Merge from rustc

81 files changed, 692 insertions, 427 deletions

diff --git a/compiler/rustc_ast_lowering/src/asm.rs b/compiler/rustc_ast_lowering/src/asm.rs
index 941d3179587..d350498bc96 100644
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@@ -44,6 +44,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     | asm::InlineAsmArch::AArch64
                     | asm::InlineAsmArch::RiscV32
                     | asm::InlineAsmArch::RiscV64
+                    | asm::InlineAsmArch::LoongArch64
             );
             if !is_stable && !self.tcx.features().asm_experimental_arch {
                 feature_err(
diff --git a/compiler/rustc_builtin_macros/src/compile_error.rs b/compiler/rustc_builtin_macros/src/compile_error.rs
index aeb3bb80045..5efc5a4e3ee 100644
--- a/compiler/rustc_builtin_macros/src/compile_error.rs
+++ b/compiler/rustc_builtin_macros/src/compile_error.rs
@@ -18,7 +18,7 @@ pub fn expand_compile_error<'cx>(
         reason = "diagnostic message is specified by user"
     )]
     #[expect(rustc::untranslatable_diagnostic, reason = "diagnostic message is specified by user")]
-    cx.span_err(sp, var.as_str());
+    cx.span_err(sp, var.to_string());
 
     DummyResult::any(sp)
 }
diff --git a/compiler/rustc_builtin_macros/src/deriving/clone.rs b/compiler/rustc_builtin_macros/src/deriving/clone.rs
index 9883563746e..9ba98d0a5d1 100644
--- a/compiler/rustc_builtin_macros/src/deriving/clone.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/clone.rs
@@ -68,7 +68,6 @@ pub fn expand_deriving_clone(
         _ => cx.span_bug(span, "`#[derive(Clone)]` on trait item or impl item"),
     }
 
-    let attrs = thin_vec![cx.attr_word(sym::inline, span)];
     let trait_def = TraitDef {
         span,
         path: path_std!(clone::Clone),
@@ -82,7 +81,7 @@ pub fn expand_deriving_clone(
             explicit_self: true,
             nonself_args: Vec::new(),
             ret_ty: Self_,
-            attributes: attrs,
+            attributes: thin_vec![cx.attr_word(sym::inline, span)],
             fieldless_variants_strategy: FieldlessVariantsStrategy::Default,
             combine_substructure: substructure,
         }],
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
index af971958680..c78a0eb04a0 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
@@ -18,11 +18,6 @@ pub fn expand_deriving_eq(
     is_const: bool,
 ) {
     let span = cx.with_def_site_ctxt(span);
-    let attrs = thin_vec![
-        cx.attr_word(sym::inline, span),
-        cx.attr_nested_word(sym::doc, sym::hidden, span),
-        cx.attr_word(sym::no_coverage, span)
-    ];
     let trait_def = TraitDef {
         span,
         path: path_std!(cmp::Eq),
@@ -36,7 +31,11 @@ pub fn expand_deriving_eq(
             explicit_self: true,
             nonself_args: vec![],
             ret_ty: Unit,
-            attributes: attrs,
+            attributes: thin_vec![
+                cx.attr_word(sym::inline, span),
+                cx.attr_nested_word(sym::doc, sym::hidden, span),
+                cx.attr_word(sym::no_coverage, span)
+            ],
             fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
             combine_substructure: combine_substructure(Box::new(|a, b, c| {
                 cs_total_eq_assert(a, b, c)
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs
index cfd36f030a1..4401cf8a9c5 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs
@@ -15,7 +15,6 @@ pub fn expand_deriving_ord(
     push: &mut dyn FnMut(Annotatable),
     is_const: bool,
 ) {
-    let attrs = thin_vec![cx.attr_word(sym::inline, span)];
     let trait_def = TraitDef {
         span,
         path: path_std!(cmp::Ord),
@@ -29,7 +28,7 @@ pub fn expand_deriving_ord(
             explicit_self: true,
             nonself_args: vec![(self_ref(), sym::other)],
             ret_ty: Path(path_std!(cmp::Ordering)),
-            attributes: attrs,
+            attributes: thin_vec![cx.attr_word(sym::inline, span)],
             fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
             combine_substructure: combine_substructure(Box::new(|a, b, c| cs_cmp(a, b, c))),
         }],
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs
index bad47db0de1..a71ecc5db7d 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs
@@ -82,14 +82,13 @@ pub fn expand_deriving_partial_eq(
 
     // No need to generate `ne`, the default suffices, and not generating it is
     // faster.
-    let attrs = thin_vec![cx.attr_word(sym::inline, span)];
     let methods = vec![MethodDef {
         name: sym::eq,
         generics: Bounds::empty(),
         explicit_self: true,
         nonself_args: vec![(self_ref(), sym::other)],
         ret_ty: Path(path_local!(bool)),
-        attributes: attrs,
+        attributes: thin_vec![cx.attr_word(sym::inline, span)],
         fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
         combine_substructure: combine_substructure(Box::new(|a, b, c| cs_eq(a, b, c))),
     }];
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs
index 9f46247908d..54b6cb7d713 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs
@@ -19,8 +19,6 @@ pub fn expand_deriving_partial_ord(
     let ret_ty =
         Path(Path::new_(pathvec_std!(option::Option), vec![Box::new(ordering_ty)], PathKind::Std));
 
-    let attrs = thin_vec![cx.attr_word(sym::inline, span)];
-
     // Order in which to perform matching
     let tag_then_data = if let Annotatable::Item(item) = item
         && let ItemKind::Enum(def, _) = &item.kind {
@@ -48,7 +46,7 @@ pub fn expand_deriving_partial_ord(
         explicit_self: true,
         nonself_args: vec![(self_ref(), sym::other)],
         ret_ty,
-        attributes: attrs,
+        attributes: thin_vec![cx.attr_word(sym::inline, span)],
         fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
         combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
             cs_partial_cmp(cx, span, substr, tag_then_data)
diff --git a/compiler/rustc_builtin_macros/src/deriving/default.rs b/compiler/rustc_builtin_macros/src/deriving/default.rs
index 33fe98b40e1..07b172bc757 100644
--- a/compiler/rustc_builtin_macros/src/deriving/default.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/default.rs
@@ -20,7 +20,6 @@ pub fn expand_deriving_default(
 ) {
     item.visit_with(&mut DetectNonVariantDefaultAttr { cx });
 
-    let attrs = thin_vec![cx.attr_word(sym::inline, span)];
     let trait_def = TraitDef {
         span,
         path: Path::new(vec![kw::Default, sym::Default]),
@@ -34,7 +33,7 @@ pub fn expand_deriving_default(
             explicit_self: false,
             nonself_args: Vec::new(),
             ret_ty: Self_,
-            attributes: attrs,
+            attributes: thin_vec![cx.attr_word(sym::inline, span)],
             fieldless_variants_strategy: FieldlessVariantsStrategy::Default,
             combine_substructure: combine_substructure(Box::new(|cx, trait_span, substr| {
                 match substr.fields {
diff --git a/compiler/rustc_builtin_macros/src/deriving/hash.rs b/compiler/rustc_builtin_macros/src/deriving/hash.rs
index 4eee573db42..101401f9c85 100644
--- a/compiler/rustc_builtin_macros/src/deriving/hash.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/hash.rs
@@ -1,7 +1,7 @@
 use crate::deriving::generic::ty::*;
 use crate::deriving::generic::*;
 use crate::deriving::{path_std, pathvec_std};
-use rustc_ast::{AttrVec, MetaItem, Mutability};
+use rustc_ast::{MetaItem, Mutability};
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
@@ -33,7 +33,7 @@ pub fn expand_deriving_hash(
             explicit_self: true,
             nonself_args: vec![(Ref(Box::new(Path(arg)), Mutability::Mut), sym::state)],
             ret_ty: Unit,
-            attributes: AttrVec::new(),
+            attributes: thin_vec![cx.attr_word(sym::inline, span)],
             fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
             combine_substructure: combine_substructure(Box::new(|a, b, c| {
                 hash_substructure(a, b, c)
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index d0d78646009..f1ab279daba 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -377,7 +377,7 @@ impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for EnvNotDefined {
                 rustc::untranslatable_diagnostic,
                 reason = "cannot translate user-provided messages"
             )]
-            handler.struct_diagnostic(msg.as_str())
+            handler.struct_diagnostic(msg.to_string())
         } else {
             handler.struct_diagnostic(crate::fluent_generated::builtin_macros_env_not_defined)
         };
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 5cc234268b0..f8bb9bf2bb5 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -23,7 +23,7 @@ use rustc_session::utils::NativeLibKind;
 use rustc_session::{filesearch, Session};
 use rustc_span::symbol::Symbol;
 use rustc_target::spec::crt_objects::{CrtObjects, LinkSelfContainedDefault};
-use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, LinkerFlavorCli, Lld, PanicStrategy};
+use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, Lld, PanicStrategy};
 use rustc_target::spec::{RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo};
 
 use super::archive::{ArchiveBuilder, ArchiveBuilderBuilder};
@@ -893,7 +893,7 @@ fn link_natively<'a>(
                     linker_path: &linker_path,
                     exit_status: prog.status,
                     command: &cmd,
-                    escaped_output: &escaped_output,
+                    escaped_output,
                 };
                 sess.diagnostic().emit_err(err);
                 // If MSVC's `link.exe` was expected but the return code
@@ -1302,44 +1302,7 @@ pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
                 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
                     sess.emit_fatal(errors::LinkerFileStem);
                 });
-
-                // Remove any version postfix.
-                let stem = stem
-                    .rsplit_once('-')
-                    .and_then(|(lhs, rhs)| rhs.chars().all(char::is_numeric).then_some(lhs))
-                    .unwrap_or(stem);
-
-                // GCC/Clang can have an optional target prefix.
-                let flavor = if stem == "emcc" {
-                    LinkerFlavor::EmCc
-                } else if stem == "gcc"
-                    || stem.ends_with("-gcc")
-                    || stem == "g++"
-                    || stem.ends_with("-g++")
-                    || stem == "clang"
-                    || stem.ends_with("-clang")
-                    || stem == "clang++"
-                    || stem.ends_with("-clang++")
-                {
-                    LinkerFlavor::from_cli(LinkerFlavorCli::Gcc, &sess.target)
-                } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
-                    LinkerFlavor::WasmLld(Cc::No)
-                } else if stem == "ld" || stem.ends_with("-ld") {
-                    LinkerFlavor::from_cli(LinkerFlavorCli::Ld, &sess.target)
-                } else if stem == "ld.lld" {
-                    LinkerFlavor::Gnu(Cc::No, Lld::Yes)
-                } else if stem == "link" {
-                    LinkerFlavor::Msvc(Lld::No)
-                } else if stem == "lld-link" {
-                    LinkerFlavor::Msvc(Lld::Yes)
-                } else if stem == "lld" || stem == "rust-lld" {
-                    let lld_flavor = sess.target.linker_flavor.lld_flavor();
-                    LinkerFlavor::from_cli(LinkerFlavorCli::Lld(lld_flavor), &sess.target)
-                } else {
-                    // fall back to the value in the target spec
-                    sess.target.linker_flavor
-                };
-
+                let flavor = sess.target.linker_flavor.with_linker_hints(stem);
                 Some((linker, flavor))
             }
             (None, None) => None,
@@ -1349,7 +1312,7 @@ pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
     // linker and linker flavor specified via command line have precedence over what the target
     // specification specifies
     let linker_flavor =
-        sess.opts.cg.linker_flavor.map(|flavor| LinkerFlavor::from_cli(flavor, &sess.target));
+        sess.opts.cg.linker_flavor.map(|flavor| sess.target.linker_flavor.with_cli_hints(flavor));
     if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), linker_flavor) {
         return ret;
     }
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index c323372bda4..10e9e5588f6 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -1800,7 +1800,7 @@ impl SharedEmitterMain {
                     handler.emit_diagnostic(&mut d);
                 }
                 Ok(SharedEmitterMessage::InlineAsmError(cookie, msg, level, source)) => {
-                    let msg = msg.strip_prefix("error: ").unwrap_or(&msg);
+                    let msg = msg.strip_prefix("error: ").unwrap_or(&msg).to_string();
 
                     let mut err = match level {
                         Level::Error { lint: false } => sess.struct_err(msg).forget_guarantee(),
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index cf4893b8226..bf37ac69f2d 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -336,7 +336,7 @@ pub struct LinkingFailed<'a> {
     pub linker_path: &'a PathBuf,
     pub exit_status: ExitStatus,
     pub command: &'a Command,
-    pub escaped_output: &'a str,
+    pub escaped_output: String,
 }
 
 impl IntoDiagnostic<'_> for LinkingFailed<'_> {
@@ -345,11 +345,13 @@ impl IntoDiagnostic<'_> for LinkingFailed<'_> {
         diag.set_arg("linker_path", format!("{}", self.linker_path.display()));
         diag.set_arg("exit_status", format!("{}", self.exit_status));
 
-        diag.note(format!("{:?}", self.command)).note(self.escaped_output);
+        let contains_undefined_ref = self.escaped_output.contains("undefined reference to");
+
+        diag.note(format!("{:?}", self.command)).note(self.escaped_output.to_string());
 
         // Trying to match an error from OS linkers
         // which by now we have no way to translate.
-        if self.escaped_output.contains("undefined reference to") {
+        if contains_undefined_ref {
             diag.note(fluent::codegen_ssa_extern_funcs_not_found)
                 .note(fluent::codegen_ssa_specify_libraries_to_link)
                 .note(fluent::codegen_ssa_use_cargo_directive);
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 0b5d737091e..14888cf4d75 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -1258,7 +1258,7 @@ pub fn install_ice_hook(bug_report_url: &'static str, extra_info: fn(&Handler))
         if let Some(msg) = info.payload().downcast_ref::<String>() {
             if msg.starts_with("failed printing to stdout: ") && msg.ends_with("(os error 232)") {
                 // the error code is already going to be reported when the panic unwinds up the stack
-                let _ = early_error_no_abort(ErrorOutputType::default(), msg.as_str());
+                let _ = early_error_no_abort(ErrorOutputType::default(), msg.clone());
                 return;
             }
         };
diff --git a/compiler/rustc_error_codes/src/error_codes/E0133.md b/compiler/rustc_error_codes/src/error_codes/E0133.md
index 1adbcc31356..8ca3f03ce15 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0133.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0133.md
@@ -1,4 +1,4 @@
-Unsafe code was used outside of an unsafe function or block.
+Unsafe code was used outside of an unsafe block.
 
 Erroneous code example:
 
@@ -30,4 +30,21 @@ fn main() {
 
 See the [unsafe section][unsafe-section] of the Book for more details.
 
+#### Unsafe code in functions
+
+Unsafe code is currently accepted in unsafe functions, but that is being phased
+out in favor of requiring unsafe blocks here too.
+
+```
+unsafe fn f() { return; }
+
+unsafe fn g() {
+    f(); // Is accepted, but no longer recommended
+    unsafe { f(); } // Recommended way to write this
+}
+```
+
+Linting against this is controlled via the `unsafe_op_in_unsafe_fn` lint, which
+is `allow` by default but will be upgraded to `warn` in a future edition.
+
 [unsafe-section]: https://doc.rust-lang.org/book/ch19-01-unsafe-rust.html
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index 0accb4ab96f..2a97c4ff7ae 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -263,8 +263,7 @@ type FluentId = Cow<'static, str>;
 #[rustc_diagnostic_item = "SubdiagnosticMessage"]
 pub enum SubdiagnosticMessage {
     /// Non-translatable diagnostic message.
-    // FIXME(davidtwco): can a `Cow<'static, str>` be used here?
-    Str(String),
+    Str(Cow<'static, str>),
     /// Translatable message which has already been translated eagerly.
     ///
     /// Some diagnostics have repeated subdiagnostics where the same interpolated variables would
@@ -275,8 +274,7 @@ pub enum SubdiagnosticMessage {
     /// incorrect diagnostics. Eager translation results in translation for a subdiagnostic
     /// happening immediately after the subdiagnostic derive's logic has been run. This variant
     /// stores messages which have been translated eagerly.
-    // FIXME(#100717): can a `Cow<'static, str>` be used here?
-    Eager(String),
+    Eager(Cow<'static, str>),
     /// Identifier of a Fluent message. Instances of this variant are generated by the
     /// `Subdiagnostic` derive.
     FluentIdentifier(FluentId),
@@ -290,17 +288,17 @@ pub enum SubdiagnosticMessage {
 
 impl From<String> for SubdiagnosticMessage {
     fn from(s: String) -> Self {
-        SubdiagnosticMessage::Str(s)
+        SubdiagnosticMessage::Str(Cow::Owned(s))
     }
 }
-impl<'a> From<&'a str> for SubdiagnosticMessage {
-    fn from(s: &'a str) -> Self {
-        SubdiagnosticMessage::Str(s.to_string())
+impl From<&'static str> for SubdiagnosticMessage {
+    fn from(s: &'static str) -> Self {
+        SubdiagnosticMessage::Str(Cow::Borrowed(s))
     }
 }
 impl From<Cow<'static, str>> for SubdiagnosticMessage {
     fn from(s: Cow<'static, str>) -> Self {
-        SubdiagnosticMessage::Str(s.to_string())
+        SubdiagnosticMessage::Str(s)
     }
 }
 
@@ -312,8 +310,7 @@ impl From<Cow<'static, str>> for SubdiagnosticMessage {
 #[rustc_diagnostic_item = "DiagnosticMessage"]
 pub enum DiagnosticMessage {
     /// Non-translatable diagnostic message.
-    // FIXME(#100717): can a `Cow<'static, str>` be used here?
-    Str(String),
+    Str(Cow<'static, str>),
     /// Translatable message which has already been translated eagerly.
     ///
     /// Some diagnostics have repeated subdiagnostics where the same interpolated variables would
@@ -324,8 +321,7 @@ pub enum DiagnosticMessage {
     /// incorrect diagnostics. Eager translation results in translation for a subdiagnostic
     /// happening immediately after the subdiagnostic derive's logic has been run. This variant
     /// stores messages which have been translated eagerly.
-    // FIXME(#100717): can a `Cow<'static, str>` be used here?
-    Eager(String),
+    Eager(Cow<'static, str>),
     /// Identifier for a Fluent message (with optional attribute) corresponding to the diagnostic
     /// message.
     ///
@@ -363,17 +359,17 @@ impl DiagnosticMessage {
 
 impl From<String> for DiagnosticMessage {
     fn from(s: String) -> Self {
-        DiagnosticMessage::Str(s)
+        DiagnosticMessage::Str(Cow::Owned(s))
     }
 }
-impl<'a> From<&'a str> for DiagnosticMessage {
-    fn from(s: &'a str) -> Self {
-        DiagnosticMessage::Str(s.to_string())
+impl From<&'static str> for DiagnosticMessage {
+    fn from(s: &'static str) -> Self {
+        DiagnosticMessage::Str(Cow::Borrowed(s))
     }
 }
 impl From<Cow<'static, str>> for DiagnosticMessage {
     fn from(s: Cow<'static, str>) -> Self {
-        DiagnosticMessage::Str(s.to_string())
+        DiagnosticMessage::Str(s)
     }
 }
 
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 29c692128bc..488f2d67ee5 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -352,14 +352,9 @@ impl Diagnostic {
 
     /// Labels all the given spans with the provided label.
     /// See [`Self::span_label()`] for more information.
-    pub fn span_labels(
-        &mut self,
-        spans: impl IntoIterator<Item = Span>,
-        label: impl AsRef<str>,
-    ) -> &mut Self {
-        let label = label.as_ref();
+    pub fn span_labels(&mut self, spans: impl IntoIterator<Item = Span>, label: &str) -> &mut Self {
         for span in spans {
-            self.span_label(span, label);
+            self.span_label(span, label.to_string());
         }
         self
     }
@@ -394,17 +389,18 @@ impl Diagnostic {
         expected: DiagnosticStyledString,
         found: DiagnosticStyledString,
     ) -> &mut Self {
-        let mut msg: Vec<_> = vec![("required when trying to coerce from type `", Style::NoStyle)];
+        let mut msg: Vec<_> =
+            vec![(Cow::from("required when trying to coerce from type `"), Style::NoStyle)];
         msg.extend(expected.0.iter().map(|x| match *x {
-            StringPart::Normal(ref s) => (s.as_str(), Style::NoStyle),
-            StringPart::Highlighted(ref s) => (s.as_str(), Style::Highlight),
+            StringPart::Normal(ref s) => (Cow::from(s.clone()), Style::NoStyle),
+            StringPart::Highlighted(ref s) => (Cow::from(s.clone()), Style::Highlight),
         }));
-        msg.push(("` to type '", Style::NoStyle));
+        msg.push((Cow::from("` to type '"), Style::NoStyle));
         msg.extend(found.0.iter().map(|x| match *x {
-            StringPart::Normal(ref s) => (s.as_str(), Style::NoStyle),
-            StringPart::Highlighted(ref s) => (s.as_str(), Style::Highlight),
+            StringPart::Normal(ref s) => (Cow::from(s.clone()), Style::NoStyle),
+            StringPart::Highlighted(ref s) => (Cow::from(s.clone()), Style::Highlight),
         }));
-        msg.push(("`", Style::NoStyle));
+        msg.push((Cow::from("`"), Style::NoStyle));
 
         // For now, just attach these as notes
         self.highlighted_note(msg);
diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index db97d96fccd..7d9d0c76450 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -558,7 +558,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         }
 
         // Take the `Diagnostic` by replacing it with a dummy.
-        let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::Str("".to_string()));
+        let dummy = Diagnostic::new(Level::Allow, DiagnosticMessage::from(""));
         let diagnostic = std::mem::replace(&mut *self.inner.diagnostic, dummy);
 
         // Disable the ICE on `Drop`.
@@ -627,7 +627,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     pub fn span_labels(
         &mut self,
         spans: impl IntoIterator<Item = Span>,
-        label: impl AsRef<str>,
+        label: &str,
     ) -> &mut Self);
 
     forward!(pub fn note_expected_found(
@@ -781,8 +781,8 @@ impl Drop for DiagnosticBuilderInner<'_> {
                 if !panicking() {
                     handler.emit_diagnostic(&mut Diagnostic::new(
                         Level::Bug,
-                        DiagnosticMessage::Str(
-                            "the following error was constructed but not emitted".to_string(),
+                        DiagnosticMessage::from(
+                            "the following error was constructed but not emitted",
                         ),
                     ));
                     handler.emit_diagnostic(&mut self.diagnostic);
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index e8cd7eaa60f..d8c997b49a1 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -367,7 +367,7 @@ pub trait Emitter: Translate {
 
                 children.push(SubDiagnostic {
                     level: Level::Note,
-                    message: vec![(DiagnosticMessage::Str(msg), Style::NoStyle)],
+                    message: vec![(DiagnosticMessage::from(msg), Style::NoStyle)],
                     span: MultiSpan::new(),
                     render_span: None,
                 });
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 3dec0d9299c..6c5f3e62454 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -628,7 +628,7 @@ impl Handler {
         message: DiagnosticMessage,
         args: impl Iterator<Item = DiagnosticArg<'a, 'static>>,
     ) -> SubdiagnosticMessage {
-        SubdiagnosticMessage::Eager(self.eagerly_translate_to_string(message, args))
+        SubdiagnosticMessage::Eager(Cow::from(self.eagerly_translate_to_string(message, args)))
     }
 
     /// Translate `message` eagerly with `args` to `String`.
@@ -1450,14 +1450,14 @@ impl HandlerInner {
         self.emit_stashed_diagnostics();
 
         let warnings = match self.deduplicated_warn_count {
-            0 => String::new(),
-            1 => "1 warning emitted".to_string(),
-            count => format!("{count} warnings emitted"),
+            0 => Cow::from(""),
+            1 => Cow::from("1 warning emitted"),
+            count => Cow::from(format!("{count} warnings emitted")),
         };
         let errors = match self.deduplicated_err_count {
-            0 => String::new(),
-            1 => "aborting due to previous error".to_string(),
-            count => format!("aborting due to {count} previous errors"),
+            0 => Cow::from(""),
+            1 => Cow::from("aborting due to previous error"),
+            count => Cow::from(format!("aborting due to {count} previous errors")),
         };
         if self.treat_err_as_bug() {
             return;
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 4671adccc54..0d43b30474b 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -1154,7 +1154,7 @@ impl<'a> ExtCtxt<'a> {
         // Fixme: does this result in errors?
         self.expansions.clear();
     }
-    pub fn bug(&self, msg: &str) -> ! {
+    pub fn bug(&self, msg: &'static str) -> ! {
         self.sess.parse_sess.span_diagnostic.bug(msg);
     }
     pub fn trace_macros(&self) -> bool {
@@ -1224,7 +1224,7 @@ pub fn resolve_path(
 pub fn expr_to_spanned_string<'a>(
     cx: &'a mut ExtCtxt<'_>,
     expr: P<ast::Expr>,
-    err_msg: &str,
+    err_msg: &'static str,
 ) -> Result<(Symbol, ast::StrStyle, Span), Option<(DiagnosticBuilder<'a, ErrorGuaranteed>, bool)>> {
     // Perform eager expansion on the expression.
     // We want to be able to handle e.g., `concat!("foo", "bar")`.
@@ -1262,7 +1262,7 @@ pub fn expr_to_spanned_string<'a>(
 pub fn expr_to_string(
     cx: &mut ExtCtxt<'_>,
     expr: P<ast::Expr>,
-    err_msg: &str,
+    err_msg: &'static str,
 ) -> Option<(Symbol, ast::StrStyle)> {
     expr_to_spanned_string(cx, expr, err_msg)
         .map_err(|err| {
diff --git a/compiler/rustc_expand/src/mbe/diagnostics.rs b/compiler/rustc_expand/src/mbe/diagnostics.rs
index cb8b4899e48..3593bed2d02 100644
--- a/compiler/rustc_expand/src/mbe/diagnostics.rs
+++ b/compiler/rustc_expand/src/mbe/diagnostics.rs
@@ -170,7 +170,7 @@ impl<'a, 'cx, 'matcher> Tracker<'matcher> for CollectTrackerAndEmitter<'a, 'cx,
             }
             Error(err_sp, msg) => {
                 let span = err_sp.substitute_dummy(self.root_span);
-                self.cx.struct_span_err(span, msg.as_str()).emit();
+                self.cx.struct_span_err(span, msg.clone()).emit();
                 self.result = Some(DummyResult::any(span));
             }
             ErrorReported(_) => self.result = Some(DummyResult::any(self.root_span)),
@@ -222,7 +222,7 @@ pub(super) fn emit_frag_parse_err(
     {
         let msg = &e.message[0];
         e.message[0] = (
-            DiagnosticMessage::Str(format!(
+            DiagnosticMessage::from(format!(
                 "macro expansion ends with an incomplete expression: {}",
                 message.replace(", found `<eof>`", ""),
             )),
@@ -313,9 +313,9 @@ pub(super) fn annotate_doc_comment(err: &mut Diagnostic, sm: &SourceMap, span: S
 
 /// Generates an appropriate parsing failure message. For EOF, this is "unexpected end...". For
 /// other tokens, this is "unexpected token...".
-pub(super) fn parse_failure_msg(tok: &Token) -> String {
+pub(super) fn parse_failure_msg(tok: &Token) -> Cow<'static, str> {
     match tok.kind {
-        token::Eof => "unexpected end of macro invocation".to_string(),
-        _ => format!("no rules expected the token `{}`", pprust::token_to_string(tok),),
+        token::Eof => Cow::from("unexpected end of macro invocation"),
+        _ => Cow::from(format!("no rules expected the token `{}`", pprust::token_to_string(tok))),
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 7df811ccdb5..18b6537a8e9 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -25,6 +25,7 @@ use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
 use rustc_trait_selection::traits::{
     self, ObligationCause, ObligationCauseCode, ObligationCtxt, Reveal,
 };
+use std::borrow::Cow;
 use std::iter;
 
 /// Checks that a method from an impl conforms to the signature of
@@ -684,7 +685,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
                 &cause,
                 hir.get_if_local(impl_m.def_id)
                     .and_then(|node| node.fn_decl())
-                    .map(|decl| (decl.output.span(), "return type in trait".to_owned())),
+                    .map(|decl| (decl.output.span(), Cow::from("return type in trait"))),
                 Some(infer::ValuePairs::Terms(ExpectedFound {
                     expected: trait_return_ty.into(),
                     found: impl_return_ty.into(),
@@ -963,7 +964,7 @@ fn report_trait_method_mismatch<'tcx>(
     infcx.err_ctxt().note_type_err(
         &mut diag,
         &cause,
-        trait_err_span.map(|sp| (sp, "type in trait".to_owned())),
+        trait_err_span.map(|sp| (sp, Cow::from("type in trait"))),
         Some(infer::ValuePairs::Sigs(ExpectedFound { expected: trait_sig, found: impl_sig })),
         terr,
         false,
@@ -1731,7 +1732,7 @@ pub(super) fn compare_impl_const_raw(
         infcx.err_ctxt().note_type_err(
             &mut diag,
             &cause,
-            trait_c_span.map(|span| (span, "type in trait".to_owned())),
+            trait_c_span.map(|span| (span, Cow::from("type in trait"))),
             Some(infer::ValuePairs::Terms(ExpectedFound {
                 expected: trait_ty.into(),
                 found: impl_ty.into(),
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index e8785235c83..fbd4a577d68 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -121,10 +121,11 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: DefId) -> hir
     if has_safe_attr != is_in_list {
         tcx.sess.struct_span_err(
             tcx.def_span(intrinsic_id),
-            DiagnosticMessage::Str(format!(
-                    "intrinsic safety mismatch between list of intrinsics within the compiler and core library intrinsics for intrinsic `{}`",
-                    tcx.item_name(intrinsic_id)
-        ))).emit();
+            DiagnosticMessage::from(format!(
+                "intrinsic safety mismatch between list of intrinsics within the compiler and core library intrinsics for intrinsic `{}`",
+                tcx.item_name(intrinsic_id)
+            )
+        )).emit();
     }
 
     is_in_list
diff --git a/compiler/rustc_hir_typeck/src/generator_interior/mod.rs b/compiler/rustc_hir_typeck/src/generator_interior/mod.rs
index 019fb86f55c..427d6f8803c 100644
--- a/compiler/rustc_hir_typeck/src/generator_interior/mod.rs
+++ b/compiler/rustc_hir_typeck/src/generator_interior/mod.rs
@@ -122,7 +122,7 @@ impl<'a, 'tcx> InteriorVisitor<'a, 'tcx> {
 
                     self.fcx
                         .need_type_info_err_in_generator(self.kind, span, unresolved_term)
-                        .span_note(yield_data.span, &*note)
+                        .span_note(yield_data.span, note)
                         .emit();
                 }
             } else {
@@ -686,7 +686,7 @@ fn check_must_not_suspend_def(
                 // Add optional reason note
                 if let Some(note) = attr.value_str() {
                     // FIXME(guswynn): consider formatting this better
-                    lint.span_note(data.source_span, note.as_str());
+                    lint.span_note(data.source_span, note.to_string());
                 }
 
                 // Add some quick suggestions on what to do
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index 35c05e80bad..f8a253c8949 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -76,6 +76,7 @@ use rustc_middle::ty::{
 };
 use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
 use rustc_target::spec::abi;
+use std::borrow::Cow;
 use std::ops::{ControlFlow, Deref};
 use std::path::PathBuf;
 use std::{cmp, fmt, iter};
@@ -1470,7 +1471,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         &self,
         diag: &mut Diagnostic,
         cause: &ObligationCause<'tcx>,
-        secondary_span: Option<(Span, String)>,
+        secondary_span: Option<(Span, Cow<'static, str>)>,
         mut values: Option<ValuePairs<'tcx>>,
         terr: TypeError<'tcx>,
         swap_secondary_and_primary: bool,
@@ -1629,7 +1630,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             }
         };
 
-        let mut label_or_note = |span: Span, msg: &str| {
+        let mut label_or_note = |span: Span, msg: Cow<'static, str>| {
             if (prefer_label && is_simple_error) || &[span] == diag.span.primary_spans() {
                 diag.span_label(span, msg);
             } else {
@@ -1643,15 +1644,15 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     ..
                 })) = values
                 {
-                    format!("expected this to be `{}`", expected)
+                    Cow::from(format!("expected this to be `{}`", expected))
                 } else {
-                    terr.to_string(self.tcx).to_string()
+                    terr.to_string(self.tcx)
                 };
-                label_or_note(sp, &terr);
-                label_or_note(span, &msg);
+                label_or_note(sp, terr);
+                label_or_note(span, msg);
             } else {
-                label_or_note(span, &terr.to_string(self.tcx));
-                label_or_note(sp, &msg);
+                label_or_note(span, terr.to_string(self.tcx));
+                label_or_note(sp, msg);
             }
         } else {
             if let Some(values) = values
@@ -1663,12 +1664,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 let expected = with_forced_trimmed_paths!(e.sort_string(self.tcx));
                 let found = with_forced_trimmed_paths!(f.sort_string(self.tcx));
                 if expected == found {
-                    label_or_note(span, &terr.to_string(self.tcx));
+                    label_or_note(span, terr.to_string(self.tcx));
                 } else {
-                    label_or_note(span, &format!("expected {expected}, found {found}"));
+                    label_or_note(span, Cow::from(format!("expected {expected}, found {found}")));
                 }
             } else {
-                label_or_note(span, &terr.to_string(self.tcx));
+                label_or_note(span, terr.to_string(self.tcx));
             }
         }
 
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
index 421eb807a14..d1f110472c9 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
@@ -234,13 +234,13 @@ impl<T> Trait<T> for X {
                         );
                     }
                     (_, ty::Alias(ty::Projection | ty::Inherent, proj_ty)) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => {
-                        let msg = format!(
+                        let msg = || format!(
                             "consider constraining the associated type `{}` to `{}`",
                             values.found, values.expected,
                         );
                         if !(self.suggest_constraining_opaque_associated_type(
                             diag,
-                            &msg,
+                            msg,
                             proj_ty,
                             values.expected,
                         ) || self.suggest_constraint(
@@ -250,7 +250,7 @@ impl<T> Trait<T> for X {
                             proj_ty,
                             values.expected,
                         )) {
-                            diag.help(msg);
+                            diag.help(msg());
                             diag.note(
                                 "for more information, visit \
                                 https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
@@ -308,7 +308,7 @@ impl<T> Trait<T> for X {
     fn suggest_constraint(
         &self,
         diag: &mut Diagnostic,
-        msg: &str,
+        msg: impl Fn() -> String,
         body_owner_def_id: DefId,
         proj_ty: &ty::AliasTy<'tcx>,
         ty: Ty<'tcx>,
@@ -340,7 +340,7 @@ impl<T> Trait<T> for X {
                         assoc,
                         assoc_substs,
                         ty,
-                        msg,
+                        &msg,
                         false,
                     ) {
                         return true;
@@ -374,10 +374,12 @@ impl<T> Trait<T> for X {
     ) {
         let tcx = self.tcx;
 
-        let msg = format!(
-            "consider constraining the associated type `{}` to `{}`",
-            values.expected, values.found
-        );
+        let msg = || {
+            format!(
+                "consider constraining the associated type `{}` to `{}`",
+                values.expected, values.found
+            )
+        };
         let body_owner = tcx.hir().get_if_local(body_owner_def_id);
         let current_method_ident = body_owner.and_then(|n| n.ident()).map(|i| i.name);
 
@@ -428,10 +430,11 @@ impl<T> Trait<T> for X {
             if callable_scope {
                 diag.help(format!(
                     "{} or calling a method that returns `{}`",
-                    msg, values.expected
+                    msg(),
+                    values.expected
                 ));
             } else {
-                diag.help(msg);
+                diag.help(msg());
             }
             diag.note(
                 "for more information, visit \
@@ -463,7 +466,7 @@ fn foo(&self) -> Self::T { String::new() }
     fn suggest_constraining_opaque_associated_type(
         &self,
         diag: &mut Diagnostic,
-        msg: &str,
+        msg: impl Fn() -> String,
         proj_ty: &ty::AliasTy<'tcx>,
         ty: Ty<'tcx>,
     ) -> bool {
@@ -635,7 +638,7 @@ fn foo(&self) -> Self::T { String::new() }
         assoc: ty::AssocItem,
         assoc_substs: &[ty::GenericArg<'tcx>],
         ty: Ty<'tcx>,
-        msg: &str,
+        msg: impl Fn() -> String,
         is_bound_surely_present: bool,
     ) -> bool {
         // FIXME: we would want to call `resolve_vars_if_possible` on `ty` before suggesting.
@@ -678,7 +681,7 @@ fn foo(&self) -> Self::T { String::new() }
         assoc: ty::AssocItem,
         assoc_substs: &[ty::GenericArg<'tcx>],
         ty: Ty<'tcx>,
-        msg: &str,
+        msg: impl Fn() -> String,
     ) -> bool {
         let tcx = self.tcx;
 
@@ -693,7 +696,7 @@ fn foo(&self) -> Self::T { String::new() }
                 let item_args = self.format_generic_args(assoc_substs);
                 (span.shrink_to_hi(), format!("<{}{} = {}>", assoc.ident(tcx), item_args, ty))
             };
-            diag.span_suggestion_verbose(span, msg, sugg, MaybeIncorrect);
+            diag.span_suggestion_verbose(span, msg(), sugg, MaybeIncorrect);
             return true;
         }
         false
diff --git a/compiler/rustc_lint/src/errors.rs b/compiler/rustc_lint/src/errors.rs
index bbae3d368f4..68167487a1b 100644
--- a/compiler/rustc_lint/src/errors.rs
+++ b/compiler/rustc_lint/src/errors.rs
@@ -39,7 +39,7 @@ impl AddToDiagnostic for OverruledAttributeSub {
                 diag.span_label(span, fluent::lint_node_source);
                 if let Some(rationale) = reason {
                     #[allow(rustc::untranslatable_diagnostic)]
-                    diag.note(rationale.as_str());
+                    diag.note(rationale.to_string());
                 }
             }
             OverruledAttributeSub::CommandLineSource => {
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index de1c2be2875..6b4d01551ae 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1527,7 +1527,7 @@ impl<'a> DecorateLint<'a, ()> for UnusedDef<'_, '_> {
         diag.set_arg("def", self.cx.tcx.def_path_str(self.def_id));
         // check for #[must_use = "..."]
         if let Some(note) = self.note {
-            diag.note(note.as_str());
+            diag.note(note.to_string());
         }
         if let Some(sugg) = self.suggestion {
             diag.subdiagnostic(sugg);
diff --git a/compiler/rustc_metadata/src/locator.rs b/compiler/rustc_metadata/src/locator.rs
index ceb348f3469..a89d7b464e2 100644
--- a/compiler/rustc_metadata/src/locator.rs
+++ b/compiler/rustc_metadata/src/locator.rs
@@ -666,31 +666,30 @@ impl<'a> CrateLocator<'a> {
             return None;
         }
 
-        let root = metadata.get_root();
-        if root.is_proc_macro_crate() != self.is_proc_macro {
+        let header = metadata.get_header();
+        if header.is_proc_macro_crate != self.is_proc_macro {
             info!(
                 "Rejecting via proc macro: expected {} got {}",
-                self.is_proc_macro,
-                root.is_proc_macro_crate(),
+                self.is_proc_macro, header.is_proc_macro_crate,
             );
             return None;
         }
 
-        if self.exact_paths.is_empty() && self.crate_name != root.name() {
+        if self.exact_paths.is_empty() && self.crate_name != header.name {
             info!("Rejecting via crate name");
             return None;
         }
 
-        if root.triple() != &self.triple {
-            info!("Rejecting via crate triple: expected {} got {}", self.triple, root.triple());
+        if header.triple != self.triple {
+            info!("Rejecting via crate triple: expected {} got {}", self.triple, header.triple);
             self.crate_rejections.via_triple.push(CrateMismatch {
                 path: libpath.to_path_buf(),
-                got: root.triple().to_string(),
+                got: header.triple.to_string(),
             });
             return None;
         }
 
-        let hash = root.hash();
+        let hash = header.hash;
         if let Some(expected_hash) = self.hash {
             if hash != expected_hash {
                 info!("Rejecting via hash: expected {} got {}", expected_hash, hash);
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 731bbb1edfb..06fdc6fe030 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -74,6 +74,7 @@ pub(crate) struct CrateMetadata {
     blob: MetadataBlob,
 
     // --- Some data pre-decoded from the metadata blob, usually for performance ---
+    /// Data about the top-level items in a crate, as well as various crate-level metadata.
     root: CrateRoot,
     /// Trait impl data.
     /// FIXME: Used only from queries and can use query cache,
@@ -449,7 +450,7 @@ impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for SyntaxContext {
                 You need to explicitly pass `(crate_metadata_ref, tcx)` to `decode` instead of just `crate_metadata_ref`.");
         };
 
-        let cname = cdata.root.name;
+        let cname = cdata.root.name();
         rustc_span::hygiene::decode_syntax_context(decoder, &cdata.hygiene_context, |_, id| {
             debug!("SpecializedDecoder<SyntaxContext>: decoding {}", id);
             cdata
@@ -564,7 +565,7 @@ impl<'a, 'tcx> Decodable<DecodeContext<'a, 'tcx>> for Span {
                 let cnum = u32::decode(decoder);
                 panic!(
                     "Decoding of crate {:?} tried to access proc-macro dep {:?}",
-                    decoder.cdata().root.name,
+                    decoder.cdata().root.header.name,
                     cnum
                 );
             }
@@ -671,6 +672,16 @@ impl MetadataBlob {
             .decode(self)
     }
 
+    pub(crate) fn get_header(&self) -> CrateHeader {
+        let slice = &self.blob()[..];
+        let offset = METADATA_HEADER.len();
+
+        let pos_bytes = slice[offset..][..4].try_into().unwrap();
+        let pos = u32::from_be_bytes(pos_bytes) as usize;
+
+        LazyValue::<CrateHeader>::from_position(NonZeroUsize::new(pos).unwrap()).decode(self)
+    }
+
     pub(crate) fn get_root(&self) -> CrateRoot {
         let slice = &self.blob()[..];
         let offset = METADATA_HEADER.len();
@@ -684,8 +695,8 @@ impl MetadataBlob {
     pub(crate) fn list_crate_metadata(&self, out: &mut dyn io::Write) -> io::Result<()> {
         let root = self.get_root();
         writeln!(out, "Crate info:")?;
-        writeln!(out, "name {}{}", root.name, root.extra_filename)?;
-        writeln!(out, "hash {} stable_crate_id {:?}", root.hash, root.stable_crate_id)?;
+        writeln!(out, "name {}{}", root.name(), root.extra_filename)?;
+        writeln!(out, "hash {} stable_crate_id {:?}", root.hash(), root.stable_crate_id)?;
         writeln!(out, "proc_macro {:?}", root.proc_macro_data.is_some())?;
         writeln!(out, "=External Dependencies=")?;
 
@@ -709,21 +720,17 @@ impl CrateRoot {
     }
 
     pub(crate) fn name(&self) -> Symbol {
-        self.name
+        self.header.name
     }
 
     pub(crate) fn hash(&self) -> Svh {
-        self.hash
+        self.header.hash
     }
 
     pub(crate) fn stable_crate_id(&self) -> StableCrateId {
         self.stable_crate_id
     }
 
-    pub(crate) fn triple(&self) -> &TargetTriple {
-        &self.triple
-    }
-
     pub(crate) fn decode_crate_deps<'a>(
         &self,
         metadata: &'a MetadataBlob,
@@ -794,7 +801,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             bug!(
                 "CrateMetadata::def_kind({:?}): id not found, in crate {:?} with number {}",
                 item_id,
-                self.root.name,
+                self.root.name(),
                 self.cnum,
             )
         })
@@ -1702,11 +1709,11 @@ impl CrateMetadata {
     }
 
     pub(crate) fn name(&self) -> Symbol {
-        self.root.name
+        self.root.header.name
     }
 
     pub(crate) fn hash(&self) -> Svh {
-        self.root.hash
+        self.root.header.hash
     }
 
     fn num_def_ids(&self) -> usize {
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 7425963d30f..3d8991d99b5 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -317,9 +317,9 @@ provide! { tcx, def_id, other, cdata,
     }
     native_libraries => { cdata.get_native_libraries(tcx.sess).collect() }
     foreign_modules => { cdata.get_foreign_modules(tcx.sess).map(|m| (m.def_id, m)).collect() }
-    crate_hash => { cdata.root.hash }
+    crate_hash => { cdata.root.header.hash }
     crate_host_hash => { cdata.host_hash }
-    crate_name => { cdata.root.name }
+    crate_name => { cdata.root.header.name }
 
     extra_filename => { cdata.root.extra_filename.clone() }
 
@@ -581,7 +581,7 @@ impl CrateStore for CStore {
     }
 
     fn crate_name(&self, cnum: CrateNum) -> Symbol {
-        self.get_crate_data(cnum).root.name
+        self.get_crate_data(cnum).root.header.name
     }
 
     fn stable_crate_id(&self, cnum: CrateNum) -> StableCrateId {
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index e3a0ce37387..f2a7762f003 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -662,10 +662,13 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         let root = stat!("final", || {
             let attrs = tcx.hir().krate_attrs();
             self.lazy(CrateRoot {
-                name: tcx.crate_name(LOCAL_CRATE),
+                header: CrateHeader {
+                    name: tcx.crate_name(LOCAL_CRATE),
+                    triple: tcx.sess.opts.target_triple.clone(),
+                    hash: tcx.crate_hash(LOCAL_CRATE),
+                    is_proc_macro_crate: proc_macro_data.is_some(),
+                },
                 extra_filename: tcx.sess.opts.cg.extra_filename.clone(),
-                triple: tcx.sess.opts.target_triple.clone(),
-                hash: tcx.crate_hash(LOCAL_CRATE),
                 stable_crate_id: tcx.def_path_hash(LOCAL_CRATE.as_def_id()).stable_crate_id(),
                 required_panic_strategy: tcx.required_panic_strategy(LOCAL_CRATE),
                 panic_in_drop_strategy: tcx.sess.opts.unstable_opts.panic_in_drop,
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 97e67fcf8fd..ce2fe70a8b2 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -56,7 +56,7 @@ pub(crate) fn rustc_version(cfg_version: &'static str) -> String {
 /// Metadata encoding version.
 /// N.B., increment this if you change the format of metadata such that
 /// the rustc version can't be found to compare with `rustc_version()`.
-const METADATA_VERSION: u8 = 7;
+const METADATA_VERSION: u8 = 8;
 
 /// Metadata header which includes `METADATA_VERSION`.
 ///
@@ -199,7 +199,27 @@ pub(crate) struct ProcMacroData {
     macros: LazyArray<DefIndex>,
 }
 
-/// Serialized metadata for a crate.
+/// Serialized crate metadata.
+///
+/// This contains just enough information to determine if we should load the `CrateRoot` or not.
+/// Prefer [`CrateRoot`] whenever possible to avoid ICEs when using `omit-git-hash` locally.
+/// See #76720 for more details.
+///
+/// If you do modify this struct, also bump the [`METADATA_VERSION`] constant.
+#[derive(MetadataEncodable, MetadataDecodable)]
+pub(crate) struct CrateHeader {
+    pub(crate) triple: TargetTriple,
+    pub(crate) hash: Svh,
+    pub(crate) name: Symbol,
+    /// Whether this is the header for a proc-macro crate.
+    ///
+    /// This is separate from [`ProcMacroData`] to avoid having to update [`METADATA_VERSION`] every
+    /// time ProcMacroData changes.
+    pub(crate) is_proc_macro_crate: bool,
+}
+
+/// Serialized `.rmeta` data for a crate.
+///
 /// When compiling a proc-macro crate, we encode many of
 /// the `LazyArray<T>` fields as `Lazy::empty()`. This serves two purposes:
 ///
@@ -217,10 +237,10 @@ pub(crate) struct ProcMacroData {
 /// to being unused.
 #[derive(MetadataEncodable, MetadataDecodable)]
 pub(crate) struct CrateRoot {
-    name: Symbol,
-    triple: TargetTriple,
+    /// A header used to detect if this is the right crate to load.
+    header: CrateHeader,
+
     extra_filename: String,
-    hash: Svh,
     stable_crate_id: StableCrateId,
     required_panic_strategy: Option<PanicStrategy>,
     panic_in_drop_strategy: PanicStrategy,
@@ -465,6 +485,7 @@ trivially_parameterized_over_tcx! {
     RawDefId,
     TraitImpls,
     IncoherentImpls,
+    CrateHeader,
     CrateRoot,
     CrateDep,
     AttrFlags,
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 14343ac1108..caf3fc26039 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -251,7 +251,7 @@ pub fn explain_lint_level_source(
         }
         LintLevelSource::Node { name: lint_attr_name, span, reason, .. } => {
             if let Some(rationale) = reason {
-                err.note(rationale.as_str());
+                err.note(rationale.to_string());
             }
             err.span_note_once(span, "the lint level is defined here");
             if lint_attr_name.as_str() != name {
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 6354c0aabde..60844c17e47 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -104,7 +104,7 @@ pub fn report_unstable(
     suggestion: Option<(Span, String, String, Applicability)>,
     is_soft: bool,
     span: Span,
-    soft_handler: impl FnOnce(&'static Lint, Span, &str),
+    soft_handler: impl FnOnce(&'static Lint, Span, String),
 ) {
     let msg = match reason {
         Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
@@ -112,7 +112,7 @@ pub fn report_unstable(
     };
 
     if is_soft {
-        soft_handler(SOFT_UNSTABLE, span, &msg)
+        soft_handler(SOFT_UNSTABLE, span, msg)
     } else {
         let mut err =
             feature_err_issue(&sess.parse_sess, feature, span, GateIssue::Library(issue), msg);
@@ -225,7 +225,7 @@ pub fn deprecation_message_and_lint(
 
 pub fn early_report_deprecation(
     lint_buffer: &mut LintBuffer,
-    message: &str,
+    message: String,
     suggestion: Option<Symbol>,
     lint: &'static Lint,
     span: Span,
@@ -241,7 +241,7 @@ pub fn early_report_deprecation(
 
 fn late_report_deprecation(
     tcx: TyCtxt<'_>,
-    message: &str,
+    message: String,
     suggestion: Option<Symbol>,
     lint: &'static Lint,
     span: Span,
@@ -396,7 +396,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
                         late_report_deprecation(
                             self,
-                            &deprecation_message(
+                            deprecation_message(
                                 is_in_effect,
                                 depr_attr.since,
                                 depr_attr.note,
@@ -619,7 +619,7 @@ impl<'tcx> TyCtxt<'tcx> {
         allow_unstable: AllowUnstable,
         unmarked: impl FnOnce(Span, DefId),
     ) -> bool {
-        let soft_handler = |lint, span, msg: &_| {
+        let soft_handler = |lint, span, msg: String| {
             self.struct_span_lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg, |lint| lint)
         };
         let eval_result =
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 2bde55bc4fd..0464336627f 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -732,7 +732,11 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` with the given
     /// `msg` to ensure it gets used.
     #[track_caller]
-    pub fn mk_re_error_with_message<S: Into<MultiSpan>>(self, span: S, msg: &str) -> Region<'tcx> {
+    pub fn mk_re_error_with_message<S: Into<MultiSpan>>(
+        self,
+        span: S,
+        msg: &'static str,
+    ) -> Region<'tcx> {
         let reported = self.sess.delay_span_bug(span, msg);
         self.mk_re_error(reported)
     }
@@ -759,7 +763,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         ty: Ty<'tcx>,
         span: S,
-        msg: &str,
+        msg: &'static str,
     ) -> Const<'tcx> {
         let reported = self.sess.delay_span_bug(span, msg);
         self.mk_const(ty::ConstKind::Error(reported), ty)
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index 6a29063b80d..9c91b778403 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -1,5 +1,6 @@
 //! Diagnostics related methods for `Ty`.
 
+use std::borrow::Cow;
 use std::ops::ControlFlow;
 
 use crate::ty::{
@@ -384,22 +385,18 @@ pub fn suggest_constraining_type_params<'a>(
 
     if suggestions.len() == 1 {
         let (span, suggestion, msg) = suggestions.pop().unwrap();
-
-        let s;
         let msg = match msg {
             SuggestChangingConstraintsMessage::RestrictBoundFurther => {
-                "consider further restricting this bound"
+                Cow::from("consider further restricting this bound")
             }
             SuggestChangingConstraintsMessage::RestrictType { ty } => {
-                s = format!("consider restricting type parameter `{}`", ty);
-                &s
+                Cow::from(format!("consider restricting type parameter `{}`", ty))
             }
             SuggestChangingConstraintsMessage::RestrictTypeFurther { ty } => {
-                s = format!("consider further restricting type parameter `{}`", ty);
-                &s
+                Cow::from(format!("consider further restricting type parameter `{}`", ty))
             }
             SuggestChangingConstraintsMessage::RemovingQSized => {
-                "consider removing the `?Sized` bound to make the type parameter `Sized`"
+                Cow::from("consider removing the `?Sized` bound to make the type parameter `Sized`")
             }
         };
 
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index cd779b0b43e..8ab38c4fb8b 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -43,6 +43,15 @@ impl<'a> Parser<'a> {
     fn parse_ty_param(&mut self, preceding_attrs: AttrVec) -> PResult<'a, GenericParam> {
         let ident = self.parse_ident()?;
 
+        // We might have a typo'd `Const` that was parsed as a type parameter.
+        if self.may_recover()
+            && ident.name.as_str().to_ascii_lowercase() == kw::Const.as_str()
+            && self.check_ident()
+        // `Const` followed by IDENT
+        {
+            return Ok(self.recover_const_param_with_mistyped_const(preceding_attrs, ident)?);
+        }
+
         // Parse optional colon and param bounds.
         let mut colon_span = None;
         let bounds = if self.eat(&token::Colon) {
@@ -120,6 +129,41 @@ impl<'a> Parser<'a> {
         })
     }
 
+    pub(crate) fn recover_const_param_with_mistyped_const(
+        &mut self,
+        preceding_attrs: AttrVec,
+        mistyped_const_ident: Ident,
+    ) -> PResult<'a, GenericParam> {
+        let ident = self.parse_ident()?;
+        self.expect(&token::Colon)?;
+        let ty = self.parse_ty()?;
+
+        // Parse optional const generics default value.
+        let default = if self.eat(&token::Eq) { Some(self.parse_const_arg()?) } else { None };
+
+        let mut err = self.struct_span_err(
+            mistyped_const_ident.span,
+            format!("`const` keyword was mistyped as `{}`", mistyped_const_ident.as_str()),
+        );
+        err.span_suggestion_verbose(
+            mistyped_const_ident.span,
+            "use the `const` keyword",
+            kw::Const.as_str(),
+            Applicability::MachineApplicable,
+        );
+        err.emit();
+
+        Ok(GenericParam {
+            ident,
+            id: ast::DUMMY_NODE_ID,
+            attrs: preceding_attrs,
+            bounds: Vec::new(),
+            kind: GenericParamKind::Const { ty, kw_span: mistyped_const_ident.span, default },
+            is_placeholder: false,
+            colon_span: None,
+        })
+    }
+
     /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
     /// a trailing comma and erroneous trailing attributes.
     pub(super) fn parse_generic_params(&mut self) -> PResult<'a, ThinVec<ast::GenericParam>> {
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 54f9fc5d2b9..9fcf51a04ec 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -23,6 +23,7 @@ use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
 use rustc_span::source_map::{BytePos, Span};
 use rustc_span::symbol::{kw, sym, Ident};
 
+use std::borrow::Cow;
 use std::mem;
 use thin_vec::{thin_vec, ThinVec};
 
@@ -364,7 +365,7 @@ impl<'a> Parser<'a> {
                         // `let...else if`. Emit the same error that `parse_block()` would,
                         // but explicitly point out that this pattern is not allowed.
                         let msg = "conditional `else if` is not supported for `let...else`";
-                        return Err(self.error_block_no_opening_brace_msg(msg));
+                        return Err(self.error_block_no_opening_brace_msg(Cow::from(msg)));
                     }
                     let els = self.parse_block()?;
                     self.check_let_else_init_bool_expr(&init);
@@ -438,7 +439,7 @@ impl<'a> Parser<'a> {
 
     fn error_block_no_opening_brace_msg(
         &mut self,
-        msg: &str,
+        msg: Cow<'static, str>,
     ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
         let sp = self.token.span;
         let mut e = self.struct_span_err(sp, msg);
@@ -502,7 +503,7 @@ impl<'a> Parser<'a> {
     fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> {
         let tok = super::token_descr(&self.token);
         let msg = format!("expected `{{`, found {}", tok);
-        Err(self.error_block_no_opening_brace_msg(&msg))
+        Err(self.error_block_no_opening_brace_msg(Cow::from(msg)))
     }
 
     /// Parses a block. Inner attributes are allowed.
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 8c6ac822a77..377652ce71b 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -2540,7 +2540,7 @@ fn show_candidates(
                 err.note(msg);
             }
             if let Some(note) = (*note).as_deref() {
-                err.note(note);
+                err.note(note.to_string());
             }
         } else {
             let (_, descr_first, _, _) = &inaccessible_path_strings[0];
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index df65825802e..f79f8d0c6ca 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -29,6 +29,7 @@ use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
 
+use std::borrow::Cow;
 use std::iter;
 use std::ops::Deref;
 
@@ -1248,7 +1249,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                     }),
                 ) if followed_by_brace => {
                     if let Some(sp) = closing_brace {
-                        err.span_label(span, fallback_label);
+                        err.span_label(span, fallback_label.to_string());
                         err.multipart_suggestion(
                             "surround the struct literal with parentheses",
                             vec![
@@ -1320,7 +1321,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                     );
                 }
                 _ => {
-                    err.span_label(span, fallback_label);
+                    err.span_label(span, fallback_label.to_string());
                 }
             }
         };
@@ -1333,7 +1334,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                 }))
                 | PathSource::Struct,
             ) => {
-                err.span_label(span, fallback_label);
+                err.span_label(span, fallback_label.to_string());
                 err.span_suggestion_verbose(
                     span.shrink_to_hi(),
                     "use `!` to invoke the macro",
@@ -1345,7 +1346,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                 }
             }
             (Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => {
-                err.span_label(span, fallback_label);
+                err.span_label(span, fallback_label.to_string());
             }
             (Res::Def(DefKind::TyAlias, def_id), PathSource::Trait(_)) => {
                 err.span_label(span, "type aliases cannot be used as traits");
@@ -1513,7 +1514,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                 );
             }
             (Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }, _) if ns == ValueNS => {
-                err.span_label(span, fallback_label);
+                err.span_label(span, fallback_label.to_string());
                 err.note("can't use `Self` as a constructor, you must use the implemented struct");
             }
             (Res::Def(DefKind::TyAlias | DefKind::AssocTy, _), _) if ns == ValueNS => {
@@ -2243,7 +2244,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
         &self,
         err: &mut Diagnostic,
         name: Option<&str>,
-        suggest: impl Fn(&mut Diagnostic, bool, Span, &str, String) -> bool,
+        suggest: impl Fn(&mut Diagnostic, bool, Span, Cow<'static, str>, String) -> bool,
     ) {
         let mut suggest_note = true;
         for rib in self.lifetime_ribs.iter().rev() {
@@ -2288,22 +2289,23 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                         (span, sugg)
                     };
                     if higher_ranked {
-                        let message = format!(
+                        let message = Cow::from(format!(
                             "consider making the {} lifetime-generic with a new `{}` lifetime",
                             kind.descr(),
                             name.unwrap_or("'a"),
-                        );
-                        should_continue = suggest(err, true, span, &message, sugg);
+                        ));
+                        should_continue = suggest(err, true, span, message, sugg);
                         err.note_once(
                             "for more information on higher-ranked polymorphism, visit \
                              https://doc.rust-lang.org/nomicon/hrtb.html",
                         );
                     } else if let Some(name) = name {
-                        let message = format!("consider introducing lifetime `{}` here", name);
-                        should_continue = suggest(err, false, span, &message, sugg);
+                        let message =
+                            Cow::from(format!("consider introducing lifetime `{}` here", name));
+                        should_continue = suggest(err, false, span, message, sugg);
                     } else {
-                        let message = "consider introducing a named lifetime parameter";
-                        should_continue = suggest(err, false, span, &message, sugg);
+                        let message = Cow::from("consider introducing a named lifetime parameter");
+                        should_continue = suggest(err, false, span, message, sugg);
                     }
                 }
                 LifetimeRibKind::Item => break,
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index df5c16a9375..d8a7bcbfff9 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -827,7 +827,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 if !is_allowed(feature) && !allowed_by_implication {
                     let lint_buffer = &mut self.lint_buffer;
                     let soft_handler =
-                        |lint, span, msg: &_| lint_buffer.buffer_lint(lint, node_id, span, msg);
+                        |lint, span, msg: String| lint_buffer.buffer_lint(lint, node_id, span, msg);
                     stability::report_unstable(
                         self.tcx.sess,
                         feature,
@@ -846,7 +846,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             let (message, lint) = stability::deprecation_message_and_lint(depr, "macro", &path);
             stability::early_report_deprecation(
                 &mut self.lint_buffer,
-                &message,
+                message,
                 depr.suggestion,
                 lint,
                 span,
diff --git a/compiler/rustc_session/messages.ftl b/compiler/rustc_session/messages.ftl
index 5a0b8f9f73c..4897bd8d5da 100644
--- a/compiler/rustc_session/messages.ftl
+++ b/compiler/rustc_session/messages.ftl
@@ -27,6 +27,10 @@ session_feature_gate_error = {$explain}
 session_file_is_not_writeable = output file {$file} is not writeable -- check its permissions
 
 session_hexadecimal_float_literal_not_supported = hexadecimal float literal is not supported
+
+session_incompatible_linker_flavor = linker flavor `{$flavor}` is incompatible with the current target
+    .note = compatible flavors are: {$compatible_list}
+
 session_incorrect_cgu_reuse_type =
     CGU-reuse for `{$cgu_user_name}` is `{$actual_reuse}` but should be {$at_least ->
     [one] {"at least "}
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 6c8c8e484f9..0ce83e79097 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -12,7 +12,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 
 use rustc_data_structures::stable_hasher::{StableOrd, ToStableHashKey};
 use rustc_target::abi::Align;
-use rustc_target::spec::{PanicStrategy, SanitizerSet, SplitDebuginfo};
+use rustc_target::spec::{LinkerFlavorCli, PanicStrategy, SanitizerSet, SplitDebuginfo};
 use rustc_target::spec::{Target, TargetTriple, TargetWarnings, TARGETS};
 
 use crate::parse::{CrateCheckConfig, CrateConfig};
@@ -2525,6 +2525,19 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         }
     }
 
+    if let Some(flavor) = cg.linker_flavor {
+        if matches!(flavor, LinkerFlavorCli::BpfLinker | LinkerFlavorCli::PtxLinker)
+            && !nightly_options::is_unstable_enabled(matches)
+        {
+            let msg = format!(
+                "linker flavor `{}` is unstable, `-Z unstable-options` \
+                 flag must also be passed to explicitly use it",
+                flavor.desc()
+            );
+            early_error(error_format, msg);
+        }
+    }
+
     let prints = collect_print_requests(&mut cg, &mut unstable_opts, matches, error_format);
 
     let cg = cg;
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 546c0fa8e03..4a3e668da11 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -422,3 +422,11 @@ pub fn report_lit_error(sess: &ParseSess, err: LitError, lit: token::Lit, span:
 pub struct OptimisationFuelExhausted {
     pub msg: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(session_incompatible_linker_flavor)]
+#[note]
+pub struct IncompatibleLinkerFlavor {
+    pub flavor: &'static str,
+    pub compatible_list: String,
+}
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 7b396dde91b..d1e4042e8d8 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -123,7 +123,7 @@ pub fn feature_err_issue(
 /// Construct a future incompatibility diagnostic for a feature gate.
 ///
 /// This diagnostic is only a warning and *does not cause compilation to fail*.
-pub fn feature_warn(sess: &ParseSess, feature: Symbol, span: Span, explain: &str) {
+pub fn feature_warn(sess: &ParseSess, feature: Symbol, span: Span, explain: &'static str) {
     feature_warn_issue(sess, feature, span, GateIssue::Language, explain);
 }
 
@@ -140,7 +140,7 @@ pub fn feature_warn_issue(
     feature: Symbol,
     span: Span,
     issue: GateIssue,
-    explain: &str,
+    explain: &'static str,
 ) {
     let mut err = sess.span_diagnostic.struct_span_warn(span, explain);
     add_feature_diagnostics_for_issue(&mut err, sess, feature, issue);
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index bbe52dbced0..1eb54cee5a1 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -1675,6 +1675,13 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
     if sess.opts.unstable_opts.instrument_xray.is_some() && !sess.target.options.supports_xray {
         sess.emit_err(errors::InstrumentationNotSupported { us: "XRay".to_string() });
     }
+
+    if let Some(flavor) = sess.opts.cg.linker_flavor {
+        if let Some(compatible_list) = sess.target.linker_flavor.check_compatibility(flavor) {
+            let flavor = flavor.desc();
+            sess.emit_err(errors::IncompatibleLinkerFlavor { flavor, compatible_list });
+        }
+    }
 }
 
 /// Holds data on the current incremental compilation session, if there is one.
diff --git a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
index 9fa49123a86..b245742e533 100644
--- a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
+++ b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
@@ -10,7 +10,6 @@
 use core::fmt::Display;
 use rustc_data_structures::base_n;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::DiagnosticMessage;
 use rustc_hir as hir;
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
 use rustc_middle::ty::{
@@ -534,10 +533,7 @@ fn encode_ty<'tcx>(
                         tcx.sess
                             .struct_span_err(
                                 cfi_encoding.span,
-                                DiagnosticMessage::Str(format!(
-                                    "invalid `cfi_encoding` for `{:?}`",
-                                    ty.kind()
-                                )),
+                                format!("invalid `cfi_encoding` for `{:?}`", ty.kind()),
                             )
                             .emit();
                     }
@@ -589,10 +585,7 @@ fn encode_ty<'tcx>(
                         tcx.sess
                             .struct_span_err(
                                 cfi_encoding.span,
-                                DiagnosticMessage::Str(format!(
-                                    "invalid `cfi_encoding` for `{:?}`",
-                                    ty.kind()
-                                )),
+                                format!("invalid `cfi_encoding` for `{:?}`", ty.kind()),
                             )
                             .emit();
                     }
diff --git a/compiler/rustc_target/src/lib.rs b/compiler/rustc_target/src/lib.rs
index dc2cc23ffb1..a7b54766bc6 100644
--- a/compiler/rustc_target/src/lib.rs
+++ b/compiler/rustc_target/src/lib.rs
@@ -11,6 +11,7 @@
 #![feature(assert_matches)]
 #![feature(associated_type_bounds)]
 #![feature(exhaustive_patterns)]
+#![feature(iter_intersperse)]
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 62f94209cf0..05cb7e87a93 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -205,15 +205,11 @@ impl ToJson for LldFlavor {
 }
 
 impl LinkerFlavor {
-    pub fn from_cli(cli: LinkerFlavorCli, target: &TargetOptions) -> LinkerFlavor {
-        Self::from_cli_impl(cli, target.linker_flavor.lld_flavor(), target.linker_flavor.is_gnu())
-    }
-
-    /// The passed CLI flavor is preferred over other args coming from the default target spec,
-    /// so this function can produce a flavor that is incompatible with the current target.
-    /// FIXME: Produce errors when `-Clinker-flavor` is set to something incompatible
-    /// with the current target.
-    fn from_cli_impl(cli: LinkerFlavorCli, lld_flavor: LldFlavor, is_gnu: bool) -> LinkerFlavor {
+    /// At this point the target's reference linker flavor doesn't yet exist and we need to infer
+    /// it. The inference always succeds and gives some result, and we don't report any flavor
+    /// incompatibility errors for json target specs. The CLI flavor is used as the main source
+    /// of truth, other flags are used in case of ambiguities.
+    fn from_cli_json(cli: LinkerFlavorCli, lld_flavor: LldFlavor, is_gnu: bool) -> LinkerFlavor {
         match cli {
             LinkerFlavorCli::Gcc => match lld_flavor {
                 LldFlavor::Ld if is_gnu => LinkerFlavor::Gnu(Cc::Yes, Lld::No),
@@ -257,6 +253,85 @@ impl LinkerFlavor {
         }
     }
 
+    fn infer_cli_hints(cli: LinkerFlavorCli) -> (Option<Cc>, Option<Lld>) {
+        match cli {
+            LinkerFlavorCli::Gcc | LinkerFlavorCli::Em => (Some(Cc::Yes), None),
+            LinkerFlavorCli::Lld(_) => (Some(Cc::No), Some(Lld::Yes)),
+            LinkerFlavorCli::Ld | LinkerFlavorCli::Msvc => (Some(Cc::No), Some(Lld::No)),
+            LinkerFlavorCli::BpfLinker | LinkerFlavorCli::PtxLinker => (None, None),
+        }
+    }
+
+    fn infer_linker_hints(linker_stem: &str) -> (Option<Cc>, Option<Lld>) {
+        // Remove any version postfix.
+        let stem = linker_stem
+            .rsplit_once('-')
+            .and_then(|(lhs, rhs)| rhs.chars().all(char::is_numeric).then_some(lhs))
+            .unwrap_or(linker_stem);
+
+        // GCC/Clang can have an optional target prefix.
+        if stem == "emcc"
+            || stem == "gcc"
+            || stem.ends_with("-gcc")
+            || stem == "g++"
+            || stem.ends_with("-g++")
+            || stem == "clang"
+            || stem.ends_with("-clang")
+            || stem == "clang++"
+            || stem.ends_with("-clang++")
+        {
+            (Some(Cc::Yes), None)
+        } else if stem == "wasm-ld"
+            || stem.ends_with("-wasm-ld")
+            || stem == "ld.lld"
+            || stem == "lld"
+            || stem == "rust-lld"
+            || stem == "lld-link"
+        {
+            (Some(Cc::No), Some(Lld::Yes))
+        } else if stem == "ld" || stem.ends_with("-ld") || stem == "link" {
+            (Some(Cc::No), Some(Lld::No))
+        } else {
+            (None, None)
+        }
+    }
+
+    fn with_hints(self, (cc_hint, lld_hint): (Option<Cc>, Option<Lld>)) -> LinkerFlavor {
+        match self {
+            LinkerFlavor::Gnu(cc, lld) => {
+                LinkerFlavor::Gnu(cc_hint.unwrap_or(cc), lld_hint.unwrap_or(lld))
+            }
+            LinkerFlavor::Darwin(cc, lld) => {
+                LinkerFlavor::Darwin(cc_hint.unwrap_or(cc), lld_hint.unwrap_or(lld))
+            }
+            LinkerFlavor::WasmLld(cc) => LinkerFlavor::WasmLld(cc_hint.unwrap_or(cc)),
+            LinkerFlavor::Unix(cc) => LinkerFlavor::Unix(cc_hint.unwrap_or(cc)),
+            LinkerFlavor::Msvc(lld) => LinkerFlavor::Msvc(lld_hint.unwrap_or(lld)),
+            LinkerFlavor::EmCc | LinkerFlavor::Bpf | LinkerFlavor::Ptx => self,
+        }
+    }
+
+    pub fn with_cli_hints(self, cli: LinkerFlavorCli) -> LinkerFlavor {
+        self.with_hints(LinkerFlavor::infer_cli_hints(cli))
+    }
+
+    pub fn with_linker_hints(self, linker_stem: &str) -> LinkerFlavor {
+        self.with_hints(LinkerFlavor::infer_linker_hints(linker_stem))
+    }
+
+    pub fn check_compatibility(self, cli: LinkerFlavorCli) -> Option<String> {
+        // The CLI flavor should be compatible with the target if it survives this roundtrip.
+        let compatible = |cli| cli == self.with_cli_hints(cli).to_cli();
+        (!compatible(cli)).then(|| {
+            LinkerFlavorCli::all()
+                .iter()
+                .filter(|cli| compatible(**cli))
+                .map(|cli| cli.desc())
+                .intersperse(", ")
+                .collect()
+        })
+    }
+
     pub fn lld_flavor(self) -> LldFlavor {
         match self {
             LinkerFlavor::Gnu(..)
@@ -278,6 +353,10 @@ impl LinkerFlavor {
 macro_rules! linker_flavor_cli_impls {
     ($(($($flavor:tt)*) $string:literal)*) => (
         impl LinkerFlavorCli {
+            const fn all() -> &'static [LinkerFlavorCli] {
+                &[$($($flavor)*,)*]
+            }
+
             pub const fn one_of() -> &'static str {
                 concat!("one of: ", $($string, " ",)*)
             }
@@ -289,8 +368,8 @@ macro_rules! linker_flavor_cli_impls {
                 })
             }
 
-            pub fn desc(&self) -> &str {
-                match *self {
+            pub fn desc(self) -> &'static str {
+                match self {
                     $($($flavor)* => $string,)*
                 }
             }
@@ -1801,7 +1880,7 @@ impl TargetOptions {
     }
 
     fn update_from_cli(&mut self) {
-        self.linker_flavor = LinkerFlavor::from_cli_impl(
+        self.linker_flavor = LinkerFlavor::from_cli_json(
             self.linker_flavor_json,
             self.lld_flavor_json,
             self.linker_is_gnu_json,
@@ -1815,12 +1894,7 @@ impl TargetOptions {
         ] {
             args.clear();
             for (flavor, args_json) in args_json {
-                // Cannot use `from_cli` due to borrow checker.
-                let linker_flavor = LinkerFlavor::from_cli_impl(
-                    *flavor,
-                    self.lld_flavor_json,
-                    self.linker_is_gnu_json,
-                );
+                let linker_flavor = self.linker_flavor.with_cli_hints(*flavor);
                 // Normalize to no lld to avoid asserts.
                 let linker_flavor = match linker_flavor {
                     LinkerFlavor::Gnu(cc, _) => LinkerFlavor::Gnu(cc, Lld::No),
diff --git a/compiler/rustc_target/src/spec/x86_64_pc_solaris.rs b/compiler/rustc_target/src/spec/x86_64_pc_solaris.rs
index cb62a817322..d2906d6c4ae 100644
--- a/compiler/rustc_target/src/spec/x86_64_pc_solaris.rs
+++ b/compiler/rustc_target/src/spec/x86_64_pc_solaris.rs
@@ -7,7 +7,7 @@ pub fn target() -> Target {
     base.vendor = "pc".into();
     base.max_atomic_width = Some(64);
     base.stack_probes = StackProbeType::X86;
-    base.supported_sanitizers = SanitizerSet::ADDRESS | SanitizerSet::CFI;
+    base.supported_sanitizers = SanitizerSet::ADDRESS | SanitizerSet::CFI | SanitizerSet::THREAD;
 
     Target {
         llvm_target: "x86_64-pc-solaris".into(),
diff --git a/compiler/rustc_target/src/spec/x86_64_unknown_illumos.rs b/compiler/rustc_target/src/spec/x86_64_unknown_illumos.rs
index 04a12a7bfa6..ca5b62e279c 100644
--- a/compiler/rustc_target/src/spec/x86_64_unknown_illumos.rs
+++ b/compiler/rustc_target/src/spec/x86_64_unknown_illumos.rs
@@ -5,7 +5,7 @@ pub fn target() -> Target {
     base.add_pre_link_args(LinkerFlavor::Unix(Cc::Yes), &["-m64", "-std=c99"]);
     base.cpu = "x86-64".into();
     base.max_atomic_width = Some(64);
-    base.supported_sanitizers = SanitizerSet::ADDRESS | SanitizerSet::CFI;
+    base.supported_sanitizers = SanitizerSet::ADDRESS | SanitizerSet::CFI | SanitizerSet::THREAD;
 
     Target {
         // LLVM does not currently have a separate illumos target,
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index a10ececbb1e..9012bda4043 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -42,6 +42,7 @@ use rustc_session::Limit;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::symbol::sym;
 use rustc_span::{ExpnKind, Span, DUMMY_SP};
+use std::borrow::Cow;
 use std::fmt;
 use std::iter;
 use std::ops::ControlFlow;
@@ -1602,7 +1603,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         }),
                     ) => Some((
                         ty.span,
-                        with_forced_trimmed_paths!(format!(
+                        with_forced_trimmed_paths!(Cow::from(format!(
                             "type mismatch resolving `{}`",
                             self.resolve_vars_if_possible(predicate)
                                 .print(FmtPrinter::new_with_limit(
@@ -1612,7 +1613,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 ))
                                 .unwrap()
                                 .into_buffer()
-                        )),
+                        ))),
                     )),
                     _ => None,
                 }
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 82bad96ea42..b5b8c7fe3ac 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -38,6 +38,7 @@ use rustc_span::def_id::LocalDefId;
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::{BytePos, DesugaringKind, ExpnKind, MacroKind, Span, DUMMY_SP};
 use rustc_target::spec::abi;
+use std::borrow::Cow;
 use std::iter;
 use std::ops::Deref;
 
@@ -186,7 +187,12 @@ pub trait TypeErrCtxtExt<'tcx> {
         trait_pred: ty::PolyTraitPredicate<'tcx>,
     ) -> bool;
 
-    fn get_closure_name(&self, def_id: DefId, err: &mut Diagnostic, msg: &str) -> Option<Symbol>;
+    fn get_closure_name(
+        &self,
+        def_id: DefId,
+        err: &mut Diagnostic,
+        msg: Cow<'static, str>,
+    ) -> Option<Symbol>;
 
     fn suggest_fn_call(
         &self,
@@ -857,7 +863,12 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
     /// Given a closure's `DefId`, return the given name of the closure.
     ///
     /// This doesn't account for reassignments, but it's only used for suggestions.
-    fn get_closure_name(&self, def_id: DefId, err: &mut Diagnostic, msg: &str) -> Option<Symbol> {
+    fn get_closure_name(
+        &self,
+        def_id: DefId,
+        err: &mut Diagnostic,
+        msg: Cow<'static, str>,
+    ) -> Option<Symbol> {
         let get_name = |err: &mut Diagnostic, kind: &hir::PatKind<'_>| -> Option<Symbol> {
             // Get the local name of this closure. This can be inaccurate because
             // of the possibility of reassignment, but this should be good enough.
@@ -934,17 +945,17 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         let msg = match def_id_or_name {
             DefIdOrName::DefId(def_id) => match self.tcx.def_kind(def_id) {
                 DefKind::Ctor(CtorOf::Struct, _) => {
-                    "use parentheses to construct this tuple struct".to_string()
+                    Cow::from("use parentheses to construct this tuple struct")
                 }
                 DefKind::Ctor(CtorOf::Variant, _) => {
-                    "use parentheses to construct this tuple variant".to_string()
+                    Cow::from("use parentheses to construct this tuple variant")
                 }
-                kind => format!(
+                kind => Cow::from(format!(
                     "use parentheses to call this {}",
                     self.tcx.def_kind_descr(kind, def_id)
-                ),
+                )),
             },
-            DefIdOrName::Name(name) => format!("use parentheses to call this {name}"),
+            DefIdOrName::Name(name) => Cow::from(format!("use parentheses to call this {name}")),
         };
 
         let args = inputs
@@ -979,7 +990,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     ..
                 })) => {
                     err.span_label(*fn_decl_span, "consider calling this closure");
-                    let Some(name) = self.get_closure_name(def_id, err, &msg) else {
+                    let Some(name) = self.get_closure_name(def_id, err, msg.clone()) else {
                         return false;
                     };
                     name.to_string()
@@ -1341,7 +1352,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         err.note(msg);
                     } else {
                         err.message =
-                            vec![(rustc_errors::DiagnosticMessage::Str(msg), Style::NoStyle)];
+                            vec![(rustc_errors::DiagnosticMessage::from(msg), Style::NoStyle)];
                     }
                     err.span_label(
                         span,
@@ -2958,7 +2969,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 for ty in bound_tys.skip_binder() {
                                     with_forced_trimmed_paths!(write!(msg, "`{}`, ", ty).unwrap());
                                 }
-                                err.note(msg.trim_end_matches(", "))
+                                err.note(msg.trim_end_matches(", ").to_string())
                             }
                             ty::GeneratorWitnessMIR(def_id, substs) => {
                                 use std::fmt::Write;
@@ -2972,7 +2983,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                     let ty = bty.subst(tcx, substs);
                                     write!(msg, "`{}`, ", ty).unwrap();
                                 }
-                                err.note(msg.trim_end_matches(", "))
+                                err.note(msg.trim_end_matches(", ").to_string())
                             }
                             ty::Generator(def_id, _, _) => {
                                 let sp = self.tcx.def_span(def_id);
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 82f3df40198..e2c9c62512e 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -41,7 +41,12 @@ impl<'tcx> TraitAliasExpansionInfo<'tcx> {
 
     /// Adds diagnostic labels to `diag` for the expansion path of a trait through all intermediate
     /// trait aliases.
-    pub fn label_with_exp_info(&self, diag: &mut Diagnostic, top_label: &str, use_desc: &str) {
+    pub fn label_with_exp_info(
+        &self,
+        diag: &mut Diagnostic,
+        top_label: &'static str,
+        use_desc: &str,
+    ) {
         diag.span_label(self.top().1, top_label);
         if self.path.len() > 1 {
             for (_, sp) in self.path.iter().rev().skip(1).take(self.path.len() - 2) {
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 1f195555229..62003ddf515 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -3113,8 +3113,9 @@ impl<T> [T] {
     ///
     /// # Current implementation
     ///
-    /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
-    /// used for [`sort_unstable`].
+    /// The current algorithm is an introselect implementation based on Pattern Defeating Quicksort, which is also
+    /// the basis for [`sort_unstable`]. The fallback algorithm is Median of Medians using Tukey's Ninther for
+    /// pivot selection, which guarantees linear runtime for all inputs.
     ///
     /// [`sort_unstable`]: slice::sort_unstable
     ///
diff --git a/src/doc/unstable-book/src/language-features/asm-experimental-arch.md b/src/doc/unstable-book/src/language-features/asm-experimental-arch.md
index 532cb9eea11..c634dc50d6d 100644
--- a/src/doc/unstable-book/src/language-features/asm-experimental-arch.md
+++ b/src/doc/unstable-book/src/language-features/asm-experimental-arch.md
@@ -17,7 +17,6 @@ This feature tracks `asm!` and `global_asm!` support for the following architect
 - AVR
 - MSP430
 - M68k
-- LoongArch
 - s390x
 
 ## Register classes
@@ -47,8 +46,6 @@ This feature tracks `asm!` and `global_asm!` support for the following architect
 | M68k         | `reg`          | `d[0-7]`, `a[0-7]`                 | `r`                  |
 | M68k         | `reg_data`     | `d[0-7]`                           | `d`                  |
 | M68k         | `reg_addr`     | `a[0-3]`                           | `a`                  |
-| LoongArch    | `reg`          | `$r1`, `$r[4-20]`, `$r[23,30]`     | `r`                  |
-| LoongArch    | `freg`         | `$f[0-31]`                         | `f`                  |
 | s390x        | `reg`          | `r[0-10]`, `r[12-14]`              | `r`                  |
 | s390x        | `freg`         | `f[0-15]`                          | `f`                  |
 
@@ -82,8 +79,6 @@ This feature tracks `asm!` and `global_asm!` support for the following architect
 | MSP430       | `reg`                           | None           | `i8`, `i16`                             |
 | M68k         | `reg`, `reg_addr`               | None           | `i16`, `i32`                            |
 | M68k         | `reg_data`                      | None           | `i8`, `i16`, `i32`                      |
-| LoongArch64  | `reg`                           | None           | `i8`, `i16`, `i32`, `i64`, `f32`, `f64` |
-| LoongArch64  | `freg`                          | None           | `f32`, `f64`                            |
 | s390x        | `reg`                           | None           | `i8`, `i16`, `i32`, `i64`               |
 | s390x        | `freg`                          | None           | `f32`, `f64`                            |
 
@@ -107,10 +102,6 @@ This feature tracks `asm!` and `global_asm!` support for the following architect
 | M68k         | `a5`          | `bp`      |
 | M68k         | `a6`          | `fp`      |
 | M68k         | `a7`          | `sp`, `usp`, `ssp`, `isp` |
-| LoongArch    | `$r0`         | `zero`    |
-| LoongArch    | `$r2`         | `tp`      |
-| LoongArch    | `$r3`         | `sp`      |
-| LoongArch    | `$r22`        | `fp`      |
 
 > **Notes**:
 > - TI does not mandate a frame pointer for MSP430, but toolchains are allowed
@@ -121,7 +112,7 @@ This feature tracks `asm!` and `global_asm!` support for the following architect
 | Architecture | Unsupported register                    | Reason                                                                                                                                                                              |
 | ------------ | --------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | All          | `sp`, `r15` (s390x)                     | The stack pointer must be restored to its original value at the end of an asm code block.                                                                                           |
-| All          | `fr` (Hexagon), `$fp` (MIPS), `Y` (AVR), `r4` (MSP430), `a6` (M68k), `$fp` (LoongArch), `r11` (s390x) | The frame pointer cannot be used as an input or output.                                                                                                                             |
+| All          | `fr` (Hexagon), `$fp` (MIPS), `Y` (AVR), `r4` (MSP430), `a6` (M68k), `r11` (s390x) | The frame pointer cannot be used as an input or output.                                                                                                                             |
 | All          | `r19` (Hexagon)                         | This is used internally by LLVM as a "base pointer" for functions with complex stack frames.                                                                                        |
 | MIPS         | `$0` or `$zero`                         | This is a constant zero register which can't be modified.                                                                                                                           |
 | MIPS         | `$1` or `$at`                           | Reserved for assembler.                                                                                                                                                             |
@@ -132,10 +123,6 @@ This feature tracks `asm!` and `global_asm!` support for the following architect
 | AVR          | `r0`, `r1`, `r1r0`                      | Due to an issue in LLVM, the `r0` and `r1` registers cannot be used as inputs or outputs.  If modified, they must be restored to their original values before the end of the block. |
 |MSP430        | `r0`, `r2`, `r3`                        | These are the program counter, status register, and constant generator respectively. Neither the status register nor constant generator can be written to.                          |
 | M68k         | `a4`, `a5`                              | Used internally by LLVM for the base pointer and global base pointer. |
-| LoongArch    | `$r0` or `$zero`                        | This is a constant zero register which can't be modified.                                                                                                                           |
-| LoongArch    | `$r2` or `$tp`                          | This is reserved for TLS.                                                                                                                                                           |
-| LoongArch    | `$r21`                                  | This is reserved by the ABI.                                                                                                                                                        |
-| LoongArch    | `$r31` or `$s8`                         | This is used internally by LLVM.                                                                                                                                                    |
 
 ## Template modifiers
 
@@ -150,8 +137,6 @@ This feature tracks `asm!` and `global_asm!` support for the following architect
 | PowerPC      | `reg`          | None     | `0`            | None          |
 | PowerPC      | `reg_nonzero`  | None     | `3`            | `b`           |
 | PowerPC      | `freg`         | None     | `0`            | None          |
-| LoongArch    | `reg`          | None     | `$r2`          | None          |
-| LoongArch    | `freg`         | None     | `$f0`          | None          |
 | s390x        | `reg`          | None     | `%r0`          | None          |
 | s390x        | `freg`         | None     | `%f0`          | None          |
 
diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs
index 9bb20022cfd..b26a5c32ec6 100644
--- a/src/librustdoc/html/markdown.rs
+++ b/src/librustdoc/html/markdown.rs
@@ -781,7 +781,7 @@ impl<'tcx> ExtraInfo<'tcx> {
         ExtraInfo { def_id, sp, tcx }
     }
 
-    fn error_invalid_codeblock_attr(&self, msg: String, help: &str) {
+    fn error_invalid_codeblock_attr(&self, msg: String, help: &'static str) {
         if let Some(def_id) = self.def_id.as_local() {
             self.tcx.struct_span_lint_hir(
                 crate::lint::INVALID_CODEBLOCK_ATTRIBUTES,
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 061a572c46b..2b0fef267e9 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -842,7 +842,7 @@ impl PreprocessingError {
         match self {
             PreprocessingError::MultipleAnchors => report_multiple_anchors(cx, diag_info),
             PreprocessingError::Disambiguator(range, msg) => {
-                disambiguator_error(cx, diag_info, range.clone(), msg.as_str())
+                disambiguator_error(cx, diag_info, range.clone(), msg.clone())
             }
             PreprocessingError::MalformedGenerics(err, path_str) => {
                 report_malformed_generics(cx, diag_info, *err, path_str)
diff --git a/src/librustdoc/passes/lint/bare_urls.rs b/src/librustdoc/passes/lint/bare_urls.rs
index a10d5fdb410..e9cee92d22b 100644
--- a/src/librustdoc/passes/lint/bare_urls.rs
+++ b/src/librustdoc/passes/lint/bare_urls.rs
@@ -20,19 +20,20 @@ pub(super) fn visit_item(cx: &DocContext<'_>, item: &Item) {
         };
     let dox = item.doc_value();
     if !dox.is_empty() {
-        let report_diag = |cx: &DocContext<'_>, msg: &str, url: &str, range: Range<usize>| {
-            let sp = source_span_for_markdown_range(cx.tcx, &dox, &range, &item.attrs)
-                .unwrap_or_else(|| item.attr_span(cx.tcx));
-            cx.tcx.struct_span_lint_hir(crate::lint::BARE_URLS, hir_id, sp, msg, |lint| {
-                lint.note("bare URLs are not automatically turned into clickable links")
-                    .span_suggestion(
-                        sp,
-                        "use an automatic link instead",
-                        format!("<{}>", url),
-                        Applicability::MachineApplicable,
-                    )
-            });
-        };
+        let report_diag =
+            |cx: &DocContext<'_>, msg: &'static str, url: &str, range: Range<usize>| {
+                let sp = source_span_for_markdown_range(cx.tcx, &dox, &range, &item.attrs)
+                    .unwrap_or_else(|| item.attr_span(cx.tcx));
+                cx.tcx.struct_span_lint_hir(crate::lint::BARE_URLS, hir_id, sp, msg, |lint| {
+                    lint.note("bare URLs are not automatically turned into clickable links")
+                        .span_suggestion(
+                            sp,
+                            "use an automatic link instead",
+                            format!("<{}>", url),
+                            Applicability::MachineApplicable,
+                        )
+                });
+            };
 
         let mut p = Parser::new_ext(&dox, main_body_opts()).into_offset_iter();
 
@@ -72,7 +73,7 @@ fn find_raw_urls(
     cx: &DocContext<'_>,
     text: &str,
     range: Range<usize>,
-    f: &impl Fn(&DocContext<'_>, &str, &str, Range<usize>),
+    f: &impl Fn(&DocContext<'_>, &'static str, &str, Range<usize>),
 ) {
     trace!("looking for raw urls in {}", text);
     // For now, we only check "full" URLs (meaning, starting with "http://" or "https://").
diff --git a/src/librustdoc/passes/lint/html_tags.rs b/src/librustdoc/passes/lint/html_tags.rs
index f0403647af0..5273f52bc6f 100644
--- a/src/librustdoc/passes/lint/html_tags.rs
+++ b/src/librustdoc/passes/lint/html_tags.rs
@@ -17,90 +17,96 @@ pub(crate) fn visit_item(cx: &DocContext<'_>, item: &Item) {
     else { return };
     let dox = item.doc_value();
     if !dox.is_empty() {
-        let report_diag = |msg: &str, range: &Range<usize>, is_open_tag: bool| {
+        let report_diag = |msg: String, range: &Range<usize>, is_open_tag: bool| {
             let sp = match source_span_for_markdown_range(tcx, &dox, range, &item.attrs) {
                 Some(sp) => sp,
                 None => item.attr_span(tcx),
             };
-            tcx.struct_span_lint_hir(crate::lint::INVALID_HTML_TAGS, hir_id, sp, msg, |lint| {
-                use rustc_lint_defs::Applicability;
-                // If a tag looks like `<this>`, it might actually be a generic.
-                // We don't try to detect stuff `<like, this>` because that's not valid HTML,
-                // and we don't try to detect stuff `<like this>` because that's not valid Rust.
-                let mut generics_end = range.end;
-                if let Some(Some(mut generics_start)) = (is_open_tag
-                    && dox[..generics_end].ends_with('>'))
-                .then(|| extract_path_backwards(&dox, range.start))
-                {
-                    while generics_start != 0
-                        && generics_end < dox.len()
-                        && dox.as_bytes()[generics_start - 1] == b'<'
-                        && dox.as_bytes()[generics_end] == b'>'
+            tcx.struct_span_lint_hir(
+                crate::lint::INVALID_HTML_TAGS,
+                hir_id,
+                sp,
+                msg.to_string(),
+                |lint| {
+                    use rustc_lint_defs::Applicability;
+                    // If a tag looks like `<this>`, it might actually be a generic.
+                    // We don't try to detect stuff `<like, this>` because that's not valid HTML,
+                    // and we don't try to detect stuff `<like this>` because that's not valid Rust.
+                    let mut generics_end = range.end;
+                    if let Some(Some(mut generics_start)) = (is_open_tag
+                        && dox[..generics_end].ends_with('>'))
+                    .then(|| extract_path_backwards(&dox, range.start))
                     {
-                        generics_end += 1;
-                        generics_start -= 1;
-                        if let Some(new_start) = extract_path_backwards(&dox, generics_start) {
-                            generics_start = new_start;
+                        while generics_start != 0
+                            && generics_end < dox.len()
+                            && dox.as_bytes()[generics_start - 1] == b'<'
+                            && dox.as_bytes()[generics_end] == b'>'
+                        {
+                            generics_end += 1;
+                            generics_start -= 1;
+                            if let Some(new_start) = extract_path_backwards(&dox, generics_start) {
+                                generics_start = new_start;
+                            }
+                            if let Some(new_end) = extract_path_forward(&dox, generics_end) {
+                                generics_end = new_end;
+                            }
                         }
                         if let Some(new_end) = extract_path_forward(&dox, generics_end) {
                             generics_end = new_end;
                         }
+                        let generics_sp = match source_span_for_markdown_range(
+                            tcx,
+                            &dox,
+                            &(generics_start..generics_end),
+                            &item.attrs,
+                        ) {
+                            Some(sp) => sp,
+                            None => item.attr_span(tcx),
+                        };
+                        // Sometimes, we only extract part of a path. For example, consider this:
+                        //
+                        //     <[u32] as IntoIter<u32>>::Item
+                        //                       ^^^^^ unclosed HTML tag `u32`
+                        //
+                        // We don't have any code for parsing fully-qualified trait paths.
+                        // In theory, we could add it, but doing it correctly would require
+                        // parsing the entire path grammar, which is problematic because of
+                        // overlap between the path grammar and Markdown.
+                        //
+                        // The example above shows that ambiguity. Is `[u32]` intended to be an
+                        // intra-doc link to the u32 primitive, or is it intended to be a slice?
+                        //
+                        // If the below conditional were removed, we would suggest this, which is
+                        // not what the user probably wants.
+                        //
+                        //     <[u32] as `IntoIter<u32>`>::Item
+                        //
+                        // We know that the user actually wants to wrap the whole thing in a code
+                        // block, but the only reason we know that is because `u32` does not, in
+                        // fact, implement IntoIter. If the example looks like this:
+                        //
+                        //     <[Vec<i32>] as IntoIter<i32>::Item
+                        //
+                        // The ideal fix would be significantly different.
+                        if (generics_start > 0 && dox.as_bytes()[generics_start - 1] == b'<')
+                            || (generics_end < dox.len() && dox.as_bytes()[generics_end] == b'>')
+                        {
+                            return lint;
+                        }
+                        // multipart form is chosen here because ``Vec<i32>`` would be confusing.
+                        lint.multipart_suggestion(
+                            "try marking as source code",
+                            vec![
+                                (generics_sp.shrink_to_lo(), String::from("`")),
+                                (generics_sp.shrink_to_hi(), String::from("`")),
+                            ],
+                            Applicability::MaybeIncorrect,
+                        );
                     }
-                    if let Some(new_end) = extract_path_forward(&dox, generics_end) {
-                        generics_end = new_end;
-                    }
-                    let generics_sp = match source_span_for_markdown_range(
-                        tcx,
-                        &dox,
-                        &(generics_start..generics_end),
-                        &item.attrs,
-                    ) {
-                        Some(sp) => sp,
-                        None => item.attr_span(tcx),
-                    };
-                    // Sometimes, we only extract part of a path. For example, consider this:
-                    //
-                    //     <[u32] as IntoIter<u32>>::Item
-                    //                       ^^^^^ unclosed HTML tag `u32`
-                    //
-                    // We don't have any code for parsing fully-qualified trait paths.
-                    // In theory, we could add it, but doing it correctly would require
-                    // parsing the entire path grammar, which is problematic because of
-                    // overlap between the path grammar and Markdown.
-                    //
-                    // The example above shows that ambiguity. Is `[u32]` intended to be an
-                    // intra-doc link to the u32 primitive, or is it intended to be a slice?
-                    //
-                    // If the below conditional were removed, we would suggest this, which is
-                    // not what the user probably wants.
-                    //
-                    //     <[u32] as `IntoIter<u32>`>::Item
-                    //
-                    // We know that the user actually wants to wrap the whole thing in a code
-                    // block, but the only reason we know that is because `u32` does not, in
-                    // fact, implement IntoIter. If the example looks like this:
-                    //
-                    //     <[Vec<i32>] as IntoIter<i32>::Item
-                    //
-                    // The ideal fix would be significantly different.
-                    if (generics_start > 0 && dox.as_bytes()[generics_start - 1] == b'<')
-                        || (generics_end < dox.len() && dox.as_bytes()[generics_end] == b'>')
-                    {
-                        return lint;
-                    }
-                    // multipart form is chosen here because ``Vec<i32>`` would be confusing.
-                    lint.multipart_suggestion(
-                        "try marking as source code",
-                        vec![
-                            (generics_sp.shrink_to_lo(), String::from("`")),
-                            (generics_sp.shrink_to_hi(), String::from("`")),
-                        ],
-                        Applicability::MaybeIncorrect,
-                    );
-                }
 
-                lint
-            });
+                    lint
+                },
+            );
         };
 
         let mut tags = Vec::new();
@@ -147,11 +153,11 @@ pub(crate) fn visit_item(cx: &DocContext<'_>, item: &Item) {
             let t = t.to_lowercase();
             !ALLOWED_UNCLOSED.contains(&t.as_str())
         }) {
-            report_diag(&format!("unclosed HTML tag `{}`", tag), range, true);
+            report_diag(format!("unclosed HTML tag `{}`", tag), range, true);
         }
 
         if let Some(range) = is_in_comment {
-            report_diag("Unclosed HTML comment", &range, false);
+            report_diag("Unclosed HTML comment".to_string(), &range, false);
         }
     }
 }
@@ -165,7 +171,7 @@ fn drop_tag(
     tags: &mut Vec<(String, Range<usize>)>,
     tag_name: String,
     range: Range<usize>,
-    f: &impl Fn(&str, &Range<usize>, bool),
+    f: &impl Fn(String, &Range<usize>, bool),
 ) {
     let tag_name_low = tag_name.to_lowercase();
     if let Some(pos) = tags.iter().rposition(|(t, _)| t.to_lowercase() == tag_name_low) {
@@ -186,14 +192,14 @@ fn drop_tag(
             // `tags` is used as a queue, meaning that everything after `pos` is included inside it.
             // So `<h2><h3></h2>` will look like `["h2", "h3"]`. So when closing `h2`, we will still
             // have `h3`, meaning the tag wasn't closed as it should have.
-            f(&format!("unclosed HTML tag `{}`", last_tag_name), &last_tag_span, true);
+            f(format!("unclosed HTML tag `{}`", last_tag_name), &last_tag_span, true);
         }
         // Remove the `tag_name` that was originally closed
         tags.pop();
     } else {
         // It can happen for example in this case: `<h2></script></h2>` (the `h2` tag isn't required
         // but it helps for the visualization).
-        f(&format!("unopened HTML tag `{}`", tag_name), &range, false);
+        f(format!("unopened HTML tag `{}`", tag_name), &range, false);
     }
 }
 
@@ -261,7 +267,7 @@ fn extract_html_tag(
     range: &Range<usize>,
     start_pos: usize,
     iter: &mut Peekable<CharIndices<'_>>,
-    f: &impl Fn(&str, &Range<usize>, bool),
+    f: &impl Fn(String, &Range<usize>, bool),
 ) {
     let mut tag_name = String::new();
     let mut is_closing = false;
@@ -347,7 +353,7 @@ fn extract_html_tag(
                     if let Some(quote_pos) = quote_pos {
                         let qr = Range { start: quote_pos, end: quote_pos };
                         f(
-                            &format!("unclosed quoted HTML attribute on tag `{}`", tag_name),
+                            format!("unclosed quoted HTML attribute on tag `{}`", tag_name),
                             &qr,
                             false,
                         );
@@ -360,7 +366,7 @@ fn extract_html_tag(
                                 at == "svg" || at == "math"
                             });
                         if !valid {
-                            f(&format!("invalid self-closing HTML tag `{}`", tag_name), &r, false);
+                            f(format!("invalid self-closing HTML tag `{}`", tag_name), &r, false);
                         }
                     } else {
                         tags.push((tag_name, r));
@@ -378,7 +384,7 @@ fn extract_tags(
     text: &str,
     range: Range<usize>,
     is_in_comment: &mut Option<Range<usize>>,
-    f: &impl Fn(&str, &Range<usize>, bool),
+    f: &impl Fn(String, &Range<usize>, bool),
 ) {
     let mut iter = text.char_indices().peekable();
 
diff --git a/src/librustdoc/passes/lint/unescaped_backticks.rs b/src/librustdoc/passes/lint/unescaped_backticks.rs
index 865212205ed..256958d7160 100644
--- a/src/librustdoc/passes/lint/unescaped_backticks.rs
+++ b/src/librustdoc/passes/lint/unescaped_backticks.rs
@@ -373,7 +373,7 @@ fn suggest_insertion(
     lint: &mut DiagnosticBuilder<'_, ()>,
     insert_index: usize,
     suggestion: char,
-    message: &str,
+    message: &'static str,
 ) {
     /// Maximum bytes of context to show around the insertion.
     const CONTEXT_MAX_LEN: usize = 80;
diff --git a/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs b/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs
index f1831a30461..3b7eccad79d 100644
--- a/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs
@@ -154,7 +154,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingConstForFn {
 
         if let Err((span, err)) = is_min_const_fn(cx.tcx, mir, &self.msrv) {
             if cx.tcx.is_const_fn_raw(def_id.to_def_id()) {
-                cx.tcx.sess.span_err(span, err.as_ref());
+                cx.tcx.sess.span_err(span, err);
             }
         } else {
             span_lint(cx, MISSING_CONST_FOR_FN, span, "this could be a `const fn`");
diff --git a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
index 0bb1775aae9..7d53fe65658 100644
--- a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
+++ b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
@@ -26,7 +26,6 @@ use rustc_span::{sym, Span};
 use rustc_target::spec::abi::Abi;
 use rustc_trait_selection::traits;
 use rustc_trait_selection::traits::misc::type_allowed_to_implement_copy;
-use std::borrow::Cow;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -240,9 +239,8 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                                         snippet_opt(cx, span)
                                             .map_or(
                                                 "change the call to".into(),
-                                                |x| Cow::from(format!("change `{x}` to")),
-                                            )
-                                            .as_ref(),
+                                                |x| format!("change `{x}` to"),
+                                            ),
                                         suggestion,
                                         Applicability::Unspecified,
                                     );
@@ -270,9 +268,8 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                                         snippet_opt(cx, span)
                                             .map_or(
                                                 "change the call to".into(),
-                                                |x| Cow::from(format!("change `{x}` to"))
-                                            )
-                                            .as_ref(),
+                                                |x| format!("change `{x}` to")
+                                            ),
                                         suggestion,
                                         Applicability::Unspecified,
                                     );
diff --git a/src/tools/clippy/clippy_lints/src/unnecessary_wraps.rs b/src/tools/clippy/clippy_lints/src/unnecessary_wraps.rs
index 8b0e0ce5a30..5073eb02bd8 100644
--- a/src/tools/clippy/clippy_lints/src/unnecessary_wraps.rs
+++ b/src/tools/clippy/clippy_lints/src/unnecessary_wraps.rs
@@ -163,7 +163,7 @@ impl<'tcx> LateLintPass<'tcx> for UnnecessaryWraps {
             span_lint_and_then(cx, UNNECESSARY_WRAPS, span, lint_msg.as_str(), |diag| {
                 diag.span_suggestion(
                     fn_decl.output.span(),
-                    return_type_sugg_msg.as_str(),
+                    return_type_sugg_msg,
                     return_type_sugg,
                     Applicability::MaybeIncorrect,
                 );
diff --git a/src/tools/clippy/clippy_utils/src/diagnostics.rs b/src/tools/clippy/clippy_utils/src/diagnostics.rs
index 812f6fe71a0..edd87546a5f 100644
--- a/src/tools/clippy/clippy_utils/src/diagnostics.rs
+++ b/src/tools/clippy/clippy_utils/src/diagnostics.rs
@@ -46,7 +46,7 @@ fn docs_link(diag: &mut Diagnostic, lint: &'static Lint) {
 ///    |     ^^^^^^^^^^^^^^^^^^^^^^^
 /// ```
 pub fn span_lint<T: LintContext>(cx: &T, lint: &'static Lint, sp: impl Into<MultiSpan>, msg: &str) {
-    cx.struct_span_lint(lint, sp, msg, |diag| {
+    cx.struct_span_lint(lint, sp, msg.to_string(), |diag| {
         docs_link(diag, lint);
         diag
     });
@@ -80,11 +80,12 @@ pub fn span_lint_and_help<T: LintContext>(
     help_span: Option<Span>,
     help: &str,
 ) {
-    cx.struct_span_lint(lint, span, msg, |diag| {
+    cx.struct_span_lint(lint, span, msg.to_string(), |diag| {
+        let help = help.to_string();
         if let Some(help_span) = help_span {
-            diag.span_help(help_span, help);
+            diag.span_help(help_span, help.to_string());
         } else {
-            diag.help(help);
+            diag.help(help.to_string());
         }
         docs_link(diag, lint);
         diag
@@ -122,7 +123,8 @@ pub fn span_lint_and_note<T: LintContext>(
     note_span: Option<Span>,
     note: &str,
 ) {
-    cx.struct_span_lint(lint, span, msg, |diag| {
+    cx.struct_span_lint(lint, span, msg.to_string(), |diag| {
+        let note = note.to_string();
         if let Some(note_span) = note_span {
             diag.span_note(note_span, note);
         } else {
@@ -143,7 +145,7 @@ where
     S: Into<MultiSpan>,
     F: FnOnce(&mut Diagnostic),
 {
-    cx.struct_span_lint(lint, sp, msg, |diag| {
+    cx.struct_span_lint(lint, sp, msg.to_string(), |diag| {
         f(diag);
         docs_link(diag, lint);
         diag
@@ -151,7 +153,7 @@ where
 }
 
 pub fn span_lint_hir(cx: &LateContext<'_>, lint: &'static Lint, hir_id: HirId, sp: Span, msg: &str) {
-    cx.tcx.struct_span_lint_hir(lint, hir_id, sp, msg, |diag| {
+    cx.tcx.struct_span_lint_hir(lint, hir_id, sp, msg.to_string(), |diag| {
         docs_link(diag, lint);
         diag
     });
@@ -165,7 +167,7 @@ pub fn span_lint_hir_and_then(
     msg: &str,
     f: impl FnOnce(&mut Diagnostic),
 ) {
-    cx.tcx.struct_span_lint_hir(lint, hir_id, sp, msg, |diag| {
+    cx.tcx.struct_span_lint_hir(lint, hir_id, sp, msg.to_string(), |diag| {
         f(diag);
         docs_link(diag, lint);
         diag
@@ -202,7 +204,7 @@ pub fn span_lint_and_sugg<T: LintContext>(
     applicability: Applicability,
 ) {
     span_lint_and_then(cx, lint, sp, msg, |diag| {
-        diag.span_suggestion(sp, help, sugg, applicability);
+        diag.span_suggestion(sp, help.to_string(), sugg, applicability);
     });
 }
 
@@ -232,5 +234,5 @@ pub fn multispan_sugg_with_applicability<I>(
 ) where
     I: IntoIterator<Item = (Span, String)>,
 {
-    diag.multipart_suggestion(help_msg, sugg.into_iter().collect(), applicability);
+    diag.multipart_suggestion(help_msg.to_string(), sugg.into_iter().collect(), applicability);
 }
diff --git a/src/tools/clippy/clippy_utils/src/sugg.rs b/src/tools/clippy/clippy_utils/src/sugg.rs
index 14f7f03016f..f477524eec5 100644
--- a/src/tools/clippy/clippy_utils/src/sugg.rs
+++ b/src/tools/clippy/clippy_utils/src/sugg.rs
@@ -741,7 +741,7 @@ impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
         if let Some(indent) = indentation(cx, item) {
             let span = item.with_hi(item.lo());
 
-            self.span_suggestion(span, msg, format!("{attr}\n{indent}"), applicability);
+            self.span_suggestion(span, msg.to_string(), format!("{attr}\n{indent}"), applicability);
         }
     }
 
@@ -762,7 +762,7 @@ impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
                 })
                 .collect::<String>();
 
-            self.span_suggestion(span, msg, format!("{new_item}\n{indent}"), applicability);
+            self.span_suggestion(span, msg.to_string(), format!("{new_item}\n{indent}"), applicability);
         }
     }
 
@@ -779,7 +779,7 @@ impl<T: LintContext> DiagnosticExt<T> for rustc_errors::Diagnostic {
             }
         }
 
-        self.span_suggestion(remove_span, msg, "", applicability);
+        self.span_suggestion(remove_span, msg.to_string(), "", applicability);
     }
 }
 
diff --git a/src/tools/miri/src/diagnostics.rs b/src/tools/miri/src/diagnostics.rs
index e3f81a78eea..14931baaadf 100644
--- a/src/tools/miri/src/diagnostics.rs
+++ b/src/tools/miri/src/diagnostics.rs
@@ -306,7 +306,7 @@ pub fn report_error<'tcx, 'mir>(
     msg.insert(0, e.to_string());
     report_msg(
         DiagLevel::Error,
-        &if let Some(title) = title { format!("{title}: {}", msg[0]) } else { msg[0].clone() },
+        if let Some(title) = title { format!("{title}: {}", msg[0]) } else { msg[0].clone() },
         msg,
         vec![],
         helps,
@@ -359,7 +359,7 @@ pub fn report_leaks<'mir, 'tcx>(
         any_pruned |= pruned;
         report_msg(
             DiagLevel::Error,
-            &format!(
+            format!(
                 "memory leaked: {id:?} ({}, size: {:?}, align: {:?}), allocated here:",
                 kind,
                 alloc.size().bytes(),
@@ -386,7 +386,7 @@ pub fn report_leaks<'mir, 'tcx>(
 /// additional `span_label` or `note` call.
 pub fn report_msg<'tcx>(
     diag_level: DiagLevel,
-    title: &str,
+    title: String,
     span_msg: Vec<String>,
     notes: Vec<(Option<SpanData>, String)>,
     helps: Vec<(Option<SpanData>, String)>,
@@ -463,15 +463,16 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
         let (stacktrace, _was_pruned) = prune_stacktrace(stacktrace, self);
 
         let (title, diag_level) = match &e {
-            RejectedIsolatedOp(_) => ("operation rejected by isolation", DiagLevel::Warning),
-            Int2Ptr { .. } => ("integer-to-pointer cast", DiagLevel::Warning),
+            RejectedIsolatedOp(_) =>
+                ("operation rejected by isolation".to_string(), DiagLevel::Warning),
+            Int2Ptr { .. } => ("integer-to-pointer cast".to_string(), DiagLevel::Warning),
             CreatedPointerTag(..)
             | PoppedPointerTag(..)
             | CreatedCallId(..)
             | CreatedAlloc(..)
             | FreedAlloc(..)
             | ProgressReport { .. }
-            | WeakMemoryOutdatedLoad => ("tracking was triggered", DiagLevel::Note),
+            | WeakMemoryOutdatedLoad => ("tracking was triggered".to_string(), DiagLevel::Note),
         };
 
         let msg = match &e {
@@ -571,7 +572,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         let stacktrace = this.generate_stacktrace();
         report_msg(
             DiagLevel::Note,
-            "the place in the program where the ICE was triggered",
+            "the place in the program where the ICE was triggered".to_string(),
             vec![],
             vec![],
             vec![],
diff --git a/src/tools/rust-analyzer/crates/proc-macro-api/src/version.rs b/src/tools/rust-analyzer/crates/proc-macro-api/src/version.rs
index cf637ec359a..13f67a0128a 100644
--- a/src/tools/rust-analyzer/crates/proc-macro-api/src/version.rs
+++ b/src/tools/rust-analyzer/crates/proc-macro-api/src/version.rs
@@ -122,7 +122,7 @@ pub fn read_version(dylib_path: &AbsPath) -> io::Result<String> {
     // https://github.com/rust-lang/rust/commit/0696e79f2740ad89309269b460579e548a5cd632
     let snappy_portion = match version {
         5 | 6 => &dot_rustc[8..],
-        7 => {
+        7 | 8 => {
             let len_bytes = &dot_rustc[8..12];
             let data_len = u32::from_be_bytes(len_bytes.try_into().unwrap()) as usize;
             &dot_rustc[12..data_len + 12]
diff --git a/tests/rustdoc-gui/search-result-display.goml b/tests/rustdoc-gui/search-result-display.goml
index ee5598e4b21..bf096f62c48 100644
--- a/tests/rustdoc-gui/search-result-display.goml
+++ b/tests/rustdoc-gui/search-result-display.goml
@@ -57,22 +57,22 @@ define-function: (
 
 call-function: ("check-filter", {
     "theme": "ayu",
-    "border": "rgb(92, 103, 115)",
+    "border": "#5c6773",
     "filter": "invert(0.41) sepia(0.12) saturate(4.87) hue-rotate(171deg) brightness(0.94) contrast(0.94)",
-    "hover_border": "rgb(224, 224, 224)",
+    "hover_border": "#e0e0e0",
     "hover_filter": "invert(0.98) sepia(0.12) saturate(0.81) hue-rotate(343deg) brightness(1.13) contrast(0.76)",
 })
 call-function: ("check-filter", {
     "theme": "dark",
-    "border": "rgb(224, 224, 224)",
+    "border": "#e0e0e0",
     "filter": "invert(0.94) sepia(0) saturate(7.21) hue-rotate(255deg) brightness(0.9) contrast(0.9)",
-    "hover_border": "rgb(33, 150, 243)",
+    "hover_border": "#2196f3",
     "hover_filter": "invert(0.69) sepia(0.6) saturate(66.13) hue-rotate(184deg) brightness(1) contrast(0.91)",
 })
 call-function: ("check-filter", {
     "theme": "light",
-    "border": "rgb(224, 224, 224)",
+    "border": "#e0e0e0",
     "filter": "invert(1) sepia(0) saturate(42.23) hue-rotate(289deg) brightness(1.14) contrast(0.76)",
-    "hover_border": "rgb(113, 113, 113)",
+    "hover_border": "#717171",
     "hover_filter": "invert(0.44) sepia(0.18) saturate(0.23) hue-rotate(317deg) brightness(0.96) contrast(0.93)",
 })
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 e4b8958b4fa..8c876213ae0 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
@@ -23,7 +23,7 @@ LL |     arg: NotIntoDiagnosticArg,
    |
    = help: normalized in stderr
 note: required by a bound in `Diagnostic::set_arg`
-  --> $COMPILER_DIR/rustc_errors/src/diagnostic.rs:964:5
+  --> $COMPILER_DIR/rustc_errors/src/diagnostic.rs:960:5
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/deriving/deriving-all-codegen.stdout b/tests/ui/deriving/deriving-all-codegen.stdout
index 5bca83e87f8..d6a2c80cc06 100644
--- a/tests/ui/deriving/deriving-all-codegen.stdout
+++ b/tests/ui/deriving/deriving-all-codegen.stdout
@@ -44,6 +44,7 @@ impl ::core::default::Default for Empty {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Empty {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {}
 }
 #[automatically_derived]
@@ -113,6 +114,7 @@ impl ::core::default::Default for Point {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Point {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.x, state);
         ::core::hash::Hash::hash(&self.y, state)
@@ -198,6 +200,7 @@ impl ::core::default::Default for PackedPoint {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for PackedPoint {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&{ self.x }, state);
         ::core::hash::Hash::hash(&{ self.y }, state)
@@ -301,6 +304,7 @@ impl ::core::default::Default for Big {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Big {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.b1, state);
         ::core::hash::Hash::hash(&self.b2, state);
@@ -478,6 +482,7 @@ impl ::core::fmt::Debug for Unsized {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Unsized {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.0, state)
     }
@@ -529,6 +534,7 @@ impl ::core::fmt::Debug for PackedUnsizedU8 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for PackedUnsizedU8 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.0, state)
     }
@@ -584,6 +590,7 @@ impl<T: ::core::default::Default + Trait, U: ::core::default::Default>
 #[automatically_derived]
 impl<T: ::core::hash::Hash + Trait, U: ::core::hash::Hash> ::core::hash::Hash
     for Generic<T, U> where T::A: ::core::hash::Hash {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&self.t, state);
         ::core::hash::Hash::hash(&self.ta, state);
@@ -701,6 +708,7 @@ impl<T: ::core::hash::Hash + ::core::marker::Copy + Trait,
     U: ::core::hash::Hash + ::core::marker::Copy> ::core::hash::Hash for
     PackedGeneric<T, U> where T::A: ::core::hash::Hash + ::core::marker::Copy
     {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         ::core::hash::Hash::hash(&{ self.0 }, state);
         ::core::hash::Hash::hash(&{ self.1 }, state);
@@ -795,6 +803,7 @@ impl ::core::fmt::Debug for Enum0 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Enum0 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         unsafe { ::core::intrinsics::unreachable() }
     }
@@ -861,6 +870,7 @@ impl ::core::fmt::Debug for Enum1 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Enum1 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         match self {
             Enum1::Single { x: __self_0 } =>
@@ -937,6 +947,7 @@ impl ::core::default::Default for Fieldless1 {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Fieldless1 {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {}
 }
 #[automatically_derived]
@@ -1004,6 +1015,7 @@ impl ::core::default::Default for Fieldless {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Fieldless {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state)
@@ -1095,6 +1107,7 @@ impl ::core::default::Default for Mixed {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Mixed {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state);
@@ -1224,6 +1237,7 @@ impl ::core::fmt::Debug for Fielded {
 }
 #[automatically_derived]
 impl ::core::hash::Hash for Fielded {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state);
@@ -1345,6 +1359,7 @@ impl<T: ::core::fmt::Debug, U: ::core::fmt::Debug> ::core::fmt::Debug for
 #[automatically_derived]
 impl<T: ::core::hash::Hash, U: ::core::hash::Hash> ::core::hash::Hash for
     EnumGeneric<T, U> {
+    #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
         let __self_tag = ::core::intrinsics::discriminant_value(self);
         ::core::hash::Hash::hash(&__self_tag, state);
diff --git a/tests/ui/linkage-attr/incompatible-flavor.rs b/tests/ui/linkage-attr/incompatible-flavor.rs
new file mode 100644
index 00000000000..90c2b612f22
--- /dev/null
+++ b/tests/ui/linkage-attr/incompatible-flavor.rs
@@ -0,0 +1,6 @@
+// compile-flags: --target=x86_64-unknown-linux-gnu -C linker-flavor=msvc --crate-type=rlib
+// error-pattern: linker flavor `msvc` is incompatible with the current target
+// needs-llvm-components:
+
+#![feature(no_core)]
+#![no_core]
diff --git a/tests/ui/linkage-attr/incompatible-flavor.stderr b/tests/ui/linkage-attr/incompatible-flavor.stderr
new file mode 100644
index 00000000000..e07e778521c
--- /dev/null
+++ b/tests/ui/linkage-attr/incompatible-flavor.stderr
@@ -0,0 +1,6 @@
+error: linker flavor `msvc` is incompatible with the current target
+   |
+   = note: compatible flavors are: gcc, ld, ld.lld
+
+error: aborting due to previous error
+
diff --git a/tests/ui/linkage-attr/issue-10755.rs b/tests/ui/linkage-attr/issue-10755.rs
index afd2dc46ca3..0df5d842cb2 100644
--- a/tests/ui/linkage-attr/issue-10755.rs
+++ b/tests/ui/linkage-attr/issue-10755.rs
@@ -1,6 +1,6 @@
 // build-fail
 // dont-check-compiler-stderr
-// compile-flags: -C linker=llllll -C linker-flavor=ld
+// compile-flags: -C linker=llllll
 // error-pattern: `llllll`
 
 // Before, the error-pattern checked for "not found". On WSL with appendWindowsPath=true, running
diff --git a/tests/ui/linkage-attr/unstable-flavor.bpf.stderr b/tests/ui/linkage-attr/unstable-flavor.bpf.stderr
new file mode 100644
index 00000000000..3346d12c20e
--- /dev/null
+++ b/tests/ui/linkage-attr/unstable-flavor.bpf.stderr
@@ -0,0 +1,2 @@
+error: linker flavor `bpf-linker` is unstable, `-Z unstable-options` flag must also be passed to explicitly use it
+
diff --git a/tests/ui/linkage-attr/unstable-flavor.ptx.stderr b/tests/ui/linkage-attr/unstable-flavor.ptx.stderr
new file mode 100644
index 00000000000..03ca2a01246
--- /dev/null
+++ b/tests/ui/linkage-attr/unstable-flavor.ptx.stderr
@@ -0,0 +1,2 @@
+error: linker flavor `ptx-linker` is unstable, `-Z unstable-options` flag must also be passed to explicitly use it
+
diff --git a/tests/ui/linkage-attr/unstable-flavor.rs b/tests/ui/linkage-attr/unstable-flavor.rs
new file mode 100644
index 00000000000..5487882dc24
--- /dev/null
+++ b/tests/ui/linkage-attr/unstable-flavor.rs
@@ -0,0 +1,10 @@
+// revisions: bpf ptx
+// [bpf] compile-flags: --target=bpfel-unknown-none -C linker-flavor=bpf-linker --crate-type=rlib
+// [bpf] error-pattern: linker flavor `bpf-linker` is unstable, `-Z unstable-options` flag
+// [bpf] needs-llvm-components:
+// [ptx] compile-flags: --target=nvptx64-nvidia-cuda -C linker-flavor=ptx-linker --crate-type=rlib
+// [ptx] error-pattern: linker flavor `ptx-linker` is unstable, `-Z unstable-options` flag
+// [ptx] needs-llvm-components:
+
+#![feature(no_core)]
+#![no_core]
diff --git a/tests/ui/parser/typod-const-in-const-param-def.rs b/tests/ui/parser/typod-const-in-const-param-def.rs
new file mode 100644
index 00000000000..85d3ebba57a
--- /dev/null
+++ b/tests/ui/parser/typod-const-in-const-param-def.rs
@@ -0,0 +1,16 @@
+pub fn foo<Const N: u8>() {}
+//~^ ERROR `const` keyword was mistyped as `Const`
+
+pub fn bar<Const>() {}
+// OK
+
+pub fn baz<Const N: u8, T>() {}
+//~^ ERROR `const` keyword was mistyped as `Const`
+
+pub fn qux<T, Const N: u8>() {}
+//~^ ERROR `const` keyword was mistyped as `Const`
+
+pub fn quux<T, Const N: u8, U>() {}
+//~^ ERROR `const` keyword was mistyped as `Const`
+
+fn main() {}
diff --git a/tests/ui/parser/typod-const-in-const-param-def.stderr b/tests/ui/parser/typod-const-in-const-param-def.stderr
new file mode 100644
index 00000000000..75d73c6ea87
--- /dev/null
+++ b/tests/ui/parser/typod-const-in-const-param-def.stderr
@@ -0,0 +1,46 @@
+error: `const` keyword was mistyped as `Const`
+  --> $DIR/typod-const-in-const-param-def.rs:1:12
+   |
+LL | pub fn foo<Const N: u8>() {}
+   |            ^^^^^
+   |
+help: use the `const` keyword
+   |
+LL | pub fn foo<const N: u8>() {}
+   |            ~~~~~
+
+error: `const` keyword was mistyped as `Const`
+  --> $DIR/typod-const-in-const-param-def.rs:7:12
+   |
+LL | pub fn baz<Const N: u8, T>() {}
+   |            ^^^^^
+   |
+help: use the `const` keyword
+   |
+LL | pub fn baz<const N: u8, T>() {}
+   |            ~~~~~
+
+error: `const` keyword was mistyped as `Const`
+  --> $DIR/typod-const-in-const-param-def.rs:10:15
+   |
+LL | pub fn qux<T, Const N: u8>() {}
+   |               ^^^^^
+   |
+help: use the `const` keyword
+   |
+LL | pub fn qux<T, const N: u8>() {}
+   |               ~~~~~
+
+error: `const` keyword was mistyped as `Const`
+  --> $DIR/typod-const-in-const-param-def.rs:13:16
+   |
+LL | pub fn quux<T, Const N: u8, U>() {}
+   |                ^^^^^
+   |
+help: use the `const` keyword
+   |
+LL | pub fn quux<T, const N: u8, U>() {}
+   |                ~~~~~
+
+error: aborting due to 4 previous errors
+