message: comment on mut-to-shr transmutes
diff: @@ -462,7 +462,8 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'a, 'mir, '
  // also using `var`, and that would be okay.
  }
  (UsageKind::Read, Borrow::Mut(Mut::Uniq(_))) => {
  - // A mut got transmuted to shr. The mut borrow must be reactivatable.
  + // A mut got transmuted to shr. Can happen even from compiler transformations:
  + // `&*x` gets optimized to `x` even when `x` is a `&mut`.
  }
  (UsageKind::Write, Borrow::Frz(_)) => {
  // This is just invalid.
  