Use it in the library, and `InstSimplify` it away in the easy places

1 files changed, 16 insertions, 1 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index c3f26da8a79..460cd377c8f 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -9,7 +9,7 @@ use rustc_middle::mir;
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_target::abi::{FieldIdx, FIRST_VARIANT};
 
-use super::{ImmTy, InterpCx, InterpResult, Machine, PlaceTy, Projectable, Scalar};
+use super::{ImmTy, Immediate, InterpCx, InterpResult, Machine, PlaceTy, Projectable, Scalar};
 use crate::util;
 
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
@@ -303,6 +303,21 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let variant_dest = self.project_downcast(dest, variant_index)?;
                 (variant_index, variant_dest, active_field_index)
             }
+            mir::AggregateKind::RawPtr(..) => {
+                // Trying to `project_field` into pointers tends not to work,
+                // so build the `Immediate` from the parts directly.
+                let [data, meta] = &operands.raw else {
+                    bug!("{kind:?} should have 2 operands, had {operands:?}");
+                };
+                let data = self.eval_operand(data, None)?;
+                let data = self.read_pointer(&data)?;
+                let meta = self.eval_operand(meta, None)?;
+                let meta = self.read_mem_place_meta(&meta)?;
+                let ptr_imm = Immediate::new_pointer_with_meta(data, meta, self);
+                let ptr = ImmTy::from_immediate(ptr_imm, dest.layout);
+                self.copy_op(&ptr, dest)?;
+                return Ok(());
+            }
             _ => (FIRST_VARIANT, dest.clone(), None),
         };
         if active_field_index.is_some() {