diff --git a/compiler/rustc_error_codes/src/error_codes/E0522.md b/compiler/rustc_error_codes/src/error_codes/E0522.md
index 83272314a8708..b0dd5a775ac14 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0522.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0522.md
@@ -6,7 +6,7 @@ Erroneous code example:
 #![feature(lang_items)]
 
 #[lang = "cookie"]
-fn cookie() -> ! { // error: definition of an unknown language item: `cookie`
+fn cookie() -> ! { // error: definition of an unknown lang item: `cookie`
     loop {}
 }
 ```
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 4f62323231a73..23b3f31b43704 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -798,7 +798,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     // ==========================================================================
     gated!(
         lang, Normal, template!(NameValueStr: "name"), DuplicatesOk, EncodeCrossCrate::No, lang_items,
-        "language items are subject to change",
+        "lang items are subject to change",
     ),
     rustc_attr!(
         rustc_pass_by_value, Normal, template!(Word), ErrorFollowing,
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 879476f890e8c..6aee1183a106e 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -1,4 +1,4 @@
-//! Defines language items.
+//! Defines lang items.
 //!
 //! Language items are items that represent concepts intrinsic to the language
 //! itself. Examples are:
@@ -16,7 +16,7 @@ use rustc_macros::HashStable_Generic;
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
 
-/// All of the language items, defined or not.
+/// All of the lang items, defined or not.
 /// Defined lang items can come from the current crate or its dependencies.
 #[derive(HashStable_Generic, Debug)]
 pub struct LanguageItems {
@@ -57,7 +57,7 @@ macro_rules! language_item_table {
     ) => {
 
         enum_from_u32! {
-            /// A representation of all the valid language items in Rust.
+            /// A representation of all the valid lang items in Rust.
             #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable)]
             pub enum LangItem {
                 $(
@@ -177,7 +177,7 @@ language_item_table! {
     CoerceUnsized,           sym::coerce_unsized,      coerce_unsized_trait,       Target::Trait,          GenericRequirement::Minimum(1);
     DispatchFromDyn,         sym::dispatch_from_dyn,   dispatch_from_dyn_trait,    Target::Trait,          GenericRequirement::Minimum(1);
 
-    // language items relating to transmutability
+    // lang items relating to transmutability
     TransmuteOpts,           sym::transmute_opts,      transmute_opts,             Target::Struct,         GenericRequirement::Exact(0);
     TransmuteTrait,          sym::transmute_trait,     transmute_trait,            Target::Trait,          GenericRequirement::Exact(2);
 
@@ -304,7 +304,7 @@ language_item_table! {
     OwnedBox,                sym::owned_box,           owned_box,                  Target::Struct,         GenericRequirement::Minimum(1);
     GlobalAlloc,             sym::global_alloc_ty,     global_alloc_ty,            Target::Struct,         GenericRequirement::None;
 
-    // Experimental language item for Miri
+    // Experimental lang item for Miri
     PtrUnique,               sym::ptr_unique,          ptr_unique,                 Target::Struct,         GenericRequirement::Exact(1);
 
     PhantomData,             sym::phantom_data,        phantom_data,               Target::Struct,         GenericRequirement::Exact(1);
diff --git a/compiler/rustc_hir_analysis/src/bounds.rs b/compiler/rustc_hir_analysis/src/bounds.rs
index d3f51195dfb29..aafb5c1c0b4bc 100644
--- a/compiler/rustc_hir_analysis/src/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/bounds.rs
@@ -43,16 +43,6 @@ impl<'tcx> Bounds<'tcx> {
         trait_ref: ty::PolyTraitRef<'tcx>,
         span: Span,
         polarity: ty::PredicatePolarity,
-    ) {
-        self.push_trait_bound_inner(tcx, trait_ref, span, polarity);
-    }
-
-    fn push_trait_bound_inner(
-        &mut self,
-        tcx: TyCtxt<'tcx>,
-        trait_ref: ty::PolyTraitRef<'tcx>,
-        span: Span,
-        polarity: ty::PredicatePolarity,
     ) {
         let clause = (
             trait_ref
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index fb4a76bf089f4..1aa73401303ac 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -535,7 +535,7 @@ pub fn check_intrinsic_type(
 
             sym::va_start | sym::va_end => match mk_va_list_ty(hir::Mutability::Mut) {
                 Some((va_list_ref_ty, _)) => (0, 0, vec![va_list_ref_ty], Ty::new_unit(tcx)),
-                None => bug!("`va_list` language item needed for C-variadic intrinsics"),
+                None => bug!("`va_list` lang item needed for C-variadic intrinsics"),
             },
 
             sym::va_copy => match mk_va_list_ty(hir::Mutability::Not) {
@@ -543,12 +543,12 @@ pub fn check_intrinsic_type(
                     let va_list_ptr_ty = Ty::new_mut_ptr(tcx, va_list_ty);
                     (0, 0, vec![va_list_ptr_ty, va_list_ref_ty], Ty::new_unit(tcx))
                 }
-                None => bug!("`va_list` language item needed for C-variadic intrinsics"),
+                None => bug!("`va_list` lang item needed for C-variadic intrinsics"),
             },
 
             sym::va_arg => match mk_va_list_ty(hir::Mutability::Mut) {
                 Some((va_list_ref_ty, _)) => (1, 0, vec![va_list_ref_ty], param(0)),
-                None => bug!("`va_list` language item needed for C-variadic intrinsics"),
+                None => bug!("`va_list` lang item needed for C-variadic intrinsics"),
             },
 
             sym::nontemporal_store => {
diff --git a/compiler/rustc_lint/src/non_fmt_panic.rs b/compiler/rustc_lint/src/non_fmt_panic.rs
index a2d07fff5067c..e81790a7348e2 100644
--- a/compiler/rustc_lint/src/non_fmt_panic.rs
+++ b/compiler/rustc_lint/src/non_fmt_panic.rs
@@ -53,7 +53,7 @@ impl<'tcx> LateLintPass<'tcx> for NonPanicFmt {
 
                 if Some(def_id) == cx.tcx.lang_items().begin_panic_fn()
                     || Some(def_id) == cx.tcx.lang_items().panic_fn()
-                    || f_diagnostic_name == Some(sym::panic_str)
+                    || f_diagnostic_name == Some(sym::panic_str_2015)
                 {
                     if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
                         if matches!(
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 596da58b091f4..c4ab4eb2657d6 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1208,7 +1208,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         tcx.arena.alloc_from_iter(self.root.stability_implications.decode(self))
     }
 
-    /// Iterates over the language items in the given crate.
+    /// Iterates over the lang items in the given crate.
     fn get_lang_items(self, tcx: TyCtxt<'tcx>) -> &'tcx [(DefId, LangItem)] {
         tcx.arena.alloc_from_iter(
             self.root
diff --git a/compiler/rustc_middle/src/middle/lang_items.rs b/compiler/rustc_middle/src/middle/lang_items.rs
index a4e193ba2c942..4fd1c1f4a1b7d 100644
--- a/compiler/rustc_middle/src/middle/lang_items.rs
+++ b/compiler/rustc_middle/src/middle/lang_items.rs
@@ -1,4 +1,4 @@
-//! Detecting language items.
+//! Detecting lang items.
 //!
 //! Language items are items that represent concepts intrinsic to the language
 //! itself. Examples are:
diff --git a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
index ca63f5550ae2e..370e930b74098 100644
--- a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
+++ b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
@@ -160,7 +160,7 @@ pub fn deduced_param_attrs<'tcx>(
         return &[];
     }
 
-    // If the Freeze language item isn't present, then don't bother.
+    // If the Freeze lang item isn't present, then don't bother.
     if tcx.lang_items().freeze_trait().is_none() {
         return &[];
     }
diff --git a/compiler/rustc_mir_transform/src/lower_slice_len.rs b/compiler/rustc_mir_transform/src/lower_slice_len.rs
index 8137525a33243..2267a621a834a 100644
--- a/compiler/rustc_mir_transform/src/lower_slice_len.rs
+++ b/compiler/rustc_mir_transform/src/lower_slice_len.rs
@@ -21,7 +21,7 @@ impl<'tcx> MirPass<'tcx> for LowerSliceLenCalls {
 pub fn lower_slice_len_calls<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let language_items = tcx.lang_items();
     let Some(slice_len_fn_item_def_id) = language_items.slice_len_fn() else {
-        // there is no language item to compare to :)
+        // there is no lang item to compare to :)
         return;
     };
 
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 32a0df2f619ad..873095dca8722 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -624,6 +624,8 @@ parse_or_pattern_not_allowed_in_let_binding = top-level or-patterns are not allo
 parse_out_of_range_hex_escape = out of range hex escape
     .label = must be a character in the range [\x00-\x7f]
 
+parse_outer_attr_ambiguous = ambiguous outer attributes
+
 parse_outer_attr_explanation = outer attributes, like `#[test]`, annotate the item following them
 
 parse_outer_attribute_not_allowed_on_if_else = outer attributes are not allowed on `if` and `else` branches
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index ca8de4240f450..b77045ee34e0d 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -495,6 +495,15 @@ pub(crate) struct OuterAttributeNotAllowedOnIfElse {
     pub attributes: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_outer_attr_ambiguous)]
+pub(crate) struct AmbiguousOuterAttributes {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub sugg: WrapInParentheses,
+}
+
 #[derive(Diagnostic)]
 #[diag(parse_missing_in_in_for_loop)]
 pub(crate) struct MissingInInForLoop {
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 8a4546107186b..8ed2a6edf1aec 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -327,7 +327,9 @@ impl<'a> Parser<'a> {
                 this.parse_expr_assoc_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
             })?;
 
-            let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
+            self.error_ambiguous_outer_attrs(&lhs, lhs_span, rhs.span);
+            let span = lhs_span.to(rhs.span);
+
             lhs = match op {
                 AssocOp::Add
                 | AssocOp::Subtract
@@ -426,6 +428,18 @@ impl<'a> Parser<'a> {
         });
     }
 
+    fn error_ambiguous_outer_attrs(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) {
+        if let Some(attr) = lhs.attrs.iter().find(|a| a.style == AttrStyle::Outer) {
+            self.dcx().emit_err(errors::AmbiguousOuterAttributes {
+                span: attr.span.to(rhs_span),
+                sugg: errors::WrapInParentheses::Expression {
+                    left: attr.span.shrink_to_lo(),
+                    right: lhs_span.shrink_to_hi(),
+                },
+            });
+        }
+    }
+
     /// Possibly translate the current token to an associative operator.
     /// The method does not advance the current token.
     ///
@@ -506,7 +520,8 @@ impl<'a> Parser<'a> {
             None
         };
         let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
-        let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
+        self.error_ambiguous_outer_attrs(&lhs, lhs.span, rhs_span);
+        let span = lhs.span.to(rhs_span);
         let limits =
             if op == AssocOp::DotDot { RangeLimits::HalfOpen } else { RangeLimits::Closed };
         let range = self.mk_range(Some(lhs), rhs, limits);
@@ -722,7 +737,8 @@ impl<'a> Parser<'a> {
         expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
     ) -> PResult<'a, P<Expr>> {
         let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
-            this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
+            this.error_ambiguous_outer_attrs(&lhs, lhs_span, rhs.span);
+            this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs))
         };
 
         // Save the state of the parser before parsing type normally, in case there is a
@@ -3813,16 +3829,6 @@ impl<'a> Parser<'a> {
         self.mk_expr(span, ExprKind::Err(guar))
     }
 
-    /// Create expression span ensuring the span of the parent node
-    /// is larger than the span of lhs and rhs, including the attributes.
-    fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
-        lhs.attrs
-            .iter()
-            .find(|a| a.style == AttrStyle::Outer)
-            .map_or(lhs_span, |a| a.span)
-            .to(rhs_span)
-    }
-
     fn collect_tokens_for_expr(
         &mut self,
         attrs: AttrWrapper,
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 4a996f89a9a3d..cd8a5600c73d7 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -162,7 +162,6 @@ pub struct Parser<'a> {
     ///
     /// See the comments in the `parse_path_segment` function for more details.
     unmatched_angle_bracket_count: u16,
-    max_angle_bracket_count: u16,
     angle_bracket_nesting: u16,
 
     last_unexpected_token_span: Option<Span>,
@@ -430,7 +429,6 @@ impl<'a> Parser<'a> {
             num_bump_calls: 0,
             break_last_token: false,
             unmatched_angle_bracket_count: 0,
-            max_angle_bracket_count: 0,
             angle_bracket_nesting: 0,
             last_unexpected_token_span: None,
             subparser_name,
@@ -778,7 +776,6 @@ impl<'a> Parser<'a> {
         if ate {
             // See doc comment for `unmatched_angle_bracket_count`.
             self.unmatched_angle_bracket_count += 1;
-            self.max_angle_bracket_count += 1;
             debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
         }
         ate
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 0f410772dd980..b97ec8c613d91 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -299,7 +299,6 @@ impl<'a> Parser<'a> {
                 // parsing a new path.
                 if style == PathStyle::Expr {
                     self.unmatched_angle_bracket_count = 0;
-                    self.max_angle_bracket_count = 0;
                 }
 
                 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index 7fc523ffe0dea..a545c170297de 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -353,7 +353,7 @@ passes_incorrect_meta_item = expected a quoted string literal
 passes_incorrect_meta_item_suggestion = consider surrounding this with quotes
 
 passes_incorrect_target =
-    `{$name}` language item must be applied to a {$kind} with {$at_least ->
+    `{$name}` lang item must be applied to a {$kind} with {$at_least ->
         [true] at least {$num}
         *[false] {$num}
     } generic {$num ->
@@ -394,12 +394,21 @@ passes_invalid_macro_export_arguments = `{$name}` isn't a valid `#[macro_export]
 
 passes_invalid_macro_export_arguments_too_many_items = `#[macro_export]` can only take 1 or 0 arguments
 
+passes_lang_item_fn = {$name ->
+    [panic_impl] `#[panic_handler]`
+    *[other] `{$name}` lang item
+} function
+
 passes_lang_item_fn_with_target_feature =
-    `{$name}` language item function is not allowed to have `#[target_feature]`
-    .label = `{$name}` language item function is not allowed to have `#[target_feature]`
+    {passes_lang_item_fn} is not allowed to have `#[target_feature]`
+    .label = {passes_lang_item_fn} is not allowed to have `#[target_feature]`
+
+passes_lang_item_fn_with_track_caller =
+    {passes_lang_item_fn} is not allowed to have `#[track_caller]`
+    .label = {passes_lang_item_fn} is not allowed to have `#[target_feature]`
 
 passes_lang_item_on_incorrect_target =
-    `{$name}` language item must be applied to a {$expected_target}
+    `{$name}` lang item must be applied to a {$expected_target}
     .label = attribute should be applied to a {$expected_target}, not a {$actual_target}
 
 passes_layout_abi =
@@ -455,7 +464,7 @@ passes_missing_const_stab_attr =
     {$descr} has missing const stability attribute
 
 passes_missing_lang_item =
-    language item required, but not found: `{$name}`
+    lang item required, but not found: `{$name}`
     .note = this can occur when a binary crate with `#![no_std]` is compiled for a target where `{$name}` is defined in the standard library
     .help = you may be able to compile for a target that doesn't need `{$name}`, specify a target with `--target` or in `.cargo/config`
 
@@ -696,8 +705,8 @@ passes_unknown_feature =
     unknown feature `{$feature}`
 
 passes_unknown_lang_item =
-    definition of an unknown language item: `{$name}`
-    .label = definition of unknown language item `{$name}`
+    definition of an unknown lang item: `{$name}`
+    .label = definition of unknown lang item `{$name}`
 
 passes_unlabeled_cf_in_while_condition =
     `break` or `continue` with no label in the condition of a `while` loop
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 1254ae8cfc8db..a2388b3bd5227 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -11,9 +11,9 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::StashKey;
 use rustc_errors::{Applicability, DiagCtxt, IntoDiagArg, MultiSpan};
 use rustc_feature::{AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
-use rustc_hir as hir;
 use rustc_hir::def_id::LocalModDefId;
 use rustc_hir::intravisit::{self, Visitor};
+use rustc_hir::{self as hir};
 use rustc_hir::{
     self, FnSig, ForeignItem, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID, CRATE_OWNER_ID,
 };
@@ -519,7 +519,26 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 self.dcx().emit_err(errors::NakedTrackedCaller { attr_span });
                 false
             }
-            Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => true,
+            Target::Fn => {
+                // `#[track_caller]` is not valid on weak lang items because they are called via
+                // `extern` declarations and `#[track_caller]` would alter their ABI.
+                if let Some((lang_item, _)) = hir::lang_items::extract(attrs)
+                    && let Some(item) = hir::LangItem::from_name(lang_item)
+                    && item.is_weak()
+                {
+                    let sig = self.tcx.hir_node(hir_id).fn_sig().unwrap();
+
+                    self.dcx().emit_err(errors::LangItemWithTrackCaller {
+                        attr_span,
+                        name: lang_item,
+                        sig_span: sig.span,
+                    });
+                    false
+                } else {
+                    true
+                }
+            }
+            Target::Method(..) | Target::ForeignFn | Target::Closure => true,
             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
             // `#[track_caller]` attribute with just a lint, because we previously
             // erroneously allowed it and some crates used it accidentally, to be compatible
@@ -602,7 +621,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     ) -> bool {
         match target {
             Target::Fn => {
-                // `#[target_feature]` is not allowed in language items.
+                // `#[target_feature]` is not allowed in lang items.
                 if let Some((lang_item, _)) = hir::lang_items::extract(attrs)
                     // Calling functions with `#[target_feature]` is
                     // not unsafe on WASM, see #84988
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 3f26ea4507d41..19b5e5495d6c6 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -819,6 +819,16 @@ pub struct MissingLangItem {
     pub name: Symbol,
 }
 
+#[derive(Diagnostic)]
+#[diag(passes_lang_item_fn_with_track_caller)]
+pub struct LangItemWithTrackCaller {
+    #[primary_span]
+    pub attr_span: Span,
+    pub name: Symbol,
+    #[label]
+    pub sig_span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(passes_lang_item_fn_with_target_feature)]
 pub struct LangItemWithTargetFeature {
diff --git a/compiler/rustc_passes/src/lang_items.rs b/compiler/rustc_passes/src/lang_items.rs
index d1368267224a7..c1da8928f3021 100644
--- a/compiler/rustc_passes/src/lang_items.rs
+++ b/compiler/rustc_passes/src/lang_items.rs
@@ -1,4 +1,4 @@
-//! Detecting language items.
+//! Detecting lang items.
 //!
 //! Language items are items that represent concepts intrinsic to the language
 //! itself. Examples are:
diff --git a/compiler/rustc_passes/src/weak_lang_items.rs b/compiler/rustc_passes/src/weak_lang_items.rs
index 4eb0c6c275e61..90691ca17908b 100644
--- a/compiler/rustc_passes/src/weak_lang_items.rs
+++ b/compiler/rustc_passes/src/weak_lang_items.rs
@@ -14,7 +14,7 @@ use crate::errors::{
 };
 
 /// Checks the crate for usage of weak lang items, returning a vector of all the
-/// language items required by this crate, but not defined yet.
+/// lang items required by this crate, but not defined yet.
 pub fn check_crate(tcx: TyCtxt<'_>, items: &mut lang_items::LanguageItems, krate: &ast::Crate) {
     // These are never called by user code, they're generated by the compiler.
     // They will never implicitly be added to the `missing` array unless we do
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index b8221d9d7f9f0..b5b6d899cc58e 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1042,7 +1042,7 @@ pub struct Resolver<'a, 'tcx> {
     block_map: NodeMap<Module<'a>>,
     /// A fake module that contains no definition and no prelude. Used so that
     /// some AST passes can generate identifiers that only resolve to local or
-    /// language items.
+    /// lang items.
     empty_module: Module<'a>,
     module_map: FxHashMap<DefId, Module<'a>>,
     binding_parent_modules: FxHashMap<NameBinding<'a>, Module<'a>>,
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 2d3053ccee6b7..8abf42e2c1392 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1348,7 +1348,7 @@ symbols! {
         panic_misaligned_pointer_dereference,
         panic_nounwind,
         panic_runtime,
-        panic_str,
+        panic_str_2015,
         panic_unwind,
         panicking,
         param_attrs,
diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index 631e1654ce075..1e3ed0f7c49f1 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -554,7 +554,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use crate::iter::{self, FusedIterator, TrustedLen};
-use crate::panicking::{panic, panic_str};
+use crate::panicking::{panic, panic_display};
 use crate::pin::Pin;
 use crate::{
     cmp, convert, hint, mem,
@@ -1991,7 +1991,7 @@ const fn unwrap_failed() -> ! {
 #[track_caller]
 #[rustc_const_unstable(feature = "const_option", issue = "67441")]
 const fn expect_failed(msg: &str) -> ! {
-    panic_str(msg)
+    panic_display(&msg)
 }
 
 /////////////////////////////////////////////////////////////////////////////
diff --git a/library/core/src/panic.rs b/library/core/src/panic.rs
index b520efe93f90d..8771f40f9b42b 100644
--- a/library/core/src/panic.rs
+++ b/library/core/src/panic.rs
@@ -27,9 +27,9 @@ pub macro panic_2015 {
     ($msg:literal $(,)?) => (
         $crate::panicking::panic($msg)
     ),
-    // Use `panic_str` instead of `panic_display::<&str>` for non_fmt_panic lint.
+    // Use `panic_str_2015` instead of `panic_display::<&str>` for non_fmt_panic lint.
     ($msg:expr $(,)?) => ({
-        $crate::panicking::panic_str($msg);
+        $crate::panicking::panic_str_2015($msg);
     }),
     // Special-case the single-argument case for const_panic.
     ("{}", $arg:expr $(,)?) => ({
diff --git a/library/core/src/panicking.rs b/library/core/src/panicking.rs
index cbb0a7d61db05..3ee56e6c5799e 100644
--- a/library/core/src/panicking.rs
+++ b/library/core/src/panicking.rs
@@ -124,8 +124,8 @@ pub const fn panic_nounwind_fmt(fmt: fmt::Arguments<'_>, force_no_backtrace: boo
 // above.
 
 /// The underlying implementation of core's `panic!` macro when no formatting is used.
-// never inline unless panic_immediate_abort to avoid code
-// bloat at the call sites as much as possible
+// Never inline unless panic_immediate_abort to avoid code
+// bloat at the call sites as much as possible.
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
 #[cfg_attr(feature = "panic_immediate_abort", inline)]
 #[track_caller]
@@ -138,6 +138,11 @@ pub const fn panic(expr: &'static str) -> ! {
     // truncation and padding (even though none is used here). Using
     // Arguments::new_const may allow the compiler to omit Formatter::pad from the
     // output binary, saving up to a few kilobytes.
+    // However, this optimization only works for `'static` strings: `new_const` also makes this
+    // message return `Some` from `Arguments::as_str`, which means it can become part of the panic
+    // payload without any allocation or copying. Shorter-lived strings would become invalid as
+    // stack frames get popped during unwinding, and couldn't be directly referenced from the
+    // payload.
     panic_fmt(fmt::Arguments::new_const(&[expr]));
 }
 
@@ -223,14 +228,6 @@ pub fn panic_nounwind_nobacktrace(expr: &'static str) -> ! {
     panic_nounwind_fmt(fmt::Arguments::new_const(&[expr]), /* force_no_backtrace */ true);
 }
 
-#[inline]
-#[track_caller]
-#[rustc_diagnostic_item = "panic_str"]
-#[rustc_const_unstable(feature = "panic_internals", issue = "none")]
-pub const fn panic_str(expr: &str) -> ! {
-    panic_display(&expr);
-}
-
 #[track_caller]
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
 #[cfg_attr(feature = "panic_immediate_abort", inline)]
@@ -246,6 +243,16 @@ pub fn unreachable_display<T: fmt::Display>(x: &T) -> ! {
     panic_fmt(format_args!("internal error: entered unreachable code: {}", *x));
 }
 
+/// This exists solely for the 2015 edition `panic!` macro to trigger
+/// a lint on `panic!(my_str_variable);`.
+#[inline]
+#[track_caller]
+#[rustc_diagnostic_item = "panic_str_2015"]
+#[rustc_const_unstable(feature = "panic_internals", issue = "none")]
+pub const fn panic_str_2015(expr: &str) -> ! {
+    panic_display(&expr);
+}
+
 #[inline]
 #[track_caller]
 #[rustc_do_not_const_check] // hooked by const-eval
diff --git a/src/tools/clippy/tests/ui/cfg_attr_rustfmt.fixed b/src/tools/clippy/tests/ui/cfg_attr_rustfmt.fixed
index 05d5b3d10eaf8..84dac431169ab 100644
--- a/src/tools/clippy/tests/ui/cfg_attr_rustfmt.fixed
+++ b/src/tools/clippy/tests/ui/cfg_attr_rustfmt.fixed
@@ -16,7 +16,7 @@ fn foo(
 
 fn skip_on_statements() {
     #[rustfmt::skip]
-    5+3;
+    { 5+3; }
 }
 
 #[rustfmt::skip]
@@ -33,11 +33,11 @@ mod foo {
 #[clippy::msrv = "1.29"]
 fn msrv_1_29() {
     #[cfg_attr(rustfmt, rustfmt::skip)]
-    1+29;
+    { 1+29; }
 }
 
 #[clippy::msrv = "1.30"]
 fn msrv_1_30() {
     #[rustfmt::skip]
-    1+30;
+    { 1+30; }
 }
diff --git a/src/tools/clippy/tests/ui/cfg_attr_rustfmt.rs b/src/tools/clippy/tests/ui/cfg_attr_rustfmt.rs
index bc29e20210e8a..4ab5c70e13b5b 100644
--- a/src/tools/clippy/tests/ui/cfg_attr_rustfmt.rs
+++ b/src/tools/clippy/tests/ui/cfg_attr_rustfmt.rs
@@ -16,7 +16,7 @@ fn foo(
 
 fn skip_on_statements() {
     #[cfg_attr(rustfmt, rustfmt::skip)]
-    5+3;
+    { 5+3; }
 }
 
 #[cfg_attr(rustfmt, rustfmt_skip)]
@@ -33,11 +33,11 @@ mod foo {
 #[clippy::msrv = "1.29"]
 fn msrv_1_29() {
     #[cfg_attr(rustfmt, rustfmt::skip)]
-    1+29;
+    { 1+29; }
 }
 
 #[clippy::msrv = "1.30"]
 fn msrv_1_30() {
     #[cfg_attr(rustfmt, rustfmt::skip)]
-    1+30;
+    { 1+30; }
 }
diff --git a/src/tools/rustfmt/tests/source/attrib.rs b/src/tools/rustfmt/tests/source/attrib.rs
index d45fba5522436..fc13cd02b03ef 100644
--- a/src/tools/rustfmt/tests/source/attrib.rs
+++ b/src/tools/rustfmt/tests/source/attrib.rs
@@ -214,8 +214,8 @@ type Os = NoSource;
 // #3313
 fn stmt_expr_attributes() {
     let foo ;
-    #[must_use]
-   foo = false ;
+    (#[must_use]
+   foo) = false ;
 }
 
 // #3509
diff --git a/src/tools/rustfmt/tests/target/attrib.rs b/src/tools/rustfmt/tests/target/attrib.rs
index 7e61f68d76a14..7b3309676de2f 100644
--- a/src/tools/rustfmt/tests/target/attrib.rs
+++ b/src/tools/rustfmt/tests/target/attrib.rs
@@ -248,8 +248,8 @@ type Os = NoSource;
 // #3313
 fn stmt_expr_attributes() {
     let foo;
-    #[must_use]
-    foo = false;
+    (#[must_use]
+    foo) = false;
 }
 
 // #3509
diff --git a/tests/pretty/ast-stmt-expr-attr.rs b/tests/pretty/ast-stmt-expr-attr.rs
index fd7272a1b1fd3..899f7173f704e 100644
--- a/tests/pretty/ast-stmt-expr-attr.rs
+++ b/tests/pretty/ast-stmt-expr-attr.rs
@@ -13,17 +13,17 @@ fn syntax() {
     let _ = #[attr] ();
     let _ = #[attr] (#[attr] 0,);
     let _ = #[attr] (#[attr] 0, 0);
-    let _ = #[attr] 0 + #[attr] 0;
-    let _ = #[attr] 0 / #[attr] 0;
-    let _ = #[attr] 0 & #[attr] 0;
-    let _ = #[attr] 0 % #[attr] 0;
+    let _ = (#[attr] 0) + #[attr] 0;
+    let _ = (#[attr] 0) / #[attr] 0;
+    let _ = (#[attr] 0) & #[attr] 0;
+    let _ = (#[attr] 0) % #[attr] 0;
     let _ = #[attr] (0 + 0);
     let _ = #[attr] !0;
     let _ = #[attr] -0;
     let _ = #[attr] false;
     let _ = #[attr] 0;
     let _ = #[attr] 'c';
-    let _ = #[attr] x as Y;
+    let _ = (#[attr] x) as Y;
     let _ = #[attr] (x as Y);
     let _ =
         #[attr] while true {
@@ -88,9 +88,9 @@ fn syntax() {
             let _ = ();
             foo
         };
-    let _ = #[attr] x = y;
+    let _ = (#[attr] x) = y;
     let _ = #[attr] (x = y);
-    let _ = #[attr] x += y;
+    let _ = (#[attr] x) += y;
     let _ = #[attr] (x += y);
     let _ = #[attr] foo.bar;
     let _ = (#[attr] foo).bar;
@@ -98,8 +98,8 @@ fn syntax() {
     let _ = (#[attr] foo).0;
     let _ = #[attr] foo[bar];
     let _ = (#[attr] foo)[bar];
-    let _ = #[attr] 0..#[attr] 0;
-    let _ = #[attr] 0..;
+    let _ = (#[attr] 0)..#[attr] 0;
+    let _ = (#[attr] 0)..;
     let _ = #[attr] (0..0);
     let _ = #[attr] (0..);
     let _ = #[attr] (..0);
diff --git a/tests/pretty/stmt_expr_attributes.rs b/tests/pretty/stmt_expr_attributes.rs
index 98ad98b863ac6..5076adf5aa47b 100644
--- a/tests/pretty/stmt_expr_attributes.rs
+++ b/tests/pretty/stmt_expr_attributes.rs
@@ -148,13 +148,13 @@ fn _11() {
     let _ = #[rustc_dummy] (0);
     let _ = #[rustc_dummy] (0,);
     let _ = #[rustc_dummy] (0, 0);
-    let _ = #[rustc_dummy] 0 + #[rustc_dummy] 0;
+    let _ = (#[rustc_dummy] 0) + #[rustc_dummy] 0;
     let _ = #[rustc_dummy] !0;
     let _ = #[rustc_dummy] -0i32;
     let _ = #[rustc_dummy] false;
     let _ = #[rustc_dummy] 'c';
     let _ = #[rustc_dummy] 0;
-    let _ = #[rustc_dummy] 0 as usize;
+    let _ = (#[rustc_dummy] 0) as usize;
     let _ =
         #[rustc_dummy] while false {
             #![rustc_dummy]
@@ -214,8 +214,8 @@ fn _11() {
                 #![rustc_dummy]
             };
     let mut x = 0;
-    let _ = #[rustc_dummy] x = 15;
-    let _ = #[rustc_dummy] x += 15;
+    let _ = (#[rustc_dummy] x) = 15;
+    let _ = (#[rustc_dummy] x) += 15;
     let s = Foo { data: () };
     let _ = #[rustc_dummy] s.data;
     let _ = (#[rustc_dummy] s).data;
@@ -225,8 +225,8 @@ fn _11() {
     let v = vec!(0);
     let _ = #[rustc_dummy] v[0];
     let _ = (#[rustc_dummy] v)[0];
-    let _ = #[rustc_dummy] 0..#[rustc_dummy] 0;
-    let _ = #[rustc_dummy] 0..;
+    let _ = (#[rustc_dummy] 0)..#[rustc_dummy] 0;
+    let _ = (#[rustc_dummy] 0)..;
     let _ = #[rustc_dummy] (0..0);
     let _ = #[rustc_dummy] (0..);
     let _ = #[rustc_dummy] (..0);
diff --git a/tests/ui-fulldeps/stable-mir/check_transform.rs b/tests/ui-fulldeps/stable-mir/check_transform.rs
index e7d852a27df0e..6345ee24f7893 100644
--- a/tests/ui-fulldeps/stable-mir/check_transform.rs
+++ b/tests/ui-fulldeps/stable-mir/check_transform.rs
@@ -137,9 +137,9 @@ fn generate_input(path: &str) -> std::io::Result<()> {
     write!(
         file,
         r#"
-        #![feature(panic_internals)]
+        fn panic_str(msg: &str) {{ panic!("{{}}", msg); }}
         pub fn dummy() {{
-            core::panicking::panic_str("oops");
+            panic_str("oops");
         }}
         "#
     )?;
diff --git a/tests/ui/assoc-lang-items.stderr b/tests/ui/assoc-lang-items.stderr
index 040792fb1cd5f..59aec8e3fdc6e 100644
--- a/tests/ui/assoc-lang-items.stderr
+++ b/tests/ui/assoc-lang-items.stderr
@@ -1,26 +1,26 @@
-error[E0522]: definition of an unknown language item: `dummy_lang_item_1`
+error[E0522]: definition of an unknown lang item: `dummy_lang_item_1`
   --> $DIR/assoc-lang-items.rs:4:5
    |
 LL |     #[lang = "dummy_lang_item_1"]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown language item `dummy_lang_item_1`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown lang item `dummy_lang_item_1`
 
-error[E0522]: definition of an unknown language item: `dummy_lang_item_2`
+error[E0522]: definition of an unknown lang item: `dummy_lang_item_2`
   --> $DIR/assoc-lang-items.rs:7:5
    |
 LL |     #[lang = "dummy_lang_item_2"]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown language item `dummy_lang_item_2`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown lang item `dummy_lang_item_2`
 
-error[E0522]: definition of an unknown language item: `dummy_lang_item_3`
+error[E0522]: definition of an unknown lang item: `dummy_lang_item_3`
   --> $DIR/assoc-lang-items.rs:10:5
    |
 LL |     #[lang = "dummy_lang_item_3"]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown language item `dummy_lang_item_3`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown lang item `dummy_lang_item_3`
 
-error[E0522]: definition of an unknown language item: `dummy_lang_item_4`
+error[E0522]: definition of an unknown lang item: `dummy_lang_item_4`
   --> $DIR/assoc-lang-items.rs:17:5
    |
 LL |     #[lang = "dummy_lang_item_4"]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown language item `dummy_lang_item_4`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ definition of unknown lang item `dummy_lang_item_4`
 
 error: aborting due to 4 previous errors
 
diff --git a/tests/ui/error-codes/E0522.rs b/tests/ui/error-codes/E0522.rs
index 1414e82408cef..ec9e6d257743e 100644
--- a/tests/ui/error-codes/E0522.rs
+++ b/tests/ui/error-codes/E0522.rs
@@ -2,7 +2,7 @@
 
 #[lang = "cookie"]
 fn cookie() -> ! {
-//~^^ ERROR definition of an unknown language item: `cookie` [E0522]
+//~^^ ERROR definition of an unknown lang item: `cookie` [E0522]
     loop {}
 }
 
diff --git a/tests/ui/error-codes/E0522.stderr b/tests/ui/error-codes/E0522.stderr
index 66359cbacc846..82bbf07959405 100644
--- a/tests/ui/error-codes/E0522.stderr
+++ b/tests/ui/error-codes/E0522.stderr
@@ -1,8 +1,8 @@
-error[E0522]: definition of an unknown language item: `cookie`
+error[E0522]: definition of an unknown lang item: `cookie`
   --> $DIR/E0522.rs:3:1
    |
 LL | #[lang = "cookie"]
-   | ^^^^^^^^^^^^^^^^^^ definition of unknown language item `cookie`
+   | ^^^^^^^^^^^^^^^^^^ definition of unknown lang item `cookie`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/error-codes/E0718.rs b/tests/ui/error-codes/E0718.rs
index 909cae0ba25a2..358bc348ec76d 100644
--- a/tests/ui/error-codes/E0718.rs
+++ b/tests/ui/error-codes/E0718.rs
@@ -1,7 +1,7 @@
 #![feature(lang_items)]
 
 // Box is expected to be a struct, so this will error.
-#[lang = "owned_box"] //~ ERROR language item must be applied to a struct
+#[lang = "owned_box"] //~ ERROR lang item must be applied to a struct
 static X: u32 = 42;
 
 fn main() {}
diff --git a/tests/ui/error-codes/E0718.stderr b/tests/ui/error-codes/E0718.stderr
index 9a3db136d23c0..ec7462765f81f 100644
--- a/tests/ui/error-codes/E0718.stderr
+++ b/tests/ui/error-codes/E0718.stderr
@@ -1,4 +1,4 @@
-error[E0718]: `owned_box` language item must be applied to a struct
+error[E0718]: `owned_box` lang item must be applied to a struct
   --> $DIR/E0718.rs:4:1
    |
 LL | #[lang = "owned_box"]
diff --git a/tests/ui/feature-gates/feature-gate-lang-items.rs b/tests/ui/feature-gates/feature-gate-lang-items.rs
index 93262f2171bfe..d6fd5472a0c1d 100644
--- a/tests/ui/feature-gates/feature-gate-lang-items.rs
+++ b/tests/ui/feature-gates/feature-gate-lang-items.rs
@@ -1,5 +1,5 @@
-#[lang = "foo"] //~ ERROR language items are subject to change
-                //~^ ERROR definition of an unknown language item: `foo`
+#[lang = "foo"] //~ ERROR lang items are subject to change
+                //~^ ERROR definition of an unknown lang item: `foo`
 trait Foo {}
 
 fn main() {}
diff --git a/tests/ui/feature-gates/feature-gate-lang-items.stderr b/tests/ui/feature-gates/feature-gate-lang-items.stderr
index 54787e03784e4..c5caffbdc94dd 100644
--- a/tests/ui/feature-gates/feature-gate-lang-items.stderr
+++ b/tests/ui/feature-gates/feature-gate-lang-items.stderr
@@ -1,4 +1,4 @@
-error[E0658]: language items are subject to change
+error[E0658]: lang items are subject to change
   --> $DIR/feature-gate-lang-items.rs:1:1
    |
 LL | #[lang = "foo"]
@@ -7,11 +7,11 @@ LL | #[lang = "foo"]
    = help: add `#![feature(lang_items)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0522]: definition of an unknown language item: `foo`
+error[E0522]: definition of an unknown lang item: `foo`
   --> $DIR/feature-gate-lang-items.rs:1:1
    |
 LL | #[lang = "foo"]
-   | ^^^^^^^^^^^^^^^ definition of unknown language item `foo`
+   | ^^^^^^^^^^^^^^^ definition of unknown lang item `foo`
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/lang-items/issue-83471.rs b/tests/ui/lang-items/issue-83471.rs
index b32aa03415152..6be345ac50765 100644
--- a/tests/ui/lang-items/issue-83471.rs
+++ b/tests/ui/lang-items/issue-83471.rs
@@ -5,12 +5,12 @@
 #![no_core]
 
 #[lang = "sized"]
-//~^ ERROR: language items are subject to change [E0658]
+//~^ ERROR: lang items are subject to change [E0658]
 trait Sized {}
 
 #[lang = "fn"]
-//~^ ERROR: language items are subject to change [E0658]
-//~| ERROR: `fn` language item must be applied to a trait with 1 generic argument
+//~^ ERROR: lang items are subject to change [E0658]
+//~| ERROR: `fn` lang item must be applied to a trait with 1 generic argument
 trait Fn {
     fn call(export_name);
     //~^ ERROR: expected type
diff --git a/tests/ui/lang-items/issue-83471.stderr b/tests/ui/lang-items/issue-83471.stderr
index 1f22d966dd7d7..244b2efeaf1e0 100644
--- a/tests/ui/lang-items/issue-83471.stderr
+++ b/tests/ui/lang-items/issue-83471.stderr
@@ -4,7 +4,7 @@ error[E0573]: expected type, found built-in attribute `export_name`
 LL |     fn call(export_name);
    |             ^^^^^^^^^^^ not a type
 
-error[E0658]: language items are subject to change
+error[E0658]: lang items are subject to change
   --> $DIR/issue-83471.rs:7:1
    |
 LL | #[lang = "sized"]
@@ -13,7 +13,7 @@ LL | #[lang = "sized"]
    = help: add `#![feature(lang_items)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0658]: language items are subject to change
+error[E0658]: lang items are subject to change
   --> $DIR/issue-83471.rs:11:1
    |
 LL | #[lang = "fn"]
@@ -32,7 +32,7 @@ LL |     fn call(export_name);
    = note: for more information, see issue #41686 <https://github.com/rust-lang/rust/issues/41686>
    = note: `#[warn(anonymous_parameters)]` on by default
 
-error[E0718]: `fn` language item must be applied to a trait with 1 generic argument
+error[E0718]: `fn` lang item must be applied to a trait with 1 generic argument
   --> $DIR/issue-83471.rs:11:1
    |
 LL | #[lang = "fn"]
diff --git a/tests/ui/lang-items/issue-87573.rs b/tests/ui/lang-items/issue-87573.rs
index aeb0c245a72ec..7b805e8b0cdb6 100644
--- a/tests/ui/lang-items/issue-87573.rs
+++ b/tests/ui/lang-items/issue-87573.rs
@@ -18,11 +18,11 @@ trait Sync {}
 impl Sync for bool {}
 
 #[lang = "drop_in_place"]
-//~^ ERROR: `drop_in_place` language item must be applied to a function with at least 1 generic argument
+//~^ ERROR: `drop_in_place` lang item must be applied to a function with at least 1 generic argument
 fn drop_fn() {
     while false {}
 }
 
 #[lang = "start"]
-//~^ ERROR: `start` language item must be applied to a function with 1 generic argument
+//~^ ERROR: `start` lang item must be applied to a function with 1 generic argument
 fn start(){}
diff --git a/tests/ui/lang-items/issue-87573.stderr b/tests/ui/lang-items/issue-87573.stderr
index 25560cfa0e6c7..7085bb8c339d4 100644
--- a/tests/ui/lang-items/issue-87573.stderr
+++ b/tests/ui/lang-items/issue-87573.stderr
@@ -1,4 +1,4 @@
-error[E0718]: `drop_in_place` language item must be applied to a function with at least 1 generic argument
+error[E0718]: `drop_in_place` lang item must be applied to a function with at least 1 generic argument
   --> $DIR/issue-87573.rs:20:1
    |
 LL | #[lang = "drop_in_place"]
@@ -7,7 +7,7 @@ LL |
 LL | fn drop_fn() {
    |           - this function has 0 generic arguments
 
-error[E0718]: `start` language item must be applied to a function with 1 generic argument
+error[E0718]: `start` lang item must be applied to a function with 1 generic argument
   --> $DIR/issue-87573.rs:26:1
    |
 LL | #[lang = "start"]
diff --git a/tests/ui/lang-items/lang-item-generic-requirements.rs b/tests/ui/lang-items/lang-item-generic-requirements.rs
index 697790023d6c9..0f982df61e8e7 100644
--- a/tests/ui/lang-items/lang-item-generic-requirements.rs
+++ b/tests/ui/lang-items/lang-item-generic-requirements.rs
@@ -9,30 +9,30 @@ trait MySized {}
 
 #[lang = "add"]
 trait MyAdd<'a, T> {}
-//~^^ ERROR: `add` language item must be applied to a trait with 1 generic argument [E0718]
+//~^^ ERROR: `add` lang item must be applied to a trait with 1 generic argument [E0718]
 
 #[lang = "drop_in_place"]
-//~^ ERROR `drop_in_place` language item must be applied to a function with at least 1 generic
+//~^ ERROR `drop_in_place` lang item must be applied to a function with at least 1 generic
 fn my_ptr_drop() {}
 
 #[lang = "index"]
 trait MyIndex<'a, T> {}
-//~^^ ERROR: `index` language item must be applied to a trait with 1 generic argument [E0718]
+//~^^ ERROR: `index` lang item must be applied to a trait with 1 generic argument [E0718]
 
 #[lang = "phantom_data"]
-//~^ ERROR `phantom_data` language item must be applied to a struct with 1 generic argument
+//~^ ERROR `phantom_data` lang item must be applied to a struct with 1 generic argument
 struct MyPhantomData<T, U>;
 //~^ ERROR `T` is never used
 //~| ERROR `U` is never used
 
 #[lang = "owned_box"]
-//~^ ERROR `owned_box` language item must be applied to a struct with at least 1 generic argument
+//~^ ERROR `owned_box` lang item must be applied to a struct with at least 1 generic argument
 struct Foo;
 
 // When the `start` lang item is missing generics very odd things can happen, especially when
 // it comes to cross-crate monomorphization
 #[lang = "start"]
-//~^ ERROR `start` language item must be applied to a function with 1 generic argument [E0718]
+//~^ ERROR `start` lang item must be applied to a function with 1 generic argument [E0718]
 fn start(_: *const u8, _: isize, _: *const *const u8) -> isize {
     0
 }
diff --git a/tests/ui/lang-items/lang-item-generic-requirements.stderr b/tests/ui/lang-items/lang-item-generic-requirements.stderr
index 30abdf84046ea..3de67d6594035 100644
--- a/tests/ui/lang-items/lang-item-generic-requirements.stderr
+++ b/tests/ui/lang-items/lang-item-generic-requirements.stderr
@@ -1,4 +1,4 @@
-error[E0718]: `add` language item must be applied to a trait with 1 generic argument
+error[E0718]: `add` lang item must be applied to a trait with 1 generic argument
   --> $DIR/lang-item-generic-requirements.rs:10:1
    |
 LL | #[lang = "add"]
@@ -6,7 +6,7 @@ LL | #[lang = "add"]
 LL | trait MyAdd<'a, T> {}
    |            ------- this trait has 2 generic arguments
 
-error[E0718]: `drop_in_place` language item must be applied to a function with at least 1 generic argument
+error[E0718]: `drop_in_place` lang item must be applied to a function with at least 1 generic argument
   --> $DIR/lang-item-generic-requirements.rs:14:1
    |
 LL | #[lang = "drop_in_place"]
@@ -15,7 +15,7 @@ LL |
 LL | fn my_ptr_drop() {}
    |               - this function has 0 generic arguments
 
-error[E0718]: `index` language item must be applied to a trait with 1 generic argument
+error[E0718]: `index` lang item must be applied to a trait with 1 generic argument
   --> $DIR/lang-item-generic-requirements.rs:18:1
    |
 LL | #[lang = "index"]
@@ -23,7 +23,7 @@ LL | #[lang = "index"]
 LL | trait MyIndex<'a, T> {}
    |              ------- this trait has 2 generic arguments
 
-error[E0718]: `phantom_data` language item must be applied to a struct with 1 generic argument
+error[E0718]: `phantom_data` lang item must be applied to a struct with 1 generic argument
   --> $DIR/lang-item-generic-requirements.rs:22:1
    |
 LL | #[lang = "phantom_data"]
@@ -32,7 +32,7 @@ LL |
 LL | struct MyPhantomData<T, U>;
    |                     ------ this struct has 2 generic arguments
 
-error[E0718]: `owned_box` language item must be applied to a struct with at least 1 generic argument
+error[E0718]: `owned_box` lang item must be applied to a struct with at least 1 generic argument
   --> $DIR/lang-item-generic-requirements.rs:28:1
    |
 LL | #[lang = "owned_box"]
@@ -41,7 +41,7 @@ LL |
 LL | struct Foo;
    |           - this struct has 0 generic arguments
 
-error[E0718]: `start` language item must be applied to a function with 1 generic argument
+error[E0718]: `start` lang item must be applied to a function with 1 generic argument
   --> $DIR/lang-item-generic-requirements.rs:34:1
    |
 LL | #[lang = "start"]
diff --git a/tests/ui/lang-items/start_lang_item_with_target_feature.rs b/tests/ui/lang-items/start_lang_item_with_target_feature.rs
index 4717304c5c6b8..eb712ba409259 100644
--- a/tests/ui/lang-items/start_lang_item_with_target_feature.rs
+++ b/tests/ui/lang-items/start_lang_item_with_target_feature.rs
@@ -11,7 +11,7 @@ pub trait Sized {}
 
 #[lang = "start"]
 #[target_feature(enable = "avx2")]
-//~^ ERROR `start` language item function is not allowed to have `#[target_feature]`
+//~^ ERROR `start` lang item function is not allowed to have `#[target_feature]`
 fn start<T>(_main: fn() -> T, _argc: isize, _argv: *const *const u8, _sigpipe: u8) -> isize {
     0
 }
diff --git a/tests/ui/lang-items/start_lang_item_with_target_feature.stderr b/tests/ui/lang-items/start_lang_item_with_target_feature.stderr
index bb0583dfde056..6214e3f8bc79a 100644
--- a/tests/ui/lang-items/start_lang_item_with_target_feature.stderr
+++ b/tests/ui/lang-items/start_lang_item_with_target_feature.stderr
@@ -1,11 +1,11 @@
-error: `start` language item function is not allowed to have `#[target_feature]`
+error: `start` lang item function is not allowed to have `#[target_feature]`
   --> $DIR/start_lang_item_with_target_feature.rs:13:1
    |
 LL | #[target_feature(enable = "avx2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | fn start<T>(_main: fn() -> T, _argc: isize, _argv: *const *const u8, _sigpipe: u8) -> isize {
-   | ------------------------------------------------------------------------------------------- `start` language item function is not allowed to have `#[target_feature]`
+   | ------------------------------------------------------------------------------------------- `start` lang item function is not allowed to have `#[target_feature]`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/lint/unused/unused-doc-comments-edge-cases.rs b/tests/ui/lint/unused/unused-doc-comments-edge-cases.rs
index ba32fb566e83b..0f9eac93930bc 100644
--- a/tests/ui/lint/unused/unused-doc-comments-edge-cases.rs
+++ b/tests/ui/lint/unused/unused-doc-comments-edge-cases.rs
@@ -20,10 +20,10 @@ fn doc_comment_between_if_else(num: u8) -> bool {
 }
 
 fn doc_comment_on_expr(num: u8) -> bool {
-    /// useless doc comment
+    (/// useless doc comment
     //~^ ERROR: attributes on expressions are experimental
     //~| ERROR: unused doc comment
-    num == 3
+    num) == 3
 }
 
 fn doc_comment_on_expr_field() -> bool {
diff --git a/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr b/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr
index 55e4834e6707a..add85b2f5e043 100644
--- a/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr
+++ b/tests/ui/lint/unused/unused-doc-comments-edge-cases.stderr
@@ -5,10 +5,10 @@ LL |     else {
    |     ^^^^ expected expression
 
 error[E0658]: attributes on expressions are experimental
-  --> $DIR/unused-doc-comments-edge-cases.rs:23:5
+  --> $DIR/unused-doc-comments-edge-cases.rs:23:6
    |
-LL |     /// useless doc comment
-   |     ^^^^^^^^^^^^^^^^^^^^^^^
+LL |     (/// useless doc comment
+   |      ^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
    = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
@@ -32,12 +32,12 @@ LL | #![deny(unused_doc_comments)]
    |         ^^^^^^^^^^^^^^^^^^^
 
 error: unused doc comment
-  --> $DIR/unused-doc-comments-edge-cases.rs:23:5
+  --> $DIR/unused-doc-comments-edge-cases.rs:23:6
    |
-LL |     /// useless doc comment
-   |     ^^^^^^^^^^^^^^^^^^^^^^^
+LL |     (/// useless doc comment
+   |      ^^^^^^^^^^^^^^^^^^^^^^^
 ...
-LL |     num == 3
+LL |     num) == 3
    |     --- rustdoc does not generate documentation for expressions
    |
    = help: use `//` for a plain comment
diff --git a/tests/ui/panic-handler/panic-handler-with-target-feature.rs b/tests/ui/panic-handler/panic-handler-with-target-feature.rs
index 3dfdd2847bf48..8d5ea0703afa5 100644
--- a/tests/ui/panic-handler/panic-handler-with-target-feature.rs
+++ b/tests/ui/panic-handler/panic-handler-with-target-feature.rs
@@ -9,7 +9,7 @@ use core::panic::PanicInfo;
 
 #[panic_handler]
 #[target_feature(enable = "avx2")]
-//~^ ERROR `panic_impl` language item function is not allowed to have `#[target_feature]`
+//~^ ERROR `#[panic_handler]` function is not allowed to have `#[target_feature]`
 fn panic(info: &PanicInfo) -> ! {
     unimplemented!();
 }
diff --git a/tests/ui/panic-handler/panic-handler-with-target-feature.stderr b/tests/ui/panic-handler/panic-handler-with-target-feature.stderr
index c38feab49c3b1..cb17da3a4efbe 100644
--- a/tests/ui/panic-handler/panic-handler-with-target-feature.stderr
+++ b/tests/ui/panic-handler/panic-handler-with-target-feature.stderr
@@ -1,11 +1,11 @@
-error: `panic_impl` language item function is not allowed to have `#[target_feature]`
+error: `#[panic_handler]` function is not allowed to have `#[target_feature]`
   --> $DIR/panic-handler-with-target-feature.rs:11:1
    |
 LL | #[target_feature(enable = "avx2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL | fn panic(info: &PanicInfo) -> ! {
-   | ------------------------------- `panic_impl` language item function is not allowed to have `#[target_feature]`
+   | ------------------------------- `#[panic_handler]` function is not allowed to have `#[target_feature]`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/panic-handler/panic-handler-with-track-caller.rs b/tests/ui/panic-handler/panic-handler-with-track-caller.rs
new file mode 100644
index 0000000000000..09c94139e1697
--- /dev/null
+++ b/tests/ui/panic-handler/panic-handler-with-track-caller.rs
@@ -0,0 +1,14 @@
+//@ compile-flags:-C panic=abort
+//@ only-x86_64
+
+#![no_std]
+#![no_main]
+
+use core::panic::PanicInfo;
+
+#[panic_handler]
+#[track_caller]
+//~^ ERROR `#[panic_handler]` function is not allowed to have `#[track_caller]`
+fn panic(info: &PanicInfo) -> ! {
+    unimplemented!();
+}
diff --git a/tests/ui/panic-handler/panic-handler-with-track-caller.stderr b/tests/ui/panic-handler/panic-handler-with-track-caller.stderr
new file mode 100644
index 0000000000000..9ed387fc8d1f4
--- /dev/null
+++ b/tests/ui/panic-handler/panic-handler-with-track-caller.stderr
@@ -0,0 +1,11 @@
+error: `#[panic_handler]` function is not allowed to have `#[track_caller]`
+  --> $DIR/panic-handler-with-track-caller.rs:10:1
+   |
+LL | #[track_caller]
+   | ^^^^^^^^^^^^^^^
+LL |
+LL | fn panic(info: &PanicInfo) -> ! {
+   | ------------------------------- `#[panic_handler]` function is not allowed to have `#[target_feature]`
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/panic-handler/panic-handler-wrong-location.rs b/tests/ui/panic-handler/panic-handler-wrong-location.rs
index fc3ef401e3db2..49685ee45926e 100644
--- a/tests/ui/panic-handler/panic-handler-wrong-location.rs
+++ b/tests/ui/panic-handler/panic-handler-wrong-location.rs
@@ -3,6 +3,6 @@
 #![no_std]
 #![no_main]
 
-#[panic_handler] //~ ERROR `panic_impl` language item must be applied to a function
+#[panic_handler] //~ ERROR `panic_impl` lang item must be applied to a function
 #[no_mangle]
 static X: u32 = 42;
diff --git a/tests/ui/panic-handler/panic-handler-wrong-location.stderr b/tests/ui/panic-handler/panic-handler-wrong-location.stderr
index ae3ed5ab12b4c..66ee91aa4c199 100644
--- a/tests/ui/panic-handler/panic-handler-wrong-location.stderr
+++ b/tests/ui/panic-handler/panic-handler-wrong-location.stderr
@@ -1,4 +1,4 @@
-error[E0718]: `panic_impl` language item must be applied to a function
+error[E0718]: `panic_impl` lang item must be applied to a function
   --> $DIR/panic-handler-wrong-location.rs:6:1
    |
 LL | #[panic_handler]
diff --git a/tests/ui/parser/attribute/attr-binary-expr-ambigous.fixed b/tests/ui/parser/attribute/attr-binary-expr-ambigous.fixed
new file mode 100644
index 0000000000000..aae71ede77132
--- /dev/null
+++ b/tests/ui/parser/attribute/attr-binary-expr-ambigous.fixed
@@ -0,0 +1,15 @@
+//@ run-rustfix
+#![feature(stmt_expr_attributes)]
+#![allow(unused_assignments, unused_attributes)]
+
+fn main() {
+    let mut x = (#[deprecated] 1) + 2; //~ ERROR ambiguous
+
+    (#[deprecated] x) = 4; //~ ERROR ambiguous
+
+    x = (#[deprecated] 5) as i32; //~ ERROR ambiguous
+
+    let _r = (#[deprecated] 1)..6; //~ ERROR ambiguous
+
+    println!("{}", x);
+}
diff --git a/tests/ui/parser/attribute/attr-binary-expr-ambigous.rs b/tests/ui/parser/attribute/attr-binary-expr-ambigous.rs
new file mode 100644
index 0000000000000..613e01d743bdd
--- /dev/null
+++ b/tests/ui/parser/attribute/attr-binary-expr-ambigous.rs
@@ -0,0 +1,15 @@
+//@ run-rustfix
+#![feature(stmt_expr_attributes)]
+#![allow(unused_assignments, unused_attributes)]
+
+fn main() {
+    let mut x = #[deprecated] 1 + 2; //~ ERROR ambiguous
+
+    #[deprecated] x = 4; //~ ERROR ambiguous
+
+    x = #[deprecated] 5 as i32; //~ ERROR ambiguous
+
+    let _r = #[deprecated] 1..6; //~ ERROR ambiguous
+
+    println!("{}", x);
+}
diff --git a/tests/ui/parser/attribute/attr-binary-expr-ambigous.stderr b/tests/ui/parser/attribute/attr-binary-expr-ambigous.stderr
new file mode 100644
index 0000000000000..0430570fd49d9
--- /dev/null
+++ b/tests/ui/parser/attribute/attr-binary-expr-ambigous.stderr
@@ -0,0 +1,46 @@
+error: ambiguous outer attributes
+  --> $DIR/attr-binary-expr-ambigous.rs:6:17
+   |
+LL |     let mut x = #[deprecated] 1 + 2;
+   |                 ^^^^^^^^^^^^^^^^^^^
+   |
+help: wrap the expression in parentheses
+   |
+LL |     let mut x = (#[deprecated] 1) + 2;
+   |                 +               +
+
+error: ambiguous outer attributes
+  --> $DIR/attr-binary-expr-ambigous.rs:8:5
+   |
+LL |     #[deprecated] x = 4;
+   |     ^^^^^^^^^^^^^^^^^^^
+   |
+help: wrap the expression in parentheses
+   |
+LL |     (#[deprecated] x) = 4;
+   |     +               +
+
+error: ambiguous outer attributes
+  --> $DIR/attr-binary-expr-ambigous.rs:10:9
+   |
+LL |     x = #[deprecated] 5 as i32;
+   |         ^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: wrap the expression in parentheses
+   |
+LL |     x = (#[deprecated] 5) as i32;
+   |         +               +
+
+error: ambiguous outer attributes
+  --> $DIR/attr-binary-expr-ambigous.rs:12:14
+   |
+LL |     let _r = #[deprecated] 1..6;
+   |              ^^^^^^^^^^^^^^^^^^
+   |
+help: wrap the expression in parentheses
+   |
+LL |     let _r = (#[deprecated] 1)..6;
+   |              +               +
+
+error: aborting due to 4 previous errors
+
diff --git a/tests/ui/proc-macro/issue-81555.rs b/tests/ui/proc-macro/issue-81555.rs
index 7a61a31952f41..b337ab7ce37db 100644
--- a/tests/ui/proc-macro/issue-81555.rs
+++ b/tests/ui/proc-macro/issue-81555.rs
@@ -10,6 +10,5 @@ use test_macros::identity_attr;
 fn main() {
     let _x;
     let y = ();
-    #[identity_attr]
-    _x = y;
+    (#[identity_attr] _x) = y;
 }
diff --git a/tests/ui/unknown-language-item.rs b/tests/ui/unknown-language-item.rs
index 20ffef71497c0..ce206d20358a1 100644
--- a/tests/ui/unknown-language-item.rs
+++ b/tests/ui/unknown-language-item.rs
@@ -3,7 +3,7 @@
 
 #[lang = "foo"]
 fn bar() -> ! {
-//~^^ ERROR definition of an unknown language item: `foo`
+//~^^ ERROR definition of an unknown lang item: `foo`
     loop {}
 }
 
diff --git a/tests/ui/unknown-language-item.stderr b/tests/ui/unknown-language-item.stderr
index 1e0256867c562..832f134241844 100644
--- a/tests/ui/unknown-language-item.stderr
+++ b/tests/ui/unknown-language-item.stderr
@@ -1,8 +1,8 @@
-error[E0522]: definition of an unknown language item: `foo`
+error[E0522]: definition of an unknown lang item: `foo`
   --> $DIR/unknown-language-item.rs:4:1
    |
 LL | #[lang = "foo"]
-   | ^^^^^^^^^^^^^^^ definition of unknown language item `foo`
+   | ^^^^^^^^^^^^^^^ definition of unknown lang item `foo`
 
 error: aborting due to 1 previous error