Remove the lifetime from `DiagnosticArgValue`.

Because it's almost always static.

This makes `impl IntoDiagnosticArg for DiagnosticArgValue` trivial,
which is nice.

There are a few diagnostics constructed in
`compiler/rustc_mir_build/src/check_unsafety.rs` and
`compiler/rustc_mir_transform/src/errors.rs` that now need symbols
converted to `String` with `to_string` instead of `&str` with `as_str`,
but that' no big deal, and worth it for the simplifications elsewhere.

38 files changed, 113 insertions, 116 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index 4cb49362863..15e1066e983 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -188,7 +188,7 @@ impl Display for RegionName {
 }
 
 impl rustc_errors::IntoDiagnosticArg for RegionName {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_codegen_gcc/src/errors.rs b/compiler/rustc_codegen_gcc/src/errors.rs
index e9283b19894..cc0fbe46dcc 100644
--- a/compiler/rustc_codegen_gcc/src/errors.rs
+++ b/compiler/rustc_codegen_gcc/src/errors.rs
@@ -35,7 +35,7 @@ pub(crate) enum PossibleFeature<'a> {
 struct ExitCode(Option<i32>);
 
 impl IntoDiagnosticArg for ExitCode {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         let ExitCode(exit_code) = self;
         match exit_code {
             Some(t) => t.into_diagnostic_arg(),
diff --git a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
index a1daadce958..ad5a74b04e4 100644
--- a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
+++ b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
@@ -206,7 +206,7 @@ impl fmt::Display for CguReuse {
 }
 
 impl IntoDiagnosticArg for CguReuse {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self.to_string()))
     }
 }
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index b13d566b40b..affd386361c 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -999,7 +999,7 @@ type DiagnosticArgName<'source> = Cow<'source, str>;
 
 struct Diagnostic {
     msgs: Vec<(DiagnosticMessage, Style)>,
-    args: FxHashMap<DiagnosticArgName<'static>, rustc_errors::DiagnosticArgValue<'static>>,
+    args: FxHashMap<DiagnosticArgName<'static>, rustc_errors::DiagnosticArgValue>,
     code: Option<ErrCode>,
     lvl: Level,
 }
@@ -1811,7 +1811,7 @@ impl Translate for SharedEmitter {
 
 impl Emitter for SharedEmitter {
     fn emit_diagnostic(&mut self, diag: &rustc_errors::Diagnostic) {
-        let args: FxHashMap<Cow<'_, str>, rustc_errors::DiagnosticArgValue<'_>> =
+        let args: FxHashMap<Cow<'_, str>, rustc_errors::DiagnosticArgValue> =
             diag.args().map(|(name, arg)| (name.clone(), arg.clone())).collect();
         drop(self.sender.send(SharedEmitterMessage::Diagnostic(Diagnostic {
             msgs: diag.messages.clone(),
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index ef291ead190..06ea5b9e8f4 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -147,7 +147,7 @@ impl<'a> CopyPath<'a> {
 struct DebugArgPath<'a>(pub &'a Path);
 
 impl IntoDiagnosticArg for DebugArgPath<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(format!("{:?}", self.0)))
     }
 }
@@ -974,7 +974,7 @@ pub enum ExpectedPointerMutability {
 }
 
 impl IntoDiagnosticArg for ExpectedPointerMutability {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         match self {
             ExpectedPointerMutability::Mut => DiagnosticArgValue::Str(Cow::Borrowed("*mut")),
             ExpectedPointerMutability::Not => DiagnosticArgValue::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 e8d0430c9d9..dabf78ef90e 100644
--- a/compiler/rustc_const_eval/src/const_eval/error.rs
+++ b/compiler/rustc_const_eval/src/const_eval/error.rs
@@ -34,7 +34,7 @@ impl MachineStopType for ConstEvalErrKind {
     }
     fn add_args(
         self: Box<Self>,
-        adder: &mut dyn FnMut(std::borrow::Cow<'static, str>, DiagnosticArgValue<'static>),
+        adder: &mut dyn FnMut(std::borrow::Cow<'static, str>, DiagnosticArgValue),
     ) {
         use ConstEvalErrKind::*;
         match *self {
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index 9e27c19e94c..4d2b1ba3eec 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -906,7 +906,7 @@ impl ReportErrorExt for ResourceExhaustionInfo {
 }
 
 impl rustc_errors::IntoDiagnosticArg for InternKind {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::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 8a32e29ddc9..b3a4e1c5843 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -24,7 +24,7 @@ pub struct SuggestionsDisabled;
 /// `DiagnosticArg` are converted to `FluentArgs` (consuming the collection) at the start of
 /// diagnostic emission.
 pub type DiagnosticArg<'iter, 'source> =
-    (&'iter DiagnosticArgName<'source>, &'iter DiagnosticArgValue<'source>);
+    (&'iter DiagnosticArgName<'source>, &'iter DiagnosticArgValue);
 
 /// Name of a diagnostic argument.
 pub type DiagnosticArgName<'source> = Cow<'source, str>;
@@ -32,10 +32,10 @@ pub type DiagnosticArgName<'source> = Cow<'source, str>;
 /// Simplified version of `FluentValue` that can implement `Encodable` and `Decodable`. Converted
 /// to a `FluentValue` by the emitter to be used in diagnostic translation.
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
-pub enum DiagnosticArgValue<'source> {
-    Str(Cow<'source, str>),
+pub enum DiagnosticArgValue {
+    Str(Cow<'static, str>),
     Number(i128),
-    StrListSepByAnd(Vec<Cow<'source, str>>),
+    StrListSepByAnd(Vec<Cow<'static, str>>),
 }
 
 /// Converts a value of a type into a `DiagnosticArg` (typically a field of an `IntoDiagnostic`
@@ -43,23 +43,17 @@ pub enum DiagnosticArgValue<'source> {
 /// being converted rather than on `DiagnosticArgValue`, which enables types from other `rustc_*`
 /// crates to implement this.
 pub trait IntoDiagnosticArg {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static>;
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue;
 }
 
-impl<'source> IntoDiagnosticArg for DiagnosticArgValue<'source> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
-        match self {
-            DiagnosticArgValue::Str(s) => DiagnosticArgValue::Str(Cow::Owned(s.into_owned())),
-            DiagnosticArgValue::Number(n) => DiagnosticArgValue::Number(n),
-            DiagnosticArgValue::StrListSepByAnd(l) => DiagnosticArgValue::StrListSepByAnd(
-                l.into_iter().map(|s| Cow::Owned(s.into_owned())).collect(),
-            ),
-        }
+impl IntoDiagnosticArg for DiagnosticArgValue {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
+        self
     }
 }
 
-impl<'source> Into<FluentValue<'source>> for DiagnosticArgValue<'source> {
-    fn into(self) -> FluentValue<'source> {
+impl Into<FluentValue<'static>> for DiagnosticArgValue {
+    fn into(self) -> FluentValue<'static> {
         match self {
             DiagnosticArgValue::Str(s) => From::from(s),
             DiagnosticArgValue::Number(n) => From::from(n),
@@ -109,7 +103,7 @@ pub struct Diagnostic {
     pub span: MultiSpan,
     pub children: Vec<SubDiagnostic>,
     pub suggestions: Result<Vec<CodeSuggestion>, SuggestionsDisabled>,
-    args: FxHashMap<DiagnosticArgName<'static>, DiagnosticArgValue<'static>>,
+    args: FxHashMap<DiagnosticArgName<'static>, DiagnosticArgValue>,
 
     /// This is not used for highlighting or rendering any error message. Rather, it can be used
     /// as a sort key to sort a buffer of diagnostics. By default, it is the primary span of
@@ -931,7 +925,7 @@ impl Diagnostic {
 
     pub fn replace_args(
         &mut self,
-        args: FxHashMap<DiagnosticArgName<'static>, DiagnosticArgValue<'static>>,
+        args: FxHashMap<DiagnosticArgName<'static>, DiagnosticArgValue>,
     ) {
         self.args = args;
     }
@@ -990,7 +984,7 @@ impl Diagnostic {
     ) -> (
         &Level,
         &[(DiagnosticMessage, Style)],
-        Vec<(&Cow<'static, str>, &DiagnosticArgValue<'static>)>,
+        Vec<(&Cow<'static, str>, &DiagnosticArgValue)>,
         &Option<ErrCode>,
         &Option<IsLint>,
         &MultiSpan,
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index df3fd4af4b4..faab3fc663a 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -23,7 +23,7 @@ use std::process::ExitStatus;
 pub struct DiagnosticArgFromDisplay<'a>(pub &'a dyn fmt::Display);
 
 impl IntoDiagnosticArg for DiagnosticArgFromDisplay<'_> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.0.to_string().into_diagnostic_arg()
     }
 }
@@ -41,7 +41,7 @@ impl<'a, T: fmt::Display> From<&'a T> for DiagnosticArgFromDisplay<'a> {
 }
 
 impl<'a, T: Clone + IntoDiagnosticArg> IntoDiagnosticArg for &'a T {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.clone().into_diagnostic_arg()
     }
 }
@@ -50,7 +50,7 @@ macro_rules! into_diagnostic_arg_using_display {
     ($( $ty:ty ),+ $(,)?) => {
         $(
             impl IntoDiagnosticArg for $ty {
-                fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+                fn into_diagnostic_arg(self) -> DiagnosticArgValue {
                     self.to_string().into_diagnostic_arg()
                 }
             }
@@ -62,7 +62,7 @@ macro_rules! into_diagnostic_arg_for_number {
     ($( $ty:ty ),+ $(,)?) => {
         $(
             impl IntoDiagnosticArg for $ty {
-                fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+                fn into_diagnostic_arg(self) -> DiagnosticArgValue {
                     // HACK: `FluentNumber` the underline backing struct represent
                     // numbers using a f64 which can't represent all the i128 numbers
                     // So in order to be able to use fluent selectors and still
@@ -99,7 +99,7 @@ into_diagnostic_arg_using_display!(
 into_diagnostic_arg_for_number!(i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize, usize);
 
 impl IntoDiagnosticArg for bool {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         if self {
             DiagnosticArgValue::Str(Cow::Borrowed("true"))
         } else {
@@ -109,13 +109,13 @@ impl IntoDiagnosticArg for bool {
 }
 
 impl IntoDiagnosticArg for char {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(format!("{self:?}")))
     }
 }
 
 impl IntoDiagnosticArg for Vec<char> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::StrListSepByAnd(
             self.into_iter().map(|c| Cow::Owned(format!("{c:?}"))).collect(),
         )
@@ -123,49 +123,49 @@ impl IntoDiagnosticArg for Vec<char> {
 }
 
 impl IntoDiagnosticArg for Symbol {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_ident_string().into_diagnostic_arg()
     }
 }
 
 impl<'a> IntoDiagnosticArg for &'a str {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
 
 impl IntoDiagnosticArg for String {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self))
     }
 }
 
 impl<'a> IntoDiagnosticArg for Cow<'a, str> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self.into_owned()))
     }
 }
 
 impl<'a> IntoDiagnosticArg for &'a Path {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self.display().to_string()))
     }
 }
 
 impl IntoDiagnosticArg for PathBuf {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self.display().to_string()))
     }
 }
 
 impl IntoDiagnosticArg for PanicStrategy {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self.desc().to_string()))
     }
 }
 
 impl IntoDiagnosticArg for hir::ConstContext {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Borrowed(match self {
             hir::ConstContext::ConstFn => "const_fn",
             hir::ConstContext::Static(_) => "static",
@@ -175,49 +175,49 @@ impl IntoDiagnosticArg for hir::ConstContext {
 }
 
 impl IntoDiagnosticArg for ast::Expr {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(pprust::expr_to_string(&self)))
     }
 }
 
 impl IntoDiagnosticArg for ast::Path {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))
     }
 }
 
 impl IntoDiagnosticArg for ast::token::Token {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(pprust::token_to_string(&self))
     }
 }
 
 impl IntoDiagnosticArg for ast::token::TokenKind {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(pprust::token_kind_to_string(&self))
     }
 }
 
 impl IntoDiagnosticArg for type_ir::FloatTy {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Borrowed(self.name_str()))
     }
 }
 
 impl IntoDiagnosticArg for std::ffi::CString {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
     }
 }
 
 impl IntoDiagnosticArg for rustc_data_structures::small_c_str::SmallCStr {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
     }
 }
 
 impl IntoDiagnosticArg for ast::Visibility {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         let s = pprust::vis_to_string(&self);
         let s = s.trim_end().to_string();
         DiagnosticArgValue::Str(Cow::Owned(s))
@@ -225,7 +225,7 @@ impl IntoDiagnosticArg for ast::Visibility {
 }
 
 impl IntoDiagnosticArg for rustc_lint_defs::Level {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Borrowed(self.to_cmd_flag()))
     }
 }
@@ -240,7 +240,7 @@ impl From<Vec<Symbol>> for DiagnosticSymbolList {
 }
 
 impl IntoDiagnosticArg for DiagnosticSymbolList {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::StrListSepByAnd(
             self.0.into_iter().map(|sym| Cow::Owned(format!("`{sym}`"))).collect(),
         )
@@ -248,7 +248,7 @@ impl IntoDiagnosticArg for DiagnosticSymbolList {
 }
 
 impl<Id> IntoDiagnosticArg for hir::def::Res<Id> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Borrowed(self.descr()))
     }
 }
@@ -334,13 +334,13 @@ pub struct DelayedAtWithoutNewline {
 }
 
 impl IntoDiagnosticArg for DiagnosticLocation {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::from(self.to_string()))
     }
 }
 
 impl IntoDiagnosticArg for Backtrace {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::from(self.to_string()))
     }
 }
@@ -353,7 +353,7 @@ pub struct InvalidFlushedDelayedDiagnosticLevel {
     pub level: Level,
 }
 impl IntoDiagnosticArg for Level {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::from(self.to_string()))
     }
 }
@@ -368,7 +368,7 @@ pub struct IndicateAnonymousLifetime {
 }
 
 impl IntoDiagnosticArg for type_ir::ClosureKind {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(self.as_str().into())
     }
 }
diff --git a/compiler/rustc_errors/src/translation.rs b/compiler/rustc_errors/src/translation.rs
index ed35eb1b6c4..af927bf9629 100644
--- a/compiler/rustc_errors/src/translation.rs
+++ b/compiler/rustc_errors/src/translation.rs
@@ -12,9 +12,9 @@ use std::error::Report;
 ///
 /// Typically performed once for each diagnostic at the start of `emit_diagnostic` and then
 /// passed around as a reference thereafter.
-pub fn to_fluent_args<'iter, 'arg: 'iter>(
-    iter: impl Iterator<Item = DiagnosticArg<'iter, 'arg>>,
-) -> FluentArgs<'arg> {
+pub fn to_fluent_args<'iter>(
+    iter: impl Iterator<Item = DiagnosticArg<'iter, 'static>>,
+) -> FluentArgs<'static> {
     let mut args = if let Some(size) = iter.size_hint().1 {
         FluentArgs::with_capacity(size)
     } else {
diff --git a/compiler/rustc_hir_typeck/src/errors.rs b/compiler/rustc_hir_typeck/src/errors.rs
index b75cf4b4e8b..0695af15b16 100644
--- a/compiler/rustc_hir_typeck/src/errors.rs
+++ b/compiler/rustc_hir_typeck/src/errors.rs
@@ -43,7 +43,7 @@ pub enum ReturnLikeStatementKind {
 }
 
 impl IntoDiagnosticArg for ReturnLikeStatementKind {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         let kind = match self {
             Self::Return => "return",
             Self::Become => "become",
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 4e9f573091b..0a128218c92 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -534,7 +534,7 @@ pub enum TyOrSig<'tcx> {
 }
 
 impl IntoDiagnosticArg for TyOrSig<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         match self {
             TyOrSig::Ty(ty) => ty.into_diagnostic_arg(),
             TyOrSig::ClosureSig(sig) => sig.into_diagnostic_arg(),
diff --git a/compiler/rustc_infer/src/errors/note_and_explain.rs b/compiler/rustc_infer/src/errors/note_and_explain.rs
index 8e45cc6d80e..331e3633e90 100644
--- a/compiler/rustc_infer/src/errors/note_and_explain.rs
+++ b/compiler/rustc_infer/src/errors/note_and_explain.rs
@@ -108,7 +108,7 @@ pub enum SuffixKind {
 }
 
 impl IntoDiagnosticArg for PrefixKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         let kind = match self {
             Self::Empty => "empty",
             Self::RefValidFor => "ref_valid_for",
@@ -130,7 +130,7 @@ impl IntoDiagnosticArg for PrefixKind {
 }
 
 impl IntoDiagnosticArg for SuffixKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         let kind = match self {
             Self::Empty => "empty",
             Self::Continues => "continues",
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index e19177fccef..db01b5bd707 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -2914,7 +2914,7 @@ impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
 pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
 
 impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         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 cf1e042c529..7287fc26053 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
@@ -134,7 +134,7 @@ impl InferenceDiagnosticsParentData {
 }
 
 impl IntoDiagnosticArg for UnderspecifiedArgKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         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/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index e1a83c86318..b3b83c8ab95 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
@@ -30,7 +30,7 @@ impl<'tcx, T> IntoDiagnosticArg for Highlighted<'tcx, T>
 where
     T: for<'a> Print<'tcx, FmtPrinter<'a, 'tcx>>,
 {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         rustc_errors::DiagnosticArgValue::Str(self.to_string().into())
     }
 }
diff --git a/compiler/rustc_metadata/src/locator.rs b/compiler/rustc_metadata/src/locator.rs
index 2376d953341..1ab965e2876 100644
--- a/compiler/rustc_metadata/src/locator.rs
+++ b/compiler/rustc_metadata/src/locator.rs
@@ -291,7 +291,7 @@ impl fmt::Display for CrateFlavor {
 }
 
 impl IntoDiagnosticArg for CrateFlavor {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         match self {
             CrateFlavor::Rlib => DiagnosticArgValue::Str(Cow::Borrowed("rlib")),
             CrateFlavor::Rmeta => DiagnosticArgValue::Str(Cow::Borrowed("rmeta")),
diff --git a/compiler/rustc_middle/src/error.rs b/compiler/rustc_middle/src/error.rs
index e0436b38c4b..211da800202 100644
--- a/compiler/rustc_middle/src/error.rs
+++ b/compiler/rustc_middle/src/error.rs
@@ -95,17 +95,14 @@ pub(super) struct ConstNotUsedTraitAlias {
 
 pub struct CustomSubdiagnostic<'a> {
     pub msg: fn() -> DiagnosticMessage,
-    pub add_args:
-        Box<dyn FnOnce(&mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>)) + 'a>,
+    pub add_args: Box<dyn FnOnce(&mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue)) + 'a>,
 }
 
 impl<'a> CustomSubdiagnostic<'a> {
     pub fn label(x: fn() -> DiagnosticMessage) -> Self {
         Self::label_and_then(x, |_| {})
     }
-    pub fn label_and_then<
-        F: FnOnce(&mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>)) + 'a,
-    >(
+    pub fn label_and_then<F: FnOnce(&mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue)) + 'a>(
         msg: fn() -> DiagnosticMessage,
         f: F,
     ) -> Self {
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index 7a1df495451..95574aee499 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -233,7 +233,7 @@ pub enum InvalidMetaKind {
 }
 
 impl IntoDiagnosticArg for InvalidMetaKind {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Borrowed(match self {
             InvalidMetaKind::SliceTooBig => "slice_too_big",
             InvalidMetaKind::TooBig => "too_big",
@@ -267,7 +267,7 @@ pub struct Misalignment {
 macro_rules! impl_into_diagnostic_arg_through_debug {
     ($($ty:ty),*$(,)?) => {$(
         impl IntoDiagnosticArg for $ty {
-            fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+            fn into_diagnostic_arg(self) -> DiagnosticArgValue {
                 DiagnosticArgValue::Str(Cow::Owned(format!("{self:?}")))
             }
         }
@@ -367,7 +367,7 @@ pub enum PointerKind {
 }
 
 impl IntoDiagnosticArg for PointerKind {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(
             match self {
                 Self::Ref => "ref",
@@ -485,10 +485,7 @@ pub trait MachineStopType: Any + fmt::Debug + Send {
     fn diagnostic_message(&self) -> DiagnosticMessage;
     /// Add diagnostic arguments by passing name and value pairs to `adder`, which are passed to
     /// fluent for formatting the translated diagnostic message.
-    fn add_args(
-        self: Box<Self>,
-        adder: &mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>),
-    );
+    fn add_args(self: Box<Self>, adder: &mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue));
 }
 
 impl dyn MachineStopType {
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index fdbbf468ece..0fe33e441f4 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -292,7 +292,7 @@ impl<O> AssertKind<O> {
         }
     }
 
-    pub fn add_args(self, adder: &mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue<'static>))
+    pub fn add_args(self, adder: &mut dyn FnMut(Cow<'static, str>, DiagnosticArgValue))
     where
         O: fmt::Debug,
     {
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index b4b8387c262..0fed4ccc62a 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -674,7 +674,7 @@ impl<'tcx> Pat<'tcx> {
 }
 
 impl<'tcx> IntoDiagnosticArg for Pat<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         format!("{self}").into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index 310cf113b11..f7c33960fdd 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -117,7 +117,7 @@ impl std::fmt::Debug for ConstInt {
 impl IntoDiagnosticArg 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) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::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 16e7b16a0bf..603d7f46aab 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -15,7 +15,7 @@ pub struct UnevaluatedConst<'tcx> {
 }
 
 impl rustc_errors::IntoDiagnosticArg for UnevaluatedConst<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         format!("{self:?}").into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index c1e2479defd..8678f388298 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -20,7 +20,7 @@ use rustc_span::{BytePos, Span};
 use rustc_type_ir::TyKind::*;
 
 impl<'tcx> IntoDiagnosticArg for Ty<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_middle/src/ty/generic_args.rs b/compiler/rustc_middle/src/ty/generic_args.rs
index 5a4b86eeffd..69ad6810c6f 100644
--- a/compiler/rustc_middle/src/ty/generic_args.rs
+++ b/compiler/rustc_middle/src/ty/generic_args.rs
@@ -56,7 +56,7 @@ unsafe impl<'tcx> Sync for GenericArg<'tcx> where
 }
 
 impl<'tcx> IntoDiagnosticArg for GenericArg<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 25473f52c03..f07a4ac29e9 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -269,7 +269,7 @@ impl<'tcx> fmt::Display for LayoutError<'tcx> {
 }
 
 impl<'tcx> IntoDiagnosticArg for LayoutError<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index dac60ae58a0..dabd50a32b9 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -583,13 +583,13 @@ impl<'tcx> Predicate<'tcx> {
 }
 
 impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
     }
 }
 
 impl rustc_errors::IntoDiagnosticArg for Clause<'_> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
     }
 }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 73052be30ae..bac5068a69b 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -2632,7 +2632,7 @@ where
 pub struct TraitRefPrintOnlyTraitPath<'tcx>(ty::TraitRef<'tcx>);
 
 impl<'tcx> rustc_errors::IntoDiagnosticArg for TraitRefPrintOnlyTraitPath<'tcx> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
@@ -2649,7 +2649,7 @@ impl<'tcx> fmt::Debug for TraitRefPrintOnlyTraitPath<'tcx> {
 pub struct TraitRefPrintSugared<'tcx>(ty::TraitRef<'tcx>);
 
 impl<'tcx> rustc_errors::IntoDiagnosticArg for TraitRefPrintSugared<'tcx> {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index b089f4a9e78..43a6281481f 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -862,7 +862,7 @@ impl<'tcx> PolyTraitRef<'tcx> {
 }
 
 impl<'tcx> IntoDiagnosticArg for TraitRef<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
@@ -908,7 +908,7 @@ impl<'tcx> ExistentialTraitRef<'tcx> {
 }
 
 impl<'tcx> IntoDiagnosticArg for ExistentialTraitRef<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
@@ -1149,7 +1149,7 @@ impl<'tcx, T> IntoDiagnosticArg for Binder<'tcx, T>
 where
     T: IntoDiagnosticArg,
 {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.value.into_diagnostic_arg()
     }
 }
@@ -1359,7 +1359,7 @@ impl<'tcx> FnSig<'tcx> {
 }
 
 impl<'tcx> IntoDiagnosticArg for FnSig<'tcx> {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index ac147afaab3..226df08ff8f 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -698,12 +698,15 @@ impl UnsafeOpKind {
                     span,
                     function: &with_no_trimmed_paths!(tcx.def_path_str(*function)),
                     missing_target_features: DiagnosticArgValue::StrListSepByAnd(
-                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                        missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
                     ),
                     missing_target_features_count: missing.len(),
                     note: if build_enabled.is_empty() { None } else { Some(()) },
                     build_target_features: DiagnosticArgValue::StrListSepByAnd(
-                        build_enabled.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                        build_enabled
+                            .iter()
+                            .map(|feature| Cow::from(feature.to_string()))
+                            .collect(),
                     ),
                     build_target_features_count: build_enabled.len(),
                     unsafe_not_inherited_note,
@@ -860,12 +863,15 @@ impl UnsafeOpKind {
                 dcx.emit_err(CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
                     span,
                     missing_target_features: DiagnosticArgValue::StrListSepByAnd(
-                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                        missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
                     ),
                     missing_target_features_count: missing.len(),
                     note: if build_enabled.is_empty() { None } else { Some(()) },
                     build_target_features: DiagnosticArgValue::StrListSepByAnd(
-                        build_enabled.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                        build_enabled
+                            .iter()
+                            .map(|feature| Cow::from(feature.to_string()))
+                            .collect(),
                     ),
                     build_target_features_count: build_enabled.len(),
                     unsafe_not_inherited_note,
@@ -876,12 +882,15 @@ impl UnsafeOpKind {
                 dcx.emit_err(CallToFunctionWithRequiresUnsafe {
                     span,
                     missing_target_features: DiagnosticArgValue::StrListSepByAnd(
-                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                        missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
                     ),
                     missing_target_features_count: missing.len(),
                     note: if build_enabled.is_empty() { None } else { Some(()) },
                     build_target_features: DiagnosticArgValue::StrListSepByAnd(
-                        build_enabled.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                        build_enabled
+                            .iter()
+                            .map(|feature| Cow::from(feature.to_string()))
+                            .collect(),
                     ),
                     build_target_features_count: build_enabled.len(),
                     unsafe_not_inherited_note,
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 6929c8040c5..147001cabb0 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -127,11 +127,11 @@ pub struct UnsafeOpInUnsafeFnCallToFunctionWithRequiresUnsafe<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
-    pub missing_target_features: DiagnosticArgValue<'a>,
+    pub missing_target_features: DiagnosticArgValue,
     pub missing_target_features_count: usize,
     #[note]
     pub note: Option<()>,
-    pub build_target_features: DiagnosticArgValue<'a>,
+    pub build_target_features: DiagnosticArgValue,
     pub build_target_features_count: usize,
     #[subdiagnostic]
     pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
@@ -379,11 +379,11 @@ pub struct CallToFunctionWithRequiresUnsafe<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
-    pub missing_target_features: DiagnosticArgValue<'a>,
+    pub missing_target_features: DiagnosticArgValue,
     pub missing_target_features_count: usize,
     #[note]
     pub note: Option<()>,
-    pub build_target_features: DiagnosticArgValue<'a>,
+    pub build_target_features: DiagnosticArgValue,
     pub build_target_features_count: usize,
     #[subdiagnostic]
     pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
@@ -397,11 +397,11 @@ pub struct CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
-    pub missing_target_features: DiagnosticArgValue<'a>,
+    pub missing_target_features: DiagnosticArgValue,
     pub missing_target_features_count: usize,
     #[note]
     pub note: Option<()>,
-    pub build_target_features: DiagnosticArgValue<'a>,
+    pub build_target_features: DiagnosticArgValue,
     pub build_target_features_count: usize,
     #[subdiagnostic]
     pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index 8b9e507c8c7..c49f92f4f85 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -34,7 +34,7 @@ pub(crate) macro throw_machine_stop_str($($tt:tt)*) {{
 
         fn add_args(
             self: Box<Self>,
-            _: &mut dyn FnMut(std::borrow::Cow<'static, str>, rustc_errors::DiagnosticArgValue<'static>),
+            _: &mut dyn FnMut(std::borrow::Cow<'static, str>, rustc_errors::DiagnosticArgValue),
         ) {}
     }
     throw_machine_stop!(Zst)
diff --git a/compiler/rustc_mir_transform/src/errors.rs b/compiler/rustc_mir_transform/src/errors.rs
index 4ef3d47d6a6..30de40e226c 100644
--- a/compiler/rustc_mir_transform/src/errors.rs
+++ b/compiler/rustc_mir_transform/src/errors.rs
@@ -125,7 +125,7 @@ impl RequiresUnsafeDetail {
                 diag.arg(
                     "missing_target_features",
                     DiagnosticArgValue::StrListSepByAnd(
-                        missing.iter().map(|feature| Cow::from(feature.as_str())).collect(),
+                        missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
                     ),
                 );
                 diag.arg("missing_target_features_count", missing.len());
@@ -136,7 +136,7 @@ impl RequiresUnsafeDetail {
                         DiagnosticArgValue::StrListSepByAnd(
                             build_enabled
                                 .iter()
-                                .map(|feature| Cow::from(feature.as_str()))
+                                .map(|feature| Cow::from(feature.to_string()))
                                 .collect(),
                         ),
                     );
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 9d9741bbe89..8f27d01794c 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -78,7 +78,7 @@ pub(crate) enum ProcMacroKind {
 }
 
 impl IntoDiagnosticArg for ProcMacroKind {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         match self {
             ProcMacroKind::Attribute => "attribute proc macro",
             ProcMacroKind::Derive => "derive proc macro",
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 0743ff03864..9788fcb3c7d 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -90,7 +90,7 @@ impl PatternSource {
 }
 
 impl IntoDiagnosticArg for PatternSource {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(Cow::Borrowed(self.descr()))
     }
 }
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 2ec1a726cef..d35f951e2ae 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -3092,7 +3092,7 @@ impl fmt::Display for CrateType {
 }
 
 impl IntoDiagnosticArg for CrateType {
-    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 7cd76ad7293..3a0ae74dd92 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -111,7 +111,7 @@ impl Mul<usize> for Limit {
 }
 
 impl rustc_errors::IntoDiagnosticArg for Limit {
-    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue {
         self.to_string().into_diagnostic_arg()
     }
 }
diff --git a/src/tools/miri/src/diagnostics.rs b/src/tools/miri/src/diagnostics.rs
index bf3284df596..92c58d48dc7 100644
--- a/src/tools/miri/src/diagnostics.rs
+++ b/src/tools/miri/src/diagnostics.rs
@@ -104,7 +104,7 @@ impl MachineStopType for TerminationInfo {
         self: Box<Self>,
         _: &mut dyn FnMut(
             std::borrow::Cow<'static, str>,
-            rustc_errors::DiagnosticArgValue<'static>,
+            rustc_errors::DiagnosticArgValue,
         ),
     ) {
     }