Reapply "Auto merge of rust-lang#133734 - scottmcm:lower-indexing-to-ptrmetadata, r=davidtwco,RalfJung"

This reverts commit 122a55b.

Author: compiler-errors

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -586,12 +586,27 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             ) => {}
             Rvalue::ShallowInitBox(_, _) => {}
 
-            Rvalue::UnaryOp(_, operand) => {
+            Rvalue::UnaryOp(op, operand) => {
                 let ty = operand.ty(self.body, self.tcx);
-                if is_int_bool_float_or_char(ty) {
-                    // Int, bool, float, and char operations are fine.
-                } else {
-                    span_bug!(self.span, "non-primitive type in `Rvalue::UnaryOp`: {:?}", ty);
+                match op {
+                    UnOp::Not | UnOp::Neg => {
+                        if is_int_bool_float_or_char(ty) {
+                            // Int, bool, float, and char operations are fine.
+                        } else {
+                            span_bug!(
+                                self.span,
+                                "non-primitive type in `Rvalue::UnaryOp{op:?}`: {ty:?}",
+                            );
+                        }
+                    }
+                    UnOp::PtrMetadata => {
+                        if !ty.is_ref() && !ty.is_unsafe_ptr() {
+                            span_bug!(
+                                self.span,
+                                "non-pointer type in `Rvalue::UnaryOp({op:?})`: {ty:?}",
+                            );
+                        }
+                    }
                 }
             }
 

compiler/rustc_const_eval/src/interpret/step.rs

@@ -9,6 +9,7 @@ use rustc_middle::ty::layout::FnAbiOf;
 use rustc_middle::ty::{self, Instance, Ty};
 use rustc_middle::{bug, mir, span_bug};
 use rustc_span::source_map::Spanned;
+use rustc_span::{DesugaringKind, Span};
 use rustc_target::callconv::FnAbi;
 use tracing::{info, instrument, trace};
 
@@ -80,7 +81,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         use rustc_middle::mir::StatementKind::*;
 
         match &stmt.kind {
-            Assign(box (place, rvalue)) => self.eval_rvalue_into_place(rvalue, *place)?,
+            Assign(box (place, rvalue)) => {
+                self.eval_rvalue_into_place(rvalue, *place, stmt.source_info.span)?
+            }
 
             SetDiscriminant { place, variant_index } => {
                 let dest = self.eval_place(**place)?;
@@ -159,6 +162,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         &mut self,
         rvalue: &mir::Rvalue<'tcx>,
         place: mir::Place<'tcx>,
+        span: Span,
     ) -> InterpResult<'tcx> {
         let dest = self.eval_place(place)?;
         // FIXME: ensure some kind of non-aliasing between LHS and RHS?
@@ -250,8 +254,13 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let src = self.eval_place(place)?;
                 let place = self.force_allocation(&src)?;
                 let mut val = ImmTy::from_immediate(place.to_ref(self), dest.layout);
-                if !place_base_raw {
+                if !place_base_raw
+                    && span.desugaring_kind() != Some(DesugaringKind::IndexBoundsCheckReborrow)
+                {
                     // If this was not already raw, it needs retagging.
+                    // As a special hack, we exclude the desugared `PtrMetadata(&raw const *_n)`
+                    // from indexing. (Really we should not do any retag on `&raw` but that does not
+                    // currently work with Stacked Borrows.)
                     val = M::retag_ptr_value(self, mir::RetagKind::Raw, &val)?;
                 }
                 self.write_immediate(*val, &dest)?;