2 files changed, 13 insertions, 11 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs
index ccf3647f0d9..de6200ef012 100644
--- a/compiler/rustc_const_eval/src/interpret/memory.rs
+++ b/compiler/rustc_const_eval/src/interpret/memory.rs
@@ -857,6 +857,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> std::fmt::Debug for DumpAllocs<'a,
 
 /// Reading and writing.
 impl<'tcx, 'a, Tag: Provenance, Extra> AllocRefMut<'a, 'tcx, Tag, Extra> {
+    /// `range` is relative to this allocation reference, not the base of the allocation.
     pub fn write_scalar(
         &mut self,
         range: AllocRange,
@@ -870,6 +871,7 @@ impl<'tcx, 'a, Tag: Provenance, Extra> AllocRefMut<'a, 'tcx, Tag, Extra> {
             .map_err(|e| e.to_interp_error(self.alloc_id))?)
     }
 
+    /// `offset` is relative to this allocation reference, not the base of the allocation.
     pub fn write_ptr_sized(
         &mut self,
         offset: Size,
@@ -888,6 +890,7 @@ impl<'tcx, 'a, Tag: Provenance, Extra> AllocRefMut<'a, 'tcx, Tag, Extra> {
 }
 
 impl<'tcx, 'a, Tag: Provenance, Extra> AllocRef<'a, 'tcx, Tag, Extra> {
+    /// `range` is relative to this allocation reference, not the base of the allocation.
     pub fn read_scalar(
         &self,
         range: AllocRange,
@@ -902,14 +905,12 @@ impl<'tcx, 'a, Tag: Provenance, Extra> AllocRef<'a, 'tcx, Tag, Extra> {
         Ok(res)
     }
 
-    pub fn read_integer(
-        &self,
-        offset: Size,
-        size: Size,
-    ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
-        self.read_scalar(alloc_range(offset, size), /*read_provenance*/ false)
+    /// `range` is relative to this allocation reference, not the base of the allocation.
+    pub fn read_integer(&self, range: AllocRange) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
+        self.read_scalar(range, /*read_provenance*/ false)
     }
 
+    /// `offset` is relative to this allocation reference, not the base of the allocation.
     pub fn read_pointer(&self, offset: Size) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
         self.read_scalar(
             alloc_range(offset, self.tcx.data_layout().pointer_size),
@@ -917,6 +918,7 @@ impl<'tcx, 'a, Tag: Provenance, Extra> AllocRef<'a, 'tcx, Tag, Extra> {
         )
     }
 
+    /// `range` is relative to this allocation reference, not the base of the allocation.
     pub fn check_bytes(
         &self,
         range: AllocRange,
diff --git a/compiler/rustc_const_eval/src/interpret/traits.rs b/compiler/rustc_const_eval/src/interpret/traits.rs
index 9c48f3e8337..22c23df7b1a 100644
--- a/compiler/rustc_const_eval/src/interpret/traits.rs
+++ b/compiler/rustc_const_eval/src/interpret/traits.rs
@@ -1,6 +1,6 @@
 use std::convert::TryFrom;
 
-use rustc_middle::mir::interpret::{InterpResult, Pointer, PointerArithmetic};
+use rustc_middle::mir::interpret::{alloc_range, InterpResult, Pointer, PointerArithmetic};
 use rustc_middle::ty::{
     self, Ty, TyCtxt, COMMON_VTABLE_ENTRIES_ALIGN, COMMON_VTABLE_ENTRIES_DROPINPLACE,
     COMMON_VTABLE_ENTRIES_SIZE,
@@ -102,18 +102,18 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             )?
             .expect("cannot be a ZST");
         let size = vtable
-            .read_integer(
+            .read_integer(alloc_range(
                 pointer_size * u64::try_from(COMMON_VTABLE_ENTRIES_SIZE).unwrap(),
                 pointer_size,
-            )?
+            ))?
             .check_init()?;
         let size = size.to_machine_usize(self)?;
         let size = Size::from_bytes(size);
         let align = vtable
-            .read_integer(
+            .read_integer(alloc_range(
                 pointer_size * u64::try_from(COMMON_VTABLE_ENTRIES_ALIGN).unwrap(),
                 pointer_size,
-            )?
+            ))?
             .check_init()?;
         let align = align.to_machine_usize(self)?;
         let align = Align::from_bytes(align).map_err(|e| err_ub!(InvalidVtableAlignment(e)))?;