Rustc changes for permissive provenance

2 files changed, 8 insertions, 5 deletions

diff --git a/compiler/rustc_middle/src/mir/interpret/pointer.rs b/compiler/rustc_middle/src/mir/interpret/pointer.rs
index c71aea417ec..26da93b9dce 100644
--- a/compiler/rustc_middle/src/mir/interpret/pointer.rs
+++ b/compiler/rustc_middle/src/mir/interpret/pointer.rs
@@ -120,9 +120,11 @@ pub trait Provenance: Copy + fmt::Debug {
     where
         Self: Sized;
 
-    /// Provenance must always be able to identify the allocation this ptr points to.
+    /// If `OFFSET_IS_ADDR == false`, provenance must always be able to
+    /// identify the allocation this ptr points to (i.e., this must return `Some`).
+    /// Otherwise this function is best-effort (but must agree with `Machine::ptr_get_alloc`).
     /// (Identifying the offset in that allocation, however, is harder -- use `Memory::ptr_get_alloc` for that.)
-    fn get_alloc_id(self) -> AllocId;
+    fn get_alloc_id(self) -> Option<AllocId>;
 }
 
 impl Provenance for AllocId {
@@ -147,8 +149,8 @@ impl Provenance for AllocId {
         Ok(())
     }
 
-    fn get_alloc_id(self) -> AllocId {
-        self
+    fn get_alloc_id(self) -> Option<AllocId> {
+        Some(self)
     }
 }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/value.rs b/compiler/rustc_middle/src/mir/interpret/value.rs
index 9cffdf2993e..eeee170f43f 100644
--- a/compiler/rustc_middle/src/mir/interpret/value.rs
+++ b/compiler/rustc_middle/src/mir/interpret/value.rs
@@ -344,7 +344,8 @@ impl<'tcx, Tag: Provenance> Scalar<Tag> {
                 } else {
                     // We know `offset` is relative, since `OFFSET_IS_ADDR == false`.
                     let (tag, offset) = ptr.into_parts();
-                    Err(Scalar::Ptr(Pointer::new(tag.get_alloc_id(), offset), sz))
+                    // Because `OFFSET_IS_ADDR == false`, this unwrap can never fail.
+                    Err(Scalar::Ptr(Pointer::new(tag.get_alloc_id().unwrap(), offset), sz))
                 }
             }
         }