about summary refs log tree commit diff
path: root/compiler
diff options
context:
space:
mode:
Diffstat (limited to 'compiler')
-rw-r--r--compiler/rustc_ast/src/ast.rs11
-rw-r--r--compiler/rustc_ast_lowering/src/asm.rs4
-rw-r--r--compiler/rustc_ast_lowering/src/expr.rs2
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs7
-rw-r--r--compiler/rustc_borrowck/src/type_check/mod.rs4
-rw-r--r--compiler/rustc_codegen_ssa/Cargo.toml2
-rw-r--r--compiler/rustc_codegen_ssa/src/back/archive.rs2
-rw-r--r--compiler/rustc_const_eval/src/check_consts/check.rs16
-rw-r--r--compiler/rustc_const_eval/src/check_consts/ops.rs44
-rw-r--r--compiler/rustc_const_eval/src/const_eval/error.rs8
-rw-r--r--compiler/rustc_const_eval/src/const_eval/machine.rs9
-rw-r--r--compiler/rustc_const_eval/src/errors.rs7
-rw-r--r--compiler/rustc_const_eval/src/interpret/operand.rs21
-rw-r--r--compiler/rustc_errors/src/markdown/parse.rs2
-rw-r--r--compiler/rustc_errors/src/translation.rs2
-rw-r--r--compiler/rustc_feature/src/accepted.rs2
-rw-r--r--compiler/rustc_feature/src/builtin_attrs.rs5
-rw-r--r--compiler/rustc_feature/src/unstable.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/collect.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs21
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs34
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs31
-rw-r--r--compiler/rustc_hir_analysis/src/variance/dump.rs32
-rw-r--r--compiler/rustc_hir_typeck/src/coercion.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/expr.rs6
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/lib.rs7
-rw-r--r--compiler/rustc_index/src/lib.rs1
-rw-r--r--compiler/rustc_interface/src/queries.rs2
-rw-r--r--compiler/rustc_lint/messages.ftl5
-rw-r--r--compiler/rustc_lint/src/lib.rs3
-rw-r--r--compiler/rustc_lint/src/types.rs54
-rw-r--r--compiler/rustc_lint_defs/src/builtin.rs35
-rw-r--r--compiler/rustc_llvm/Cargo.toml2
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder.rs2
-rw-r--r--compiler/rustc_middle/src/lib.rs1
-rw-r--r--compiler/rustc_middle/src/mir/interpret/allocation.rs6
-rw-r--r--compiler/rustc_middle/src/traits/mod.rs2
-rw-r--r--compiler/rustc_middle/src/ty/consts.rs32
-rw-r--r--compiler/rustc_middle/src/ty/generics.rs2
-rw-r--r--compiler/rustc_mir_build/src/errors.rs2
-rw-r--r--compiler/rustc_parse/src/parser/attr.rs38
-rw-r--r--compiler/rustc_parse/src/parser/stmt.rs5
-rw-r--r--compiler/rustc_passes/messages.ftl4
-rw-r--r--compiler/rustc_passes/src/check_attr.rs23
-rw-r--r--compiler/rustc_passes/src/errors.rs9
-rw-r--r--compiler/rustc_resolve/src/def_collector.rs16
-rw-r--r--compiler/rustc_span/src/symbol.rs3
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs60
-rw-r--r--compiler/rustc_ty_utils/src/needs_drop.rs2
-rw-r--r--compiler/rustc_type_ir/Cargo.toml4
-rw-r--r--compiler/rustc_type_ir/src/data_structures.rs15
-rw-r--r--compiler/rustc_type_ir/src/elaborate.rs2
-rw-r--r--compiler/rustc_type_ir/src/outlives.rs3
-rw-r--r--compiler/rustc_type_ir/src/search_graph/mod.rs2
57 files changed, 381 insertions, 248 deletions
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index a44ed828504..85d38a0e28b 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -2902,6 +2902,17 @@ pub struct AttrItem {
     pub tokens: Option<LazyAttrTokenStream>,
 }
 
+impl AttrItem {
+    pub fn is_valid_for_outer_style(&self) -> bool {
+        self.path == sym::cfg_attr
+            || self.path == sym::cfg
+            || self.path == sym::forbid
+            || self.path == sym::warn
+            || self.path == sym::allow
+            || self.path == sym::deny
+    }
+}
+
 /// `TraitRef`s appear in impls.
 ///
 /// Resolution maps each `TraitRef`'s `ref_id` to its defining trait; that's all
diff --git a/compiler/rustc_ast_lowering/src/asm.rs b/compiler/rustc_ast_lowering/src/asm.rs
index 51cbe808a3a..e077c544965 100644
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@@ -220,7 +220,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             let parent_def_id = self.current_def_id_parent;
                             let node_id = self.next_node_id();
                             // HACK(min_generic_const_args): see lower_anon_const
-                            if !expr.is_potential_trivial_const_arg() {
+                            if !self.tcx.features().const_arg_path
+                                || !expr.is_potential_trivial_const_arg()
+                            {
                                 self.create_def(
                                     parent_def_id,
                                     node_id,
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index b5d8a547a8f..bb86e5c9325 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -387,7 +387,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let node_id = self.next_node_id();
 
                 // HACK(min_generic_const_args): see lower_anon_const
-                if !arg.is_potential_trivial_const_arg() {
+                if !self.tcx.features().const_arg_path || !arg.is_potential_trivial_const_arg() {
                     // Add a definition for the in-band const def.
                     self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, f.span);
                 }
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 81d17a9dec2..4b8c47ac4b4 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -2358,7 +2358,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         span: Span,
     ) -> &'hir hir::ConstArg<'hir> {
         let ct_kind = match res {
-            Res::Def(DefKind::ConstParam, _) => {
+            Res::Def(DefKind::ConstParam, _) if self.tcx.features().const_arg_path => {
                 let qpath = self.lower_qpath(
                     ty_id,
                     &None,
@@ -2433,7 +2433,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             self.resolver.get_partial_res(expr.id).and_then(|partial_res| partial_res.full_res());
         debug!("res={:?}", maybe_res);
         // FIXME(min_generic_const_args): for now we only lower params to ConstArgKind::Path
-        if let Some(res) = maybe_res
+        if self.tcx.features().const_arg_path
+            && let Some(res) = maybe_res
             && let Res::Def(DefKind::ConstParam, _) = res
             && let ExprKind::Path(qself, path) = &expr.kind
         {
@@ -2464,7 +2465,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     /// See [`hir::ConstArg`] for when to use this function vs
     /// [`Self::lower_anon_const_to_const_arg`].
     fn lower_anon_const_to_anon_const(&mut self, c: &AnonConst) -> &'hir hir::AnonConst {
-        if c.value.is_potential_trivial_const_arg() {
+        if self.tcx.features().const_arg_path && c.value.is_potential_trivial_const_arg() {
             // HACK(min_generic_const_args): see DefCollector::visit_anon_const
             // Over there, we guess if this is a bare param and only create a def if
             // we think it's not. However we may can guess wrong (see there for example)
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 6983cda6ddf..3b3898ccd4d 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2043,9 +2043,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                         let ty_fn_ptr_from = tcx.safe_to_unsafe_fn_ty(fn_sig);
 
-                        if let Err(terr) = self.eq_types(
-                            *ty,
+                        if let Err(terr) = self.sub_types(
                             ty_fn_ptr_from,
+                            *ty,
                             location.to_locations(),
                             ConstraintCategory::Cast { unsize_to: None },
                         ) {
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 56b75f9b329..e78039bafd8 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2021"
 ar_archive_writer = "0.4.2"
 arrayvec = { version = "0.7", default-features = false }
 bitflags = "2.4.1"
-cc = "1.0.90"
+cc = "=1.0.105" # FIXME(cc): pinned to keep support for VS2013
 either = "1.5.0"
 itertools = "0.12"
 jobserver = "0.1.28"
diff --git a/compiler/rustc_codegen_ssa/src/back/archive.rs b/compiler/rustc_codegen_ssa/src/back/archive.rs
index c8c1bd3e8f9..76a94de5433 100644
--- a/compiler/rustc_codegen_ssa/src/back/archive.rs
+++ b/compiler/rustc_codegen_ssa/src/back/archive.rs
@@ -125,7 +125,7 @@ pub trait ArchiveBuilderBuilder {
         rlib: &'a Path,
         outdir: &Path,
         bundled_lib_file_names: &FxIndexSet<Symbol>,
-    ) -> Result<(), ExtractBundledLibsError<'_>> {
+    ) -> Result<(), ExtractBundledLibsError<'a>> {
         let archive_map = unsafe {
             Mmap::map(
                 File::open(rlib)
diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index 86a5afa65ba..c80b3e673b0 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -575,10 +575,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             Rvalue::UnaryOp(_, operand) => {
                 let ty = operand.ty(self.body, self.tcx);
-                if is_int_bool_or_char(ty) {
-                    // Int, bool, and char operations are fine.
-                } else if ty.is_floating_point() {
-                    self.check_op(ops::FloatingPointOp);
+                if is_int_bool_float_or_char(ty) {
+                    // Int, bool, float, and char operations are fine.
                 } else {
                     span_bug!(self.span, "non-primitive type in `Rvalue::UnaryOp`: {:?}", ty);
                 }
@@ -588,8 +586,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 let lhs_ty = lhs.ty(self.body, self.tcx);
                 let rhs_ty = rhs.ty(self.body, self.tcx);
 
-                if is_int_bool_or_char(lhs_ty) && is_int_bool_or_char(rhs_ty) {
-                    // Int, bool, and char operations are fine.
+                if is_int_bool_float_or_char(lhs_ty) && is_int_bool_float_or_char(rhs_ty) {
+                    // Int, bool, float, and char operations are fine.
                 } else if lhs_ty.is_fn_ptr() || lhs_ty.is_unsafe_ptr() {
                     assert_matches!(
                         op,
@@ -603,8 +601,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     );
 
                     self.check_op(ops::RawPtrComparison);
-                } else if lhs_ty.is_floating_point() || rhs_ty.is_floating_point() {
-                    self.check_op(ops::FloatingPointOp);
                 } else {
                     span_bug!(
                         self.span,
@@ -1009,8 +1005,8 @@ fn place_as_reborrow<'tcx>(
     }
 }
 
-fn is_int_bool_or_char(ty: Ty<'_>) -> bool {
-    ty.is_bool() || ty.is_integral() || ty.is_char()
+fn is_int_bool_float_or_char(ty: Ty<'_>) -> bool {
+    ty.is_bool() || ty.is_integral() || ty.is_char() || ty.is_floating_point()
 }
 
 fn emit_unstable_in_stable_error(ccx: &ConstCx<'_, '_>, span: Span, gate: Symbol) {
diff --git a/compiler/rustc_const_eval/src/check_consts/ops.rs b/compiler/rustc_const_eval/src/check_consts/ops.rs
index 259114dbdc2..93fafa60557 100644
--- a/compiler/rustc_const_eval/src/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/check_consts/ops.rs
@@ -55,28 +55,6 @@ pub trait NonConstOp<'tcx>: std::fmt::Debug {
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx>;
 }
 
-#[derive(Debug)]
-pub struct FloatingPointOp;
-impl<'tcx> NonConstOp<'tcx> for FloatingPointOp {
-    fn status_in_item(&self, ccx: &ConstCx<'_, 'tcx>) -> Status {
-        if ccx.const_kind() == hir::ConstContext::ConstFn {
-            Status::Unstable(sym::const_fn_floating_point_arithmetic)
-        } else {
-            Status::Allowed
-        }
-    }
-
-    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
-    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        feature_err(
-            &ccx.tcx.sess,
-            sym::const_fn_floating_point_arithmetic,
-            span,
-            format!("floating point arithmetic is not allowed in {}s", ccx.const_kind()),
-        )
-    }
-}
-
 /// A function call where the callee is a pointer.
 #[derive(Debug)]
 pub struct FnCallIndirect;
@@ -440,22 +418,12 @@ impl<'tcx> NonConstOp<'tcx> for CellBorrow {
         DiagImportance::Secondary
     }
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        // FIXME: Maybe a more elegant solution to this if else case
-        if let hir::ConstContext::Static(_) = ccx.const_kind() {
-            ccx.dcx().create_err(errors::InteriorMutableDataRefer {
-                span,
-                opt_help: true,
-                kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0492),
-            })
-        } else {
-            ccx.dcx().create_err(errors::InteriorMutableDataRefer {
-                span,
-                opt_help: false,
-                kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0492),
-            })
-        }
+        ccx.dcx().create_err(errors::InteriorMutableDataRefer {
+            span,
+            opt_help: matches!(ccx.const_kind(), hir::ConstContext::Static(_)),
+            kind: ccx.const_kind(),
+            teach: ccx.tcx.sess.teach(E0492),
+        })
     }
 }
 
diff --git a/compiler/rustc_const_eval/src/const_eval/error.rs b/compiler/rustc_const_eval/src/const_eval/error.rs
index 00bbd9337f7..25b32785b7d 100644
--- a/compiler/rustc_const_eval/src/const_eval/error.rs
+++ b/compiler/rustc_const_eval/src/const_eval/error.rs
@@ -22,6 +22,7 @@ pub enum ConstEvalErrKind {
     RecursiveStatic,
     AssertFailure(AssertKind<ConstInt>),
     Panic { msg: Symbol, line: u32, col: u32, file: Symbol },
+    WriteThroughImmutablePointer,
 }
 
 impl MachineStopType for ConstEvalErrKind {
@@ -35,12 +36,16 @@ impl MachineStopType for ConstEvalErrKind {
             Panic { .. } => const_eval_panic,
             RecursiveStatic => const_eval_recursive_static,
             AssertFailure(x) => x.diagnostic_message(),
+            WriteThroughImmutablePointer => const_eval_write_through_immutable_pointer,
         }
     }
     fn add_args(self: Box<Self>, adder: &mut dyn FnMut(DiagArgName, DiagArgValue)) {
         use ConstEvalErrKind::*;
         match *self {
-            RecursiveStatic | ConstAccessesMutGlobal | ModifiedGlobal => {}
+            RecursiveStatic
+            | ConstAccessesMutGlobal
+            | ModifiedGlobal
+            | WriteThroughImmutablePointer => {}
             AssertFailure(kind) => kind.add_args(adder),
             Panic { msg, line, col, file } => {
                 adder("msg".into(), msg.into_diag_arg());
@@ -159,6 +164,7 @@ where
 
 /// Emit a lint from a const-eval situation, with a backtrace.
 // Even if this is unused, please don't remove it -- chances are we will need to emit a lint during const-eval again in the future!
+#[allow(unused)]
 pub(super) fn lint<'tcx, L>(
     tcx: TyCtxtAt<'tcx>,
     machine: &CompileTimeMachine<'tcx>,
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index c3d94ca0e59..9c1fef095f5 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -12,7 +12,6 @@ use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::{FnAbiOf, TyAndLayout};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::{bug, mir};
-use rustc_session::lint::builtin::WRITES_THROUGH_IMMUTABLE_POINTER;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
 use rustc_target::abi::{Align, Size};
@@ -732,8 +731,8 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
     }
 
     fn before_memory_write(
-        tcx: TyCtxtAt<'tcx>,
-        machine: &mut Self,
+        _tcx: TyCtxtAt<'tcx>,
+        _machine: &mut Self,
         _alloc_extra: &mut Self::AllocExtra,
         (_alloc_id, immutable): (AllocId, bool),
         range: AllocRange,
@@ -744,9 +743,7 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
         }
         // Reject writes through immutable pointers.
         if immutable {
-            super::lint(tcx, machine, WRITES_THROUGH_IMMUTABLE_POINTER, |frames| {
-                crate::errors::WriteThroughImmutablePointer { frames }
-            });
+            return Err(ConstEvalErrKind::WriteThroughImmutablePointer.into());
         }
         // Everything else is fine.
         Ok(())
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index 6075f3f84cd..0b366b43f95 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -407,13 +407,6 @@ pub struct ConstEvalError {
     pub frame_notes: Vec<FrameNote>,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(const_eval_write_through_immutable_pointer)]
-pub struct WriteThroughImmutablePointer {
-    #[subdiagnostic]
-    pub frames: Vec<FrameNote>,
-}
-
 #[derive(Diagnostic)]
 #[diag(const_eval_nullary_intrinsic_fail)]
 pub struct NullaryIntrinsicError {
diff --git a/compiler/rustc_const_eval/src/interpret/operand.rs b/compiler/rustc_const_eval/src/interpret/operand.rs
index ad87d6953d3..9a8ccaa7cc5 100644
--- a/compiler/rustc_const_eval/src/interpret/operand.rs
+++ b/compiler/rustc_const_eval/src/interpret/operand.rs
@@ -319,6 +319,7 @@ impl<'tcx, Prov: Provenance> ImmTy<'tcx, Prov> {
             // some fieldless enum variants can have non-zero size but still `Aggregate` ABI... try
             // to detect those here and also give them no data
             _ if matches!(layout.abi, Abi::Aggregate { .. })
+                && matches!(layout.variants, abi::Variants::Single { .. })
                 && matches!(&layout.fields, abi::FieldsShape::Arbitrary { offsets, .. } if offsets.len() == 0) =>
             {
                 Immediate::Uninit
@@ -328,8 +329,9 @@ impl<'tcx, Prov: Provenance> ImmTy<'tcx, Prov> {
                 assert_eq!(offset.bytes(), 0);
                 assert!(
                     match (self.layout.abi, layout.abi) {
-                        (Abi::Scalar(..), Abi::Scalar(..)) => true,
-                        (Abi::ScalarPair(..), Abi::ScalarPair(..)) => true,
+                        (Abi::Scalar(l), Abi::Scalar(r)) => l.size(cx) == r.size(cx),
+                        (Abi::ScalarPair(l1, l2), Abi::ScalarPair(r1, r2)) =>
+                            l1.size(cx) == r1.size(cx) && l2.size(cx) == r2.size(cx),
                         _ => false,
                     },
                     "cannot project into {} immediate with equally-sized field {}\nouter ABI: {:#?}\nfield ABI: {:#?}",
@@ -344,16 +346,23 @@ impl<'tcx, Prov: Provenance> ImmTy<'tcx, Prov> {
             (Immediate::ScalarPair(a_val, b_val), Abi::ScalarPair(a, b)) => {
                 assert_matches!(layout.abi, Abi::Scalar(..));
                 Immediate::from(if offset.bytes() == 0 {
-                    debug_assert_eq!(layout.size, a.size(cx));
+                    // It is "okay" to transmute from `usize` to a pointer (GVN relies on that).
+                    // So only compare the size.
+                    assert_eq!(layout.size, a.size(cx));
                     a_val
                 } else {
-                    debug_assert_eq!(offset, a.size(cx).align_to(b.align(cx).abi));
-                    debug_assert_eq!(layout.size, b.size(cx));
+                    assert_eq!(offset, a.size(cx).align_to(b.align(cx).abi));
+                    assert_eq!(layout.size, b.size(cx));
                     b_val
                 })
             }
             // everything else is a bug
-            _ => bug!("invalid field access on immediate {}, layout {:#?}", self, self.layout),
+            _ => bug!(
+                "invalid field access on immediate {} at offset {}, original layout {:#?}",
+                self,
+                offset.bytes(),
+                self.layout
+            ),
         };
 
         ImmTy::from_immediate(inner_val, layout)
diff --git a/compiler/rustc_errors/src/markdown/parse.rs b/compiler/rustc_errors/src/markdown/parse.rs
index c44f136120a..46f8959b6f2 100644
--- a/compiler/rustc_errors/src/markdown/parse.rs
+++ b/compiler/rustc_errors/src/markdown/parse.rs
@@ -80,7 +80,7 @@ pub fn entrypoint(txt: &str) -> MdStream<'_> {
 }
 
 /// Parse a buffer with specified context
-fn parse_recursive<'a>(buf: &'a [u8], ctx: Context) -> MdStream<'_> {
+fn parse_recursive<'a>(buf: &'a [u8], ctx: Context) -> MdStream<'a> {
     use ParseOpt as Po;
     use Prev::{Escape, Newline, Whitespace};
 
diff --git a/compiler/rustc_errors/src/translation.rs b/compiler/rustc_errors/src/translation.rs
index a44e794ee12..e0b64b276eb 100644
--- a/compiler/rustc_errors/src/translation.rs
+++ b/compiler/rustc_errors/src/translation.rs
@@ -59,7 +59,7 @@ pub trait Translate {
         &'a self,
         message: &'a DiagMessage,
         args: &'a FluentArgs<'_>,
-    ) -> Result<Cow<'_, str>, TranslateError<'_>> {
+    ) -> Result<Cow<'a, str>, TranslateError<'a>> {
         trace!(?message, ?args);
         let (identifier, attr) = match message {
             DiagMessage::Str(msg) | DiagMessage::Translated(msg) => {
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index a4a2028e26e..9223c3c322a 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -115,6 +115,8 @@ declare_features! (
     (accepted, conservative_impl_trait, "1.26.0", Some(34511)),
     /// Allows calling constructor functions in `const fn`.
     (accepted, const_constructor, "1.40.0", Some(61456)),
+    /// Allows basic arithmetic on floating point types in a `const fn`.
+    (accepted, const_fn_floating_point_arithmetic, "CURRENT_RUSTC_VERSION", Some(57241)),
     /// Allows using and casting function pointers in a `const fn`.
     (accepted, const_fn_fn_ptr_basics, "1.61.0", Some(57563)),
     /// Allows trait bounds in `const fn`.
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index d4c54b67f24..2747a14d60a 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -641,6 +641,11 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         ErrorFollowing, EncodeCrossCrate::Yes,
         "rustc_deprecated_safe_2024 is supposed to be used in libstd only",
     ),
+    rustc_attr!(
+        rustc_pub_transparent, Normal, template!(Word),
+        WarnFollowing, EncodeCrossCrate::Yes,
+        "used internally to mark types with a `transparent` representation when it is guaranteed by the documentation",
+    ),
 
 
     // ==========================================================================
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index a1741ac33ca..4524458023d 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -193,6 +193,8 @@ declare_features! (
     (unstable, anonymous_lifetime_in_impl_trait, "1.63.0", None),
     /// Allows identifying the `compiler_builtins` crate.
     (internal, compiler_builtins, "1.13.0", None),
+    /// Gating for a new desugaring of const arguments of usages of const parameters
+    (internal, const_arg_path, "1.81.0", None),
     /// Allows writing custom MIR
     (internal, custom_mir, "1.65.0", None),
     /// Outputs useful `assert!` messages
@@ -400,8 +402,6 @@ declare_features! (
     (incomplete, const_closures, "1.68.0", Some(106003)),
     /// Allows the definition of `const extern fn` and `const unsafe extern fn`.
     (unstable, const_extern_fn, "1.40.0", Some(64926)),
-    /// Allows basic arithmetic on floating point types in a `const fn`.
-    (unstable, const_fn_floating_point_arithmetic, "1.48.0", Some(57241)),
     /// Allows `for _ in _` loops in const contexts.
     (unstable, const_for, "1.56.0", Some(87575)),
     /// Allows using `&mut` in constant functions.
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 14c5f8d9f16..728c3790098 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -1259,7 +1259,8 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
                 ty::Tuple(list) => list.iter().try_for_each(|t| check_non_exhaustive(tcx, t)),
                 ty::Array(ty, _) => check_non_exhaustive(tcx, *ty),
                 ty::Adt(def, args) => {
-                    if !def.did().is_local() {
+                    if !def.did().is_local() && !tcx.has_attr(def.did(), sym::rustc_pub_transparent)
+                    {
                         let non_exhaustive = def.is_variant_list_non_exhaustive()
                             || def
                                 .variants()
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index f75954c9edf..9e6c431a6e6 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -392,7 +392,7 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
     }
 
     fn re_infer(&self, span: Span, reason: RegionInferReason<'_>) -> ty::Region<'tcx> {
-        if let RegionInferReason::BorrowedObjectLifetimeDefault = reason {
+        if let RegionInferReason::ObjectLifetimeDefault = reason {
             let e = struct_span_code_err!(
                 self.dcx(),
                 span,
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index d1048b742a0..c8b0f03a929 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -331,7 +331,7 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: LocalDefId,
     owner_def_id: LocalDefId,
-) -> Ty<'_> {
+) -> Ty<'tcx> {
     let tables = tcx.typeck(owner_def_id);
 
     // Check that all of the opaques we inferred during HIR are compatible.
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
index 6aff518390f..7be45463f15 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
@@ -15,11 +15,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ///
     /// *Bare* trait object types are ones that aren't preceded by the keyword `dyn`.
     /// In edition 2021 and onward we emit a hard error for them.
-    pub(super) fn prohibit_or_lint_bare_trait_object_ty(
-        &self,
-        self_ty: &hir::Ty<'_>,
-        in_path: bool,
-    ) {
+    pub(super) fn prohibit_or_lint_bare_trait_object_ty(&self, self_ty: &hir::Ty<'_>) {
         let tcx = self.tcx();
 
         let hir::TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
@@ -28,6 +24,21 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             return;
         };
 
+        let in_path = match tcx.parent_hir_node(self_ty.hir_id) {
+            hir::Node::Ty(hir::Ty {
+                kind: hir::TyKind::Path(hir::QPath::TypeRelative(qself, _)),
+                ..
+            })
+            | hir::Node::Expr(hir::Expr {
+                kind: hir::ExprKind::Path(hir::QPath::TypeRelative(qself, _)),
+                ..
+            })
+            | hir::Node::Pat(hir::Pat {
+                kind: hir::PatKind::Path(hir::QPath::TypeRelative(qself, _)),
+                ..
+            }) if qself.hir_id == self_ty.hir_id => true,
+            _ => false,
+        };
         let needs_bracket = in_path
             && !tcx
                 .sess
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 5c8ecf254a5..010d58bfb67 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -85,10 +85,9 @@ pub enum PredicateFilter {
 
 #[derive(Debug)]
 pub enum RegionInferReason<'a> {
-    /// Lifetime on a trait object behind a reference.
-    /// This allows inferring information from the reference.
-    BorrowedObjectLifetimeDefault,
-    /// A trait object's lifetime.
+    /// Lifetime on a trait object that is spelled explicitly, e.g. `+ 'a` or `+ '_`.
+    ExplicitObjectLifetime,
+    /// A trait object's lifetime when it is elided, e.g. `dyn Any`.
     ObjectLifetimeDefault,
     /// Generic lifetime parameter
     Param(&'a ty::GenericParamDef),
@@ -1999,16 +1998,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
     }
 
-    /// Lower a type from the HIR to our internal notion of a type.
-    pub fn lower_ty(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
-        self.lower_ty_common(hir_ty, false, false)
-    }
-
-    /// Lower a type inside of a path from the HIR to our internal notion of a type.
-    pub fn lower_ty_in_path(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
-        self.lower_ty_common(hir_ty, false, true)
-    }
-
     fn lower_delegation_ty(&self, idx: hir::InferDelegationKind) -> Ty<'tcx> {
         let delegation_sig = self.tcx().inherit_sig_for_delegation_item(self.item_def_id());
         match idx {
@@ -2026,7 +2015,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// 2. `in_path`: Whether the type appears inside of a path.
     ///    Used to provide correct diagnostics for bare trait object types.
     #[instrument(level = "debug", skip(self), ret)]
-    fn lower_ty_common(&self, hir_ty: &hir::Ty<'tcx>, borrowed: bool, in_path: bool) -> Ty<'tcx> {
+    pub fn lower_ty(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> {
         let tcx = self.tcx();
 
         let result_ty = match &hir_ty.kind {
@@ -2036,7 +2025,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             hir::TyKind::Ref(region, mt) => {
                 let r = self.lower_lifetime(region, RegionInferReason::Reference);
                 debug!(?r);
-                let t = self.lower_ty_common(mt.ty, true, false);
+                let t = self.lower_ty(mt.ty);
                 Ty::new_ref(tcx, r, t, mt.mutbl)
             }
             hir::TyKind::Never => tcx.types.never,
@@ -2065,20 +2054,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 )
             }
             hir::TyKind::TraitObject(bounds, lifetime, repr) => {
-                self.prohibit_or_lint_bare_trait_object_ty(hir_ty, in_path);
+                self.prohibit_or_lint_bare_trait_object_ty(hir_ty);
 
                 let repr = match repr {
                     TraitObjectSyntax::Dyn | TraitObjectSyntax::None => ty::Dyn,
                     TraitObjectSyntax::DynStar => ty::DynStar,
                 };
-                self.lower_trait_object_ty(
-                    hir_ty.span,
-                    hir_ty.hir_id,
-                    bounds,
-                    lifetime,
-                    borrowed,
-                    repr,
-                )
+                self.lower_trait_object_ty(hir_ty.span, hir_ty.hir_id, bounds, lifetime, repr)
             }
             hir::TyKind::Path(hir::QPath::Resolved(maybe_qself, path)) => {
                 debug!(?maybe_qself, ?path);
@@ -2106,7 +2088,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
             hir::TyKind::Path(hir::QPath::TypeRelative(qself, segment)) => {
                 debug!(?qself, ?segment);
-                let ty = self.lower_ty_common(qself, false, true);
+                let ty = self.lower_ty(qself);
                 self.lower_assoc_path(hir_ty.hir_id, hir_ty.span, ty, qself, segment, false)
                     .map(|(ty, _, _)| ty)
                     .unwrap_or_else(|guar| Ty::new_error(tcx, guar))
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs
index 31d1750f33d..52e167379b5 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs
@@ -30,7 +30,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         hir_id: hir::HirId,
         hir_trait_bounds: &[(hir::PolyTraitRef<'tcx>, hir::TraitBoundModifier)],
         lifetime: &hir::Lifetime,
-        borrowed: bool,
         representation: DynKind,
     ) -> Ty<'tcx> {
         let tcx = self.tcx();
@@ -325,22 +324,32 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         v.dedup();
         let existential_predicates = tcx.mk_poly_existential_predicates(&v);
 
-        // Use explicitly-specified region bound.
+        // Use explicitly-specified region bound, unless the bound is missing.
         let region_bound = if !lifetime.is_elided() {
-            self.lower_lifetime(lifetime, RegionInferReason::ObjectLifetimeDefault)
+            self.lower_lifetime(lifetime, RegionInferReason::ExplicitObjectLifetime)
         } else {
             self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
+                // Curiously, we prefer object lifetime default for `+ '_`...
                 if tcx.named_bound_var(lifetime.hir_id).is_some() {
-                    self.lower_lifetime(lifetime, RegionInferReason::ObjectLifetimeDefault)
+                    self.lower_lifetime(lifetime, RegionInferReason::ExplicitObjectLifetime)
                 } else {
-                    self.re_infer(
-                        span,
-                        if borrowed {
-                            RegionInferReason::ObjectLifetimeDefault
+                    let reason =
+                        if let hir::LifetimeName::ImplicitObjectLifetimeDefault = lifetime.res {
+                            if let hir::Node::Ty(hir::Ty {
+                                kind: hir::TyKind::Ref(parent_lifetime, _),
+                                ..
+                            }) = tcx.parent_hir_node(hir_id)
+                                && tcx.named_bound_var(parent_lifetime.hir_id).is_none()
+                            {
+                                // Parent lifetime must have failed to resolve. Don't emit a redundant error.
+                                RegionInferReason::ExplicitObjectLifetime
+                            } else {
+                                RegionInferReason::ObjectLifetimeDefault
+                            }
                         } else {
-                            RegionInferReason::BorrowedObjectLifetimeDefault
-                        },
-                    )
+                            RegionInferReason::ExplicitObjectLifetime
+                        };
+                    self.re_infer(span, reason)
                 }
             })
         };
diff --git a/compiler/rustc_hir_analysis/src/variance/dump.rs b/compiler/rustc_hir_analysis/src/variance/dump.rs
index 1a17dabb677..ace183986bd 100644
--- a/compiler/rustc_hir_analysis/src/variance/dump.rs
+++ b/compiler/rustc_hir_analysis/src/variance/dump.rs
@@ -1,18 +1,36 @@
+use std::fmt::Write;
+
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::CRATE_DEF_ID;
-use rustc_middle::ty::TyCtxt;
+use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
+use rustc_middle::ty::{GenericArgs, TyCtxt};
 use rustc_span::symbol::sym;
 
+fn format_variances(tcx: TyCtxt<'_>, def_id: LocalDefId) -> String {
+    let variances = tcx.variances_of(def_id);
+    let generics = GenericArgs::identity_for_item(tcx, def_id);
+    // 7 = 2-letter parameter + ": " + 1-letter variance + ", "
+    let mut ret = String::with_capacity(2 + 7 * variances.len());
+    ret.push('[');
+    for (arg, variance) in generics.iter().zip(variances.iter()) {
+        write!(ret, "{arg}: {variance:?}, ").unwrap();
+    }
+    // Remove trailing `, `.
+    if !variances.is_empty() {
+        ret.pop();
+        ret.pop();
+    }
+    ret.push(']');
+    ret
+}
+
 pub(crate) fn variances(tcx: TyCtxt<'_>) {
     if tcx.has_attr(CRATE_DEF_ID, sym::rustc_variance_of_opaques) {
         for id in tcx.hir().items() {
             let DefKind::OpaqueTy = tcx.def_kind(id.owner_id) else { continue };
 
-            let variances = tcx.variances_of(id.owner_id);
-
             tcx.dcx().emit_err(crate::errors::VariancesOf {
                 span: tcx.def_span(id.owner_id),
-                variances: format!("{variances:?}"),
+                variances: format_variances(tcx, id.owner_id.def_id),
             });
         }
     }
@@ -22,11 +40,9 @@ pub(crate) fn variances(tcx: TyCtxt<'_>) {
             continue;
         }
 
-        let variances = tcx.variances_of(id.owner_id);
-
         tcx.dcx().emit_err(crate::errors::VariancesOf {
             span: tcx.def_span(id.owner_id),
-            variances: format!("{variances:?}"),
+            variances: format_variances(tcx, id.owner_id.def_id),
         });
     }
 }
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 9b34c59f1f1..b47d8a97bce 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -106,7 +106,7 @@ fn identity(_: Ty<'_>) -> Vec<Adjustment<'_>> {
     vec![]
 }
 
-fn simple<'tcx>(kind: Adjust<'tcx>) -> impl FnOnce(Ty<'tcx>) -> Vec<Adjustment<'_>> {
+fn simple<'tcx>(kind: Adjust<'tcx>) -> impl FnOnce(Ty<'tcx>) -> Vec<Adjustment<'tcx>> {
     move |target| vec![Adjustment { kind, target }]
 }
 
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index fec6efdc0f7..91778a36668 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -841,6 +841,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let ret_ty = ret_coercion.borrow().expected_ty();
         let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty);
         let mut span = return_expr.span;
+        let mut hir_id = return_expr.hir_id;
         // Use the span of the trailing expression for our cause,
         // not the span of the entire function
         if !explicit_return
@@ -848,6 +849,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             && let Some(last_expr) = body.expr
         {
             span = last_expr.span;
+            hir_id = last_expr.hir_id;
         }
         ret_coercion.borrow_mut().coerce(
             self,
@@ -864,6 +866,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.select_obligations_where_possible(|errors| {
                 self.point_at_return_for_opaque_ty_error(
                     errors,
+                    hir_id,
                     span,
                     return_expr_ty,
                     return_expr.span,
@@ -921,6 +924,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn point_at_return_for_opaque_ty_error(
         &self,
         errors: &mut Vec<traits::FulfillmentError<'tcx>>,
+        hir_id: HirId,
         span: Span,
         return_expr_ty: Ty<'tcx>,
         return_span: Span,
@@ -935,7 +939,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let new_cause = ObligationCause::new(
                     cause.span,
                     cause.body_id,
-                    ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, span))),
+                    ObligationCauseCode::OpaqueReturnType(Some((return_expr_ty, hir_id))),
                 );
                 *cause = new_cause;
             }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index b169f75796b..21e6ac9332c 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -798,7 +798,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // to be object-safe.
                 // We manually call `register_wf_obligation` in the success path
                 // below.
-                let ty = self.lowerer().lower_ty_in_path(qself);
+                let ty = self.lowerer().lower_ty(qself);
                 (LoweredTy::from_raw(self, span, ty), qself, segment)
             }
             QPath::LangItem(..) => {
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 9ec101196a4..8ff4c11f24a 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -87,14 +87,17 @@ fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &UnordSet<LocalDef
     &tcx.typeck(def_id).used_trait_imports
 }
 
-fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
+fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx ty::TypeckResults<'tcx> {
     let fallback = move || tcx.type_of(def_id.to_def_id()).instantiate_identity();
     typeck_with_fallback(tcx, def_id, fallback, None)
 }
 
 /// Used only to get `TypeckResults` for type inference during error recovery.
 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
-fn diagnostic_only_typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
+fn diagnostic_only_typeck<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    def_id: LocalDefId,
+) -> &'tcx ty::TypeckResults<'tcx> {
     let fallback = move || {
         let span = tcx.hir().span(tcx.local_def_id_to_hir_id(def_id));
         Ty::new_error_with_message(tcx, span, "diagnostic only typeck table used")
diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs
index b5e4f02a8d1..b9d2a43206b 100644
--- a/compiler/rustc_index/src/lib.rs
+++ b/compiler/rustc_index/src/lib.rs
@@ -2,6 +2,7 @@
 #![cfg_attr(all(feature = "nightly", test), feature(stmt_expr_attributes))]
 #![cfg_attr(feature = "nightly", allow(internal_features))]
 #![cfg_attr(feature = "nightly", feature(extend_one, new_uninit, step_trait, test))]
+#![cfg_attr(feature = "nightly", feature(new_zeroed_alloc))]
 // tidy-alphabetical-end
 
 pub mod bit_set;
diff --git a/compiler/rustc_interface/src/queries.rs b/compiler/rustc_interface/src/queries.rs
index c5d56c15c6e..44e07b36b61 100644
--- a/compiler/rustc_interface/src/queries.rs
+++ b/compiler/rustc_interface/src/queries.rs
@@ -98,7 +98,7 @@ impl<'tcx> Queries<'tcx> {
         self.parse.compute(|| passes::parse(&self.compiler.sess))
     }
 
-    pub fn global_ctxt(&'tcx self) -> Result<QueryResult<'_, &'tcx GlobalCtxt<'tcx>>> {
+    pub fn global_ctxt(&'tcx self) -> Result<QueryResult<'tcx, &'tcx GlobalCtxt<'tcx>>> {
         self.gcx.compute(|| {
             let krate = self.parse()?.steal();
 
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index 28aef9055ef..08a50050a36 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -361,6 +361,11 @@ lint_improper_ctypes_box = box cannot be represented as a single pointer
 lint_improper_ctypes_char_help = consider using `u32` or `libc::wchar_t` instead
 
 lint_improper_ctypes_char_reason = the `char` type has no C equivalent
+
+lint_improper_ctypes_cstr_help =
+    consider passing a `*const std::ffi::c_char` instead, and use `CStr::as_ptr()`
+lint_improper_ctypes_cstr_reason = `CStr`/`CString` do not have a guaranteed layout
+
 lint_improper_ctypes_dyn = trait objects have no C equivalent
 
 lint_improper_ctypes_enum_repr_help =
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index 1828b6ea93c..a6e7d288f08 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -572,7 +572,8 @@ fn register_builtins(store: &mut LintStore) {
         "byte_slice_in_packed_struct_with_derive",
         "converted into hard error, see issue #107457 \
          <https://github.com/rust-lang/rust/issues/107457> for more information",
-    )
+    );
+    store.register_removed("writes_through_immutable_pointer", "converted into hard error");
 }
 
 fn register_internals(store: &mut LintStore) {
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index cb7a07116ce..f1da14bb1f3 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -985,6 +985,14 @@ struct ImproperCTypesVisitor<'a, 'tcx> {
     mode: CItemKind,
 }
 
+/// Accumulator for recursive ffi type checking
+struct CTypesVisitorState<'tcx> {
+    cache: FxHashSet<Ty<'tcx>>,
+    /// The original type being checked, before we recursed
+    /// to any other types it contains.
+    base_ty: Ty<'tcx>,
+}
+
 enum FfiResult<'tcx> {
     FfiSafe,
     FfiPhantom(Ty<'tcx>),
@@ -1213,7 +1221,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
     /// Checks if the given field's type is "ffi-safe".
     fn check_field_type_for_ffi(
         &self,
-        cache: &mut FxHashSet<Ty<'tcx>>,
+        acc: &mut CTypesVisitorState<'tcx>,
         field: &ty::FieldDef,
         args: GenericArgsRef<'tcx>,
     ) -> FfiResult<'tcx> {
@@ -1223,13 +1231,13 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             .tcx
             .try_normalize_erasing_regions(self.cx.param_env, field_ty)
             .unwrap_or(field_ty);
-        self.check_type_for_ffi(cache, field_ty)
+        self.check_type_for_ffi(acc, field_ty)
     }
 
     /// Checks if the given `VariantDef`'s field types are "ffi-safe".
     fn check_variant_for_ffi(
         &self,
-        cache: &mut FxHashSet<Ty<'tcx>>,
+        acc: &mut CTypesVisitorState<'tcx>,
         ty: Ty<'tcx>,
         def: ty::AdtDef<'tcx>,
         variant: &ty::VariantDef,
@@ -1239,7 +1247,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         let transparent_with_all_zst_fields = if def.repr().transparent() {
             if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
                 // Transparent newtypes have at most one non-ZST field which needs to be checked..
-                match self.check_field_type_for_ffi(cache, field, args) {
+                match self.check_field_type_for_ffi(acc, field, args) {
                     FfiUnsafe { ty, .. } if ty.is_unit() => (),
                     r => return r,
                 }
@@ -1257,7 +1265,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         // We can't completely trust `repr(C)` markings, so make sure the fields are actually safe.
         let mut all_phantom = !variant.fields.is_empty();
         for field in &variant.fields {
-            all_phantom &= match self.check_field_type_for_ffi(cache, field, args) {
+            all_phantom &= match self.check_field_type_for_ffi(acc, field, args) {
                 FfiSafe => false,
                 // `()` fields are FFI-safe!
                 FfiUnsafe { ty, .. } if ty.is_unit() => false,
@@ -1277,7 +1285,11 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
     /// Checks if the given type is "ffi-safe" (has a stable, well-defined
     /// representation which can be exported to C code).
-    fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
+    fn check_type_for_ffi(
+        &self,
+        acc: &mut CTypesVisitorState<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> FfiResult<'tcx> {
         use FfiResult::*;
 
         let tcx = self.cx.tcx;
@@ -1286,7 +1298,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         // `struct S(*mut S);`.
         // FIXME: A recursion limit is necessary as well, for irregular
         // recursive types.
-        if !cache.insert(ty) {
+        if !acc.cache.insert(ty) {
             return FfiSafe;
         }
 
@@ -1308,6 +1320,17 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                 }
                 match def.adt_kind() {
                     AdtKind::Struct | AdtKind::Union => {
+                        if let Some(sym::cstring_type | sym::cstr_type) =
+                            tcx.get_diagnostic_name(def.did())
+                            && !acc.base_ty.is_mutable_ptr()
+                        {
+                            return FfiUnsafe {
+                                ty,
+                                reason: fluent::lint_improper_ctypes_cstr_reason,
+                                help: Some(fluent::lint_improper_ctypes_cstr_help),
+                            };
+                        }
+
                         if !def.repr().c() && !def.repr().transparent() {
                             return FfiUnsafe {
                                 ty,
@@ -1354,7 +1377,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                             };
                         }
 
-                        self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), args)
+                        self.check_variant_for_ffi(acc, ty, def, def.non_enum_variant(), args)
                     }
                     AdtKind::Enum => {
                         if def.variants().is_empty() {
@@ -1378,7 +1401,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                             if let Some(ty) =
                                 repr_nullable_ptr(self.cx.tcx, self.cx.param_env, ty, self.mode)
                             {
-                                return self.check_type_for_ffi(cache, ty);
+                                return self.check_type_for_ffi(acc, ty);
                             }
 
                             return FfiUnsafe {
@@ -1399,7 +1422,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                                 };
                             }
 
-                            match self.check_variant_for_ffi(cache, ty, def, variant, args) {
+                            match self.check_variant_for_ffi(acc, ty, def, variant, args) {
                                 FfiSafe => (),
                                 r => return r,
                             }
@@ -1469,9 +1492,9 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                 FfiSafe
             }
 
-            ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.check_type_for_ffi(cache, ty),
+            ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.check_type_for_ffi(acc, ty),
 
-            ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
+            ty::Array(inner_ty, _) => self.check_type_for_ffi(acc, inner_ty),
 
             ty::FnPtr(sig_tys, hdr) => {
                 let sig = sig_tys.with(hdr);
@@ -1485,7 +1508,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
                 let sig = tcx.instantiate_bound_regions_with_erased(sig);
                 for arg in sig.inputs() {
-                    match self.check_type_for_ffi(cache, *arg) {
+                    match self.check_type_for_ffi(acc, *arg) {
                         FfiSafe => {}
                         r => return r,
                     }
@@ -1496,7 +1519,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                     return FfiSafe;
                 }
 
-                self.check_type_for_ffi(cache, ret_ty)
+                self.check_type_for_ffi(acc, ret_ty)
             }
 
             ty::Foreign(..) => FfiSafe,
@@ -1619,7 +1642,8 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             return;
         }
 
-        match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
+        let mut acc = CTypesVisitorState { cache: FxHashSet::default(), base_ty: ty };
+        match self.check_type_for_ffi(&mut acc, ty) {
             FfiResult::FfiSafe => {}
             FfiResult::FfiPhantom(ty) => {
                 self.emit_ffi_unsafe_type_lint(
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index a65d30eb817..44c72e0c4fe 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -142,7 +142,6 @@ declare_lint_pass! {
         USELESS_DEPRECATED,
         WARNINGS,
         WASM_C_ABI,
-        WRITES_THROUGH_IMMUTABLE_POINTER,
         // tidy-alphabetical-end
     ]
 }
@@ -4697,40 +4696,6 @@ declare_lint! {
 }
 
 declare_lint! {
-    /// The `writes_through_immutable_pointer` lint detects writes through pointers derived from
-    /// shared references.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// #![feature(const_mut_refs)]
-    /// const WRITE_AFTER_CAST: () = unsafe {
-    ///     let mut x = 0;
-    ///     let ptr = &x as *const i32 as *mut i32;
-    ///     *ptr = 0;
-    /// };
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// Shared references are immutable (when there is no `UnsafeCell` involved),
-    /// and writing through them or through pointers derived from them is Undefined Behavior.
-    /// The compiler recently learned to detect such Undefined Behavior during compile-time
-    /// evaluation, and in the future this will raise a hard error.
-    ///
-    /// [future-incompatible]: ../index.md#future-incompatible-lints
-    pub WRITES_THROUGH_IMMUTABLE_POINTER,
-    Warn,
-    "shared references are immutable, and pointers derived from them must not be written to",
-    @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
-        reference: "issue #X <https://github.com/rust-lang/rust/issues/X>",
-    };
-}
-
-declare_lint! {
     /// The `private_macro_use` lint detects private macros that are imported
     /// with `#[macro_use]`.
     ///
diff --git a/compiler/rustc_llvm/Cargo.toml b/compiler/rustc_llvm/Cargo.toml
index 83fda7ef07c..1f74aaf9965 100644
--- a/compiler/rustc_llvm/Cargo.toml
+++ b/compiler/rustc_llvm/Cargo.toml
@@ -10,5 +10,5 @@ libc = "0.2.73"
 
 [build-dependencies]
 # tidy-alphabetical-start
-cc = "1.0.97"
+cc = "=1.0.105" # FIXME(cc): pinned to keep support for VS2013
 # tidy-alphabetical-end
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 8c0ea3eaea9..a13eac08c9f 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1487,7 +1487,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             .decode((self, sess))
     }
 
-    fn get_foreign_modules(self, sess: &'a Session) -> impl Iterator<Item = ForeignModule> + '_ {
+    fn get_foreign_modules(self, sess: &'a Session) -> impl Iterator<Item = ForeignModule> + 'a {
         self.root.foreign_modules.decode((self, sess))
     }
 
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index 5bd7736a3f3..6886562d9b7 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -34,6 +34,7 @@
 #![feature(allocator_api)]
 #![feature(array_windows)]
 #![feature(assert_matches)]
+#![feature(box_as_ptr)]
 #![feature(box_patterns)]
 #![feature(closure_track_caller)]
 #![feature(const_option)]
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 665ab2797f2..3e101c0c635 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -62,13 +62,11 @@ impl AllocBytes for Box<[u8]> {
     }
 
     fn as_mut_ptr(&mut self) -> *mut u8 {
-        // Carefully avoiding any intermediate references.
-        ptr::addr_of_mut!(**self).cast()
+        Box::as_mut_ptr(self).cast()
     }
 
     fn as_ptr(&self) -> *const u8 {
-        // Carefully avoiding any intermediate references.
-        ptr::addr_of!(**self).cast()
+        Box::as_ptr(self).cast()
     }
 }
 
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index d54e2ca0a74..a3277fb96d2 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -353,7 +353,7 @@ pub enum ObligationCauseCode<'tcx> {
     ReturnValue(HirId),
 
     /// Opaque return type of this function
-    OpaqueReturnType(Option<(Ty<'tcx>, Span)>),
+    OpaqueReturnType(Option<(Ty<'tcx>, HirId)>),
 
     /// Block implicit return
     BlockTailExpression(HirId, hir::MatchSource),
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index e373292741b..362ff8e988d 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -240,7 +240,7 @@ impl<'tcx> Const<'tcx> {
 
         let ty = tcx.type_of(def).no_bound_vars().expect("const parameter types cannot be generic");
 
-        match Self::try_from_lit(tcx, ty, expr) {
+        match Self::try_from_lit_or_param(tcx, ty, expr) {
             Some(v) => v,
             None => ty::Const::new_unevaluated(
                 tcx,
@@ -281,7 +281,11 @@ impl<'tcx> Const<'tcx> {
     }
 
     #[instrument(skip(tcx), level = "debug")]
-    fn try_from_lit(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, expr: &'tcx hir::Expr<'tcx>) -> Option<Self> {
+    fn try_from_lit_or_param(
+        tcx: TyCtxt<'tcx>,
+        ty: Ty<'tcx>,
+        expr: &'tcx hir::Expr<'tcx>,
+    ) -> Option<Self> {
         // Unwrap a block, so that e.g. `{ P }` is recognised as a parameter. Const arguments
         // currently have to be wrapped in curly brackets, so it's necessary to special-case.
         let expr = match &expr.kind {
@@ -291,6 +295,22 @@ impl<'tcx> Const<'tcx> {
             _ => expr,
         };
 
+        if let hir::ExprKind::Path(
+            qpath @ hir::QPath::Resolved(
+                _,
+                &hir::Path { res: Res::Def(DefKind::ConstParam, _), .. },
+            ),
+        ) = expr.kind
+        {
+            if tcx.features().const_arg_path {
+                span_bug!(
+                    expr.span,
+                    "try_from_lit: received const param which shouldn't be possible"
+                );
+            }
+            return Some(Const::from_param(tcx, qpath, expr.hir_id));
+        };
+
         let lit_input = match expr.kind {
             hir::ExprKind::Lit(lit) => Some(LitToConstInput { lit: &lit.node, ty, neg: false }),
             hir::ExprKind::Unary(hir::UnOp::Neg, expr) => match expr.kind {
@@ -318,14 +338,6 @@ impl<'tcx> Const<'tcx> {
             }
         }
 
-        if let hir::ExprKind::Path(hir::QPath::Resolved(
-            _,
-            &hir::Path { res: Res::Def(DefKind::ConstParam, _), .. },
-        )) = expr.kind
-        {
-            span_bug!(expr.span, "try_from_lit: received const param which shouldn't be possible")
-        }
-
         None
     }
 
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 8cb8e9af11c..bbc696e0f08 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -269,7 +269,7 @@ impl<'tcx> Generics {
     }
 
     /// Returns the `GenericParamDef` associated with this `ParamConst`.
-    pub fn const_param(&'tcx self, param: ParamConst, tcx: TyCtxt<'tcx>) -> &GenericParamDef {
+    pub fn const_param(&'tcx self, param: ParamConst, tcx: TyCtxt<'tcx>) -> &'tcx GenericParamDef {
         let param = self.param_at(param.index as usize, tcx);
         match param.kind {
             GenericParamDefKind::Const { .. } => param,
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 843ac2eb240..7f9eefd1d52 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -493,7 +493,7 @@ pub(crate) struct NonExhaustivePatternsTypeNotEmpty<'p, 'tcx, 'm> {
 }
 
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for NonExhaustivePatternsTypeNotEmpty<'_, '_, '_> {
-    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'_, G> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let mut diag =
             Diag::new(dcx, level, fluent::mir_build_non_exhaustive_patterns_type_not_empty);
         diag.span(self.scrut_span);
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
index 6391ff901cb..c65cf3f40f6 100644
--- a/compiler/rustc_parse/src/parser/attr.rs
+++ b/compiler/rustc_parse/src/parser/attr.rs
@@ -76,6 +76,7 @@ impl<'a> Parser<'a> {
                             token::CommentKind::Line => OuterAttributeType::DocComment,
                             token::CommentKind::Block => OuterAttributeType::DocBlockComment,
                         },
+                        true,
                     ) {
                         err.note(fluent::parse_note);
                         err.span_suggestion_verbose(
@@ -139,7 +140,11 @@ impl<'a> Parser<'a> {
 
             // Emit error if inner attribute is encountered and forbidden.
             if style == ast::AttrStyle::Inner {
-                this.error_on_forbidden_inner_attr(attr_sp, inner_parse_policy);
+                this.error_on_forbidden_inner_attr(
+                    attr_sp,
+                    inner_parse_policy,
+                    item.is_valid_for_outer_style(),
+                );
             }
 
             Ok(attr::mk_attr_from_item(&self.psess.attr_id_generator, item, None, style, attr_sp))
@@ -151,6 +156,7 @@ impl<'a> Parser<'a> {
         err: &mut Diag<'_>,
         span: Span,
         attr_type: OuterAttributeType,
+        suggest_to_outer: bool,
     ) -> Option<Span> {
         let mut snapshot = self.create_snapshot_for_diagnostic();
         let lo = span.lo()
@@ -185,16 +191,18 @@ impl<'a> Parser<'a> {
                 // FIXME(#100717)
                 err.arg("item", item.kind.descr());
                 err.span_label(item.span, fluent::parse_label_does_not_annotate_this);
-                err.span_suggestion_verbose(
-                    replacement_span,
-                    fluent::parse_sugg_change_inner_to_outer,
-                    match attr_type {
-                        OuterAttributeType::Attribute => "",
-                        OuterAttributeType::DocBlockComment => "*",
-                        OuterAttributeType::DocComment => "/",
-                    },
-                    rustc_errors::Applicability::MachineApplicable,
-                );
+                if suggest_to_outer {
+                    err.span_suggestion_verbose(
+                        replacement_span,
+                        fluent::parse_sugg_change_inner_to_outer,
+                        match attr_type {
+                            OuterAttributeType::Attribute => "",
+                            OuterAttributeType::DocBlockComment => "*",
+                            OuterAttributeType::DocComment => "/",
+                        },
+                        rustc_errors::Applicability::MachineApplicable,
+                    );
+                }
                 return None;
             }
             Err(item_err) => {
@@ -205,7 +213,12 @@ impl<'a> Parser<'a> {
         Some(replacement_span)
     }
 
-    pub(super) fn error_on_forbidden_inner_attr(&self, attr_sp: Span, policy: InnerAttrPolicy) {
+    pub(super) fn error_on_forbidden_inner_attr(
+        &self,
+        attr_sp: Span,
+        policy: InnerAttrPolicy,
+        suggest_to_outer: bool,
+    ) {
         if let InnerAttrPolicy::Forbidden(reason) = policy {
             let mut diag = match reason.as_ref().copied() {
                 Some(InnerAttrForbiddenReason::AfterOuterDocComment { prev_doc_comment_span }) => {
@@ -239,6 +252,7 @@ impl<'a> Parser<'a> {
                     &mut diag,
                     attr_sp,
                     OuterAttributeType::Attribute,
+                    suggest_to_outer,
                 )
                 .is_some()
             {
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 69044192780..26ad39e06cd 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -459,11 +459,16 @@ impl<'a> Parser<'a> {
     pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
         let (attrs, block) = self.parse_inner_attrs_and_block()?;
         if let [.., last] = &*attrs {
+            let suggest_to_outer = match &last.kind {
+                ast::AttrKind::Normal(attr) => attr.item.is_valid_for_outer_style(),
+                _ => false,
+            };
             self.error_on_forbidden_inner_attr(
                 last.span,
                 super::attr::InnerAttrPolicy::Forbidden(Some(
                     InnerAttrForbiddenReason::InCodeBlock,
                 )),
+                suggest_to_outer,
             );
         }
         Ok(block)
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index bdc229a6c09..e7f208d5ad5 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -653,6 +653,10 @@ passes_rustc_lint_opt_ty =
     `#[rustc_lint_opt_ty]` should be applied to a struct
     .label = not a struct
 
+passes_rustc_pub_transparent =
+    attribute should be applied to `#[repr(transparent)]` types
+    .label = not a `#[repr(transparent)]` type
+
 passes_rustc_safe_intrinsic =
     attribute should be applied to intrinsic functions
     .label = not an intrinsic function
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index c93fb5c23b1..d1dac9ca6da 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -245,6 +245,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     self.check_coroutine(attr, target);
                 }
                 [sym::linkage, ..] => self.check_linkage(attr, span, target),
+                [sym::rustc_pub_transparent, ..] => self.check_rustc_pub_transparent( attr.span, span, attrs),
                 [
                     // ok
                     sym::allow
@@ -951,6 +952,16 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         bare_fn_ty.decl.inputs.len() == 1
                     } else {
                         false
+                    }
+                    || if let Some(&[hir::GenericArg::Type(ty)]) = i
+                        .of_trait
+                        .as_ref()
+                        .and_then(|trait_ref| trait_ref.path.segments.last())
+                        .map(|last_segment| last_segment.args().args)
+                    {
+                        matches!(&ty.kind, hir::TyKind::Tup([_]))
+                    } else {
+                        false
                     };
                 if !is_valid {
                     self.dcx().emit_err(errors::DocFakeVariadicNotValid { span: meta.span() });
@@ -2381,6 +2392,18 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             }
         }
     }
+
+    fn check_rustc_pub_transparent(&self, attr_span: Span, span: Span, attrs: &[Attribute]) {
+        if !attrs
+            .iter()
+            .filter(|attr| attr.has_name(sym::repr))
+            .filter_map(|attr| attr.meta_item_list())
+            .flatten()
+            .any(|nmi| nmi.has_name(sym::transparent))
+        {
+            self.dcx().emit_err(errors::RustcPubTransparent { span, attr_span });
+        }
+    }
 }
 
 impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 644ae23a761..1202351bdcd 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -616,6 +616,15 @@ pub struct RustcStdInternalSymbol {
 }
 
 #[derive(Diagnostic)]
+#[diag(passes_rustc_pub_transparent)]
+pub struct RustcPubTransparent {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(passes_link_ordinal)]
 pub struct LinkOrdinal {
     #[primary_span]
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index ed23870dfdf..3595db78e93 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -314,13 +314,15 @@ impl<'a, 'b, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'b, 'tcx> {
     }
 
     fn visit_anon_const(&mut self, constant: &'a AnonConst) {
-        // HACK(min_generic_const_args): don't create defs for anon consts if we think they will
-        // later be turned into ConstArgKind::Path's. because this is before resolve is done, we
-        // may accidentally identify a construction of a unit struct as a param and not create a
-        // def. we'll then create a def later in ast lowering in this case. the parent of nested
-        // items will be messed up, but that's ok because there can't be any if we're just looking
-        // for bare idents.
-        if constant.value.is_potential_trivial_const_arg() {
+        if self.resolver.tcx.features().const_arg_path
+            && constant.value.is_potential_trivial_const_arg()
+        {
+            // HACK(min_generic_const_args): don't create defs for anon consts if we think they will
+            // later be turned into ConstArgKind::Path's. because this is before resolve is done, we
+            // may accidentally identify a construction of a unit struct as a param and not create a
+            // def. we'll then create a def later in ast lowering in this case. the parent of nested
+            // items will be messed up, but that's ok because there can't be any if we're just looking
+            // for bare idents.
             visit::walk_anon_const(self, constant)
         } else {
             let def =
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index a2e94492f8c..2957105288b 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -595,6 +595,7 @@ symbols! {
         conservative_impl_trait,
         console,
         const_allocate,
+        const_arg_path,
         const_async_blocks,
         const_closures,
         const_compare_raw_pointers,
@@ -673,6 +674,7 @@ symbols! {
         crate_visibility_modifier,
         crt_dash_static: "crt-static",
         csky_target_feature,
+        cstr_type,
         cstring_type,
         ctlz,
         ctlz_nonzero,
@@ -1672,6 +1674,7 @@ symbols! {
         rustc_private,
         rustc_proc_macro_decls,
         rustc_promotable,
+        rustc_pub_transparent,
         rustc_reallocator,
         rustc_regions,
         rustc_reservation_impl,
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index a962be54c3d..3cb95294fb6 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2727,6 +2727,20 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
         let tcx = self.tcx;
         let predicate = predicate.upcast(tcx);
+        let suggest_remove_deref = |err: &mut Diag<'_, G>, expr: &hir::Expr<'_>| {
+            if let Some(pred) = predicate.as_trait_clause()
+                && tcx.is_lang_item(pred.def_id(), LangItem::Sized)
+                && let hir::ExprKind::Unary(hir::UnOp::Deref, inner) = expr.kind
+            {
+                err.span_suggestion_verbose(
+                    expr.span.until(inner.span),
+                    "references are always `Sized`, even if they point to unsized data; consider \
+                     not dereferencing the expression",
+                    String::new(),
+                    Applicability::MaybeIncorrect,
+                );
+            }
+        };
         match *cause_code {
             ObligationCauseCode::ExprAssignable
             | ObligationCauseCode::MatchExpressionArm { .. }
@@ -2773,6 +2787,19 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             | ObligationCauseCode::WhereClauseInExpr(item_def_id, span, ..)
                 if !span.is_dummy() =>
             {
+                if let ObligationCauseCode::WhereClauseInExpr(_, _, hir_id, pos) = &cause_code {
+                    if let Node::Expr(expr) = tcx.parent_hir_node(*hir_id)
+                        && let hir::ExprKind::Call(_, args) = expr.kind
+                        && let Some(expr) = args.get(*pos)
+                    {
+                        suggest_remove_deref(err, &expr);
+                    } else if let Node::Expr(expr) = self.tcx.hir_node(*hir_id)
+                        && let hir::ExprKind::MethodCall(_, _, args, _) = expr.kind
+                        && let Some(expr) = args.get(*pos)
+                    {
+                        suggest_remove_deref(err, &expr);
+                    }
+                }
                 let item_name = tcx.def_path_str(item_def_id);
                 let short_item_name = with_forced_trimmed_paths!(tcx.def_path_str(item_def_id));
                 let mut multispan = MultiSpan::from(span);
@@ -2970,6 +2997,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     ));
                     err.downgrade_to_delayed_bug();
                 }
+                let mut local = true;
                 match tcx.parent_hir_node(hir_id) {
                     Node::LetStmt(hir::LetStmt { ty: Some(ty), .. }) => {
                         err.span_suggestion_verbose(
@@ -2978,7 +3006,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             "&",
                             Applicability::MachineApplicable,
                         );
-                        err.note("all local variables must have a statically known size");
                     }
                     Node::LetStmt(hir::LetStmt {
                         init: Some(hir::Expr { kind: hir::ExprKind::Index(..), span, .. }),
@@ -2993,7 +3020,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             "&",
                             Applicability::MachineApplicable,
                         );
-                        err.note("all local variables must have a statically known size");
+                    }
+                    Node::LetStmt(hir::LetStmt { init: Some(expr), .. }) => {
+                        // When encountering an assignment of an unsized trait, like `let x = *"";`,
+                        // we check if the RHS is a deref operation, to suggest removing it.
+                        suggest_remove_deref(err, &expr);
                     }
                     Node::Param(param) => {
                         err.span_suggestion_verbose(
@@ -3003,10 +3034,12 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             "&",
                             Applicability::MachineApplicable,
                         );
+                        local = false;
                     }
-                    _ => {
-                        err.note("all local variables must have a statically known size");
-                    }
+                    _ => {}
+                }
+                if local {
+                    err.note("all local variables must have a statically known size");
                 }
                 if !tcx.features().unsized_locals {
                     err.help("unsized locals are gated as an unstable feature");
@@ -3529,14 +3562,16 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 );
             }
             ObligationCauseCode::OpaqueReturnType(expr_info) => {
-                if let Some((expr_ty, expr_span)) = expr_info {
+                if let Some((expr_ty, hir_id)) = expr_info {
                     let expr_ty = self.tcx.short_ty_string(expr_ty, &mut long_ty_file);
+                    let expr = self.infcx.tcx.hir().expect_expr(hir_id);
                     err.span_label(
-                        expr_span,
+                        expr.span,
                         with_forced_trimmed_paths!(format!(
                             "return type was inferred to be `{expr_ty}` here",
                         )),
                     );
+                    suggest_remove_deref(err, &expr);
                 }
             }
         }
@@ -4667,10 +4702,15 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             if let hir::ExprKind::Block(b, _) = body.value.kind
                 && b.expr.is_none()
             {
+                // The span of '}' in the end of block.
+                let span = self.tcx.sess.source_map().end_point(b.span);
                 sugg_spans.push((
-                    // The span will point to the closing curly brace `}` of the block.
-                    b.span.shrink_to_hi().with_lo(b.span.hi() - BytePos(1)),
-                    "\n    Ok(())\n}".to_string(),
+                    span.shrink_to_lo(),
+                    format!(
+                        "{}{}",
+                        "    Ok(())\n",
+                        self.tcx.sess.source_map().indentation_before(span).unwrap_or_default(),
+                    ),
                 ));
             }
             err.multipart_suggestion_verbose(
diff --git a/compiler/rustc_ty_utils/src/needs_drop.rs b/compiler/rustc_ty_utils/src/needs_drop.rs
index d274a934d52..9a3956596d2 100644
--- a/compiler/rustc_ty_utils/src/needs_drop.rs
+++ b/compiler/rustc_ty_utils/src/needs_drop.rs
@@ -366,7 +366,7 @@ fn adt_consider_insignificant_dtor<'tcx>(
 fn adt_drop_tys<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: DefId,
-) -> Result<&ty::List<Ty<'tcx>>, AlwaysRequiresDrop> {
+) -> Result<&'tcx ty::List<Ty<'tcx>>, AlwaysRequiresDrop> {
     // This is for the "adt_drop_tys" query, that considers all `Drop` impls, therefore all dtors are
     // significant.
     let adt_has_dtor =
diff --git a/compiler/rustc_type_ir/Cargo.toml b/compiler/rustc_type_ir/Cargo.toml
index 2750838bbe9..98cc116bd00 100644
--- a/compiler/rustc_type_ir/Cargo.toml
+++ b/compiler/rustc_type_ir/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2021"
 bitflags = "2.4.1"
 derive-where = "1.2.7"
 indexmap = "2.0.0"
+rustc-hash = "1.1.0"
 rustc_ast_ir = { path = "../rustc_ast_ir", default-features = false }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_index = { path = "../rustc_index", default-features = false }
@@ -31,3 +32,6 @@ nightly = [
     "rustc_index/nightly",
     "rustc_ast_ir/nightly"
 ]
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(bootstrap)'] }
diff --git a/compiler/rustc_type_ir/src/data_structures.rs b/compiler/rustc_type_ir/src/data_structures.rs
index 4ca97c0c86c..96036e53b0a 100644
--- a/compiler/rustc_type_ir/src/data_structures.rs
+++ b/compiler/rustc_type_ir/src/data_structures.rs
@@ -1,8 +1,13 @@
+use std::hash::BuildHasherDefault;
+
+use rustc_hash::FxHasher;
+pub use rustc_hash::{FxHashMap as HashMap, FxHashSet as HashSet};
+
+pub type IndexMap<K, V> = indexmap::IndexMap<K, V, BuildHasherDefault<FxHasher>>;
+pub type IndexSet<V> = indexmap::IndexSet<V, BuildHasherDefault<FxHasher>>;
+
 #[cfg(feature = "nightly")]
 mod impl_ {
-    pub use rustc_data_structures::fx::{
-        FxHashMap as HashMap, FxHashSet as HashSet, FxIndexMap as IndexMap, FxIndexSet as IndexSet,
-    };
     pub use rustc_data_structures::sso::{SsoHashMap, SsoHashSet};
     pub use rustc_data_structures::stack::ensure_sufficient_stack;
     pub use rustc_data_structures::sync::Lrc;
@@ -10,11 +15,9 @@ mod impl_ {
 
 #[cfg(not(feature = "nightly"))]
 mod impl_ {
-    pub use std::collections::{HashMap, HashMap as SsoHashMap, HashSet, HashSet as SsoHashSet};
+    pub use std::collections::{HashMap as SsoHashMap, HashSet as SsoHashSet};
     pub use std::sync::Arc as Lrc;
 
-    pub use indexmap::{IndexMap, IndexSet};
-
     #[inline]
     pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
         f()
diff --git a/compiler/rustc_type_ir/src/elaborate.rs b/compiler/rustc_type_ir/src/elaborate.rs
index f30419c801f..433c444e701 100644
--- a/compiler/rustc_type_ir/src/elaborate.rs
+++ b/compiler/rustc_type_ir/src/elaborate.rs
@@ -237,7 +237,7 @@ pub fn supertrait_def_ids<I: Interner>(
     cx: I,
     trait_def_id: I::DefId,
 ) -> impl Iterator<Item = I::DefId> {
-    let mut set = HashSet::default();
+    let mut set: HashSet<I::DefId> = HashSet::default();
     let mut stack = vec![trait_def_id];
 
     set.insert(trait_def_id);
diff --git a/compiler/rustc_type_ir/src/outlives.rs b/compiler/rustc_type_ir/src/outlives.rs
index bfcea6a81d3..e8afaf1a480 100644
--- a/compiler/rustc_type_ir/src/outlives.rs
+++ b/compiler/rustc_type_ir/src/outlives.rs
@@ -68,6 +68,9 @@ struct OutlivesCollector<'a, I: Interner> {
 }
 
 impl<I: Interner> TypeVisitor<I> for OutlivesCollector<'_, I> {
+    #[cfg(not(feature = "nightly"))]
+    type Result = ();
+
     fn visit_ty(&mut self, ty: I::Ty) -> Self::Result {
         if !self.visited.insert(ty) {
             return;
diff --git a/compiler/rustc_type_ir/src/search_graph/mod.rs b/compiler/rustc_type_ir/src/search_graph/mod.rs
index d47c9e725f3..418139c3aad 100644
--- a/compiler/rustc_type_ir/src/search_graph/mod.rs
+++ b/compiler/rustc_type_ir/src/search_graph/mod.rs
@@ -287,7 +287,7 @@ impl<X: Cx> NestedGoals<X> {
         }
     }
 
-    #[rustc_lint_query_instability]
+    #[cfg_attr(feature = "nightly", rustc_lint_query_instability)]
     #[allow(rustc::potential_query_instability)]
     fn iter(&self) -> impl Iterator<Item = (X::Input, UsageKind)> + '_ {
         self.nested_goals.iter().map(|(i, p)| (*i, *p))