diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 48840c76cac8b..cf9cf1b70aaa7 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -1839,6 +1839,27 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         simd_neg: Int => neg, Float => fneg;
     }
 
+    if name == sym::simd_arith_offset {
+        // This also checks that the first operand is a ptr type.
+        let pointee = in_elem.builtin_deref(true).unwrap_or_else(|| {
+            span_bug!(span, "must be called with a vector of pointer types as first argument")
+        });
+        let layout = bx.layout_of(pointee.ty);
+        let ptrs = args[0].immediate();
+        // The second argument must be a ptr-sized integer.
+        // (We don't care about the signedness, this is wrapping anyway.)
+        let (_offsets_len, offsets_elem) = arg_tys[1].simd_size_and_type(bx.tcx());
+        if !matches!(offsets_elem.kind(), ty::Int(ty::IntTy::Isize) | ty::Uint(ty::UintTy::Usize)) {
+            span_bug!(
+                span,
+                "must be called with a vector of pointer-sized integers as second argument"
+            );
+        }
+        let offsets = args[1].immediate();
+
+        return Ok(bx.gep(bx.backend_type(layout), ptrs, &[offsets]));
+    }
+
     if name == sym::simd_saturating_add || name == sym::simd_saturating_sub {
         let lhs = args[0].immediate();
         let rhs = args[1].immediate();
diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index eb1a184bf9b21..e6dfdf54a32d1 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -196,27 +196,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.write_immediate(*val, &dest)?;
             }
 
-            Aggregate(ref kind, ref operands) => {
-                // active_field_index is for union initialization.
-                let (dest, active_field_index) = match **kind {
-                    mir::AggregateKind::Adt(adt_did, variant_index, _, _, active_field_index) => {
-                        self.write_discriminant(variant_index, &dest)?;
-                        if self.tcx.adt_def(adt_did).is_enum() {
-                            assert!(active_field_index.is_none());
-                            (self.place_downcast(&dest, variant_index)?, None)
-                        } else {
-                            if active_field_index.is_some() {
-                                assert_eq!(operands.len(), 1);
-                            }
-                            (dest, active_field_index)
-                        }
-                    }
-                    _ => (dest, None),
-                };
+            Aggregate(box ref kind, ref operands) => {
+                assert!(matches!(kind, mir::AggregateKind::Array(..)));
 
-                for (i, operand) in operands.iter().enumerate() {
+                for (field_index, operand) in operands.iter().enumerate() {
                     let op = self.eval_operand(operand, None)?;
-                    let field_index = active_field_index.unwrap_or(i);
                     let field_dest = self.place_field(&dest, field_index)?;
                     self.copy_op(&op, &field_dest)?;
                 }
diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
index 01af95851357e..79d427ccc4469 100644
--- a/compiler/rustc_const_eval/src/transform/validate.rs
+++ b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -315,9 +315,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                                     | ty::FnPtr(..)
                             )
                         }
-                        // None of the possible types have lifetimes, so we can just compare
-                        // directly
-                        if a != b {
+                        // The function pointer types can have lifetimes
+                        if !self.mir_assign_valid_types(a, b) {
                             self.fail(
                                 location,
                                 format!("Cannot compare unequal types {:?} and {:?}", a, b),
@@ -464,7 +463,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                 };
                 // since CopyNonOverlapping is parametrized by 1 type,
                 // we only need to check that they are equal and not keep an extra parameter.
-                if op_src_ty != op_dst_ty {
+                if !self.mir_assign_valid_types(op_src_ty, op_dst_ty) {
                     self.fail(location, format!("bad arg ({:?} != {:?})", op_src_ty, op_dst_ty));
                 }
 
diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index 1a3fe65252156..98d4870e6454e 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -27,7 +27,6 @@
 #![feature(thread_id_value)]
 #![feature(vec_into_raw_parts)]
 #![allow(rustc::default_hash_types)]
-#![deny(unaligned_references)]
 #![allow(rustc::potential_query_instability)]
 
 #[macro_use]
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 2a01b677e33bf..08987dff660a4 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -629,11 +629,15 @@ fn write_out_deps(
         });
         files.extend(extra_tracked_files);
 
-        if let Some(ref backend) = sess.opts.debugging_opts.codegen_backend {
-            files.push(backend.to_string());
-        }
-
         if sess.binary_dep_depinfo() {
+            if let Some(ref backend) = sess.opts.debugging_opts.codegen_backend {
+                if backend.contains('.') {
+                    // If the backend name contain a `.`, it is the path to an external dynamic
+                    // library. If not, it is not a path.
+                    files.push(backend.to_string());
+                }
+            }
+
             boxed_resolver.borrow_mut().access(|resolver| {
                 for cnum in resolver.cstore().crates_untracked() {
                     let source = resolver.cstore().crate_source_untracked(cnum);
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 89ce307d12cd7..a42e3d5d95785 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -1110,8 +1110,6 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust,compile_fail
-    /// #![deny(unaligned_references)]
-    ///
     /// #[repr(packed)]
     /// pub struct Foo {
     ///     field1: u64,
@@ -1139,10 +1137,11 @@ declare_lint! {
     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     /// [issue #82523]: https://github.com/rust-lang/rust/issues/82523
     pub UNALIGNED_REFERENCES,
-    Warn,
+    Deny,
     "detects unaligned references to fields of packed structs",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #82523 <https://github.com/rust-lang/rust/issues/82523>",
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
     };
     report_in_external_macro
 }
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index db7e973fb6223..49769b7ae3d89 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -2518,7 +2518,8 @@ pub enum Rvalue<'tcx> {
     /// * `Offset` has the same semantics as [`offset`](pointer::offset), except that the second
     ///   parameter may be a `usize` as well.
     /// * The comparison operations accept `bool`s, `char`s, signed or unsigned integers, floats,
-    ///   raw pointers, or function pointers of matching types and return a `bool`.
+    ///   raw pointers, or function pointers and return a `bool`. The types of the operands must be
+    ///   matching, up to the usual caveat of the lifetimes in function pointers.
     /// * Left and right shift operations accept signed or unsigned integers not necessarily of the
     ///   same type and return a value of the same type as their LHS. Like in Rust, the RHS is
     ///   truncated as needed.
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 79f0237fd9b74..bfa13ce79bab4 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -182,16 +182,7 @@ impl<'a> StringReader<'a> {
             }
             rustc_lexer::TokenKind::BlockComment { doc_style, terminated } => {
                 if !terminated {
-                    let msg = match doc_style {
-                        Some(_) => "unterminated block doc-comment",
-                        None => "unterminated block comment",
-                    };
-                    let last_bpos = self.pos;
-                    self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start, last_bpos),
-                        msg,
-                        error_code!(E0758),
-                    );
+                    self.report_unterminated_block_comment(start, doc_style);
                 }
 
                 // Skip non-doc comments
@@ -553,6 +544,55 @@ impl<'a> StringReader<'a> {
         err.emit()
     }
 
+    fn report_unterminated_block_comment(&self, start: BytePos, doc_style: Option<DocStyle>) {
+        let msg = match doc_style {
+            Some(_) => "unterminated block doc-comment",
+            None => "unterminated block comment",
+        };
+        let last_bpos = self.pos;
+        let mut err = self.sess.span_diagnostic.struct_span_fatal_with_code(
+            self.mk_sp(start, last_bpos),
+            msg,
+            error_code!(E0758),
+        );
+        let mut nested_block_comment_open_idxs = vec![];
+        let mut last_nested_block_comment_idxs = None;
+        let mut content_chars = self.str_from(start).char_indices().peekable();
+
+        while let Some((idx, current_char)) = content_chars.next() {
+            match content_chars.peek() {
+                Some((_, '*')) if current_char == '/' => {
+                    nested_block_comment_open_idxs.push(idx);
+                }
+                Some((_, '/')) if current_char == '*' => {
+                    last_nested_block_comment_idxs =
+                        nested_block_comment_open_idxs.pop().map(|open_idx| (open_idx, idx));
+                }
+                _ => {}
+            };
+        }
+
+        if let Some((nested_open_idx, nested_close_idx)) = last_nested_block_comment_idxs {
+            err.span_label(self.mk_sp(start, start + BytePos(2)), msg)
+                .span_label(
+                    self.mk_sp(
+                        start + BytePos(nested_open_idx as u32),
+                        start + BytePos(nested_open_idx as u32 + 2),
+                    ),
+                    "...as last nested comment starts here, maybe you want to close this instead?",
+                )
+                .span_label(
+                    self.mk_sp(
+                        start + BytePos(nested_close_idx as u32),
+                        start + BytePos(nested_close_idx as u32 + 2),
+                    ),
+                    "...and last nested comment terminates here.",
+                );
+        }
+
+        err.emit();
+    }
+
     // RFC 3101 introduced the idea of (reserved) prefixes. As of Rust 2021,
     // using a (unknown) prefix is an error. In earlier editions, however, they
     // only result in a (allowed by default) lint, and are treated as regular
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index f6acb3c76fe58..d9bada295894f 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1247,6 +1247,7 @@ symbols! {
         simd,
         simd_add,
         simd_and,
+        simd_arith_offset,
         simd_as,
         simd_bitmask,
         simd_cast,
diff --git a/compiler/rustc_typeck/src/check/intrinsic.rs b/compiler/rustc_typeck/src/check/intrinsic.rs
index 78e7758067942..0dd8ee88ca2ad 100644
--- a/compiler/rustc_typeck/src/check/intrinsic.rs
+++ b/compiler/rustc_typeck/src/check/intrinsic.rs
@@ -437,6 +437,7 @@ pub fn check_platform_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>)
         | sym::simd_fpow
         | sym::simd_saturating_add
         | sym::simd_saturating_sub => (1, vec![param(0), param(0)], param(0)),
+        sym::simd_arith_offset => (2, vec![param(0), param(1)], param(0)),
         sym::simd_neg
         | sym::simd_fsqrt
         | sym::simd_fsin
diff --git a/library/alloc/src/collections/btree/map/tests.rs b/library/alloc/src/collections/btree/map/tests.rs
index cc986e93698b7..47ba1777ae903 100644
--- a/library/alloc/src/collections/btree/map/tests.rs
+++ b/library/alloc/src/collections/btree/map/tests.rs
@@ -1878,6 +1878,96 @@ fn test_first_last_entry() {
     a.check();
 }
 
+#[test]
+fn test_pop_first_last() {
+    let mut map = BTreeMap::new();
+    assert_eq!(map.pop_first(), None);
+    assert_eq!(map.pop_last(), None);
+
+    map.insert(1, 10);
+    map.insert(2, 20);
+    map.insert(3, 30);
+    map.insert(4, 40);
+
+    assert_eq!(map.len(), 4);
+
+    let (key, val) = map.pop_first().unwrap();
+    assert_eq!(key, 1);
+    assert_eq!(val, 10);
+    assert_eq!(map.len(), 3);
+
+    let (key, val) = map.pop_first().unwrap();
+    assert_eq!(key, 2);
+    assert_eq!(val, 20);
+    assert_eq!(map.len(), 2);
+    let (key, val) = map.pop_last().unwrap();
+    assert_eq!(key, 4);
+    assert_eq!(val, 40);
+    assert_eq!(map.len(), 1);
+
+    map.insert(5, 50);
+    map.insert(6, 60);
+    assert_eq!(map.len(), 3);
+
+    let (key, val) = map.pop_first().unwrap();
+    assert_eq!(key, 3);
+    assert_eq!(val, 30);
+    assert_eq!(map.len(), 2);
+
+    let (key, val) = map.pop_last().unwrap();
+    assert_eq!(key, 6);
+    assert_eq!(val, 60);
+    assert_eq!(map.len(), 1);
+
+    let (key, val) = map.pop_last().unwrap();
+    assert_eq!(key, 5);
+    assert_eq!(val, 50);
+    assert_eq!(map.len(), 0);
+
+    assert_eq!(map.pop_first(), None);
+    assert_eq!(map.pop_last(), None);
+
+    map.insert(7, 70);
+    map.insert(8, 80);
+
+    let (key, val) = map.pop_last().unwrap();
+    assert_eq!(key, 8);
+    assert_eq!(val, 80);
+    assert_eq!(map.len(), 1);
+
+    let (key, val) = map.pop_last().unwrap();
+    assert_eq!(key, 7);
+    assert_eq!(val, 70);
+    assert_eq!(map.len(), 0);
+
+    assert_eq!(map.pop_first(), None);
+    assert_eq!(map.pop_last(), None);
+}
+
+#[test]
+fn test_get_key_value() {
+    let mut map = BTreeMap::new();
+
+    assert!(map.is_empty());
+    assert_eq!(map.get_key_value(&1), None);
+    assert_eq!(map.get_key_value(&2), None);
+
+    map.insert(1, 10);
+    map.insert(2, 20);
+    map.insert(3, 30);
+
+    assert_eq!(map.len(), 3);
+    assert_eq!(map.get_key_value(&1), Some((&1, &10)));
+    assert_eq!(map.get_key_value(&3), Some((&3, &30)));
+    assert_eq!(map.get_key_value(&4), None);
+
+    map.remove(&3);
+
+    assert_eq!(map.len(), 2);
+    assert_eq!(map.get_key_value(&3), None);
+    assert_eq!(map.get_key_value(&2), Some((&2, &20)));
+}
+
 #[test]
 fn test_insert_into_full_height_0() {
     let size = node::CAPACITY;
@@ -1904,6 +1994,21 @@ fn test_insert_into_full_height_1() {
     }
 }
 
+#[test]
+fn test_try_insert() {
+    let mut map = BTreeMap::new();
+
+    assert!(map.is_empty());
+
+    assert_eq!(map.try_insert(1, 10).unwrap(), &10);
+    assert_eq!(map.try_insert(2, 20).unwrap(), &20);
+
+    let err = map.try_insert(2, 200).unwrap_err();
+    assert_eq!(err.entry.key(), &2);
+    assert_eq!(err.entry.get(), &20);
+    assert_eq!(err.value, 200);
+}
+
 macro_rules! create_append_test {
     ($name:ident, $len:expr) => {
         #[test]
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 8aa355a554d70..dafd07b161785 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -117,6 +117,7 @@
 #![feature(const_intrinsic_copy)]
 #![feature(const_intrinsic_forget)]
 #![feature(const_likely)]
+#![feature(const_maybe_uninit_uninit_array)]
 #![feature(const_maybe_uninit_as_mut_ptr)]
 #![feature(const_maybe_uninit_assume_init)]
 #![feature(const_num_from_num)]
diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs
index 58d682fc4c8d4..cac7f435573a5 100644
--- a/library/core/src/mem/maybe_uninit.rs
+++ b/library/core/src/mem/maybe_uninit.rs
@@ -350,13 +350,13 @@ impl<T> MaybeUninit<T> {
     /// let mut buf: [MaybeUninit<u8>; 32] = MaybeUninit::uninit_array();
     /// let data = read(&mut buf);
     /// ```
-    #[unstable(feature = "maybe_uninit_uninit_array", issue = "none")]
-    #[rustc_const_unstable(feature = "maybe_uninit_uninit_array", issue = "none")]
+    #[unstable(feature = "maybe_uninit_uninit_array", issue = "96097")]
+    #[rustc_const_unstable(feature = "const_maybe_uninit_uninit_array", issue = "96097")]
     #[must_use]
     #[inline(always)]
-    pub const fn uninit_array<const LEN: usize>() -> [Self; LEN] {
+    pub const fn uninit_array<const N: usize>() -> [Self; N] {
         // SAFETY: An uninitialized `[MaybeUninit<_>; LEN]` is valid.
-        unsafe { MaybeUninit::<[MaybeUninit<T>; LEN]>::uninit().assume_init() }
+        unsafe { MaybeUninit::<[MaybeUninit<T>; N]>::uninit().assume_init() }
     }
 
     /// Creates a new `MaybeUninit<T>` in an uninitialized state, with the memory being
@@ -942,19 +942,24 @@ impl<T> MaybeUninit<T> {
     ///
     /// assert_eq!(array, [0, 1, 2]);
     /// ```
-    #[unstable(feature = "maybe_uninit_array_assume_init", issue = "80908")]
+    #[unstable(feature = "maybe_uninit_array_assume_init", issue = "96097")]
+    #[rustc_const_unstable(feature = "const_maybe_uninit_array_assume_init", issue = "96097")]
     #[inline(always)]
     #[track_caller]
-    pub unsafe fn array_assume_init<const N: usize>(array: [Self; N]) -> [T; N] {
+    pub const unsafe fn array_assume_init<const N: usize>(array: [Self; N]) -> [T; N] {
         // SAFETY:
         // * The caller guarantees that all elements of the array are initialized
         // * `MaybeUninit<T>` and T are guaranteed to have the same layout
         // * `MaybeUninit` does not drop, so there are no double-frees
         // And thus the conversion is safe
-        unsafe {
+        let ret = unsafe {
             intrinsics::assert_inhabited::<[T; N]>();
             (&array as *const _ as *const [T; N]).read()
-        }
+        };
+
+        // FIXME: required to avoid `~const Destruct` bound
+        super::forget(array);
+        ret
     }
 
     /// Assuming all the elements are initialized, get a slice to them.
diff --git a/library/portable-simd/crates/core_simd/src/intrinsics.rs b/library/portable-simd/crates/core_simd/src/intrinsics.rs
index 426c4de6ab1ea..82508c6882dab 100644
--- a/library/portable-simd/crates/core_simd/src/intrinsics.rs
+++ b/library/portable-simd/crates/core_simd/src/intrinsics.rs
@@ -61,6 +61,10 @@ extern "platform-intrinsic" {
     /// xor
     pub(crate) fn simd_xor<T>(x: T, y: T) -> T;
 
+    /// getelementptr (without inbounds)
+    #[cfg(not(bootstrap))]
+    pub(crate) fn simd_arith_offset<T, U>(ptrs: T, offsets: U) -> T;
+
     /// fptoui/fptosi/uitofp/sitofp
     /// casting floats to integers is truncating, so it is safe to convert values like e.g. 1.5
     /// but the truncated value must fit in the target type or the result is poison.
diff --git a/library/portable-simd/crates/core_simd/src/vector/ptr.rs b/library/portable-simd/crates/core_simd/src/vector/ptr.rs
index 417d255c28d63..68a9c67f795af 100644
--- a/library/portable-simd/crates/core_simd/src/vector/ptr.rs
+++ b/library/portable-simd/crates/core_simd/src/vector/ptr.rs
@@ -1,5 +1,8 @@
 //! Private implementation details of public gather/scatter APIs.
+#[cfg(not(bootstrap))]
+use crate::simd::intrinsics;
 use crate::simd::{LaneCount, Simd, SupportedLaneCount};
+#[cfg(bootstrap)]
 use core::mem;
 
 /// A vector of *const T.
@@ -21,12 +24,16 @@ where
     #[inline]
     #[must_use]
     pub fn wrapping_add(self, addend: Simd<usize, LANES>) -> Self {
+        #[cfg(bootstrap)]
         // Safety: converting pointers to usize and vice-versa is safe
         // (even if using that pointer is not)
         unsafe {
             let x: Simd<usize, LANES> = mem::transmute_copy(&self);
             mem::transmute_copy(&{ x + (addend * Simd::splat(mem::size_of::<T>())) })
         }
+        #[cfg(not(bootstrap))]
+        // Safety: this intrinsic doesn't have a precondition
+        unsafe { intrinsics::simd_arith_offset(self, addend) }
     }
 }
 
@@ -49,11 +56,15 @@ where
     #[inline]
     #[must_use]
     pub fn wrapping_add(self, addend: Simd<usize, LANES>) -> Self {
+        #[cfg(bootstrap)]
         // Safety: converting pointers to usize and vice-versa is safe
         // (even if using that pointer is not)
         unsafe {
             let x: Simd<usize, LANES> = mem::transmute_copy(&self);
             mem::transmute_copy(&{ x + (addend * Simd::splat(mem::size_of::<T>())) })
         }
+        #[cfg(not(bootstrap))]
+        // Safety: this intrinsic doesn't have a precondition
+        unsafe { intrinsics::simd_arith_offset(self, addend) }
     }
 }
diff --git a/src/doc/rustc/src/SUMMARY.md b/src/doc/rustc/src/SUMMARY.md
index 2cf2660327384..952d8ef48fe57 100644
--- a/src/doc/rustc/src/SUMMARY.md
+++ b/src/doc/rustc/src/SUMMARY.md
@@ -15,12 +15,15 @@
 - [Platform Support](platform-support.md)
     - [Template for target-specific documentation](platform-support/TEMPLATE.md)
     - [aarch64-apple-ios-sim](platform-support/aarch64-apple-ios-sim.md)
+    - [aarch64-unknown-none-hermitkernel](platform-support/aarch64-unknown-none-hermitkernel.md)
     - [armv7-unknown-linux-uclibceabi](platform-support/armv7-unknown-linux-uclibceabi.md)
     - [armv7-unknown-linux-uclibceabihf](platform-support/armv7-unknown-linux-uclibceabihf.md)
     - [\*-kmc-solid_\*](platform-support/kmc-solid.md)
+    - [m68k-unknown-linux-gnu](platform-support/m68k-unknown-linux-gnu.md)
+    - [mips64-openwrt-linux-musl](platform-support/mips64-openwrt-linux-musl.md)
     - [*-unknown-openbsd](platform-support/openbsd.md)
-    - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
+    - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)
 - [Target Tier Policy](target-tier-policy.md)
 - [Targets](targets/index.md)
     - [Built-in Targets](targets/built-in.md)
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index b3c4a52c414b2..12ac575210aa3 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -248,9 +248,9 @@ target | std | host | notes
 `i686-uwp-windows-gnu` | ? |  |
 `i686-uwp-windows-msvc` | ? |  |
 `i686-wrs-vxworks` | ? |  |
-`m68k-unknown-linux-gnu` | ? |  | Motorola 680x0 Linux
+[`m68k-unknown-linux-gnu`](platform-support/m68k-unknown-linux-gnu.md) | ? |  | Motorola 680x0 Linux
 `mips-unknown-linux-uclibc` | ✓ |  | MIPS Linux with uClibc
-`mips64-openwrt-linux-musl` | ? |  | MIPS64 for OpenWrt Linux MUSL
+[`mips64-openwrt-linux-musl`](platform-support/mips64-openwrt-linux-musl.md) | ? |  | MIPS64 for OpenWrt Linux MUSL
 `mipsel-sony-psp` | * |  | MIPS (LE) Sony PlayStation Portable (PSP)
 `mipsel-unknown-linux-uclibc` | ✓ |  | MIPS (LE) Linux with uClibc
 `mipsel-unknown-none` | * |  | Bare MIPS (LE) softfloat
diff --git a/src/test/codegen/simd_arith_offset.rs b/src/test/codegen/simd_arith_offset.rs
new file mode 100644
index 0000000000000..a858270d4e76d
--- /dev/null
+++ b/src/test/codegen/simd_arith_offset.rs
@@ -0,0 +1,26 @@
+// compile-flags: -C no-prepopulate-passes
+// only-64bit (because the LLVM type of i64 for usize shows up)
+//
+
+#![crate_type = "lib"]
+#![feature(repr_simd, platform_intrinsics)]
+
+extern "platform-intrinsic" {
+    pub(crate) fn simd_arith_offset<T, U>(ptrs: T, offsets: U) -> T;
+}
+
+/// A vector of *const T.
+#[derive(Debug, Copy, Clone)]
+#[repr(simd)]
+pub struct SimdConstPtr<T, const LANES: usize>([*const T; LANES]);
+
+#[derive(Debug, Copy, Clone)]
+#[repr(simd)]
+pub struct Simd<T, const LANES: usize>([T; LANES]);
+
+// CHECK-LABEL: smoke
+#[no_mangle]
+pub fn smoke(ptrs: SimdConstPtr<u8, 8>, offsets: Simd<usize, 8>) -> SimdConstPtr<u8, 8> {
+    // CHECK: getelementptr i8, <8 x i8*> %_3, <8 x i64> %_4
+    unsafe { simd_arith_offset(ptrs, offsets) }
+}
diff --git a/src/test/run-make-fulldeps/hotplug_codegen_backend/Makefile b/src/test/run-make-fulldeps/hotplug_codegen_backend/Makefile
index d8ceace7fff25..4cda243ffb5a3 100644
--- a/src/test/run-make-fulldeps/hotplug_codegen_backend/Makefile
+++ b/src/test/run-make-fulldeps/hotplug_codegen_backend/Makefile
@@ -2,10 +2,25 @@ include ../tools.mk
 
 # ignore-stage1
 
+# This test both exists as a check that -Zcodegen-backend is capable of loading external codegen
+# backends and that this external codegen backend is only included in the dep info if
+# -Zbinary-dep-depinfo is used.
+
 all:
 	/bin/echo || exit 0 # This test requires /bin/echo to exist
 	$(RUSTC) the_backend.rs --crate-name the_backend --crate-type dylib \
 		-o $(TMPDIR)/the_backend.dylib
+
+	$(RUSTC) some_crate.rs --crate-name some_crate --crate-type lib -o $(TMPDIR)/some_crate \
+		-Z codegen-backend=$(TMPDIR)/the_backend.dylib -Z unstable-options \
+		--emit link,dep-info
+	grep -x "This has been \"compiled\" successfully." $(TMPDIR)/libsome_crate.rlib
+	# don't declare a dependency on the codegen backend if -Zbinary-dep-depinfo isn't used.
+	grep -v "the_backend.dylib" $(TMPDIR)/some_crate.d
+	
 	$(RUSTC) some_crate.rs --crate-name some_crate --crate-type lib -o $(TMPDIR)/some_crate \
-		-Z codegen-backend=$(TMPDIR)/the_backend.dylib -Z unstable-options
-	grep -x "This has been \"compiled\" successfully." $(TMPDIR)/some_crate
+		-Z codegen-backend=$(TMPDIR)/the_backend.dylib -Z unstable-options \
+		--emit link,dep-info -Zbinary-dep-depinfo
+	grep -x "This has been \"compiled\" successfully." $(TMPDIR)/libsome_crate.rlib
+	# but declare a dependency on the codegen backend if -Zbinary-dep-depinfo it used.
+	grep "the_backend.dylib" $(TMPDIR)/some_crate.d
diff --git a/src/test/ui/binding/issue-53114-safety-checks.rs b/src/test/ui/binding/issue-53114-safety-checks.rs
index ca4f0efd2392b..5042ad024afff 100644
--- a/src/test/ui/binding/issue-53114-safety-checks.rs
+++ b/src/test/ui/binding/issue-53114-safety-checks.rs
@@ -20,13 +20,13 @@ fn let_wild_gets_unsafe_field() {
     let u1 = U { a: I(0) };
     let u2 = U { a: I(1) };
     let p = P { a: &2, b: &3 };
-    let _ = &p.b;  //~ WARN    reference to packed field
+    let _ = &p.b;  //~ ERROR    reference to packed field
     //~^  WARN will become a hard error
     let _ = u1.a;  // #53114: should eventually signal error as well
     let _ = &u2.a; //~ ERROR  [E0133]
 
     // variation on above with `_` in substructure
-    let (_,) = (&p.b,);  //~ WARN     reference to packed field
+    let (_,) = (&p.b,);  //~ ERROR     reference to packed field
     //~^  WARN will become a hard error
     let (_,) = (u1.a,);  //~ ERROR   [E0133]
     let (_,) = (&u2.a,); //~ ERROR   [E0133]
@@ -36,13 +36,13 @@ fn match_unsafe_field_to_wild() {
     let u1 = U { a: I(0) };
     let u2 = U { a: I(1) };
     let p = P { a: &2, b: &3 };
-    match &p.b  { _ => { } } //~ WARN     reference to packed field
+    match &p.b  { _ => { } } //~ ERROR     reference to packed field
     //~^  WARN will become a hard error
     match u1.a  { _ => { } } //~ ERROR   [E0133]
     match &u2.a { _ => { } } //~ ERROR   [E0133]
 
     // variation on above with `_` in substructure
-    match (&p.b,)  { (_,) => { } } //~ WARN     reference to packed field
+    match (&p.b,)  { (_,) => { } } //~ ERROR     reference to packed field
     //~^  WARN will become a hard error
     match (u1.a,)  { (_,) => { } } //~ ERROR   [E0133]
     match (&u2.a,) { (_,) => { } } //~ ERROR   [E0133]
diff --git a/src/test/ui/binding/issue-53114-safety-checks.stderr b/src/test/ui/binding/issue-53114-safety-checks.stderr
index 84cdb1453f82d..f3840273cfaf7 100644
--- a/src/test/ui/binding/issue-53114-safety-checks.stderr
+++ b/src/test/ui/binding/issue-53114-safety-checks.stderr
@@ -1,16 +1,16 @@
-warning: reference to packed field is unaligned
+error: reference to packed field is unaligned
   --> $DIR/issue-53114-safety-checks.rs:23:13
    |
 LL |     let _ = &p.b;
    |             ^^^^
    |
-   = note: `#[warn(unaligned_references)]` on by default
+   = note: `#[deny(unaligned_references)]` on by default
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
-warning: reference to packed field is unaligned
+error: reference to packed field is unaligned
   --> $DIR/issue-53114-safety-checks.rs:29:17
    |
 LL |     let (_,) = (&p.b,);
@@ -21,7 +21,7 @@ LL |     let (_,) = (&p.b,);
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
-warning: reference to packed field is unaligned
+error: reference to packed field is unaligned
   --> $DIR/issue-53114-safety-checks.rs:39:11
    |
 LL |     match &p.b  { _ => { } }
@@ -32,7 +32,7 @@ LL |     match &p.b  { _ => { } }
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
-warning: reference to packed field is unaligned
+error: reference to packed field is unaligned
   --> $DIR/issue-53114-safety-checks.rs:45:12
    |
 LL |     match (&p.b,)  { (_,) => { } }
@@ -99,6 +99,58 @@ LL |     match (&u2.a,) { (_,) => { } }
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
-error: aborting due to 7 previous errors; 4 warnings emitted
+error: aborting due to 11 previous errors
 
 For more information about this error, try `rustc --explain E0133`.
+Future incompatibility report: Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-53114-safety-checks.rs:23:13
+   |
+LL |     let _ = &p.b;
+   |             ^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-53114-safety-checks.rs:29:17
+   |
+LL |     let (_,) = (&p.b,);
+   |                 ^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-53114-safety-checks.rs:39:11
+   |
+LL |     match &p.b  { _ => { } }
+   |           ^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-53114-safety-checks.rs:45:12
+   |
+LL |     match (&p.b,)  { (_,) => { } }
+   |            ^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
diff --git a/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.rs b/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.rs
index 4799f488d7d52..1488f329648bb 100644
--- a/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.rs
+++ b/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.rs
@@ -1,7 +1,5 @@
 // edition:2021
 
-// check-pass
-
 // Given how the closure desugaring is implemented (at least at the time of writing this test),
 // we don't need to truncate the captured path to a reference into a packed-struct if the field
 // being referenced will be moved into the closure, since it's safe to move out a field from a
@@ -11,9 +9,8 @@
 // inlined we will truncate the capture to access just the struct regardless of if the field
 // might get moved into the closure.
 //
-// It is possible for someone to try writing the code that relies on the desugaring to access a ref
-// into a packed-struct without explicity using unsafe. Here we test that the compiler warns the
-// user that such an access is still unsafe.
+// It is possible for someone to try writing the code that relies on the desugaring to create a ref
+// into a packed-struct. Here we test that the compiler still detects that case.
 fn test_missing_unsafe_warning_on_repr_packed() {
     #[repr(packed)]
     struct Foo { x: String }
@@ -22,7 +19,7 @@ fn test_missing_unsafe_warning_on_repr_packed() {
 
     let c = || {
         println!("{}", foo.x);
-        //~^ WARNING: reference to packed field is unaligned
+        //~^ ERROR: reference to packed field is unaligned
         //~| WARNING: this was previously accepted by the compiler but is being phased out
         let _z = foo.x;
     };
diff --git a/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.stderr b/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.stderr
index fc0179d2cb4ca..8629837ba8d34 100644
--- a/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.stderr
+++ b/src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.stderr
@@ -1,15 +1,29 @@
-warning: reference to packed field is unaligned
-  --> $DIR/repr_packed.rs:24:24
+error: reference to packed field is unaligned
+  --> $DIR/repr_packed.rs:21:24
    |
 LL |         println!("{}", foo.x);
    |                        ^^^^^
    |
-   = note: `#[warn(unaligned_references)]` on by default
+   = note: `#[deny(unaligned_references)]` on by default
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
-   = note: this warning originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-warning: 1 warning emitted
+error: aborting due to previous error
+
+Future incompatibility report: Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/repr_packed.rs:21:24
+   |
+LL |         println!("{}", foo.x);
+   |                        ^^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
diff --git a/src/test/ui/derives/deriving-with-repr-packed.stderr b/src/test/ui/derives/deriving-with-repr-packed.stderr
index 667f82ee0cfef..1002b359f60ba 100644
--- a/src/test/ui/derives/deriving-with-repr-packed.stderr
+++ b/src/test/ui/derives/deriving-with-repr-packed.stderr
@@ -45,3 +45,67 @@ LL | #[derive(PartialEq)]
 
 error: aborting due to 4 previous errors
 
+Future incompatibility report: Future breakage diagnostic:
+error: `#[derive]` can't be used on a `#[repr(packed)]` struct with type or const parameters (error E0133)
+  --> $DIR/deriving-with-repr-packed.rs:8:16
+   |
+LL | #[derive(Copy, Clone, PartialEq, Eq)]
+   |                ^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/deriving-with-repr-packed.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: this error originates in the derive macro `Clone` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+Future breakage diagnostic:
+error: `#[derive]` can't be used on a `#[repr(packed)]` struct with type or const parameters (error E0133)
+  --> $DIR/deriving-with-repr-packed.rs:8:23
+   |
+LL | #[derive(Copy, Clone, PartialEq, Eq)]
+   |                       ^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/deriving-with-repr-packed.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: this error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+Future breakage diagnostic:
+error: `#[derive]` can't be used on a `#[repr(packed)]` struct that does not derive Copy (error E0133)
+  --> $DIR/deriving-with-repr-packed.rs:16:10
+   |
+LL | #[derive(PartialEq, Eq)]
+   |          ^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/deriving-with-repr-packed.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: this error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+Future breakage diagnostic:
+error: `#[derive]` can't be used on a `#[repr(packed)]` struct that does not derive Copy (error E0133)
+  --> $DIR/deriving-with-repr-packed.rs:25:10
+   |
+LL | #[derive(PartialEq)]
+   |          ^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/deriving-with-repr-packed.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: this error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)
+
diff --git a/src/test/ui/lint/unaligned_references.stderr b/src/test/ui/lint/unaligned_references.stderr
index 53c9380fb7efb..ed5dd2ec01181 100644
--- a/src/test/ui/lint/unaligned_references.stderr
+++ b/src/test/ui/lint/unaligned_references.stderr
@@ -82,3 +82,122 @@ LL |         let _ = &packed2.x;
 
 error: aborting due to 7 previous errors
 
+Future incompatibility report: Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references.rs:22:17
+   |
+LL |         let _ = &good.ptr;
+   |                 ^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references.rs:24:17
+   |
+LL |         let _ = &good.data;
+   |                 ^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references.rs:27:17
+   |
+LL |         let _ = &good.data as *const _;
+   |                 ^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references.rs:29:27
+   |
+LL |         let _: *const _ = &good.data;
+   |                           ^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references.rs:32:17
+   |
+LL |         let _ = good.data.clone();
+   |                 ^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references.rs:35:17
+   |
+LL |         let _ = &good.data2[0];
+   |                 ^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references.rs:45:17
+   |
+LL |         let _ = &packed2.x;
+   |                 ^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references.rs:1:9
+   |
+LL | #![deny(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
diff --git a/src/test/ui/lint/unaligned_references_external_macro.stderr b/src/test/ui/lint/unaligned_references_external_macro.stderr
index 01e2395049df4..1262c21ee78e2 100644
--- a/src/test/ui/lint/unaligned_references_external_macro.stderr
+++ b/src/test/ui/lint/unaligned_references_external_macro.stderr
@@ -29,3 +29,33 @@ LL | | }
 
 error: aborting due to previous error
 
+Future incompatibility report: Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/unaligned_references_external_macro.rs:5:1
+   |
+LL | / unaligned_references_external_crate::mac! {
+LL | |
+LL | |     #[repr(packed)]
+LL | |     pub struct X {
+LL | |         pub field: u16
+LL | |     }
+LL | | }
+   | |_^
+   |
+note: the lint level is defined here
+  --> $DIR/unaligned_references_external_macro.rs:5:1
+   |
+LL | / unaligned_references_external_crate::mac! {
+LL | |
+LL | |     #[repr(packed)]
+LL | |     pub struct X {
+LL | |         pub field: u16
+LL | |     }
+LL | | }
+   | |_^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+   = note: this error originates in the macro `unaligned_references_external_crate::mac` (in Nightly builds, run with -Z macro-backtrace for more info)
+
diff --git a/src/test/ui/mir/issue-95978-validator-lifetime-comparison.rs b/src/test/ui/mir/issue-95978-validator-lifetime-comparison.rs
new file mode 100644
index 0000000000000..cd6c5bf271935
--- /dev/null
+++ b/src/test/ui/mir/issue-95978-validator-lifetime-comparison.rs
@@ -0,0 +1,10 @@
+// check-pass
+// compile-flags: -Zvalidate-mir
+
+fn foo(_a: &str) {}
+
+fn main() {
+    let x = foo as fn(&'static str);
+
+    let _ = x == foo;
+}
diff --git a/src/test/ui/packed/issue-27060-rpass.stderr b/src/test/ui/packed/issue-27060-rpass.stderr
new file mode 100644
index 0000000000000..667b70afb8787
--- /dev/null
+++ b/src/test/ui/packed/issue-27060-rpass.stderr
@@ -0,0 +1,68 @@
+Future incompatibility report: Future breakage diagnostic:
+warning: reference to packed field is unaligned
+  --> $DIR/issue-27060-rpass.rs:15:13
+   |
+LL |     let _ = &good.data; // ok
+   |             ^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-27060-rpass.rs:11:9
+   |
+LL | #[allow(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+warning: reference to packed field is unaligned
+  --> $DIR/issue-27060-rpass.rs:16:13
+   |
+LL |     let _ = &good.data2[0]; // ok
+   |             ^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-27060-rpass.rs:11:9
+   |
+LL | #[allow(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+warning: reference to packed field is unaligned
+  --> $DIR/issue-27060-rpass.rs:18:13
+   |
+LL |     let _ = &good.data;
+   |             ^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-27060-rpass.rs:11:9
+   |
+LL | #[allow(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+warning: reference to packed field is unaligned
+  --> $DIR/issue-27060-rpass.rs:19:13
+   |
+LL |     let _ = &good.data2[0];
+   |             ^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-27060-rpass.rs:11:9
+   |
+LL | #[allow(unaligned_references)]
+   |         ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
diff --git a/src/test/ui/packed/issue-27060.rs b/src/test/ui/packed/issue-27060.rs
index 5317a61671945..886a00239f98c 100644
--- a/src/test/ui/packed/issue-27060.rs
+++ b/src/test/ui/packed/issue-27060.rs
@@ -5,7 +5,6 @@ pub struct Good {
     aligned: [u8; 32],
 }
 
-#[deny(unaligned_references)]
 fn main() {
     let good = Good {
         data: &0,
diff --git a/src/test/ui/packed/issue-27060.stderr b/src/test/ui/packed/issue-27060.stderr
index bba056d59f831..1bab16e6ddaa3 100644
--- a/src/test/ui/packed/issue-27060.stderr
+++ b/src/test/ui/packed/issue-27060.stderr
@@ -1,21 +1,17 @@
 error: reference to packed field is unaligned
-  --> $DIR/issue-27060.rs:16:13
+  --> $DIR/issue-27060.rs:15:13
    |
 LL |     let _ = &good.data;
    |             ^^^^^^^^^^
    |
-note: the lint level is defined here
-  --> $DIR/issue-27060.rs:8:8
-   |
-LL | #[deny(unaligned_references)]
-   |        ^^^^^^^^^^^^^^^^^^^^
+   = note: `#[deny(unaligned_references)]` on by default
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
 error: reference to packed field is unaligned
-  --> $DIR/issue-27060.rs:18:13
+  --> $DIR/issue-27060.rs:17:13
    |
 LL |     let _ = &good.data2[0];
    |             ^^^^^^^^^^^^^^
@@ -26,7 +22,7 @@ LL |     let _ = &good.data2[0];
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
 error: reference to packed field is unaligned
-  --> $DIR/issue-27060.rs:21:13
+  --> $DIR/issue-27060.rs:20:13
    |
 LL |     let _ = &good.data;
    |             ^^^^^^^^^^
@@ -37,7 +33,7 @@ LL |     let _ = &good.data;
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
 error: reference to packed field is unaligned
-  --> $DIR/issue-27060.rs:23:13
+  --> $DIR/issue-27060.rs:22:13
    |
 LL |     let _ = &good.data2[0];
    |             ^^^^^^^^^^^^^^
@@ -49,3 +45,55 @@ LL |     let _ = &good.data2[0];
 
 error: aborting due to 4 previous errors
 
+Future incompatibility report: Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-27060.rs:15:13
+   |
+LL |     let _ = &good.data;
+   |             ^^^^^^^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-27060.rs:17:13
+   |
+LL |     let _ = &good.data2[0];
+   |             ^^^^^^^^^^^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-27060.rs:20:13
+   |
+LL |     let _ = &good.data;
+   |             ^^^^^^^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+error: reference to packed field is unaligned
+  --> $DIR/issue-27060.rs:22:13
+   |
+LL |     let _ = &good.data2[0];
+   |             ^^^^^^^^^^^^^^
+   |
+   = note: `#[deny(unaligned_references)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
diff --git a/src/test/ui/packed/packed-struct-address-of-element.rs b/src/test/ui/packed/packed-struct-address-of-element.rs
index fb3875e680496..d86698cbf3848 100644
--- a/src/test/ui/packed/packed-struct-address-of-element.rs
+++ b/src/test/ui/packed/packed-struct-address-of-element.rs
@@ -1,6 +1,5 @@
 // run-pass
 #![allow(dead_code)]
-#![deny(unaligned_references)]
 #![feature(raw_ref_op)]
 // ignore-emscripten weird assertion?
 
diff --git a/src/test/ui/packed/packed-struct-borrow-element-64bit.rs b/src/test/ui/packed/packed-struct-borrow-element-64bit.rs
index ad932fdcd01c4..00bddfe40b25b 100644
--- a/src/test/ui/packed/packed-struct-borrow-element-64bit.rs
+++ b/src/test/ui/packed/packed-struct-borrow-element-64bit.rs
@@ -9,6 +9,7 @@ struct Foo4C {
     baz: usize
 }
 
+#[warn(unaligned_references)]
 pub fn main() {
     let foo = Foo4C { bar: 1, baz: 2 };
     let brw = &foo.baz; //~WARN reference to packed field is unaligned
diff --git a/src/test/ui/packed/packed-struct-borrow-element-64bit.stderr b/src/test/ui/packed/packed-struct-borrow-element-64bit.stderr
index 04585b499862b..dcd1c19fa16a8 100644
--- a/src/test/ui/packed/packed-struct-borrow-element-64bit.stderr
+++ b/src/test/ui/packed/packed-struct-borrow-element-64bit.stderr
@@ -1,10 +1,14 @@
 warning: reference to packed field is unaligned
-  --> $DIR/packed-struct-borrow-element-64bit.rs:14:15
+  --> $DIR/packed-struct-borrow-element-64bit.rs:15:15
    |
 LL |     let brw = &foo.baz;
    |               ^^^^^^^^
    |
-   = note: `#[warn(unaligned_references)]` on by default
+note: the lint level is defined here
+  --> $DIR/packed-struct-borrow-element-64bit.rs:12:8
+   |
+LL | #[warn(unaligned_references)]
+   |        ^^^^^^^^^^^^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
@@ -12,3 +16,20 @@ LL |     let brw = &foo.baz;
 
 warning: 1 warning emitted
 
+Future incompatibility report: Future breakage diagnostic:
+warning: reference to packed field is unaligned
+  --> $DIR/packed-struct-borrow-element-64bit.rs:15:15
+   |
+LL |     let brw = &foo.baz;
+   |               ^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/packed-struct-borrow-element-64bit.rs:12:8
+   |
+LL | #[warn(unaligned_references)]
+   |        ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
diff --git a/src/test/ui/packed/packed-struct-borrow-element.rs b/src/test/ui/packed/packed-struct-borrow-element.rs
index fb6c9c11d5694..a6ee90cef44f0 100644
--- a/src/test/ui/packed/packed-struct-borrow-element.rs
+++ b/src/test/ui/packed/packed-struct-borrow-element.rs
@@ -20,6 +20,7 @@ struct Foo4C {
     baz: usize
 }
 
+#[warn(unaligned_references)]
 pub fn main() {
     let foo = Foo1 { bar: 1, baz: 2 };
     let brw = &foo.baz; //~WARN reference to packed field is unaligned
diff --git a/src/test/ui/packed/packed-struct-borrow-element.stderr b/src/test/ui/packed/packed-struct-borrow-element.stderr
index a50b130200151..fb483227e20c1 100644
--- a/src/test/ui/packed/packed-struct-borrow-element.stderr
+++ b/src/test/ui/packed/packed-struct-borrow-element.stderr
@@ -1,17 +1,21 @@
 warning: reference to packed field is unaligned
-  --> $DIR/packed-struct-borrow-element.rs:25:15
+  --> $DIR/packed-struct-borrow-element.rs:26:15
    |
 LL |     let brw = &foo.baz;
    |               ^^^^^^^^
    |
-   = note: `#[warn(unaligned_references)]` on by default
+note: the lint level is defined here
+  --> $DIR/packed-struct-borrow-element.rs:23:8
+   |
+LL | #[warn(unaligned_references)]
+   |        ^^^^^^^^^^^^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
 warning: reference to packed field is unaligned
-  --> $DIR/packed-struct-borrow-element.rs:30:15
+  --> $DIR/packed-struct-borrow-element.rs:31:15
    |
 LL |     let brw = &foo.baz;
    |               ^^^^^^^^
@@ -23,3 +27,37 @@ LL |     let brw = &foo.baz;
 
 warning: 2 warnings emitted
 
+Future incompatibility report: Future breakage diagnostic:
+warning: reference to packed field is unaligned
+  --> $DIR/packed-struct-borrow-element.rs:26:15
+   |
+LL |     let brw = &foo.baz;
+   |               ^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/packed-struct-borrow-element.rs:23:8
+   |
+LL | #[warn(unaligned_references)]
+   |        ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+Future breakage diagnostic:
+warning: reference to packed field is unaligned
+  --> $DIR/packed-struct-borrow-element.rs:31:15
+   |
+LL |     let brw = &foo.baz;
+   |               ^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/packed-struct-borrow-element.rs:23:8
+   |
+LL | #[warn(unaligned_references)]
+   |        ^^^^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
+   = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
diff --git a/src/test/ui/unterminated-nested-comment.rs b/src/test/ui/unterminated-nested-comment.rs
new file mode 100644
index 0000000000000..db5f2f3ba1358
--- /dev/null
+++ b/src/test/ui/unterminated-nested-comment.rs
@@ -0,0 +1,4 @@
+/* //~ ERROR E0758
+/* */
+/*
+*/
diff --git a/src/test/ui/unterminated-nested-comment.stderr b/src/test/ui/unterminated-nested-comment.stderr
new file mode 100644
index 0000000000000..3653e76c9cbda
--- /dev/null
+++ b/src/test/ui/unterminated-nested-comment.stderr
@@ -0,0 +1,21 @@
+error[E0758]: unterminated block comment
+  --> $DIR/unterminated-nested-comment.rs:1:1
+   |
+LL |   /*
+   |   ^-
+   |   |
+   |  _unterminated block comment
+   | |
+LL | | /* */
+LL | | /*
+   | | --
+   | | |
+   | | ...as last nested comment starts here, maybe you want to close this instead?
+LL | | */
+   | |_--^
+   |   |
+   |   ...and last nested comment terminates here.
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0758`.