interpret: fix TypeId pointers being considered data pointers

Author: RalfJung

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -67,8 +67,8 @@ pub enum AllocKind {
     LiveData,
     /// A function allocation (that fn ptrs point to).
     Function,
-    /// A (symbolic) vtable allocation.
-    VTable,
+    /// A "virtual" allocation, used for vtables and TypeId.
+    Virtual,
     /// A dead allocation.
     Dead,
 }
@@ -950,11 +950,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             let (size, align) = global_alloc.size_and_align(*self.tcx, self.typing_env);
             let mutbl = global_alloc.mutability(*self.tcx, self.typing_env);
             let kind = match global_alloc {
-                GlobalAlloc::TypeId { .. }
-                | GlobalAlloc::Static { .. }
-                | GlobalAlloc::Memory { .. } => AllocKind::LiveData,
+                GlobalAlloc::Static { .. } | GlobalAlloc::Memory { .. } => AllocKind::LiveData,
                 GlobalAlloc::Function { .. } => bug!("We already checked function pointers above"),
-                GlobalAlloc::VTable { .. } => AllocKind::VTable,
+                GlobalAlloc::VTable { .. } | GlobalAlloc::TypeId { .. } => AllocKind::Virtual,
             };
             return AllocInfo::new(size, align, kind, mutbl);
         }

library/core/src/any.rs

@@ -783,7 +783,7 @@ impl TypeId {
 
         // This is a provenance-stripping memcpy.
         for (i, chunk) in self.data.iter().copied().enumerate() {
-            let chunk = chunk.expose_provenance().to_ne_bytes();
+            let chunk = chunk.addr().to_ne_bytes();
             let start = i * chunk.len();
             bytes[start..(start + chunk.len())].copy_from_slice(&chunk);
         }

src/tools/miri/src/alloc_addresses/mod.rs

@@ -157,7 +157,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                         this.get_alloc_bytes_unchecked_raw(alloc_id)?
                     }
                 }
-                AllocKind::Function | AllocKind::VTable => {
+                AllocKind::Function | AllocKind::Virtual => {
                     // Allocate some dummy memory to get a unique address for this function/vtable.
                     let alloc_bytes = MiriAllocBytes::from_bytes(
                         &[0u8; 1],

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

@@ -650,7 +650,7 @@ trait EvalContextPrivExt<'tcx, 'ecx>: crate::MiriInterpCxExt<'tcx> {
                         dcx.log_protector();
                     }
                 },
-                AllocKind::Function | AllocKind::VTable | AllocKind::Dead => {
+                AllocKind::Function | AllocKind::Virtual | AllocKind::Dead => {
                     // No stacked borrows on these allocations.
                 }
             }
@@ -1021,7 +1021,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 trace!("Stacked Borrows tag {tag:?} exposed in {alloc_id:?}");
                 alloc_extra.borrow_tracker_sb().borrow_mut().exposed_tags.insert(tag);
             }
-            AllocKind::Function | AllocKind::VTable | AllocKind::Dead => {
+            AllocKind::Function | AllocKind::Virtual | AllocKind::Dead => {
                 // No stacked borrows on these allocations.
             }
         }

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

@@ -673,7 +673,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 trace!("Tree Borrows tag {tag:?} exposed in {alloc_id:?}");
                 alloc_extra.borrow_tracker_tb().borrow_mut().expose_tag(tag);
             }
-            AllocKind::Function | AllocKind::VTable | AllocKind::Dead => {
+            AllocKind::Function | AllocKind::Virtual | AllocKind::Dead => {
                 // No tree borrows on these allocations.
             }
         }

src/tools/miri/tests/pass/intrinsics/type-id.rs

@@ -0,0 +1,19 @@
+use std::any::{Any, TypeId};
+
+fn main() {
+    let t1 = TypeId::of::<u64>();
+    let t2 = TypeId::of::<u64>();
+    assert_eq!(t1, t2);
+    let t3 = TypeId::of::<usize>();
+    assert_ne!(t1, t3);
+
+    let _ = format!("{t1:?}"); // test that we can debug-print
+
+    let b = Box::new(0u64) as Box<dyn Any>;
+    assert_eq!(*b.downcast_ref::<u64>().unwrap(), 0);
+    assert!(b.downcast_ref::<usize>().is_none());
+
+    // Get the first pointer chunk and try to make it a ZST ref.
+    // This used to trigger an error because TypeId allocs got misclassified as "LiveData".
+    let _raw_chunk = unsafe { (&raw const t1).cast::<&()>().read() };
+}