fn build_union_fields_for_direct_tag_enum<'ll, 'tcx>( cx: &CodegenCx<'ll, 'tcx>, enum_adt_def: AdtDef<'tcx>, enum_type_and_layout: TyAndLayout<'tcx>, enum_type_di_node: &'ll DIType, variant_indices: &mut dyn Iterator<Item = VariantIdx>, tag_field: usize) -> SmallVec<[&'ll DIType; 16]>