const-eval interner: from-scratch rewrite using mutability information from provenance rather than types

compiler/rustc_const_eval/messages.ftl

@@ -46,8 +46,8 @@ const_eval_dangling_int_pointer =
     {$bad_pointer_message}: {$pointer} is a dangling pointer (it has no provenance)
 const_eval_dangling_null_pointer =
     {$bad_pointer_message}: null pointer is a dangling pointer (it has no provenance)
-const_eval_dangling_ptr_in_final = encountered dangling pointer in final constant
 
+const_eval_dangling_ptr_in_final = encountered dangling pointer in final value of {const_eval_intern_kind}
 const_eval_dead_local =
     accessing a dead local variable
 const_eval_dealloc_immutable =
@@ -134,6 +134,14 @@ const_eval_interior_mutable_data_refer =
         This would make multiple uses of a constant to be able to see different values and allow circumventing
         the `Send` and `Sync` requirements for shared mutable data, which is unsound.
 
+const_eval_intern_kind = {$kind ->
+    [static] static
+    [static_mut] mutable static
+    [const] constant
+    [promoted] promoted
+    *[other] {""}
+}
+
 const_eval_invalid_align =
     align has to be a power of 2
 
@@ -205,6 +213,8 @@ const_eval_modified_global =
 const_eval_mut_deref =
     mutation through a reference is not allowed in {const_eval_const_context}s
 
+const_eval_mutable_ptr_in_final = encountered mutable pointer in final value of {const_eval_intern_kind}
+
 const_eval_non_const_fmt_macro_call =
     cannot call non-const formatting macro in {const_eval_const_context}s
 
@@ -392,9 +402,6 @@ const_eval_unstable_in_stable =
     .unstable_sugg = if it is not part of the public API, make this function unstably const
     .bypass_sugg = otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks
 
-const_eval_unsupported_untyped_pointer = unsupported untyped pointer in constant
-    .note = memory only reachable via raw pointers is not supported
-
 const_eval_unterminated_c_string =
     reading a null-terminated string starting at {$pointer} with no null found before end of allocation
 
@@ -406,7 +413,6 @@ const_eval_upcast_mismatch =
 
 ## The `front_matter`s here refer to either `const_eval_front_matter_invalid_value` or `const_eval_front_matter_invalid_value_with_path`.
 ## (We'd love to sort this differently to make that more clear but tidy won't let us...)
-const_eval_validation_box_to_mut = {$front_matter}: encountered a box pointing to mutable memory in a constant
 const_eval_validation_box_to_static = {$front_matter}: encountered a box pointing to a static variable in a constant
 const_eval_validation_box_to_uninhabited = {$front_matter}: encountered a box pointing to uninhabited type {$ty}
 const_eval_validation_dangling_box_no_provenance = {$front_matter}: encountered a dangling box ({$pointer} has no provenance)
@@ -441,7 +447,8 @@ const_eval_validation_invalid_fn_ptr = {$front_matter}: encountered {$value}, bu
 const_eval_validation_invalid_ref_meta = {$front_matter}: encountered invalid reference metadata: total size is bigger than largest supported object
 const_eval_validation_invalid_ref_slice_meta = {$front_matter}: encountered invalid reference metadata: slice is bigger than largest supported object
 const_eval_validation_invalid_vtable_ptr = {$front_matter}: encountered {$value}, but expected a vtable pointer
-const_eval_validation_mutable_ref_in_const = {$front_matter}: encountered mutable reference in a `const`
+const_eval_validation_mutable_ref_in_const = {$front_matter}: encountered mutable reference in a `const` or `static`
+const_eval_validation_mutable_ref_to_immutable = {$front_matter}: encountered mutable reference or box pointing to read-only memory
 const_eval_validation_never_val = {$front_matter}: encountered a value of the never type `!`
 const_eval_validation_null_box = {$front_matter}: encountered a null box
 const_eval_validation_null_fn_ptr = {$front_matter}: encountered a null function pointer
@@ -451,7 +458,6 @@ const_eval_validation_out_of_range = {$front_matter}: encountered {$value}, but
 const_eval_validation_partial_pointer = {$front_matter}: encountered a partial pointer or a mix of pointers
 const_eval_validation_pointer_as_int = {$front_matter}: encountered a pointer, but {$expected}
 const_eval_validation_ptr_out_of_range = {$front_matter}: encountered a pointer, but expected something that cannot possibly fail to be {$in_range}
-const_eval_validation_ref_to_mut = {$front_matter}: encountered a reference pointing to mutable memory in a constant
 const_eval_validation_ref_to_static = {$front_matter}: encountered a reference pointing to a static variable in a constant
 const_eval_validation_ref_to_uninhabited = {$front_matter}: encountered a reference pointing to uninhabited type {$ty}
 const_eval_validation_unaligned_box = {$front_matter}: encountered an unaligned box (required {$required_bytes} byte alignment but found {$found_bytes})
@@ -459,7 +465,7 @@ const_eval_validation_unaligned_ref = {$front_matter}: encountered an unaligned
 const_eval_validation_uninhabited_enum_variant = {$front_matter}: encountered an uninhabited enum variant
 const_eval_validation_uninhabited_val = {$front_matter}: encountered a value of uninhabited type `{$ty}`
 const_eval_validation_uninit = {$front_matter}: encountered uninitialized memory, but {$expected}
-const_eval_validation_unsafe_cell = {$front_matter}: encountered `UnsafeCell` in a `const`
+const_eval_validation_unsafe_cell = {$front_matter}: encountered `UnsafeCell` in read-only memory
 
 const_eval_write_through_immutable_pointer =
     writing through a pointer that was derived from a shared (immutable) reference

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -293,6 +293,9 @@ pub fn eval_in_interpreter<'mir, 'tcx>(
     cid: GlobalId<'tcx>,
     is_static: bool,
 ) -> ::rustc_middle::mir::interpret::EvalToAllocationRawResult<'tcx> {
+    // `is_static` just means "in static", it could still be a promoted!
+    debug_assert_eq!(is_static, ecx.tcx.static_mutability(cid.instance.def_id()).is_some());
+
     let res = ecx.load_mir(cid.instance.def, cid.promoted);
     match res.and_then(|body| eval_body_using_ecx(&mut ecx, cid, body)) {
         Err(error) => {
@@ -330,8 +333,7 @@ pub fn eval_in_interpreter<'mir, 'tcx>(
         Ok(mplace) => {
             // Since evaluation had no errors, validate the resulting constant.
             // This is a separate `try` block to provide more targeted error reporting.
-            let validation =
+            let validation = const_validate_mplace(&ecx, &mplace, cid);
-                const_validate_mplace(&ecx, &mplace, is_static, cid.promoted.is_some());
 
             let alloc_id = mplace.ptr().provenance.unwrap().alloc_id();
 
@@ -350,22 +352,26 @@ pub fn eval_in_interpreter<'mir, 'tcx>(
 pub fn const_validate_mplace<'mir, 'tcx>(
     ecx: &InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>>,
     mplace: &MPlaceTy<'tcx>,
-    is_static: bool,
+    cid: GlobalId<'tcx>,
-    is_promoted: bool,
 ) -> InterpResult<'tcx> {
     let mut ref_tracking = RefTracking::new(mplace.clone());
     let mut inner = false;
     while let Some((mplace, path)) = ref_tracking.todo.pop() {
-        let mode = if is_static {
+        let mode = match ecx.tcx.static_mutability(cid.instance.def_id()) {
-            if is_promoted {
+            Some(_) if cid.promoted.is_some() => {
-                // Promoteds in statics are allowed to point to statics.
+                // Promoteds in statics are consts that re allowed to point to statics.
-                CtfeValidationMode::Const { inner, allow_static_ptrs: true }
+                CtfeValidationMode::Const {
-            } else {
+                    allow_immutable_unsafe_cell: false,
-                // a `static`
+                    allow_static_ptrs: true,
-                CtfeValidationMode::Regular
+                }
+            }
+            Some(mutbl) => CtfeValidationMode::Static { mutbl }, // a `static`
+            None => {
+                // In normal `const` (not promoted), the outermost allocation is always only copied,
+                // so having `UnsafeCell` in there is okay despite them being in immutable memory.
+                let allow_immutable_unsafe_cell = cid.promoted.is_none() && !inner;
+                CtfeValidationMode::Const { allow_immutable_unsafe_cell, allow_static_ptrs: false }
             }
-        } else {
-            CtfeValidationMode::Const { inner, allow_static_ptrs: false }
         };
         ecx.const_validate_operand(&mplace.into(), path, &mut ref_tracking, mode)?;
         inner = true;

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -723,7 +723,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
             && ty.is_freeze(*ecx.tcx, ecx.param_env)
         {
             let place = ecx.ref_to_mplace(val)?;
-            let new_place = place.map_provenance(|p| p.map(CtfeProvenance::as_immutable));
+            let new_place = place.map_provenance(CtfeProvenance::as_immutable);
             Ok(ImmTy::from_immediate(new_place.to_ref(ecx), val.layout))
         } else {
             Ok(val.clone())

compiler/rustc_const_eval/src/errors.rs

@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use rustc_errors::{
     DiagCtxt, DiagnosticArgValue, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee,
     IntoDiagnostic, Level,
@@ -13,12 +15,24 @@ use rustc_middle::ty::{self, Ty};
 use rustc_span::Span;
 use rustc_target::abi::call::AdjustForForeignAbiError;
 use rustc_target::abi::{Size, WrappingRange};
+use rustc_type_ir::Mutability;
+
+use crate::interpret::InternKind;
 
 #[derive(Diagnostic)]
 #[diag(const_eval_dangling_ptr_in_final)]
 pub(crate) struct DanglingPtrInFinal {
     #[primary_span]
     pub span: Span,
+    pub kind: InternKind,
+}
+
+#[derive(Diagnostic)]
+#[diag(const_eval_mutable_ptr_in_final)]
+pub(crate) struct MutablePtrInFinal {
+    #[primary_span]
+    pub span: Span,
+    pub kind: InternKind,
 }
 
 #[derive(Diagnostic)]
@@ -194,14 +208,6 @@ pub(crate) struct UnallowedInlineAsm {
     pub kind: ConstContext,
 }
 
-#[derive(Diagnostic)]
-#[diag(const_eval_unsupported_untyped_pointer)]
-#[note]
-pub(crate) struct UnsupportedUntypedPointer {
-    #[primary_span]
-    pub span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(const_eval_interior_mutable_data_refer, code = "E0492")]
 pub(crate) struct InteriorMutableDataRefer {
@@ -615,18 +621,16 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
             PtrToStatic { ptr_kind: PointerKind::Box } => const_eval_validation_box_to_static,
             PtrToStatic { ptr_kind: PointerKind::Ref } => const_eval_validation_ref_to_static,
 
-            PtrToMut { ptr_kind: PointerKind::Box } => const_eval_validation_box_to_mut,
-            PtrToMut { ptr_kind: PointerKind::Ref } => const_eval_validation_ref_to_mut,
-
             PointerAsInt { .. } => const_eval_validation_pointer_as_int,
             PartialPointer => const_eval_validation_partial_pointer,
             MutableRefInConst => const_eval_validation_mutable_ref_in_const,
+            MutableRefToImmutable => const_eval_validation_mutable_ref_to_immutable,
             NullFnPtr => const_eval_validation_null_fn_ptr,
             NeverVal => const_eval_validation_never_val,
             NullablePtrOutOfRange { .. } => const_eval_validation_nullable_ptr_out_of_range,
             PtrOutOfRange { .. } => const_eval_validation_ptr_out_of_range,
             OutOfRange { .. } => const_eval_validation_out_of_range,
-            UnsafeCell => const_eval_validation_unsafe_cell,
+            UnsafeCellInImmutable => const_eval_validation_unsafe_cell,
             UninhabitedVal { .. } => const_eval_validation_uninhabited_val,
             InvalidEnumTag { .. } => const_eval_validation_invalid_enum_tag,
             UninhabitedEnumVariant => const_eval_validation_uninhabited_enum_variant,
@@ -772,11 +776,11 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
             }
             NullPtr { .. }
             | PtrToStatic { .. }
-            | PtrToMut { .. }
             | MutableRefInConst
+            | MutableRefToImmutable
             | NullFnPtr
             | NeverVal
-            | UnsafeCell
+            | UnsafeCellInImmutable
             | InvalidMetaSliceTooLarge { .. }
             | InvalidMetaTooLarge { .. }
             | DanglingPtrUseAfterFree { .. }
@@ -905,3 +909,14 @@ impl ReportErrorExt for ResourceExhaustionInfo {
     }
     fn add_args<G: EmissionGuarantee>(self, _: &DiagCtxt, _: &mut DiagnosticBuilder<'_, G>) {}
 }
+
+impl rustc_errors::IntoDiagnosticArg for InternKind {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Borrowed(match self {
+            InternKind::Static(Mutability::Not) => "static",
+            InternKind::Static(Mutability::Mut) => "static_mut",
+            InternKind::Constant => "const",
+            InternKind::Promoted => "promoted",
+        }))
+    }
+}

compiler/rustc_const_eval/src/interpret/intern.rs

@@ -5,30 +5,24 @@
 //!
 //! In principle, this is not very complicated: we recursively walk the final value, follow all the
 //! pointers, and move all reachable allocations to the global `tcx` memory. The only complication
-//! is picking the right mutability for the allocations in a `static` initializer: we want to make
+//! is picking the right mutability: the outermost allocation generally has a clear mutability, but
-//! as many allocations as possible immutable so LLVM can put them into read-only memory. At the
+//! what about the other allocations it points to that have also been created with this value? We
-//! same time, we need to make memory that could be mutated by the program mutable to avoid
+//! don't want to do guesswork here. The rules are: `static`, `const`, and promoted can only create
-//! incorrect compilations. To achieve this, we do a type-based traversal of the final value,
+//! immutable allocations that way. `static mut` can be initialized with expressions like `&mut 42`,
-//! tracking mutable and shared references and `UnsafeCell` to determine the current mutability.
+//! so all inner allocations are marked mutable. Some of them could potentially be made immutable,
-//! (In principle, we could skip this type-based part for `const` and promoteds, as they need to be
+//! but that would require relying on type information, and given how many ways Rust has to lie
-//! always immutable. At least for `const` however we use this opportunity to reject any `const`
+//! about type information, we want to avoid doing that.
-//! that contains allocations whose mutability we cannot identify.)
 
-use super::validity::RefTracking;
+use rustc_ast::Mutability;
-use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_middle::mir::interpret::{CtfeProvenance, InterpResult};
-use rustc_middle::ty::{self, layout::TyAndLayout, Ty};
+use rustc_middle::ty::layout::TyAndLayout;
 
-use rustc_ast::Mutability;
+use super::{AllocId, Allocation, InterpCx, MPlaceTy, Machine, MemoryKind, PlaceTy};
-
-use super::{
-    AllocId, Allocation, InterpCx, MPlaceTy, Machine, MemoryKind, PlaceTy, Projectable,
-    ValueVisitor,
-};
 use crate::const_eval;
-use crate::errors::{DanglingPtrInFinal, UnsupportedUntypedPointer};
+use crate::errors::{DanglingPtrInFinal, MutablePtrInFinal};
 
 pub trait CompileTimeMachine<'mir, 'tcx: 'mir, T> = Machine<
         'mir,
@@ -41,271 +35,44 @@ pub trait CompileTimeMachine<'mir, 'tcx: 'mir, T> = Machine<
         MemoryMap = FxIndexMap<AllocId, (MemoryKind<T>, Allocation)>,
     >;
 
-struct InternVisitor<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx, const_eval::MemoryKind>> {
+/// Intern an allocation. Returns `Err` if the allocation does not exist in the local memory.
-    /// The ectx from which we intern.
+///
+/// `mutability` can be used to force immutable interning: if it is `Mutability::Not`, the
+/// allocation is interned immutably; if it is `Mutability::Mut`, then the allocation *must be*
+/// already mutable (as a sanity check).
+///
+/// `recursive_alloc` is called for all recursively encountered allocations.
+fn intern_shallow<'rt, 'mir, 'tcx, T, M: CompileTimeMachine<'mir, 'tcx, T>>(
     ecx: &'rt mut InterpCx<'mir, 'tcx, M>,
-    /// Previously encountered safe references.
-    ref_tracking: &'rt mut RefTracking<(MPlaceTy<'tcx>, InternMode)>,
-    /// A list of all encountered allocations. After type-based interning, we traverse this list to
-    /// also intern allocations that are only referenced by a raw pointer or inside a union.
-    leftover_allocations: &'rt mut FxIndexSet<AllocId>,
-    /// The root kind of the value that we're looking at. This field is never mutated for a
-    /// particular allocation. It is primarily used to make as many allocations as possible
-    /// read-only so LLVM can place them in const memory.
-    mode: InternMode,
-    /// This field stores whether we are *currently* inside an `UnsafeCell`. This can affect
-    /// the intern mode of references we encounter.
-    inside_unsafe_cell: bool,
-}
-
-#[derive(Copy, Clone, Debug, PartialEq, Hash, Eq)]
-enum InternMode {
-    /// A static and its current mutability. Below shared references inside a `static mut`,
-    /// this is *immutable*, and below mutable references inside an `UnsafeCell`, this
-    /// is *mutable*.
-    Static(hir::Mutability),
-    /// A `const`.
-    Const,
-}
-
-/// Signalling data structure to ensure we don't recurse
-/// into the memory of other constants or statics
-struct IsStaticOrFn;
-
-/// Intern an allocation without looking at its children.
-/// `mode` is the mode of the environment where we found this pointer.
-/// `mutability` is the mutability of the place to be interned; even if that says
-/// `immutable` things might become mutable if `ty` is not frozen.
-/// `ty` can be `None` if there is no potential interior mutability
-/// to account for (e.g. for vtables).
-fn intern_shallow<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx, const_eval::MemoryKind>>(
-    ecx: &'rt mut InterpCx<'mir, 'tcx, M>,
-    leftover_allocations: &'rt mut FxIndexSet<AllocId>,
     alloc_id: AllocId,
-    mode: InternMode,
+    mutability: Mutability,
-    ty: Option<Ty<'tcx>>,
+    mut recursive_alloc: impl FnMut(&InterpCx<'mir, 'tcx, M>, CtfeProvenance),
-) -> Option<IsStaticOrFn> {
+) -> Result<(), ()> {
-    trace!("intern_shallow {:?} with {:?}", alloc_id, mode);
+    trace!("intern_shallow {:?}", alloc_id);
     // remove allocation
-    let tcx = ecx.tcx;
+    let Some((_kind, mut alloc)) = ecx.memory.alloc_map.remove(&alloc_id) else {
-    let Some((kind, mut alloc)) = ecx.memory.alloc_map.remove(&alloc_id) else {
+        return Err(());
-        // Pointer not found in local memory map. It is either a pointer to the global
-        // map, or dangling.
-        // If the pointer is dangling (neither in local nor global memory), we leave it
-        // to validation to error -- it has the much better error messages, pointing out where
-        // in the value the dangling reference lies.
-        // The `span_delayed_bug` ensures that we don't forget such a check in validation.
-        if tcx.try_get_global_alloc(alloc_id).is_none() {
-            tcx.dcx().span_delayed_bug(ecx.tcx.span, "tried to intern dangling pointer");
-        }
-        // treat dangling pointers like other statics
-        // just to stop trying to recurse into them
-        return Some(IsStaticOrFn);
     };
-    // This match is just a canary for future changes to `MemoryKind`, which most likely need
-    // changes in this function.
-    match kind {
-        MemoryKind::Stack
-        | MemoryKind::Machine(const_eval::MemoryKind::Heap)
-        | MemoryKind::CallerLocation => {}
-    }
     // Set allocation mutability as appropriate. This is used by LLVM to put things into
     // read-only memory, and also by Miri when evaluating other globals that
     // access this one.
-    if let InternMode::Static(mutability) = mode {
+    match mutability {
-        // For this, we need to take into account `UnsafeCell`. When `ty` is `None`, we assume
-        // no interior mutability.
-        let frozen = ty.map_or(true, |ty| ty.is_freeze(*ecx.tcx, ecx.param_env));
-        // For statics, allocation mutability is the combination of place mutability and
-        // type mutability.
-        // The entire allocation needs to be mutable if it contains an `UnsafeCell` anywhere.
-        let immutable = mutability == Mutability::Not && frozen;
-        if immutable {
-            alloc.mutability = Mutability::Not;
-        } else {
-            // Just making sure we are not "upgrading" an immutable allocation to mutable.
-            assert_eq!(alloc.mutability, Mutability::Mut);
-        }
-    } else {
-        // No matter what, *constants are never mutable*. Mutating them is UB.
-        // See const_eval::machine::MemoryExtra::can_access_statics for why
-        // immutability is so important.
-
-        // Validation will ensure that there is no `UnsafeCell` on an immutable allocation.
-        alloc.mutability = Mutability::Not;
-    };
-    // link the alloc id to the actual allocation
-    leftover_allocations.extend(alloc.provenance().ptrs().iter().map(|&(_, prov)| prov.alloc_id()));
-    let alloc = tcx.mk_const_alloc(alloc);
-    tcx.set_alloc_id_memory(alloc_id, alloc);
-    None
-}
-
-impl<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx, const_eval::MemoryKind>>
-    InternVisitor<'rt, 'mir, 'tcx, M>
-{
-    fn intern_shallow(
-        &mut self,
-        alloc_id: AllocId,
-        mode: InternMode,
-        ty: Option<Ty<'tcx>>,
-    ) -> Option<IsStaticOrFn> {
-        intern_shallow(self.ecx, self.leftover_allocations, alloc_id, mode, ty)
-    }
-}
-
-impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx, const_eval::MemoryKind>>
-    ValueVisitor<'mir, 'tcx, M> for InternVisitor<'rt, 'mir, 'tcx, M>
-{
-    type V = MPlaceTy<'tcx>;
-
-    #[inline(always)]
-    fn ecx(&self) -> &InterpCx<'mir, 'tcx, M> {
-        self.ecx
-    }
-
-    fn visit_value(&mut self, mplace: &MPlaceTy<'tcx>) -> InterpResult<'tcx> {
-        // Handle Reference types, as these are the only types with provenance supported by const eval.
-        // Raw pointers (and boxes) are handled by the `leftover_allocations` logic.
-        let tcx = self.ecx.tcx;
-        let ty = mplace.layout.ty;
-        if let ty::Ref(_, referenced_ty, ref_mutability) = *ty.kind() {
-            let value = self.ecx.read_immediate(mplace)?;
-            let mplace = self.ecx.ref_to_mplace(&value)?;
-            assert_eq!(mplace.layout.ty, referenced_ty);
-            // Handle trait object vtables.
-            if let ty::Dynamic(_, _, ty::Dyn) =
-                tcx.struct_tail_erasing_lifetimes(referenced_ty, self.ecx.param_env).kind()
-            {
-                let ptr = mplace.meta().unwrap_meta().to_pointer(&tcx)?;
-                if let Some(prov) = ptr.provenance {
-                    // Explicitly choose const mode here, since vtables are immutable, even
-                    // if the reference of the fat pointer is mutable.
-                    self.intern_shallow(prov.alloc_id(), InternMode::Const, None);
-                } else {
-                    // Validation will error (with a better message) on an invalid vtable pointer.
-                    // Let validation show the error message, but make sure it *does* error.
-                    tcx.dcx()
-                        .span_delayed_bug(tcx.span, "vtables pointers cannot be integer pointers");
-                }
-            }
-            // Check if we have encountered this pointer+layout combination before.
-            // Only recurse for allocation-backed pointers.
-            if let Some(prov) = mplace.ptr().provenance {
-                // Compute the mode with which we intern this. Our goal here is to make as many
-                // statics as we can immutable so they can be placed in read-only memory by LLVM.
-                let ref_mode = match self.mode {
-                    InternMode::Static(mutbl) => {
-                        // In statics, merge outer mutability with reference mutability and
-                        // take into account whether we are in an `UnsafeCell`.
-
-                        // The only way a mutable reference actually works as a mutable reference is
-                        // by being in a `static mut` directly or behind another mutable reference.
-                        // If there's an immutable reference or we are inside a `static`, then our
-                        // mutable reference is equivalent to an immutable one. As an example:
-                        // `&&mut Foo` is semantically equivalent to `&&Foo`
-                        match ref_mutability {
-                            _ if self.inside_unsafe_cell => {
-                                // Inside an `UnsafeCell` is like inside a `static mut`, the "outer"
-                                // mutability does not matter.
-                                InternMode::Static(ref_mutability)
-                            }
         Mutability::Not => {
-                                // A shared reference, things become immutable.
+            alloc.mutability = Mutability::Not;
-                                // We do *not* consider `freeze` here: `intern_shallow` considers
-                                // `freeze` for the actual mutability of this allocation; the intern
-                                // mode for references contained in this allocation is tracked more
-                                // precisely when traversing the referenced data (by tracking
-                                // `UnsafeCell`). This makes sure that `&(&i32, &Cell<i32>)` still
-                                // has the left inner reference interned into a read-only
-                                // allocation.
-                                InternMode::Static(Mutability::Not)
         }
         Mutability::Mut => {
-                                // Mutable reference.
+            // This must be already mutable, we won't "un-freeze" allocations ever.
-                                InternMode::Static(mutbl)
+            assert_eq!(alloc.mutability, Mutability::Mut);
         }
     }
+    // record child allocations
+    for &(_, prov) in alloc.provenance().ptrs().iter() {
+        recursive_alloc(ecx, prov);
     }
-                    InternMode::Const => {
+    // link the alloc id to the actual allocation
-                        // Ignore `UnsafeCell`, everything is immutable. Validity does some sanity
+    let alloc = ecx.tcx.mk_const_alloc(alloc);
-                        // checking for mutable references that we encounter -- they must all be
+    ecx.tcx.set_alloc_id_memory(alloc_id, alloc);
-                        // ZST.
-                        InternMode::Const
-                    }
-                };
-                match self.intern_shallow(prov.alloc_id(), ref_mode, Some(referenced_ty)) {
-                    // No need to recurse, these are interned already and statics may have
-                    // cycles, so we don't want to recurse there
-                    Some(IsStaticOrFn) => {}
-                    // intern everything referenced by this value. The mutability is taken from the
-                    // reference. It is checked above that mutable references only happen in
-                    // `static mut`
-                    None => self.ref_tracking.track((mplace, ref_mode), || ()),
-                }
-            }
     Ok(())
-        } else {
-            // Not a reference. Check if we want to recurse.
-            let is_walk_needed = |mplace: &MPlaceTy<'tcx>| -> InterpResult<'tcx, bool> {
-                // ZSTs cannot contain pointers, we can avoid the interning walk.
-                if mplace.layout.is_zst() {
-                    return Ok(false);
-                }
-
-                // Now, check whether this allocation could contain references.
-                //
-                // Note, this check may sometimes not be cheap, so we only do it when the walk we'd like
-                // to avoid could be expensive: on the potentially larger types, arrays and slices,
-                // rather than on all aggregates unconditionally.
-                if matches!(mplace.layout.ty.kind(), ty::Array(..) | ty::Slice(..)) {
-                    let Some((size, _align)) = self.ecx.size_and_align_of_mplace(mplace)? else {
-                        // We do the walk if we can't determine the size of the mplace: we may be
-                        // dealing with extern types here in the future.
-                        return Ok(true);
-                    };
-
-                    // If there is no provenance in this allocation, it does not contain references
-                    // that point to another allocation, and we can avoid the interning walk.
-                    if let Some(alloc) = self.ecx.get_ptr_alloc(mplace.ptr(), size)? {
-                        if !alloc.has_provenance() {
-                            return Ok(false);
-                        }
-                    } else {
-                        // We're encountering a ZST here, and can avoid the walk as well.
-                        return Ok(false);
-                    }
-                }
-
-                // In the general case, we do the walk.
-                Ok(true)
-            };
-
-            // If this allocation contains no references to intern, we avoid the potentially costly
-            // walk.
-            //
-            // We can do this before the checks for interior mutability below, because only references
-            // are relevant in that situation, and we're checking if there are any here.
-            if !is_walk_needed(mplace)? {
-                return Ok(());
-            }
-
-            if let Some(def) = mplace.layout.ty.ty_adt_def() {
-                if def.is_unsafe_cell() {
-                    // We are crossing over an `UnsafeCell`, we can mutate again. This means that
-                    // References we encounter inside here are interned as pointing to mutable
-                    // allocations.
-                    // Remember the `old` value to handle nested `UnsafeCell`.
-                    let old = std::mem::replace(&mut self.inside_unsafe_cell, true);
-                    let walked = self.walk_value(mplace);
-                    self.inside_unsafe_cell = old;
-                    return walked;
-                }
-            }
-
-            self.walk_value(mplace)
-        }
-    }
 }
 
 /// How a constant value should be interned.
@@ -332,122 +99,105 @@ pub fn intern_const_alloc_recursive<
     intern_kind: InternKind,
     ret: &MPlaceTy<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
-    let tcx = ecx.tcx;
+    // We are interning recursively, and for mutability we are distinguishing the "root" allocation
-    let base_intern_mode = match intern_kind {
+    // that we are starting in, and all other allocations that we are encountering recursively.
-        InternKind::Static(mutbl) => InternMode::Static(mutbl),
+    let (base_mutability, inner_mutability) = match intern_kind {
-        // `Constant` includes array lengths.
+        InternKind::Constant | InternKind::Promoted => {
-        InternKind::Constant | InternKind::Promoted => InternMode::Const,
+            // Completely immutable. Interning anything mutably here can only lead to unsoundness,
+            // since all consts are conceptually independent values but share the same underlying
+            // memory.
+            (Mutability::Not, Mutability::Not)
+        }
+        InternKind::Static(Mutability::Not) => {
+            (
+                // Outermost allocation is mutable if `!Freeze`.
+                if ret.layout.ty.is_freeze(*ecx.tcx, ecx.param_env) {
+                    Mutability::Not
+                } else {
+                    Mutability::Mut
+                },
+                // Inner allocations are never mutable. They can only arise via the "tail
+                // expression" / "outer scope" rule, and we treat them consistently with `const`.
+                Mutability::Not,
+            )
+        }
+        InternKind::Static(Mutability::Mut) => {
+            // Just make everything mutable. We accept code like
+            // `static mut X = &mut [42]`, so even inner allocations need to be mutable.
+            (Mutability::Mut, Mutability::Mut)
+        }
     };
 
-    // Type based interning.
+    // Initialize recursive interning.
-    // `ref_tracking` tracks typed references we have already interned and still need to crawl for
+    let base_alloc_id = ret.ptr().provenance.unwrap().alloc_id();
-    // more typed information inside them.
+    let mut todo = vec![(base_alloc_id, base_mutability)];
-    // `leftover_allocations` collects *all* allocations we see, because some might not
+    // We need to distinguish "has just been interned" from "was already in `tcx`",
-    // be available in a typed way. They get interned at the end.
+    // so we track this in a separate set.
-    let mut ref_tracking = RefTracking::empty();
+    let mut just_interned = FxHashSet::default();
-    let leftover_allocations = &mut FxIndexSet::default();
+    // Whether we encountered a bad mutable pointer.
+    // We want to first report "dangling" and then "mutable", so we need to delay reporting these
+    // errors.
+    let mut found_bad_mutable_pointer = false;
 
-    // start with the outermost allocation
+    // Keep interning as long as there are things to intern.
-    intern_shallow(
+    // We show errors if there are dangling pointers, or mutable pointers in immutable contexts
-        ecx,
+    // (i.e., everything except for `static mut`). When these errors affect references, it is
-        leftover_allocations,
+    // unfortunate that we show these errors here and not during validation, since validation can
-        // The outermost allocation must exist, because we allocated it with
+    // show much nicer errors. However, we do need these checks to be run on all pointers, including
-        // `Memory::allocate`.
+    // raw pointers, so we cannot rely on validation to catch them -- and since interning runs
-        ret.ptr().provenance.unwrap().alloc_id(),
+    // before validation, and interning doesn't know the type of anything, this means we can't show
-        base_intern_mode,
+    // better errors. Maybe we should consider doing validation before interning in the future.
-        Some(ret.layout.ty),
+    while let Some((alloc_id, mutability)) = todo.pop() {
-    );
+        if ecx.tcx.try_get_global_alloc(alloc_id).is_some() {
-
+            // Already interned.
-    ref_tracking.track((ret.clone(), base_intern_mode), || ());
+            debug_assert!(!ecx.memory.alloc_map.contains_key(&alloc_id));
-
+            continue;
-    while let Some(((mplace, mode), _)) = ref_tracking.todo.pop() {
-        let res = InternVisitor {
-            ref_tracking: &mut ref_tracking,
-            ecx,
-            mode,
-            leftover_allocations,
-            inside_unsafe_cell: false,
         }
-        .visit_value(&mplace);
+        just_interned.insert(alloc_id);
-        // We deliberately *ignore* interpreter errors here. When there is a problem, the remaining
+        intern_shallow(ecx, alloc_id, mutability, |ecx, prov| {
-        // references are "leftover"-interned, and later validation will show a proper error
-        // and point at the right part of the value causing the problem.
-        match res {
-            Ok(()) => {}
-            Err(error) => {
-                ecx.tcx.dcx().span_delayed_bug(
-                    ecx.tcx.span,
-                    format!(
-                        "error during interning should later cause validation failure: {}",
-                        ecx.format_error(error),
-                    ),
-                );
-            }
-        }
-    }
-
-    // Intern the rest of the allocations as mutable. These might be inside unions, padding, raw
-    // pointers, ... So we can't intern them according to their type rules
-
-    let mut todo: Vec<_> = leftover_allocations.iter().cloned().collect();
-    debug!(?todo);
-    debug!("dead_alloc_map: {:#?}", ecx.memory.dead_alloc_map);
-    while let Some(alloc_id) = todo.pop() {
-        if let Some((_, mut alloc)) = ecx.memory.alloc_map.remove(&alloc_id) {
-            // We can't call the `intern_shallow` method here, as its logic is tailored to safe
-            // references and a `leftover_allocations` set (where we only have a todo-list here).
-            // So we hand-roll the interning logic here again.
-            match intern_kind {
-                // Statics may point to mutable allocations.
-                // Even for immutable statics it would be ok to have mutable allocations behind
-                // raw pointers, e.g. for `static FOO: *const AtomicUsize = &AtomicUsize::new(42)`.
-                InternKind::Static(_) => {}
-                // Raw pointers in promoteds may only point to immutable things so we mark
-                // everything as immutable.
-                // It is UB to mutate through a raw pointer obtained via an immutable reference:
-                // Since all references and pointers inside a promoted must by their very definition
-                // be created from an immutable reference (and promotion also excludes interior
-                // mutability), mutating through them would be UB.
-                // There's no way we can check whether the user is using raw pointers correctly,
-                // so all we can do is mark this as immutable here.
-                InternKind::Promoted => {
-                    // See const_eval::machine::MemoryExtra::can_access_statics for why
-                    // immutability is so important.
-                    alloc.mutability = Mutability::Not;
-                }
-                // If it's a constant, we should not have any "leftovers" as everything
-                // is tracked by const-checking.
-                // FIXME: downgrade this to a warning? It rejects some legitimate consts,
-                // such as `const CONST_RAW: *const Vec<i32> = &Vec::new() as *const _;`.
-                //
-                // NOTE: it looks likes this code path is only reachable when we try to intern
-                // something that cannot be promoted, which in constants means values that have
-                // drop glue, such as the example above.
-                InternKind::Constant => {
-                    ecx.tcx.dcx().emit_err(UnsupportedUntypedPointer { span: ecx.tcx.span });
-                    // For better errors later, mark the allocation as immutable.
-                    alloc.mutability = Mutability::Not;
-                }
-            }
-            let alloc = tcx.mk_const_alloc(alloc);
-            tcx.set_alloc_id_memory(alloc_id, alloc);
-            for &(_, prov) in alloc.inner().provenance().ptrs().iter() {
             let alloc_id = prov.alloc_id();
-                if leftover_allocations.insert(alloc_id) {
+            if intern_kind != InternKind::Promoted
-                    todo.push(alloc_id);
+                && inner_mutability == Mutability::Not
+                && !prov.immutable()
+            {
+                if ecx.tcx.try_get_global_alloc(alloc_id).is_some()
+                    && !just_interned.contains(&alloc_id)
+                {
+                    // This is a pointer to some memory from another constant. We encounter mutable
+                    // pointers to such memory since we do not always track immutability through
+                    // these "global" pointers. Allowing them is harmless; the point of these checks
+                    // during interning is to justify why we intern the *new* allocations immutably,
+                    // so we can completely ignore existing allocations. We also don't need to add
+                    // this to the todo list, since after all it is already interned.
+                    return;
                 }
+                // Found a mutable pointer inside a const where inner allocations should be
+                // immutable. We exclude promoteds from this, since things like `&mut []` and
+                // `&None::<Cell<i32>>` lead to promotion that can produce mutable pointers. We rely
+                // on the promotion analysis not screwing up to ensure that it is sound to intern
+                // promoteds as immutable.
+                found_bad_mutable_pointer = true;
             }
-        } else if ecx.memory.dead_alloc_map.contains_key(&alloc_id) {
+            // It is tempting to intern as immutable if `prov.immutable()`. However, there
-            // Codegen does not like dangling pointers, and generally `tcx` assumes that
+            // might be multiple pointers to the same allocation, and if *at least one* of
-            // all allocations referenced anywhere actually exist. So, make sure we error here.
+            // them is mutable, the allocation must be interned mutably. We will intern the
-            let reported = ecx.tcx.dcx().emit_err(DanglingPtrInFinal { span: ecx.tcx.span });
+            // allocation when we encounter the first pointer. Therefore we always intern
-            return Err(reported);
+            // with `inner_mutability`, and furthermore we ensured above that if that is
-        } else if ecx.tcx.try_get_global_alloc(alloc_id).is_none() {
+            // "immutable", then there are *no* mutable pointers anywhere in the newly
-            // We have hit an `AllocId` that is neither in local or global memory and isn't
+            // interned memory.
-            // marked as dangling by local memory. That should be impossible.
+            todo.push((alloc_id, inner_mutability));
-            span_bug!(ecx.tcx.span, "encountered unknown alloc id {:?}", alloc_id);
+        })
+        .map_err(|()| {
+            ecx.tcx.dcx().emit_err(DanglingPtrInFinal { span: ecx.tcx.span, kind: intern_kind })
+        })?;
     }
+    if found_bad_mutable_pointer {
+        return Err(ecx
+            .tcx
+            .dcx()
+            .emit_err(MutablePtrInFinal { span: ecx.tcx.span, kind: intern_kind }));
     }
+
     Ok(())
 }
 
@@ -462,29 +212,18 @@ pub fn intern_const_alloc_for_constprop<
     ecx: &mut InterpCx<'mir, 'tcx, M>,
     alloc_id: AllocId,
 ) -> InterpResult<'tcx, ()> {
-    // Move allocation to `tcx`.
+    if ecx.tcx.try_get_global_alloc(alloc_id).is_some() {
-    let Some((_, mut alloc)) = ecx.memory.alloc_map.remove(&alloc_id) else {
-        // Pointer not found in local memory map. It is either a pointer to the global
-        // map, or dangling.
-        if ecx.tcx.try_get_global_alloc(alloc_id).is_none() {
-            throw_ub!(DeadLocal)
-        }
         // The constant is already in global memory. Do nothing.
         return Ok(());
-    };
+    }
-
+    // Move allocation to `tcx`.
-    alloc.mutability = Mutability::Not;
+    intern_shallow(ecx, alloc_id, Mutability::Not, |_ecx, _| {
-
         // We are not doing recursive interning, so we don't currently support provenance.
         // (If this assertion ever triggers, we should just implement a
-    // proper recursive interning loop.)
+        // proper recursive interning loop -- or just call `intern_const_alloc_recursive`.
-    assert!(alloc.provenance().ptrs().is_empty());
+        panic!("`intern_const_alloc_for_constprop` called on allocation with nested provenance")
-
+    })
-    // Link the alloc id to the actual allocation
+    .map_err(|()| err_ub!(DeadLocal).into())
-    let alloc = ecx.tcx.mk_const_alloc(alloc);
-    ecx.tcx.set_alloc_id_memory(alloc_id, alloc);
-
-    Ok(())
 }
 
 impl<'mir, 'tcx: 'mir, M: super::intern::CompileTimeMachine<'mir, 'tcx, !>>
@@ -504,12 +243,16 @@ impl<'mir, 'tcx: 'mir, M: super::intern::CompileTimeMachine<'mir, 'tcx, !>>
         // `allocate` picks a fresh AllocId that we will associate with its data below.
         let dest = self.allocate(layout, MemoryKind::Stack)?;
         f(self, &dest.clone().into())?;
-        let mut alloc =
-            self.memory.alloc_map.remove(&dest.ptr().provenance.unwrap().alloc_id()).unwrap().1;
-        alloc.mutability = Mutability::Not;
-        let alloc = self.tcx.mk_const_alloc(alloc);
         let alloc_id = dest.ptr().provenance.unwrap().alloc_id(); // this was just allocated, it must have provenance
-        self.tcx.set_alloc_id_memory(alloc_id, alloc);
+        intern_shallow(self, alloc_id, Mutability::Not, |ecx, prov| {
+            // We are not doing recursive interning, so we don't currently support provenance.
+            // (If this assertion ever triggers, we should just implement a
+            // proper recursive interning loop -- or just call `intern_const_alloc_recursive`.
+            if !ecx.tcx.try_get_global_alloc(prov.alloc_id()).is_some() {
+                panic!("`intern_with_temp_alloc` with nested allocations");
+            }
+        })
+        .unwrap();
         Ok(alloc_id)
     }
 }

compiler/rustc_const_eval/src/interpret/place.rs

@@ -62,8 +62,8 @@ pub(super) struct MemPlace<Prov: Provenance = CtfeProvenance> {
 
 impl<Prov: Provenance> MemPlace<Prov> {
     /// Adjust the provenance of the main pointer (metadata is unaffected).
-    pub fn map_provenance(self, f: impl FnOnce(Option<Prov>) -> Option<Prov>) -> Self {
+    pub fn map_provenance(self, f: impl FnOnce(Prov) -> Prov) -> Self {
-        MemPlace { ptr: self.ptr.map_provenance(f), ..self }
+        MemPlace { ptr: self.ptr.map_provenance(|p| p.map(f)), ..self }
     }
 
     /// Turn a mplace into a (thin or wide) pointer, as a reference, pointing to the same space.
@@ -128,7 +128,7 @@ impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
     }
 
     /// Adjust the provenance of the main pointer (metadata is unaffected).
-    pub fn map_provenance(self, f: impl FnOnce(Option<Prov>) -> Option<Prov>) -> Self {
+    pub fn map_provenance(self, f: impl FnOnce(Prov) -> Prov) -> Self {
         MPlaceTy { mplace: self.mplace.map_provenance(f), ..self }
     }
 

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -9,12 +9,13 @@ use std::num::NonZeroUsize;
 
 use either::{Left, Right};
 
+use hir::def::DefKind;
 use rustc_ast::Mutability;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
 use rustc_middle::mir::interpret::{
-    ExpectedKind, InterpError, InvalidMetaKind, Misalignment, PointerKind, ValidationErrorInfo,
+    ExpectedKind, InterpError, InvalidMetaKind, Misalignment, PointerKind, Provenance,
-    ValidationErrorKind, ValidationErrorKind::*,
+    ValidationErrorInfo, ValidationErrorKind, ValidationErrorKind::*,
 };
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
@@ -123,15 +124,41 @@ pub enum PathElem {
 }
 
 /// Extra things to check for during validation of CTFE results.
+#[derive(Copy, Clone)]
 pub enum CtfeValidationMode {
-    /// Regular validation, nothing special happening.
+    /// Validation of a `static`
-    Regular,
+    Static { mutbl: Mutability },
-    /// Validation of a `const`.
+    /// Validation of a `const` (including promoteds).
-    /// `inner` says if this is an inner, indirect allocation (as opposed to the top-level const
+    /// `allow_immutable_unsafe_cell` says whether we allow `UnsafeCell` in immutable memory (which is the
-    /// allocation). Being an inner allocation makes a difference because the top-level allocation
+    /// case for the top-level allocation of a `const`, where this is fine because the allocation will be
-    /// of a `const` is copied for each use, but the inner allocations are implicitly shared.
+    /// copied at each use site).
     /// `allow_static_ptrs` says if pointers to statics are permitted (which is the case for promoteds in statics).
-    Const { inner: bool, allow_static_ptrs: bool },
+    Const { allow_immutable_unsafe_cell: bool, allow_static_ptrs: bool },
+}
+
+impl CtfeValidationMode {
+    fn allow_immutable_unsafe_cell(self) -> bool {
+        match self {
+            CtfeValidationMode::Static { .. } => false,
+            CtfeValidationMode::Const { allow_immutable_unsafe_cell, .. } => {
+                allow_immutable_unsafe_cell
+            }
+        }
+    }
+
+    fn allow_static_ptrs(self) -> bool {
+        match self {
+            CtfeValidationMode::Static { .. } => true, // statics can point to statics
+            CtfeValidationMode::Const { allow_static_ptrs, .. } => allow_static_ptrs,
+        }
+    }
+
+    fn may_contain_mutable_ref(self) -> bool {
+        match self {
+            CtfeValidationMode::Static { mutbl } => mutbl == Mutability::Mut,
+            CtfeValidationMode::Const { .. } => false,
+        }
+    }
 }
 
 /// State for tracking recursive validation of references
@@ -418,6 +445,22 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
         }
         // Recursive checking
         if let Some(ref_tracking) = self.ref_tracking.as_deref_mut() {
+            // Determine whether this pointer expects to be pointing to something mutable.
+            let ptr_expected_mutbl = match ptr_kind {
+                PointerKind::Box => Mutability::Mut,
+                PointerKind::Ref => {
+                    let tam = value.layout.ty.builtin_deref(false).unwrap();
+                    // ZST never require mutability. We do not take into account interior mutability
+                    // here since we cannot know if there really is an `UnsafeCell` inside
+                    // `Option<UnsafeCell>` -- so we check that in the recursive descent behind this
+                    // reference.
+                    if size == Size::ZERO || tam.mutbl == Mutability::Not {
+                        Mutability::Not
+                    } else {
+                        Mutability::Mut
+                    }
+                }
+            };
             // Proceed recursively even for ZST, no reason to skip them!
             // `!` is a ZST and we want to validate it.
             if let Ok((alloc_id, _offset, _prov)) = self.ecx.ptr_try_get_alloc_id(place.ptr()) {
@@ -428,16 +471,29 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                         // Special handling for pointers to statics (irrespective of their type).
                         assert!(!self.ecx.tcx.is_thread_local_static(did));
                         assert!(self.ecx.tcx.is_static(did));
-                        if matches!(
+                        if self.ctfe_mode.is_some_and(|c| !c.allow_static_ptrs()) {
-                            self.ctfe_mode,
-                            Some(CtfeValidationMode::Const { allow_static_ptrs: false, .. })
-                        ) {
                             // See const_eval::machine::MemoryExtra::can_access_statics for why
                             // this check is so important.
                             // This check is reachable when the const just referenced the static,
                             // but never read it (so we never entered `before_access_global`).
                             throw_validation_failure!(self.path, PtrToStatic { ptr_kind });
                         }
+                        // Mutability check.
+                        if ptr_expected_mutbl == Mutability::Mut {
+                            if matches!(
+                                self.ecx.tcx.def_kind(did),
+                                DefKind::Static(Mutability::Not)
+                            ) && self
+                                .ecx
+                                .tcx
+                                .type_of(did)
+                                .no_bound_vars()
+                                .expect("statics should not have generic parameters")
+                                .is_freeze(*self.ecx.tcx, ty::ParamEnv::reveal_all())
+                            {
+                                throw_validation_failure!(self.path, MutableRefToImmutable);
+                            }
+                        }
                         // We skip recursively checking other statics. These statics must be sound by
                         // themselves, and the only way to get broken statics here is by using
                         // unsafe code.
@@ -454,14 +510,29 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                         if alloc.inner().mutability == Mutability::Mut
                             && matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
                         {
-                            // This should be unreachable, but if someone manages to copy a pointer
+                            // This is impossible: this can only be some inner allocation of a
-                            // out of a `static`, then that pointer might point to mutable memory,
+                            // `static mut` (everything else either hits the `GlobalAlloc::Static`
-                            // and we would catch that here.
+                            // case or is interned immutably). To get such a pointer we'd have to
-                            throw_validation_failure!(self.path, PtrToMut { ptr_kind });
+                            // load it from a static, but such loads lead to a CTFE error.
+                            span_bug!(
+                                self.ecx.tcx.span,
+                                "encountered reference to mutable memory inside a `const`"
+                            );
+                        }
+                        if ptr_expected_mutbl == Mutability::Mut
+                            && alloc.inner().mutability == Mutability::Not
+                        {
+                            throw_validation_failure!(self.path, MutableRefToImmutable);
                         }
                     }
-                    // Nothing to check for these.
+                    Some(GlobalAlloc::Function(..) | GlobalAlloc::VTable(..)) => {
-                    None | Some(GlobalAlloc::Function(..) | GlobalAlloc::VTable(..)) => {}
+                        // These are immutable, we better don't allow mutable pointers here.
+                        if ptr_expected_mutbl == Mutability::Mut {
+                            throw_validation_failure!(self.path, MutableRefToImmutable);
+                        }
+                    }
+                    // Dangling, already handled.
+                    None => bug!(),
                 }
             }
             let path = &self.path;
@@ -532,11 +603,9 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 Ok(true)
             }
             ty::Ref(_, ty, mutbl) => {
-                if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
+                if self.ctfe_mode.is_some_and(|c| !c.may_contain_mutable_ref())
                     && *mutbl == Mutability::Mut
                 {
-                    // A mutable reference inside a const? That does not seem right (except if it is
-                    // a ZST).
                     let layout = self.ecx.layout_of(*ty)?;
                     if !layout.is_zst() {
                         throw_validation_failure!(self.path, MutableRefInConst);
@@ -642,6 +711,19 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
             )
         }
     }
+
+    fn in_mutable_memory(&self, op: &OpTy<'tcx, M::Provenance>) -> bool {
+        if let Some(mplace) = op.as_mplace_or_imm().left() {
+            if let Some(alloc_id) = mplace.ptr().provenance.and_then(|p| p.get_alloc_id()) {
+                if self.ecx.tcx.global_alloc(alloc_id).unwrap_memory().inner().mutability
+                    == Mutability::Mut
+                {
+                    return true;
+                }
+            }
+        }
+        false
+    }
 }
 
 impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
@@ -705,10 +787,12 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
         op: &OpTy<'tcx, M::Provenance>,
         _fields: NonZeroUsize,
     ) -> InterpResult<'tcx> {
-        // Special check preventing `UnsafeCell` inside unions in the inner part of constants.
+        // Special check for CTFE validation, preventing `UnsafeCell` inside unions in immutable memory.
-        if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. })) {
+        if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
-            if !op.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.param_env) {
+            if !op.layout.is_zst() && !op.layout.ty.is_freeze(*self.ecx.tcx, self.ecx.param_env) {
-                throw_validation_failure!(self.path, UnsafeCell);
+                if !self.in_mutable_memory(op) {
+                    throw_validation_failure!(self.path, UnsafeCellInImmutable);
+                }
             }
         }
         Ok(())
@@ -730,11 +814,14 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
         }
 
         // Special check preventing `UnsafeCell` in the inner part of constants
-        if let Some(def) = op.layout.ty.ty_adt_def() {
+        if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {
-            if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. }))
+            if !op.layout.is_zst()
+                && let Some(def) = op.layout.ty.ty_adt_def()
                 && def.is_unsafe_cell()
             {
-                throw_validation_failure!(self.path, UnsafeCell);
+                if !self.in_mutable_memory(op) {
+                    throw_validation_failure!(self.path, UnsafeCellInImmutable);
+                }
             }
         }
 

compiler/rustc_const_eval/src/util/caller_location.rs

@@ -27,6 +27,7 @@ fn alloc_caller_location<'mir, 'tcx>(
         // See https://github.com/rust-lang/rust/pull/89920#discussion_r730012398
         ecx.allocate_str("<redacted>", MemoryKind::CallerLocation, Mutability::Not).unwrap()
     };
+    let file = file.map_provenance(CtfeProvenance::as_immutable);
     let line = if loc_details.line { Scalar::from_u32(line) } else { Scalar::from_u32(0) };
     let col = if loc_details.column { Scalar::from_u32(col) } else { Scalar::from_u32(0) };
 

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -416,14 +416,14 @@ pub enum ValidationErrorKind<'tcx> {
     PartialPointer,
     PtrToUninhabited { ptr_kind: PointerKind, ty: Ty<'tcx> },
     PtrToStatic { ptr_kind: PointerKind },
-    PtrToMut { ptr_kind: PointerKind },
     MutableRefInConst,
+    MutableRefToImmutable,
+    UnsafeCellInImmutable,
     NullFnPtr,
     NeverVal,
     NullablePtrOutOfRange { range: WrappingRange, max_value: u128 },
     PtrOutOfRange { range: WrappingRange, max_value: u128 },
     OutOfRange { value: String, range: WrappingRange, max_value: u128 },
-    UnsafeCell,
     UninhabitedVal { ty: Ty<'tcx> },
     InvalidEnumTag { value: String },
     UninhabitedEnumVariant,

compiler/rustc_middle/src/mir/interpret/pointer.rs

@@ -277,6 +277,12 @@ impl From<AllocId> for Pointer {
         Pointer::new(alloc_id.into(), Size::ZERO)
     }
 }
+impl From<CtfeProvenance> for Pointer {
+    #[inline(always)]
+    fn from(prov: CtfeProvenance) -> Self {
+        Pointer::new(prov, Size::ZERO)
+    }
+}
 
 impl<Prov> From<Pointer<Prov>> for Pointer<Option<Prov>> {
     #[inline(always)]

src/tools/miri/src/borrow_tracker/stacked_borrows/mod.rs

@@ -830,7 +830,9 @@ trait EvalContextPrivExt<'mir: 'ecx, 'tcx: 'mir, 'ecx>: crate::MiriInterpCxExt<'
         let new_prov = this.sb_reborrow(place, size, new_perm, new_tag, info)?;
 
         // Adjust place.
-        Ok(place.clone().map_provenance(|_| new_prov))
+        // (If the closure gets called, that means the old provenance was `Some`, and hence the new
+        // one must also be `Some`.)
+        Ok(place.clone().map_provenance(|_| new_prov.unwrap()))
     }
 
     /// Retags an individual pointer, returning the retagged version.

src/tools/miri/src/borrow_tracker/tree_borrows/mod.rs

@@ -351,7 +351,9 @@ trait EvalContextPrivExt<'mir: 'ecx, 'tcx: 'mir, 'ecx>: crate::MiriInterpCxExt<'
         let new_prov = this.tb_reborrow(place, reborrow_size, new_perm, new_tag)?;
 
         // Adjust place.
-        Ok(place.clone().map_provenance(|_| new_prov))
+        // (If the closure gets called, that means the old provenance was `Some`, and hence the new
+        // one must also be `Some`.)
+        Ok(place.clone().map_provenance(|_| new_prov.unwrap()))
     }
 
     /// Retags an individual pointer, returning the retagged version.

tests/ui/consts/const-eval/heap/alloc_intrinsic_nontransient.rs

@@ -5,6 +5,7 @@
 use std::intrinsics;
 
 const FOO: &i32 = foo();
+const FOO_RAW: *const i32 = foo();
 
 const fn foo() -> &'static i32 {
     let t = unsafe {
@@ -15,5 +16,6 @@ const fn foo() -> &'static i32 {
     unsafe { &*t }
 }
 fn main() {
-    assert_eq!(*FOO, 20)
+    assert_eq!(*FOO, 20);
+    assert_eq!(unsafe { *FOO_RAW }, 20);
 }

tests/ui/consts/const-eval/heap/alloc_intrinsic_nontransient_fail.rs

@@ -1,18 +0,0 @@
-#![feature(core_intrinsics)]
-#![feature(const_heap)]
-#![feature(const_mut_refs)]
-use std::intrinsics;
-
-const FOO: *const i32 = foo();
-//~^ ERROR unsupported untyped pointer in constant
-
-const fn foo() -> &'static i32 {
-    let t = unsafe {
-        let i = intrinsics::const_allocate(4, 4) as *mut i32;
-        *i = 20;
-        i
-    };
-    unsafe { &*t }
-}
-fn main() {
-}

tests/ui/consts/const-eval/heap/alloc_intrinsic_nontransient_fail.stderr

@@ -1,10 +0,0 @@
-error: unsupported untyped pointer in constant
-  --> $DIR/alloc_intrinsic_nontransient_fail.rs:6:1
-   |
-LL | const FOO: *const i32 = foo();
-   | ^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: memory only reachable via raw pointers is not supported
-
-error: aborting due to 1 previous error
-

tests/ui/consts/const-eval/heap/alloc_intrinsic_untyped.rs

@@ -4,6 +4,6 @@
 use std::intrinsics;
 
 const BAR: *mut i32 = unsafe { intrinsics::const_allocate(4, 4) as *mut i32 };
-//~^ error: unsupported untyped pointer in constant
+//~^ error: mutable pointer in final value of constant
 
 fn main() {}

tests/ui/consts/const-eval/heap/alloc_intrinsic_untyped.stderr

@@ -1,10 +1,8 @@
-error: unsupported untyped pointer in constant
+error: encountered mutable pointer in final value of constant
   --> $DIR/alloc_intrinsic_untyped.rs:6:1
    |
 LL | const BAR: *mut i32 = unsafe { intrinsics::const_allocate(4, 4) as *mut i32 };
    | ^^^^^^^^^^^^^^^^^^^
-   |
-   = note: memory only reachable via raw pointers is not supported
 
 error: aborting due to 1 previous error
 

tests/ui/consts/const-eval/heap/dealloc_intrinsic_dangling.rs

@@ -5,7 +5,7 @@
 use std::intrinsics;
 
 const _X: &'static u8 = unsafe {
-    //~^ error: dangling pointer in final constant
+    //~^ error: dangling pointer in final value of constant
     let ptr = intrinsics::const_allocate(4, 4);
     intrinsics::const_deallocate(ptr, 4, 4);
     &*ptr

tests/ui/consts/const-eval/heap/dealloc_intrinsic_dangling.stderr

@@ -1,4 +1,4 @@
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
   --> $DIR/dealloc_intrinsic_dangling.rs:7:1
    |
 LL | const _X: &'static u8 = unsafe {

tests/ui/consts/const-mut-refs/mut_ref_in_final.rs

@@ -44,6 +44,21 @@ static mut FOO3: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
 // the enclosing scope rule.
 const BAR: NotAMutex<&i32> = NotAMutex(UnsafeCell::new(&42));
 
+struct SyncPtr<T> { x : *const T }
+unsafe impl<T> Sync for SyncPtr<T> {}
+
+// These pass the lifetime checks because of the "tail expression" / "outer scope" rule.
+// (This relies on `SyncPtr` being a curly brace struct.)
+// However, we intern the inner memory as read-only, so this must be rejected.
+static RAW_MUT_CAST_S: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+//~^ ERROR mutable references are not allowed
+static RAW_MUT_COERCE_S: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+//~^ ERROR mutable references are not allowed
+const RAW_MUT_CAST_C: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+//~^ ERROR mutable references are not allowed
+const RAW_MUT_COERCE_C: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+//~^ ERROR mutable references are not allowed
+
 fn main() {
     println!("{}", unsafe { *A });
     unsafe { *B = 4 } // Bad news

tests/ui/consts/const-mut-refs/mut_ref_in_final.stderr

@@ -54,7 +54,31 @@ LL | static mut FOO3: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
    |                                        |                              creates a temporary value which is freed while still in use
    |                                        using this value as a static requires that borrow lasts for `'static`
 
-error: aborting due to 6 previous errors
+error[E0764]: mutable references are not allowed in the final value of statics
+  --> $DIR/mut_ref_in_final.rs:53:53
+   |
+LL | static RAW_MUT_CAST_S: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   |                                                     ^^^^^^^
+
+error[E0764]: mutable references are not allowed in the final value of statics
+  --> $DIR/mut_ref_in_final.rs:55:54
+   |
+LL | static RAW_MUT_COERCE_S: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   |                                                      ^^^^^^
+
+error[E0764]: mutable references are not allowed in the final value of constants
+  --> $DIR/mut_ref_in_final.rs:57:52
+   |
+LL | const RAW_MUT_CAST_C: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   |                                                    ^^^^^^^
+
+error[E0764]: mutable references are not allowed in the final value of constants
+  --> $DIR/mut_ref_in_final.rs:59:53
+   |
+LL | const RAW_MUT_COERCE_C: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   |                                                     ^^^^^^
+
+error: aborting due to 10 previous errors
 
 Some errors have detailed explanations: E0716, E0764.
 For more information about an error, try `rustc --explain E0716`.

tests/ui/consts/const-mut-refs/mut_ref_in_final_dynamic_check.32bit.stderr

@@ -1,16 +1,16 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/mut_ref_in_final_dynamic_check.rs:17:1
+  --> $DIR/mut_ref_in_final_dynamic_check.rs:15:1
    |
 LL | const A: Option<&mut i32> = helper();
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<enum-variant(Some)>.0: encountered mutable reference in a `const`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<enum-variant(Some)>.0: encountered mutable reference in a `const` or `static`
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 4, align: 4) {
                2a 00 00 00                                     │ *...
            }
 
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
-  --> $DIR/mut_ref_in_final_dynamic_check.rs:24:1
+  --> $DIR/mut_ref_in_final_dynamic_check.rs:22:1
    |
 LL | const B: Option<&mut i32> = helper2();
    | ^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/consts/const-mut-refs/mut_ref_in_final_dynamic_check.64bit.stderr

@@ -1,16 +1,16 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/mut_ref_in_final_dynamic_check.rs:17:1
+  --> $DIR/mut_ref_in_final_dynamic_check.rs:15:1
    |
 LL | const A: Option<&mut i32> = helper();
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<enum-variant(Some)>.0: encountered mutable reference in a `const`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<enum-variant(Some)>.0: encountered mutable reference in a `const` or `static`
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 8, align: 8) {
                2a 00 00 00 00 00 00 00                         │ *.......
            }
 
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
-  --> $DIR/mut_ref_in_final_dynamic_check.rs:24:1
+  --> $DIR/mut_ref_in_final_dynamic_check.rs:22:1
    |
 LL | const B: Option<&mut i32> = helper2();
    | ^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/consts/const-mut-refs/mut_ref_in_final_dynamic_check.rs

@@ -12,8 +12,6 @@ const fn helper() -> Option<&'static mut i32> { unsafe {
     // Undefined behaviour (integer as pointer), who doesn't love tests like this.
     Some(&mut *(42 as *mut i32))
 } }
-// The error is an evaluation error and not a validation error, so the error is reported
-// directly at the site where it occurs.
 const A: Option<&mut i32> = helper(); //~ ERROR it is undefined behavior to use this value
 //~^ encountered mutable reference in a `const`
 
@@ -21,6 +19,6 @@ const fn helper2() -> Option<&'static mut i32> { unsafe {
     // Undefined behaviour (dangling pointer), who doesn't love tests like this.
     Some(&mut *(&mut 42 as *mut i32))
 } }
-const B: Option<&mut i32> = helper2(); //~ ERROR encountered dangling pointer in final constant
+const B: Option<&mut i32> = helper2(); //~ ERROR encountered dangling pointer in final value of constant
 
 fn main() {}

tests/ui/consts/const-points-to-static.32bit.stderr

@@ -1,22 +0,0 @@
-error[E0080]: it is undefined behavior to use this value
-  --> $DIR/const-points-to-static.rs:6:1
-   |
-LL | const TEST: &u8 = &MY_STATIC;
-   | ^^^^^^^^^^^^^^^ constructing invalid value: encountered a reference pointing to a static variable in a constant
-   |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
-   = note: the raw bytes of the constant (size: 4, align: 4) {
-               ╾ALLOC0<imm>╼                                     │ ╾──╼
-           }
-
-warning: skipping const checks
-   |
-help: skipping check that does not even have a feature gate
-  --> $DIR/const-points-to-static.rs:6:20
-   |
-LL | const TEST: &u8 = &MY_STATIC;
-   |                    ^^^^^^^^^
-
-error: aborting due to 1 previous error; 1 warning emitted
-
-For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/const-points-to-static.64bit.stderr

@@ -1,22 +0,0 @@
-error[E0080]: it is undefined behavior to use this value
-  --> $DIR/const-points-to-static.rs:6:1
-   |
-LL | const TEST: &u8 = &MY_STATIC;
-   | ^^^^^^^^^^^^^^^ constructing invalid value: encountered a reference pointing to a static variable in a constant
-   |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
-   = note: the raw bytes of the constant (size: 8, align: 8) {
-               ╾ALLOC0<imm>╼                         │ ╾──────╼
-           }
-
-warning: skipping const checks
-   |
-help: skipping check that does not even have a feature gate
-  --> $DIR/const-points-to-static.rs:6:20
-   |
-LL | const TEST: &u8 = &MY_STATIC;
-   |                    ^^^^^^^^^
-
-error: aborting due to 1 previous error; 1 warning emitted
-
-For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/const-points-to-static.rs

@@ -1,13 +0,0 @@
-// compile-flags: -Zunleash-the-miri-inside-of-you
-// stderr-per-bitwidth
-
-#![allow(dead_code)]
-
-const TEST: &u8 = &MY_STATIC;
-//~^ ERROR it is undefined behavior to use this value
-//~| encountered a reference pointing to a static variable
-
-static MY_STATIC: u8 = 4;
-
-fn main() {
-}

tests/ui/consts/dangling-alloc-id-ice.rs

@@ -6,7 +6,7 @@ union Foo<'a> {
 }
 
 const FOO: &() = {
-//~^ ERROR encountered dangling pointer in final constant
+//~^ ERROR encountered dangling pointer in final value of constant
     let y = ();
     unsafe { Foo { y: &y }.long_live_the_unit }
 };

tests/ui/consts/dangling-alloc-id-ice.stderr

@@ -1,4 +1,4 @@
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
   --> $DIR/dangling-alloc-id-ice.rs:8:1
    |
 LL | const FOO: &() = {

tests/ui/consts/dangling_raw_ptr.rs

@@ -1,4 +1,4 @@
-const FOO: *const u32 = { //~ ERROR encountered dangling pointer in final constant
+const FOO: *const u32 = { //~ ERROR encountered dangling pointer in final value of constant
     let x = 42;
     &x
 };

tests/ui/consts/dangling_raw_ptr.stderr

@@ -1,4 +1,4 @@
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
   --> $DIR/dangling_raw_ptr.rs:1:1
    |
 LL | const FOO: *const u32 = {

tests/ui/consts/interior-mut-const-via-union.32bit.stderr

@@ -1,8 +1,8 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/invalid-union.rs:35:1
+  --> $DIR/interior-mut-const-via-union.rs:35:1
    |
 LL | fn main() {
-   | ^^^^^^^^^ constructing invalid value at .<deref>.y.<enum-variant(B)>.0: encountered `UnsafeCell` in a `const`
+   | ^^^^^^^^^ constructing invalid value at .<deref>.y.<enum-variant(B)>.0: encountered `UnsafeCell` in read-only memory
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 4, align: 4) {
@@ -10,13 +10,13 @@ LL | fn main() {
            }
 
 note: erroneous constant encountered
-  --> $DIR/invalid-union.rs:37:25
+  --> $DIR/interior-mut-const-via-union.rs:37:25
    |
 LL |     let _: &'static _ = &C;
    |                         ^^
 
 note: erroneous constant encountered
-  --> $DIR/invalid-union.rs:37:25
+  --> $DIR/interior-mut-const-via-union.rs:37:25
    |
 LL |     let _: &'static _ = &C;
    |                         ^^

tests/ui/consts/interior-mut-const-via-union.64bit.stderr

@@ -1,8 +1,8 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/invalid-union.rs:35:1
+  --> $DIR/interior-mut-const-via-union.rs:35:1
    |
 LL | fn main() {
-   | ^^^^^^^^^ constructing invalid value at .<deref>.y.<enum-variant(B)>.0: encountered `UnsafeCell` in a `const`
+   | ^^^^^^^^^ constructing invalid value at .<deref>.y.<enum-variant(B)>.0: encountered `UnsafeCell` in read-only memory
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 8, align: 8) {
@@ -10,13 +10,13 @@ LL | fn main() {
            }
 
 note: erroneous constant encountered
-  --> $DIR/invalid-union.rs:37:25
+  --> $DIR/interior-mut-const-via-union.rs:37:25
    |
 LL |     let _: &'static _ = &C;
    |                         ^^
 
 note: erroneous constant encountered
-  --> $DIR/invalid-union.rs:37:25
+  --> $DIR/interior-mut-const-via-union.rs:37:25
    |
 LL |     let _: &'static _ = &C;
    |                         ^^

tests/ui/consts/miri_unleashed/const_refers_to_static.32bit.stderr

@@ -38,6 +38,17 @@ LL | const READ_IMMUT: &usize = {
                ╾ALLOC1<imm>╼                                     │ ╾──╼
            }
 
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/const_refers_to_static.rs:34:1
+   |
+LL | const REF_IMMUT: &u8 = &MY_STATIC;
+   | ^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered a reference pointing to a static variable in a constant
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               ╾ALLOC2<imm>╼                                     │ ╾──╼
+           }
+
 warning: skipping const checks
    |
 help: skipping check that does not even have a feature gate
@@ -75,7 +86,12 @@ help: skipping check that does not even have a feature gate
    |
 LL |     &FOO
    |      ^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/const_refers_to_static.rs:34:25
+   |
+LL | const REF_IMMUT: &u8 = &MY_STATIC;
+   |                         ^^^^^^^^^
 
-error: aborting due to 5 previous errors; 1 warning emitted
+error: aborting due to 6 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/miri_unleashed/const_refers_to_static.64bit.stderr

@@ -38,6 +38,17 @@ LL | const READ_IMMUT: &usize = {
                ╾ALLOC1<imm>╼                         │ ╾──────╼
            }
 
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/const_refers_to_static.rs:34:1
+   |
+LL | const REF_IMMUT: &u8 = &MY_STATIC;
+   | ^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered a reference pointing to a static variable in a constant
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾ALLOC2<imm>╼                         │ ╾──────╼
+           }
+
 warning: skipping const checks
    |
 help: skipping check that does not even have a feature gate
@@ -75,7 +86,12 @@ help: skipping check that does not even have a feature gate
    |
 LL |     &FOO
    |      ^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/const_refers_to_static.rs:34:25
+   |
+LL | const REF_IMMUT: &u8 = &MY_STATIC;
+   |                         ^^^^^^^^^
 
-error: aborting due to 5 previous errors; 1 warning emitted
+error: aborting due to 6 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/miri_unleashed/const_refers_to_static.rs

@@ -30,4 +30,9 @@ const READ_IMMUT: &usize = { //~ ERROR it is undefined behavior to use this valu
     &FOO
 };
 
+static MY_STATIC: u8 = 4;
+const REF_IMMUT: &u8 = &MY_STATIC;
+//~^ ERROR it is undefined behavior to use this value
+//~| encountered a reference pointing to a static variable
+
 fn main() {}

tests/ui/consts/miri_unleashed/mutable_references_err.32bit.stderr

@@ -1,54 +1,199 @@
-error[E0080]: it is undefined behavior to use this value
+error: encountered mutable pointer in final value of constant
-  --> $DIR/mutable_references_err.rs:15:1
+  --> $DIR/mutable_references_err.rs:17:1
    |
 LL | const MUH: Meh = Meh {
-   | ^^^^^^^^^^^^^^ constructing invalid value at .x.<deref>: encountered `UnsafeCell` in a `const`
+   | ^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:27:1
+   |
+LL | const SNEAKY: &dyn Sync = &Synced { x: UnsafeCell::new(42) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/mutable_references_err.rs:32:1
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   | ^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered mutable reference in a `const` or `static`
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 4, align: 4) {
                ╾ALLOC0╼                                     │ ╾──╼
            }
 
-error[E0080]: it is undefined behavior to use this value
+error: encountered mutable pointer in final value of constant
-  --> $DIR/mutable_references_err.rs:25:1
+  --> $DIR/mutable_references_err.rs:35:1
-   |
-LL | const SNEAKY: &dyn Sync = &Synced { x: UnsafeCell::new(42) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<deref>.<dyn-downcast>.x: encountered `UnsafeCell` in a `const`
-   |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
-   = note: the raw bytes of the constant (size: 8, align: 4) {
-               ╾ALLOC1╼ ╾ALLOC2╼                         │ ╾──╼╾──╼
-           }
-
-error[E0080]: it is undefined behavior to use this value
-  --> $DIR/mutable_references_err.rs:29:1
    |
 LL | const BLUNT: &mut i32 = &mut 42;
-   | ^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered mutable reference in a `const`
+   | ^^^^^^^^^^^^^^^^^^^^^
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/mutable_references_err.rs:40:1
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered mutable reference or box pointing to read-only memory
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 4, align: 4) {
-               ╾ALLOC3╼                                     │ ╾──╼
+               ╾ALLOC1<imm>╼                                     │ ╾──╼
            }
 
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/mutable_references_err.rs:47:1
+   |
+LL | const POINTS_TO_MUTABLE1: &i32 = unsafe { &MUTABLE };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered a reference pointing to a static variable in a constant
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               ╾ALLOC2<imm>╼                                     │ ╾──╼
+           }
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/mutable_references_err.rs:51:43
+   |
+LL | const POINTS_TO_MUTABLE2: &i32 = unsafe { &*MUTABLE_REF };
+   |                                           ^^^^^^^^^^^^^ constant accesses static
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:55:1
+   |
+LL | const POINTS_TO_MUTABLE_INNER: *const i32 = &mut 42 as *mut _ as *const _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:57:1
+   |
+LL | const POINTS_TO_MUTABLE_INNER2: *const i32 = &mut 42 as *const _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:59:1
+   |
+LL | const INTERIOR_MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:69:1
+   |
+LL | const RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:71:1
+   |
+LL | const RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:73:1
+   |
+LL | const RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 warning: skipping const checks
    |
 help: skipping check that does not even have a feature gate
-  --> $DIR/mutable_references_err.rs:16:8
+  --> $DIR/mutable_references_err.rs:18:8
    |
 LL |     x: &UnsafeCell::new(42),
    |        ^^^^^^^^^^^^^^^^^^^^
 help: skipping check that does not even have a feature gate
-  --> $DIR/mutable_references_err.rs:25:27
+  --> $DIR/mutable_references_err.rs:27:27
    |
 LL | const SNEAKY: &dyn Sync = &Synced { x: UnsafeCell::new(42) };
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 help: skipping check that does not even have a feature gate
-  --> $DIR/mutable_references_err.rs:29:25
+  --> $DIR/mutable_references_err.rs:32:40
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   |                                        ^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:32:40
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   |                                        ^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:32:35
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   |                                   ^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:35:25
    |
 LL | const BLUNT: &mut i32 = &mut 42;
    |                         ^^^^^^^
+help: skipping check for `const_mut_refs` feature
+  --> $DIR/mutable_references_err.rs:40:49
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: skipping check for `const_mut_refs` feature
+  --> $DIR/mutable_references_err.rs:40:49
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:40:49
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:47:44
+   |
+LL | const POINTS_TO_MUTABLE1: &i32 = unsafe { &MUTABLE };
+   |                                            ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:47:44
+   |
+LL | const POINTS_TO_MUTABLE1: &i32 = unsafe { &MUTABLE };
+   |                                            ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:50:36
+   |
+LL | static mut MUTABLE_REF: &mut i32 = &mut 42;
+   |                                    ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:51:45
+   |
+LL | const POINTS_TO_MUTABLE2: &i32 = unsafe { &*MUTABLE_REF };
+   |                                             ^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:51:45
+   |
+LL | const POINTS_TO_MUTABLE2: &i32 = unsafe { &*MUTABLE_REF };
+   |                                             ^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:55:45
+   |
+LL | const POINTS_TO_MUTABLE_INNER: *const i32 = &mut 42 as *mut _ as *const _;
+   |                                             ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:57:46
+   |
+LL | const POINTS_TO_MUTABLE_INNER2: *const i32 = &mut 42 as *const _;
+   |                                              ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:59:47
+   |
+LL | const INTERIOR_MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
+   |                                               ^^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:69:51
+   |
+LL | const RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   |                                                   ^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:71:50
+   |
+LL | const RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   |                                                  ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:73:51
+   |
+LL | const RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   |                                                   ^^^^^^
 
-error: aborting due to 3 previous errors; 1 warning emitted
+error: aborting due to 13 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/miri_unleashed/mutable_references_err.64bit.stderr

@@ -1,54 +1,199 @@
-error[E0080]: it is undefined behavior to use this value
+error: encountered mutable pointer in final value of constant
-  --> $DIR/mutable_references_err.rs:15:1
+  --> $DIR/mutable_references_err.rs:17:1
    |
 LL | const MUH: Meh = Meh {
-   | ^^^^^^^^^^^^^^ constructing invalid value at .x.<deref>: encountered `UnsafeCell` in a `const`
+   | ^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:27:1
+   |
+LL | const SNEAKY: &dyn Sync = &Synced { x: UnsafeCell::new(42) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/mutable_references_err.rs:32:1
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   | ^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered mutable reference in a `const` or `static`
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 8, align: 8) {
                ╾ALLOC0╼                         │ ╾──────╼
            }
 
-error[E0080]: it is undefined behavior to use this value
+error: encountered mutable pointer in final value of constant
-  --> $DIR/mutable_references_err.rs:25:1
+  --> $DIR/mutable_references_err.rs:35:1
-   |
-LL | const SNEAKY: &dyn Sync = &Synced { x: UnsafeCell::new(42) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .<deref>.<dyn-downcast>.x: encountered `UnsafeCell` in a `const`
-   |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
-   = note: the raw bytes of the constant (size: 16, align: 8) {
-               ╾ALLOC1╼ ╾ALLOC2╼ │ ╾──────╼╾──────╼
-           }
-
-error[E0080]: it is undefined behavior to use this value
-  --> $DIR/mutable_references_err.rs:29:1
    |
 LL | const BLUNT: &mut i32 = &mut 42;
-   | ^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered mutable reference in a `const`
+   | ^^^^^^^^^^^^^^^^^^^^^
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/mutable_references_err.rs:40:1
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered mutable reference or box pointing to read-only memory
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 8, align: 8) {
-               ╾ALLOC3╼                         │ ╾──────╼
+               ╾ALLOC1<imm>╼                         │ ╾──────╼
            }
 
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/mutable_references_err.rs:47:1
+   |
+LL | const POINTS_TO_MUTABLE1: &i32 = unsafe { &MUTABLE };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered a reference pointing to a static variable in a constant
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾ALLOC2<imm>╼                         │ ╾──────╼
+           }
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/mutable_references_err.rs:51:43
+   |
+LL | const POINTS_TO_MUTABLE2: &i32 = unsafe { &*MUTABLE_REF };
+   |                                           ^^^^^^^^^^^^^ constant accesses static
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:55:1
+   |
+LL | const POINTS_TO_MUTABLE_INNER: *const i32 = &mut 42 as *mut _ as *const _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:57:1
+   |
+LL | const POINTS_TO_MUTABLE_INNER2: *const i32 = &mut 42 as *const _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:59:1
+   |
+LL | const INTERIOR_MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:69:1
+   |
+LL | const RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:71:1
+   |
+LL | const RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of constant
+  --> $DIR/mutable_references_err.rs:73:1
+   |
+LL | const RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 warning: skipping const checks
    |
 help: skipping check that does not even have a feature gate
-  --> $DIR/mutable_references_err.rs:16:8
+  --> $DIR/mutable_references_err.rs:18:8
    |
 LL |     x: &UnsafeCell::new(42),
    |        ^^^^^^^^^^^^^^^^^^^^
 help: skipping check that does not even have a feature gate
-  --> $DIR/mutable_references_err.rs:25:27
+  --> $DIR/mutable_references_err.rs:27:27
    |
 LL | const SNEAKY: &dyn Sync = &Synced { x: UnsafeCell::new(42) };
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 help: skipping check that does not even have a feature gate
-  --> $DIR/mutable_references_err.rs:29:25
+  --> $DIR/mutable_references_err.rs:32:40
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   |                                        ^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:32:40
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   |                                        ^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:32:35
+   |
+LL | const SUBTLE: &mut i32 = unsafe { &mut FOO };
+   |                                   ^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:35:25
    |
 LL | const BLUNT: &mut i32 = &mut 42;
    |                         ^^^^^^^
+help: skipping check for `const_mut_refs` feature
+  --> $DIR/mutable_references_err.rs:40:49
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: skipping check for `const_mut_refs` feature
+  --> $DIR/mutable_references_err.rs:40:49
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:40:49
+   |
+LL | static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:47:44
+   |
+LL | const POINTS_TO_MUTABLE1: &i32 = unsafe { &MUTABLE };
+   |                                            ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:47:44
+   |
+LL | const POINTS_TO_MUTABLE1: &i32 = unsafe { &MUTABLE };
+   |                                            ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:50:36
+   |
+LL | static mut MUTABLE_REF: &mut i32 = &mut 42;
+   |                                    ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:51:45
+   |
+LL | const POINTS_TO_MUTABLE2: &i32 = unsafe { &*MUTABLE_REF };
+   |                                             ^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:51:45
+   |
+LL | const POINTS_TO_MUTABLE2: &i32 = unsafe { &*MUTABLE_REF };
+   |                                             ^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:55:45
+   |
+LL | const POINTS_TO_MUTABLE_INNER: *const i32 = &mut 42 as *mut _ as *const _;
+   |                                             ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:57:46
+   |
+LL | const POINTS_TO_MUTABLE_INNER2: *const i32 = &mut 42 as *const _;
+   |                                              ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:59:47
+   |
+LL | const INTERIOR_MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
+   |                                               ^^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:69:51
+   |
+LL | const RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   |                                                   ^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:71:50
+   |
+LL | const RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   |                                                  ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/mutable_references_err.rs:73:51
+   |
+LL | const RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   |                                                   ^^^^^^
 
-error: aborting due to 3 previous errors; 1 warning emitted
+error: aborting due to 13 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/miri_unleashed/mutable_references_err.rs

@@ -1,6 +1,8 @@
 // stderr-per-bitwidth
 // compile-flags: -Zunleash-the-miri-inside-of-you
+#![allow(invalid_reference_casting, static_mut_ref)]
 
+use std::sync::atomic::*;
 use std::cell::UnsafeCell;
 
 // this test ensures that our mutability story is sound
@@ -12,7 +14,7 @@ unsafe impl Sync for Meh {}
 
 // the following will never be ok! no interior mut behind consts, because
 // all allocs interned here will be marked immutable.
-const MUH: Meh = Meh { //~ ERROR: it is undefined behavior to use this value
+const MUH: Meh = Meh { //~ ERROR: mutable pointer in final value
     x: &UnsafeCell::new(42),
 };
 
@@ -23,11 +25,53 @@ unsafe impl Sync for Synced {}
 
 // Make sure we also catch this behind a type-erased `dyn Trait` reference.
 const SNEAKY: &dyn Sync = &Synced { x: UnsafeCell::new(42) };
-//~^ ERROR: it is undefined behavior to use this value
+//~^ ERROR: mutable pointer in final value
 
-// Make sure we also catch mutable references.
+// Make sure we also catch mutable references in values that shouldn't have them.
-const BLUNT: &mut i32 = &mut 42;
+static mut FOO: i32 = 0;
+const SUBTLE: &mut i32 = unsafe { &mut FOO };
 //~^ ERROR: it is undefined behavior to use this value
+//~| static
+const BLUNT: &mut i32 = &mut 42;
+//~^ ERROR: mutable pointer in final value
+
+// Check for mutable references to read-only memory.
+static READONLY: i32 = 0;
+static mut MUT_TO_READONLY: &mut i32 = unsafe { &mut *(&READONLY as *const _ as *mut _) };
+//~^ ERROR: it is undefined behavior to use this value
+//~| pointing to read-only memory
+
+// Check for consts pointing to mutable memory.
+// Currently it's not even possible to create such a const.
+static mut MUTABLE: i32 = 42;
+const POINTS_TO_MUTABLE1: &i32 = unsafe { &MUTABLE };
+//~^ ERROR: undefined behavior to use this value
+//~| pointing to a static
+static mut MUTABLE_REF: &mut i32 = &mut 42;
+const POINTS_TO_MUTABLE2: &i32 = unsafe { &*MUTABLE_REF };
+//~^ ERROR: evaluation of constant value failed
+//~| accesses static
+
+const POINTS_TO_MUTABLE_INNER: *const i32 = &mut 42 as *mut _ as *const _;
+//~^ ERROR: mutable pointer in final value
+const POINTS_TO_MUTABLE_INNER2: *const i32 = &mut 42 as *const _;
+//~^ ERROR: mutable pointer in final value
+const INTERIOR_MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
+//~^ ERROR: mutable pointer in final value
+
+struct SyncPtr<T> { x : *const T }
+unsafe impl<T> Sync for SyncPtr<T> {}
+
+// These pass the lifetime checks because of the "tail expression" / "outer scope" rule.
+// (This relies on `SyncPtr` being a curly brace struct.)
+// However, we intern the inner memory as read-only, so this must be rejected.
+// (Also see `static-no-inner-mut` for similar tests on `static`.)
+const RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+//~^ ERROR mutable pointer in final value
+const RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+//~^ ERROR mutable pointer in final value
+const RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+//~^ ERROR mutable pointer in final value
 
 fn main() {
     unsafe {

tests/ui/consts/miri_unleashed/raw_mutable_const.rs

@@ -1,8 +0,0 @@
-// compile-flags: -Zunleash-the-miri-inside-of-you
-
-use std::cell::UnsafeCell;
-
-const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
-//~^ ERROR: unsupported untyped pointer in constant
-
-fn main() {}

tests/ui/consts/miri_unleashed/raw_mutable_const.stderr

@@ -1,18 +0,0 @@
-error: unsupported untyped pointer in constant
-  --> $DIR/raw_mutable_const.rs:5:1
-   |
-LL | const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: memory only reachable via raw pointers is not supported
-
-warning: skipping const checks
-   |
-help: skipping check that does not even have a feature gate
-  --> $DIR/raw_mutable_const.rs:5:38
-   |
-LL | const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
-   |                                      ^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 1 previous error; 1 warning emitted
-

tests/ui/consts/miri_unleashed/static-no-inner-mut.32bit.stderr

@@ -0,0 +1,82 @@
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:9:1
+   |
+LL | static REF: &AtomicI32 = &AtomicI32::new(42);
+   | ^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:10:1
+   |
+LL | static REFMUT: &mut i32 = &mut 0;
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:13:1
+   |
+LL | static REF2: &AtomicI32 = {let x = AtomicI32::new(42); &{x}};
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:14:1
+   |
+LL | static REFMUT2: &mut i32 = {let mut x = 0; &mut {x}};
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:29:1
+   |
+LL | static RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:31:1
+   |
+LL | static RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:33:1
+   |
+LL | static RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: skipping const checks
+   |
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:9:26
+   |
+LL | static REF: &AtomicI32 = &AtomicI32::new(42);
+   |                          ^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:10:27
+   |
+LL | static REFMUT: &mut i32 = &mut 0;
+   |                           ^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:13:56
+   |
+LL | static REF2: &AtomicI32 = {let x = AtomicI32::new(42); &{x}};
+   |                                                        ^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:14:44
+   |
+LL | static REFMUT2: &mut i32 = {let mut x = 0; &mut {x}};
+   |                                            ^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:29:52
+   |
+LL | static RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   |                                                    ^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:31:51
+   |
+LL | static RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   |                                                   ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:33:52
+   |
+LL | static RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   |                                                    ^^^^^^
+
+error: aborting due to 7 previous errors; 1 warning emitted
+

tests/ui/consts/miri_unleashed/static-no-inner-mut.64bit.stderr

@@ -0,0 +1,82 @@
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:9:1
+   |
+LL | static REF: &AtomicI32 = &AtomicI32::new(42);
+   | ^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:10:1
+   |
+LL | static REFMUT: &mut i32 = &mut 0;
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:13:1
+   |
+LL | static REF2: &AtomicI32 = {let x = AtomicI32::new(42); &{x}};
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:14:1
+   |
+LL | static REFMUT2: &mut i32 = {let mut x = 0; &mut {x}};
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:29:1
+   |
+LL | static RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:31:1
+   |
+LL | static RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: encountered mutable pointer in final value of static
+  --> $DIR/static-no-inner-mut.rs:33:1
+   |
+LL | static RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: skipping const checks
+   |
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:9:26
+   |
+LL | static REF: &AtomicI32 = &AtomicI32::new(42);
+   |                          ^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:10:27
+   |
+LL | static REFMUT: &mut i32 = &mut 0;
+   |                           ^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:13:56
+   |
+LL | static REF2: &AtomicI32 = {let x = AtomicI32::new(42); &{x}};
+   |                                                        ^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:14:44
+   |
+LL | static REFMUT2: &mut i32 = {let mut x = 0; &mut {x}};
+   |                                            ^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:29:52
+   |
+LL | static RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+   |                                                    ^^^^^^^^^^^^^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:31:51
+   |
+LL | static RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+   |                                                   ^^^^^^^
+help: skipping check that does not even have a feature gate
+  --> $DIR/static-no-inner-mut.rs:33:52
+   |
+LL | static RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+   |                                                    ^^^^^^
+
+error: aborting due to 7 previous errors; 1 warning emitted
+

tests/ui/consts/miri_unleashed/static-no-inner-mut.rs

@@ -0,0 +1,36 @@
+// stderr-per-bitwidth
+// compile-flags: -Zunleash-the-miri-inside-of-you
+#![feature(const_refs_to_cell, const_mut_refs)]
+// All "inner" allocations that come with a `static` are interned immutably. This means it is
+// crucial that we do not accept any form of (interior) mutability there.
+
+use std::sync::atomic::*;
+
+static REF: &AtomicI32 = &AtomicI32::new(42); //~ERROR mutable pointer in final value
+static REFMUT: &mut i32 = &mut 0; //~ERROR mutable pointer in final value
+
+// Different way of writing this that avoids promotion.
+static REF2: &AtomicI32 = {let x = AtomicI32::new(42); &{x}}; //~ERROR mutable pointer in final value
+static REFMUT2: &mut i32 = {let mut x = 0; &mut {x}}; //~ERROR mutable pointer in final value
+
+// This one is obvious, since it is non-Sync. (It also suppresses the other errors, so it is
+// commented out.)
+// static RAW: *const AtomicI32 = &AtomicI32::new(42);
+
+struct SyncPtr<T> { x : *const T }
+unsafe impl<T> Sync for SyncPtr<T> {}
+
+// All of these pass the lifetime checks because of the "tail expression" / "outer scope" rule.
+// (This relies on `SyncPtr` being a curly brace struct.)
+// Then they get interned immutably, which is not great.
+// `mut_ref_in_final.rs` and `std/cell.rs` ensure that we don't accept this even with the feature
+// fate, but for unleashed Miri there's not really any way we can reject them: it's just
+// non-dangling raw pointers.
+static RAW_SYNC: SyncPtr<AtomicI32> = SyncPtr { x: &AtomicI32::new(42) };
+//~^ ERROR mutable pointer in final value
+static RAW_MUT_CAST: SyncPtr<i32> = SyncPtr { x : &mut 42 as *mut _ as *const _ };
+//~^ ERROR mutable pointer in final value
+static RAW_MUT_COERCE: SyncPtr<i32> = SyncPtr { x: &mut 0 };
+//~^ ERROR mutable pointer in final value
+
+fn main() {}

tests/ui/consts/raw-ptr-const.rs

@@ -1,8 +1,8 @@
+// check-pass
+
 // This is a regression test for a `span_delayed_bug` during interning when a constant
-// evaluates to a (non-dangling) raw pointer.  For now this errors; potentially it
+// evaluates to a (non-dangling) raw pointer.
-// could also be allowed.
 
 const CONST_RAW: *const Vec<i32> = &Vec::new() as *const _;
-//~^ ERROR unsupported untyped pointer in constant
 
 fn main() {}

tests/ui/consts/raw-ptr-const.stderr

@@ -1,10 +0,0 @@
-error: unsupported untyped pointer in constant
-  --> $DIR/raw-ptr-const.rs:5:1
-   |
-LL | const CONST_RAW: *const Vec<i32> = &Vec::new() as *const _;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: memory only reachable via raw pointers is not supported
-
-error: aborting due to 1 previous error
-

tests/ui/consts/raw-ptr-temp-const.rs

@@ -0,0 +1,6 @@
+// A variant of raw-ptr-const that directly constructs a raw pointer.
+
+const CONST_RAW: *const Vec<i32> = std::ptr::addr_of!(Vec::new());
+//~^ ERROR cannot take address of a temporary
+
+fn main() {}

tests/ui/consts/raw-ptr-temp-const.stderr

@@ -0,0 +1,9 @@
+error[E0745]: cannot take address of a temporary
+  --> $DIR/raw-ptr-temp-const.rs:3:55
+   |
+LL | const CONST_RAW: *const Vec<i32> = std::ptr::addr_of!(Vec::new());
+   |                                                       ^^^^^^^^^^ temporary value
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0745`.

tests/ui/consts/refs-to-cell-in-final.rs

@@ -0,0 +1,18 @@
+#![feature(const_refs_to_cell)]
+
+use std::cell::*;
+
+struct SyncPtr<T> { x : *const T }
+unsafe impl<T> Sync for SyncPtr<T> {}
+
+// These pass the lifetime checks because of the "tail expression" / "outer scope" rule.
+// (This relies on `SyncPtr` being a curly brace struct.)
+// However, we intern the inner memory as read-only.
+// The resulting constant would pass all validation checks, so it is crucial that this gets rejected
+// by static const checks!
+static RAW_SYNC_S: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
+//~^ ERROR: cannot refer to interior mutable data
+const RAW_SYNC_C: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
+//~^ ERROR: cannot refer to interior mutable data
+
+fn main() {}

tests/ui/consts/refs-to-cell-in-final.stderr

@@ -0,0 +1,17 @@
+error[E0492]: statics cannot refer to interior mutable data
+  --> $DIR/refs-to-cell-in-final.rs:13:54
+   |
+LL | static RAW_SYNC_S: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
+   |                                                      ^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
+   |
+   = help: to fix this, the value can be extracted to a separate `static` item and then referenced
+
+error[E0492]: constants cannot refer to interior mutable data
+  --> $DIR/refs-to-cell-in-final.rs:15:53
+   |
+LL | const RAW_SYNC_C: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
+   |                                                     ^^^^^^^^^^^^^^ this borrow of an interior mutable value may end up in the final value
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0492`.

tests/ui/consts/std/cell.stderr

@@ -1,22 +1,22 @@
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of static
   --> $DIR/cell.rs:6:1
    |
 LL | static FOO: Wrap<*mut u32> = Wrap(Cell::new(42).as_ptr());
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
   --> $DIR/cell.rs:8:1
    |
 LL | const FOO_CONST: Wrap<*mut u32> = Wrap(Cell::new(42).as_ptr());
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
   --> $DIR/cell.rs:22:1
    |
 LL | const FOO4_CONST: Wrap<*mut u32> = Wrap(FOO3_CONST.0.as_ptr());
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: encountered dangling pointer in final constant
+error: encountered dangling pointer in final value of constant
   --> $DIR/cell.rs:27:1
    |
 LL | const FOO2: *mut u32 = Cell::new(42).as_ptr();