by `#[derive(LintDiagnostic)]`).
     #[track_caller]
     pub fn emit_node_span_lint(
@@ -2137,7 +2137,7 @@ impl<'tcx> TyCtxt<'tcx> {
         lint: &'static Lint,
         hir_id: HirId,
         span: impl Into<MultiSpan>,
-        decorator: impl for<'a> DecorateLint<'a, ()>,
+        decorator: impl for<'a> LintDiagnostic<'a, ()>,
     ) {
         let msg = decorator.msg();
         let (level, src) = self.lint_level_at_node(lint, hir_id);
@@ -2163,14 +2163,14 @@ impl<'tcx> TyCtxt<'tcx> {
         lint_level(self.sess, lint, level, src, Some(span.into()), msg, decorate);
     }
 
-    /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
+    /// Emit a lint from a lint struct (some type that implements `LintDiagnostic`, typically
     /// generated by `#[derive(LintDiagnostic)]`).
     #[track_caller]
     pub fn emit_node_lint(
         self,
         lint: &'static Lint,
         id: HirId,
-        decorator: impl for<'a> DecorateLint<'a, ()>,
+        decorator: impl for<'a> LintDiagnostic<'a, ()>,
     ) {
         self.node_lint(lint, id, decorator.msg(), |diag| {
             decorator.decorate_lint(diag);
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index 2506456f1fb..05463b8554f 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -11,7 +11,7 @@ use crate::ty::{
 };
 
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{Applicability, Diag, DiagArgValue, IntoDiagnosticArg};
+use rustc_errors::{Applicability, Diag, DiagArgValue, IntoDiagArg};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
@@ -19,9 +19,9 @@ use rustc_hir::{PredicateOrigin, WherePredicate};
 use rustc_span::{BytePos, Span};
 use rustc_type_ir::TyKind::*;
 
-impl<'tcx> IntoDiagnosticArg for Ty<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> IntoDiagArg for Ty<'tcx> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/generic_args.rs b/compiler/rustc_middle/src/ty/generic_args.rs
index 8079ad121ad..02b58c035d4 100644
--- a/compiler/rustc_middle/src/ty/generic_args.rs
+++ b/compiler/rustc_middle/src/ty/generic_args.rs
@@ -9,7 +9,7 @@ use crate::ty::{self, Lift, List, ParamConst, Ty, TyCtxt};
 use rustc_ast_ir::visit::VisitorResult;
 use rustc_ast_ir::walk_visitable_list;
 use rustc_data_structures::intern::Interned;
-use rustc_errors::{DiagArgValue, IntoDiagnosticArg};
+use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
 use rustc_serialize::{Decodable, Encodable};
@@ -57,9 +57,9 @@ unsafe impl<'tcx> Sync for GenericArg<'tcx> where
 {
 }
 
-impl<'tcx> IntoDiagnosticArg for GenericArg<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> IntoDiagArg for GenericArg<'tcx> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index b1bfd2f1105..11fd73c9094 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, ConstKind, Ty, TyCtxt, TypeVisitableExt};
 use rustc_error_messages::DiagMessage;
 use rustc_errors::{
-    Diag, DiagArgValue, DiagCtxt, EmissionGuarantee, IntoDiagnostic, IntoDiagnosticArg, Level,
+    Diag, DiagArgValue, DiagCtxt, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
 };
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
@@ -254,9 +254,9 @@ impl<'tcx> fmt::Display for LayoutError<'tcx> {
     }
 }
 
-impl<'tcx> IntoDiagnosticArg for LayoutError<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> IntoDiagArg for LayoutError<'tcx> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
@@ -1267,14 +1267,14 @@ pub enum FnAbiError<'tcx> {
     AdjustForForeignAbi(call::AdjustForForeignAbiError),
 }
 
-impl<'a, 'b, G: EmissionGuarantee> IntoDiagnostic<'a, G> for FnAbiError<'b> {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+impl<'a, 'b, G: EmissionGuarantee> Diagnostic<'a, G> for FnAbiError<'b> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         match self {
-            Self::Layout(e) => e.into_diagnostic().into_diagnostic(dcx, level),
+            Self::Layout(e) => e.into_diagnostic().into_diag(dcx, level),
             Self::AdjustForForeignAbi(call::AdjustForForeignAbiError::Unsupported {
                 arch,
                 abi,
-            }) => UnsupportedFnAbi { arch, abi: abi.name() }.into_diagnostic(dcx, level),
+            }) => UnsupportedFnAbi { arch, abi: abi.name() }.into_diag(dcx, level),
         }
     }
 }
diff --git a/compiler/rustc_middle/src/ty/predicate.rs b/compiler/rustc_middle/src/ty/predicate.rs
index 8dd95daed36..62822505fa5 100644
--- a/compiler/rustc_middle/src/ty/predicate.rs
+++ b/compiler/rustc_middle/src/ty/predicate.rs
@@ -1,6 +1,6 @@
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::intern::Interned;
-use rustc_errors::{DiagArgValue, IntoDiagnosticArg};
+use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_hir::def_id::DefId;
 use rustc_hir::LangItem;
 use rustc_span::Span;
@@ -120,14 +120,14 @@ impl<'tcx> Predicate<'tcx> {
     }
 }
 
-impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl rustc_errors::IntoDiagArg for Predicate<'_> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         rustc_errors::DiagArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
     }
 }
 
-impl rustc_errors::IntoDiagnosticArg for Clause<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl rustc_errors::IntoDiagArg for Clause<'_> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         rustc_errors::DiagArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
     }
 }
@@ -407,9 +407,9 @@ impl<'tcx> PolyTraitRef<'tcx> {
     }
 }
 
-impl<'tcx> IntoDiagnosticArg for TraitRef<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> IntoDiagArg for TraitRef<'tcx> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
@@ -453,9 +453,9 @@ impl<'tcx> ExistentialTraitRef<'tcx> {
     }
 }
 
-impl<'tcx> IntoDiagnosticArg for ExistentialTraitRef<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> IntoDiagArg for ExistentialTraitRef<'tcx> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index c8c9afa7f4d..33d63c2a505 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -2722,9 +2722,9 @@ where
 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
 pub struct TraitRefPrintOnlyTraitPath<'tcx>(ty::TraitRef<'tcx>);
 
-impl<'tcx> rustc_errors::IntoDiagnosticArg for TraitRefPrintOnlyTraitPath<'tcx> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> rustc_errors::IntoDiagArg for TraitRefPrintOnlyTraitPath<'tcx> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
@@ -2739,9 +2739,9 @@ impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitPath<'tcx> {
 #[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
 pub struct TraitRefPrintSugared<'tcx>(ty::TraitRef<'tcx>);
 
-impl<'tcx> rustc_errors::IntoDiagnosticArg for TraitRefPrintSugared<'tcx> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> rustc_errors::IntoDiagArg for TraitRefPrintSugared<'tcx> {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 39b5d3b6ea7..cac12e5ee0b 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -13,7 +13,7 @@ use crate::ty::{GenericArg, GenericArgs, GenericArgsRef};
 use crate::ty::{List, ParamEnv};
 use hir::def::DefKind;
 use rustc_data_structures::captures::Captures;
-use rustc_errors::{DiagArgValue, ErrorGuaranteed, IntoDiagnosticArg, MultiSpan};
+use rustc_errors::{DiagArgValue, ErrorGuaranteed, IntoDiagArg, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::LangItem;
@@ -1094,12 +1094,12 @@ impl<'tcx, T: IntoIterator> Binder<'tcx, T> {
     }
 }
 
-impl<'tcx, T> IntoDiagnosticArg for Binder<'tcx, T>
+impl<'tcx, T> IntoDiagArg for Binder<'tcx, T>
 where
-    T: IntoDiagnosticArg,
+    T: IntoDiagArg,
 {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.value.into_diagnostic_arg()
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.value.into_diag_arg()
     }
 }
 
@@ -1307,9 +1307,9 @@ impl<'tcx> FnSig<'tcx> {
     }
 }
 
-impl<'tcx> IntoDiagnosticArg for FnSig<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl<'tcx> IntoDiagArg for FnSig<'tcx> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 9a298a13eb6..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, EmissionGuarantee, IntoDiagnostic,
-    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,
@@ -461,10 +461,8 @@ pub(crate) struct NonExhaustivePatternsTypeNotEmpty<'p, 'tcx, 'm> {
     pub ty: Ty<'tcx>,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G>
-    for NonExhaustivePatternsTypeNotEmpty<'_, '_, '_>
-{
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for NonExhaustivePatternsTypeNotEmpty<'_, '_, '_> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'_, G> {
         let mut diag =
             Diag::new(dcx, level, fluent::mir_build_non_exhaustive_patterns_type_not_empty);
         diag.span(self.span);
@@ -867,8 +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_mir_transform/src/errors.rs b/compiler/rustc_mir_transform/src/errors.rs
index 80e9172bbe1..9297bc51fad 100644
--- a/compiler/rustc_mir_transform/src/errors.rs
+++ b/compiler/rustc_mir_transform/src/errors.rs
@@ -1,8 +1,8 @@
 use std::borrow::Cow;
 
 use rustc_errors::{
-    codes::*, Applicability, DecorateLint, Diag, DiagArgValue, DiagCtxt, DiagMessage,
-    EmissionGuarantee, IntoDiagnostic, Level,
+    codes::*, Applicability, Diag, DiagArgValue, DiagCtxt, DiagMessage, Diagnostic,
+    EmissionGuarantee, Level, LintDiagnostic,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::mir::{AssertKind, UnsafetyViolationDetails};
@@ -62,9 +62,9 @@ pub(crate) struct RequiresUnsafe {
 // so we need to eagerly translate the label here, which isn't supported by the derive API
 // We could also exhaustively list out the primary messages for all unsafe violations,
 // but this would result in a lot of duplication.
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for RequiresUnsafe {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for RequiresUnsafe {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         let mut diag = Diag::new(dcx, level, fluent::mir_transform_requires_unsafe);
         diag.code(E0133);
         diag.span(self.span);
@@ -181,7 +181,7 @@ pub(crate) struct UnsafeOpInUnsafeFn {
     pub suggest_unsafe_block: Option<(Span, Span, Span)>,
 }
 
-impl<'a> DecorateLint<'a, ()> for UnsafeOpInUnsafeFn {
+impl<'a> LintDiagnostic<'a, ()> for UnsafeOpInUnsafeFn {
     #[track_caller]
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         let desc = diag.dcx.eagerly_translate_to_string(self.details.label(), [].into_iter());
@@ -215,7 +215,7 @@ pub(crate) enum AssertLintKind {
     UnconditionalPanic,
 }
 
-impl<'a, P: std::fmt::Debug> DecorateLint<'a, ()> for AssertLint<P> {
+impl<'a, P: std::fmt::Debug> LintDiagnostic<'a, ()> for AssertLint<P> {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         let message = self.assert_kind.diagnostic_message();
         self.assert_kind.add_args(&mut |name, value| {
@@ -269,7 +269,7 @@ pub(crate) struct MustNotSupend<'tcx, 'a> {
 }
 
 // Needed for def_path_str
-impl<'a> DecorateLint<'a, ()> for MustNotSupend<'_, '_> {
+impl<'a> LintDiagnostic<'a, ()> for MustNotSupend<'_, '_> {
     fn decorate_lint<'b>(self, diag: &'b mut rustc_errors::Diag<'a, ()>) {
         diag.span_label(self.yield_sp, fluent::_subdiag::label);
         if let Some(reason) = self.reason {
diff --git a/compiler/rustc_monomorphize/src/errors.rs b/compiler/rustc_monomorphize/src/errors.rs
index 1303ac9939c..35fc78f2045 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, EmissionGuarantee, IntoDiagnostic, Level};
+use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
 use rustc_macros::{Diagnostic, LintDiagnostic};
 use rustc_span::{Span, Symbol};
 
@@ -46,9 +46,9 @@ pub struct UnusedGenericParamsHint {
     pub param_names: Vec<String>,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for UnusedGenericParamsHint {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for UnusedGenericParamsHint {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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 c72b7e2cfa7..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, EmissionGuarantee, IntoDiagnostic,
-    Level, SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_session::errors::ExprParenthesesNeeded;
@@ -1065,9 +1065,9 @@ pub(crate) struct ExpectedIdentifier {
     pub help_cannot_start_number: Option<HelpIdentifierStartsWithNumber>,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for ExpectedIdentifier {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for ExpectedIdentifier {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         let token_descr = TokenDescription::from_token(&self.token);
 
         let mut diag = Diag::new(
@@ -1093,17 +1093,17 @@ impl<'a, G: EmissionGuarantee> IntoDiagnostic<'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
@@ -1125,9 +1125,9 @@ pub(crate) struct ExpectedSemi {
     pub sugg: ExpectedSemiSugg,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for ExpectedSemi {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for ExpectedSemi {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         let token_descr = TokenDescription::from_token(&self.token);
 
         let mut diag = Diag::new(
@@ -1154,7 +1154,7 @@ impl<'a, G: EmissionGuarantee> IntoDiagnostic<'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 de088b9364b..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;
@@ -298,7 +298,7 @@ impl<'a> Parser<'a> {
         {
             recovered_ident = Some((ident, IdentIsRaw::Yes));
 
-            // `Symbol::to_string()` is different from `Symbol::into_diagnostic_arg()`,
+            // `Symbol::to_string()` is different from `Symbol::into_diag_arg()`,
             // which uses `Symbol::to_ident_string()` and "helpfully" adds an implicit `r#`
             let ident_name = ident.name.to_string();
 
@@ -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/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index a99db9cb8cc..91ab5b30dea 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -9,7 +9,7 @@ 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, IntoDiagnosticArg, MultiSpan};
+use rustc_errors::{Applicability, DiagCtxt, IntoDiagArg, MultiSpan};
 use rustc_feature::{AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalModDefId;
@@ -79,14 +79,14 @@ pub(crate) enum ProcMacroKind {
     Attribute,
 }
 
-impl IntoDiagnosticArg for ProcMacroKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
+impl IntoDiagArg for ProcMacroKind {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
         match self {
             ProcMacroKind::Attribute => "attribute proc macro",
             ProcMacroKind::Derive => "derive proc macro",
             ProcMacroKind::FunctionLike => "function-like proc macro",
         }
-        .into_diagnostic_arg()
+        .into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 69104a30495..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, EmissionGuarantee,
-    IntoDiagnostic, 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};
@@ -862,9 +862,9 @@ pub struct ItemFollowingInnerAttr {
     pub kind: &'static str,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for InvalidAttrAtCrateLevel {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for InvalidAttrAtCrateLevel {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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);
@@ -1012,9 +1012,9 @@ pub struct BreakNonLoop<'a> {
     pub break_expr_span: Span,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'_, G> for BreakNonLoop<'a> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'_, G> for BreakNonLoop<'a> {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::passes_break_non_loop);
         diag.span(self.span);
         diag.code(E0571);
@@ -1156,9 +1156,9 @@ pub struct NakedFunctionsAsmBlock {
     pub non_asms: Vec<Span>,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for NakedFunctionsAsmBlock {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for NakedFunctionsAsmBlock {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::passes_naked_functions_asm_block);
         diag.span(self.span);
         diag.code(E0787);
@@ -1267,9 +1267,9 @@ pub struct NoMainErr {
     pub add_teach_note: bool,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for NoMainErr {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for NoMainErr {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         let mut diag = Diag::new(dcx, level, fluent::passes_no_main_function);
         diag.span(DUMMY_SP);
         diag.code(E0601);
@@ -1325,9 +1325,9 @@ pub struct DuplicateLangItem {
     pub(crate) duplicate: Duplicate,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for DuplicateLangItem {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for DuplicateLangItem {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(
             dcx,
             level,
@@ -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_pattern_analysis/src/lints.rs b/compiler/rustc_pattern_analysis/src/lints.rs
index 30e775733de..16530960656 100644
--- a/compiler/rustc_pattern_analysis/src/lints.rs
+++ b/compiler/rustc_pattern_analysis/src/lints.rs
@@ -97,7 +97,7 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'p, 'tcx>(
                     lint_name: "non_exhaustive_omitted_patterns",
                 };
 
-                use rustc_errors::DecorateLint;
+                use rustc_errors::LintDiagnostic;
                 let mut err = rcx.tcx.dcx().struct_span_warn(arm.pat.data().unwrap().span, "");
                 err.primary_message(decorator.msg());
                 decorator.decorate_lint(&mut err);
diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index a9f5ed9908b..5eee6a51fd2 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -521,7 +521,7 @@ pub(crate) struct ToolModuleImported {
 #[diag(resolve_module_only)]
 pub(crate) struct ModuleOnly(#[primary_span] pub(crate) Span);
 
-#[derive(Diagnostic, Default)]
+#[derive(Diagnostic)]
 #[diag(resolve_macro_expected_found)]
 pub(crate) struct MacroExpectedFound<'a> {
     #[primary_span]
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index d2aea0056b3..ea07ed9e654 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -17,7 +17,7 @@ use rustc_ast::visit::{walk_list, AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor}
 use rustc_ast::*;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_errors::{
-    codes::*, struct_span_code_err, Applicability, DiagArgValue, IntoDiagnosticArg, StashKey,
+    codes::*, struct_span_code_err, Applicability, DiagArgValue, IntoDiagArg, StashKey,
 };
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, DefKind, LifetimeRes, NonMacroAttrKind, PartialRes, PerNS};
@@ -89,8 +89,8 @@ impl PatternSource {
     }
 }
 
-impl IntoDiagnosticArg for PatternSource {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
+impl IntoDiagArg for PatternSource {
+    fn into_diag_arg(self) -> DiagArgValue {
         DiagArgValue::Str(Cow::Borrowed(self.descr()))
     }
 }
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index c7bb2a573b1..d8fd8d22439 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -562,7 +562,8 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 expected,
                 found: res.descr(),
                 macro_path: &path_str,
-                ..Default::default() // Subdiagnostics default to None
+                remove_surrounding_derive: None,
+                add_as_non_derive: None,
             };
 
             // Suggest moving the macro out of the derive() if the macro isn't Derive
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 61a220428b0..1573920c8c0 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -13,7 +13,7 @@ use crate::{EarlyDiagCtxt, Session};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::{StableOrd, ToStableHashKey};
 use rustc_errors::emitter::HumanReadableErrorType;
-use rustc_errors::{ColorConfig, DiagArgValue, DiagCtxtFlags, IntoDiagnosticArg};
+use rustc_errors::{ColorConfig, DiagArgValue, DiagCtxtFlags, IntoDiagArg};
 use rustc_feature::UnstableFeatures;
 use rustc_span::edition::{Edition, DEFAULT_EDITION, EDITION_NAME_LIST, LATEST_STABLE_EDITION};
 use rustc_span::source_map::FilePathMapping;
@@ -3098,9 +3098,9 @@ impl fmt::Display for CrateType {
     }
 }
 
-impl IntoDiagnosticArg for CrateType {
-    fn into_diagnostic_arg(self) -> DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl IntoDiagArg for CrateType {
+    fn into_diag_arg(self) -> DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 3c8ad27c07c..5f04915a9e7 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, EmissionGuarantee, ErrorGuaranteed, IntoDiagnostic,
-    Level, MultiSpan,
+    codes::*, Diag, DiagCtxt, DiagMessage, Diagnostic, EmissionGuarantee, ErrorGuaranteed, Level,
+    MultiSpan,
 };
 use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
@@ -17,9 +17,9 @@ pub struct FeatureGateError {
     pub explain: DiagMessage,
 }
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for FeatureGateError {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for FeatureGateError {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         Diag::new(dcx, level, self.explain).with_span(self.span).with_code(E0658)
     }
 }
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index ae1dbd13204..e9b8a300939 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, ErrorGuaranteed, FatalAbort,
-    FluentBundle, IntoDiagnostic, LazyFallbackBundle, TerminalUrl,
+    codes::*, fallback_fluent_bundle, Diag, DiagCtxt, DiagMessage, Diagnostic, ErrorGuaranteed,
+    FatalAbort, FluentBundle, LazyFallbackBundle, TerminalUrl,
 };
 use rustc_macros::HashStable_Generic;
 pub use rustc_span::def_id::StableCrateId;
@@ -111,9 +111,9 @@ impl Mul<usize> for Limit {
     }
 }
 
-impl rustc_errors::IntoDiagnosticArg for Limit {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagArgValue {
-        self.to_string().into_diagnostic_arg()
+impl rustc_errors::IntoDiagArg for Limit {
+    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
+        self.to_string().into_diag_arg()
     }
 }
 
@@ -305,11 +305,7 @@ impl Session {
     }
 
     #[track_caller]
-    pub fn create_feature_err<'a>(
-        &'a self,
-        err: impl IntoDiagnostic<'a>,
-        feature: Symbol,
-    ) -> Diag<'a> {
+    pub fn create_feature_err<'a>(&'a self, err: impl Diagnostic<'a>, feature: Symbol) -> Diag<'a> {
         let mut err = self.dcx().create_err(err);
         if err.code.is_none() {
             #[allow(rustc::diagnostic_outside_of_impl)]
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 708349e85ae..a8426d78cac 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,
@@ -184,10 +183,10 @@ symbols! {
         DebugStruct,
         Decodable,
         Decoder,
-        DecorateLint,
         Default,
         Deref,
         DiagMessage,
+        Diagnostic,
         DirBuilder,
         Display,
         DoubleEndedIterator,
@@ -223,7 +222,6 @@ symbols! {
         Input,
         Instant,
         Into,
-        IntoDiagnostic,
         IntoFuture,
         IntoIterator,
         IoLines,
@@ -243,6 +241,7 @@ symbols! {
         Layout,
         Left,
         LinkedList,
+        LintDiagnostic,
         LintPass,
         LocalKey,
         Mutex,
@@ -305,6 +304,7 @@ symbols! {
         String,
         StructuralPartialEq,
         SubdiagMessage,
+        Subdiagnostic,
         Sync,
         T,
         Target,
diff --git a/compiler/rustc_symbol_mangling/src/errors.rs b/compiler/rustc_symbol_mangling/src/errors.rs
index b84e2f7b4ea..b5721ee489d 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, EmissionGuarantee, IntoDiagnostic, Level};
+use rustc_errors::{Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level};
 use rustc_span::Span;
 use std::fmt;
 
@@ -13,8 +13,8 @@ pub struct TestOutput {
 // This diagnostic doesn't need translation because (a) it doesn't contain any
 // natural language, and (b) it's only used in tests. So we construct it
 // manually and avoid the fluent machinery.
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TestOutput {
-    fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> Diag<'_, G> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for TestOutput {
+    fn into_diag(self, dcx: &'_ DiagCtxt, 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 e37640d0689..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, EmissionGuarantee, IntoDiagnostic,
-    Level, SubdiagMessageOp,
+    codes::*, Applicability, Diag, DiagCtxt, Diagnostic, EmissionGuarantee, Level,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::Diagnostic;
 use rustc_middle::ty::{self, ClosureKind, PolyTraitRef, Ty};
@@ -57,9 +57,9 @@ pub struct NegativePositiveConflict<'tcx> {
     pub positive_impl_span: Result<Span, Symbol>,
 }
 
-impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for NegativePositiveConflict<'_> {
+impl<G: EmissionGuarantee> Diagnostic<'_, G> for NegativePositiveConflict<'_> {
     #[track_caller]
-    fn into_diagnostic(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: &DiagCtxt, 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()));
@@ -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 f73fdc0882f..d443681d5db 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,
-    IntoDiagnostic, Level, SubdiagMessageOp,
+    Diag, DiagCtxt, DiagInner, DiagMessage, Diagnostic, EmissionGuarantee, Level, LintDiagnostic,
+    SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
@@ -36,27 +36,27 @@ struct Note {
     span: Span,
 }
 
-pub struct UntranslatableInIntoDiagnostic;
+pub struct UntranslatableInDiagnostic;
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for UntranslatableInIntoDiagnostic {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UntranslatableInDiagnostic {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         Diag::new(dcx, level, "untranslatable diagnostic")
         //~^ ERROR diagnostics should be created using translatable messages
     }
 }
 
-pub struct TranslatableInIntoDiagnostic;
+pub struct TranslatableInDiagnostic;
 
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for TranslatableInIntoDiagnostic {
-    fn into_diagnostic(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for TranslatableInDiagnostic {
+    fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> {
         Diag::new(dcx, level, crate::fluent_generated::no_crate_example)
     }
 }
 
-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,
@@ -78,9 +78,9 @@ impl AddToDiagnostic for TranslatableInAddToDiagnostic {
     }
 }
 
-pub struct UntranslatableInDecorateLint;
+pub struct UntranslatableInLintDiagnostic;
 
-impl<'a> DecorateLint<'a, ()> for UntranslatableInDecorateLint {
+impl<'a> LintDiagnostic<'a, ()> for UntranslatableInLintDiagnostic {
     fn decorate_lint<'b, >(self, diag: &'b mut Diag<'a, ()>) {
         diag.note("untranslatable diagnostic");
         //~^ ERROR diagnostics should be created using translatable messages
@@ -91,9 +91,9 @@ impl<'a> DecorateLint<'a, ()> for UntranslatableInDecorateLint {
     }
 }
 
-pub struct TranslatableInDecorateLint;
+pub struct TranslatableInLintDiagnostic;
 
-impl<'a> DecorateLint<'a, ()> for TranslatableInDecorateLint {
+impl<'a> LintDiagnostic<'a, ()> for TranslatableInLintDiagnostic {
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
         diag.note(crate::fluent_generated::no_crate_note);
     }
@@ -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 `IntoDiagnostic`/`AddToDiagnostic` impls
+    //~^ ERROR diagnostics should only be created in `Diagnostic`/`Subdiagnostic`/`LintDiagnostic` impls
 
     let _diag = dcx.struct_err("untranslatable diagnostic");
-    //~^ ERROR diagnostics should only be created in `IntoDiagnostic`/`AddToDiagnostic` impls
+    //~^ ERROR diagnostics should only be created in `Diagnostic`/`Subdiagnostic`/`LintDiagnostic` 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 b8fbee1ff00..ee5400f6f95 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 `IntoDiagnostic`/`AddToDiagnostic` impls
+error: diagnostics should only be created in `Diagnostic`/`Subdiagnostic`/`LintDiagnostic` 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 `IntoDiagnostic`/`AddToDiagnostic` impls
+error: diagnostics should only be created in `Diagnostic`/`Subdiagnostic`/`LintDiagnostic` impls
   --> $DIR/diagnostics.rs:110:21
    |
 LL |     let _diag = dcx.struct_err("untranslatable diagnostic");
diff --git a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.rs b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.rs
index 40df9cc5dca..432ede89826 100644
--- a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.rs
+++ b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.rs
@@ -1,6 +1,6 @@
 //@ check-fail
 // Tests that a doc comment will not preclude a field from being considered a diagnostic argument
-//@ normalize-stderr-test "the following other types implement trait `IntoDiagnosticArg`:(?:.*\n){0,9}\s+and \d+ others" -> "normalized in stderr"
+//@ normalize-stderr-test "the following other types implement trait `IntoDiagArg`:(?:.*\n){0,9}\s+and \d+ others" -> "normalized in stderr"
 //@ normalize-stderr-test "(COMPILER_DIR/.*\.rs):[0-9]+:[0-9]+" -> "$1:LL:CC"
 
 // The proc_macro2 crate handles spans differently when on beta/stable release rather than nightly,
@@ -25,7 +25,7 @@ use rustc_span::Span;
 
 rustc_fluent_macro::fluent_messages! { "./example.ftl" }
 
-struct NotIntoDiagnosticArg;
+struct NotIntoDiagArg;
 
 #[derive(Diagnostic)]
 #[diag(no_crate_example)]
@@ -33,8 +33,8 @@ struct Test {
     #[primary_span]
     span: Span,
     /// A doc comment
-    arg: NotIntoDiagnosticArg,
-    //~^ ERROR the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+    arg: NotIntoDiagArg,
+    //~^ ERROR the trait bound `NotIntoDiagArg: IntoDiagArg` is not satisfied
 }
 
 #[derive(Subdiagnostic)]
@@ -43,6 +43,6 @@ struct SubTest {
     #[primary_span]
     span: Span,
     /// A doc comment
-    arg: NotIntoDiagnosticArg,
-    //~^ ERROR the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+    arg: NotIntoDiagArg,
+    //~^ ERROR the trait bound `NotIntoDiagArg: IntoDiagArg` is not satisfied
 }
diff --git a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr
index 98600d28229..7377b0dfd0a 100644
--- a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr
+++ b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr
@@ -1,25 +1,25 @@
-error[E0277]: the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+error[E0277]: the trait bound `NotIntoDiagArg: IntoDiagArg` is not satisfied
   --> $DIR/diagnostic-derive-doc-comment-field.rs:36:10
    |
 LL | #[derive(Diagnostic)]
    |          ---------- required by a bound introduced by this call
 ...
-LL |     arg: NotIntoDiagnosticArg,
-   |          ^^^^^^^^^^^^^^^^^^^^ the trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
+LL |     arg: NotIntoDiagArg,
+   |          ^^^^^^^^^^^^^^ the trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
    |
    = help: normalized in stderr
 note: required by a bound in `Diag::<'a, G>::arg`
   --> $COMPILER_DIR/rustc_errors/src/diagnostic.rs:LL:CC
    = note: this error originates in the macro `with_fn` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+error[E0277]: the trait bound `NotIntoDiagArg: IntoDiagArg` is not satisfied
   --> $DIR/diagnostic-derive-doc-comment-field.rs:46:10
    |
 LL | #[derive(Subdiagnostic)]
    |          ------------- required by a bound introduced by this call
 ...
-LL |     arg: NotIntoDiagnosticArg,
-   |          ^^^^^^^^^^^^^^^^^^^^ the trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
+LL |     arg: NotIntoDiagArg,
+   |          ^^^^^^^^^^^^^^ the trait `IntoDiagArg` is not implemented for `NotIntoDiagArg`
    |
    = help: normalized in stderr
 note: required by a bound in `Diag::<'a, G>::arg`
diff --git a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.rs b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.rs
index 11070972394..043c7c16654 100644
--- a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.rs
+++ b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.rs
@@ -1,6 +1,6 @@
 //@ check-fail
 // Tests error conditions for specifying diagnostics using #[derive(Diagnostic)]
-//@ normalize-stderr-test "the following other types implement trait `IntoDiagnosticArg`:(?:.*\n){0,9}\s+and \d+ others" -> "normalized in stderr"
+//@ normalize-stderr-test "the following other types implement trait `IntoDiagArg`:(?:.*\n){0,9}\s+and \d+ others" -> "normalized in stderr"
 //@ normalize-stderr-test "(COMPILER_DIR/.*\.rs):[0-9]+:[0-9]+" -> "$1:LL:CC"
 
 // The proc_macro2 crate handles spans differently when on beta/stable release rather than nightly,
@@ -347,7 +347,7 @@ struct ArgFieldWithoutSkip {
     #[primary_span]
     span: Span,
     other: Hello,
-    //~^ ERROR the trait bound `Hello: IntoDiagnosticArg` is not satisfied
+    //~^ ERROR the trait bound `Hello: IntoDiagArg` is not satisfied
 }
 
 #[derive(Diagnostic)]
@@ -355,7 +355,7 @@ struct ArgFieldWithoutSkip {
 struct ArgFieldWithSkip {
     #[primary_span]
     span: Span,
-    // `Hello` does not implement `IntoDiagnosticArg` so this would result in an error if
+    // `Hello` does not implement `IntoDiagArg` so this would result in an error if
     // not for `#[skip_arg]`.
     #[skip_arg]
     other: Hello,
diff --git a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
index 058c88d315b..1266430e2f7 100644
--- a/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
+++ b/tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
@@ -618,14 +618,14 @@ LL | #[derive(Diagnostic)]
    |
    = note: this error originates in the derive macro `Diagnostic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: the trait bound `Hello: IntoDiagnosticArg` is not satisfied
+error[E0277]: the trait bound `Hello: IntoDiagArg` is not satisfied
   --> $DIR/diagnostic-derive.rs:349:12
    |
 LL | #[derive(Diagnostic)]
    |          ---------- required by a bound introduced by this call
 ...
 LL |     other: Hello,
-   |            ^^^^^ the trait `IntoDiagnosticArg` is not implemented for `Hello`
+   |            ^^^^^ the trait `IntoDiagArg` is not implemented for `Hello`
    |
    = help: normalized in stderr
 note: required by a bound in `Diag::<'a, G>::arg`