Represent the raw pointer for a array length check as a new kind of fake borrow

compiler/stable_mir/src/mir/body.rs

@@ -457,7 +457,7 @@ pub enum Rvalue {
     ///
     /// This is generated by pointer casts like `&v as *const _` or raw address of expressions like
     /// `&raw v` or `addr_of!(v)`.
-    AddressOf(Mutability, Place),
+    AddressOf(RawPtrKind, Place),
 
     /// Creates an aggregate value, like a tuple or struct.
     ///
@@ -577,7 +577,7 @@ impl Rvalue {
             }
             Rvalue::AddressOf(mutability, place) => {
                 let place_ty = place.ty(locals)?;
-                Ok(Ty::new_ptr(place_ty, *mutability))
+                Ok(Ty::new_ptr(place_ty, mutability.to_mutable_lossy()))
             }
             Rvalue::Len(..) => Ok(Ty::usize_ty()),
             Rvalue::Cast(.., ty) => Ok(*ty),
@@ -903,6 +903,24 @@ impl BorrowKind {
     }
 }
 
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Serialize)]
+pub enum RawPtrKind {
+    Mut,
+    Const,
+    FakeForPtrMetadata,
+}
+
+impl RawPtrKind {
+    pub fn to_mutable_lossy(self) -> Mutability {
+        match self {
+            RawPtrKind::Mut { .. } => Mutability::Mut,
+            RawPtrKind::Const => Mutability::Not,
+            // FIXME: There's no type corresponding to a shallow borrow, so use `&` as an approximation.
+            RawPtrKind::FakeForPtrMetadata => Mutability::Not,
+        }
+    }
+}
+
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Serialize)]
 pub enum MutBorrowKind {
     Default,

compiler/stable_mir/src/mir/pretty.rs

@@ -6,7 +6,9 @@ use std::{fmt, io, iter};
 use fmt::{Display, Formatter};
 
 use super::{AggregateKind, AssertMessage, BinOp, BorrowKind, FakeBorrowKind, TerminatorKind};
-use crate::mir::{Operand, Place, Rvalue, StatementKind, UnwindAction, VarDebugInfoContents};
+use crate::mir::{
+    Operand, Place, RawPtrKind, Rvalue, StatementKind, UnwindAction, VarDebugInfoContents,
+};
 use crate::ty::{AdtKind, IndexedVal, MirConst, Ty, TyConst};
 use crate::{Body, CrateDef, Mutability, with};
 
@@ -325,7 +327,7 @@ fn pretty_ty_const(ct: &TyConst) -> String {
 fn pretty_rvalue<W: Write>(writer: &mut W, rval: &Rvalue) -> io::Result<()> {
     match rval {
         Rvalue::AddressOf(mutability, place) => {
-            write!(writer, "&raw {} {:?}", pretty_mut(*mutability), place)
+            write!(writer, "&raw {} {:?}", pretty_raw_ptr_kind(*mutability), place)
         }
         Rvalue::Aggregate(aggregate_kind, operands) => {
             // FIXME: Add pretty_aggregate function that returns a pretty string
@@ -437,3 +439,11 @@ fn pretty_mut(mutability: Mutability) -> &'static str {
         Mutability::Mut => "mut ",
     }
 }
+
+fn pretty_raw_ptr_kind(kind: RawPtrKind) -> &'static str {
+    match kind {
+        RawPtrKind::Const => "const",
+        RawPtrKind::Mut => "mut",
+        RawPtrKind::FakeForPtrMetadata => "const (fake)",
+    }
+}

compiler/stable_mir/src/mir/visit.rs

@@ -308,7 +308,7 @@ pub trait MirVisitor {
     fn super_rvalue(&mut self, rvalue: &Rvalue, location: Location) {
         match rvalue {
             Rvalue::AddressOf(mutability, place) => {
-                let pcx = PlaceContext { is_mut: *mutability == Mutability::Mut };
+                let pcx = PlaceContext { is_mut: *mutability == RawPtrKind::Mut };
                 self.visit_place(place, pcx, location);
             }
             Rvalue::Aggregate(_, operands) => {