miri: do not apply aliasing restrictions to Box with custom allocator

5 files changed, 18 insertions, 12 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index ff1cb43db86..c568f9acfd3 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -17,8 +17,8 @@ use rustc_middle::mir::interpret::{
     ExpectedKind, InterpError, InvalidMetaKind, Misalignment, PointerKind, Provenance,
     ValidationErrorInfo, ValidationErrorKind, ValidationErrorKind::*,
 };
-use rustc_middle::ty;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
+use rustc_middle::ty::{self, Ty};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_target::abi::{
     Abi, FieldIdx, Scalar as ScalarAbi, Size, VariantIdx, Variants, WrappingRange,
@@ -783,7 +783,11 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
     }
 
     #[inline]
-    fn visit_box(&mut self, op: &OpTy<'tcx, M::Provenance>) -> InterpResult<'tcx> {
+    fn visit_box(
+        &mut self,
+        _box_ty: Ty<'tcx>,
+        op: &OpTy<'tcx, M::Provenance>,
+    ) -> InterpResult<'tcx> {
         self.check_safe_pointer(op, PointerKind::Box)?;
         Ok(())
     }
diff --git a/compiler/rustc_const_eval/src/interpret/visitor.rs b/compiler/rustc_const_eval/src/interpret/visitor.rs
index b200ecbf73a..0e824f3f592 100644
--- a/compiler/rustc_const_eval/src/interpret/visitor.rs
+++ b/compiler/rustc_const_eval/src/interpret/visitor.rs
@@ -3,7 +3,7 @@
 
 use rustc_index::IndexVec;
 use rustc_middle::mir::interpret::InterpResult;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, Ty};
 use rustc_target::abi::FieldIdx;
 use rustc_target::abi::{FieldsShape, VariantIdx, Variants};
 
@@ -47,10 +47,10 @@ pub trait ValueVisitor<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
         Ok(())
     }
     /// Visits the given value as the pointer of a `Box`. There is nothing to recurse into.
-    /// The type of `v` will be a raw pointer, but this is a field of `Box<T>` and the
-    /// pointee type is the actual `T`.
+    /// The type of `v` will be a raw pointer to `T`, but this is a field of `Box<T>` and the
+    /// pointee type is the actual `T`. `box_ty` provides the full type of the `Box` itself.
     #[inline(always)]
-    fn visit_box(&mut self, _v: &Self::V) -> InterpResult<'tcx> {
+    fn visit_box(&mut self, _box_ty: Ty<'tcx>, _v: &Self::V) -> InterpResult<'tcx> {
         Ok(())
     }
 
@@ -144,7 +144,7 @@ pub trait ValueVisitor<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
                 assert_eq!(nonnull_ptr.layout().fields.count(), 1);
                 let raw_ptr = self.ecx().project_field(&nonnull_ptr, 0)?; // the actual raw ptr
                 // ... whose only field finally is a raw ptr we can dereference.
-                self.visit_box(&raw_ptr)?;
+                self.visit_box(ty, &raw_ptr)?;
 
                 // The second `Box` field is the allocator, which we recursively check for validity
                 // like in regular structs.
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index 95c51cc0486..5a74bdc8a84 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -657,6 +657,10 @@ pub fn check_intrinsic_type(
             sym::simd_shuffle => (3, 0, vec![param(0), param(0), param(1)], param(2)),
             sym::simd_shuffle_generic => (2, 1, vec![param(0), param(0)], param(1)),
 
+            sym::retag_box_to_raw => {
+                (2, 0, vec![Ty::new_mut_ptr(tcx, param(0))], Ty::new_mut_ptr(tcx, param(0)))
+            }
+
             other => {
                 tcx.dcx().emit_err(UnrecognizedIntrinsicFunction { span, name: other });
                 return;
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 427c0f04bd1..39b5d3b6ea7 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -2008,13 +2008,10 @@ impl<'tcx> Ty<'tcx> {
                     // Single-argument Box is always global. (for "minicore" tests)
                     return true;
                 };
-                if let Some(alloc_adt) = alloc.expect_ty().ty_adt_def() {
+                alloc.expect_ty().ty_adt_def().is_some_and(|alloc_adt| {
                     let global_alloc = tcx.require_lang_item(LangItem::GlobalAlloc, None);
                     alloc_adt.did() == global_alloc
-                } else {
-                    // Allocator is not an ADT...
-                    false
-                }
+                })
             }
             _ => false,
         }
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 9dadd471247..283c685eaa3 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1450,6 +1450,7 @@ symbols! {
         residual,
         result,
         resume,
+        retag_box_to_raw,
         return_position_impl_trait_in_trait,
         return_type_notation,
         rhs,