message: Improve PlaceElem::Subslice handling
diff: @@ -678,11 +678,10 @@ pub fn trans_place<'tcx>(
  // slice[from:-to] in Python terms.
  match cplace.layout().ty.kind {
  - ty::Array(elem_ty, len) => {
  + ty::Array(elem_ty, _len) => {
  + assert!(!from_end, "array subslices are never `from_end`");
  let elem_layout = fx.layout_of(elem_ty);
  let ptr = cplace.to_ptr(fx);
  - let len = crate::constant::force_eval_const(fx, len)
  - .eval_usize(fx.tcx, ParamEnv::reveal_all());
  cplace = CPlace::for_ptr(
  ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * from as i64),
  fx.layout_of(fx.tcx.mk_array(elem_ty, to as u64 - from as u64)),
  