{"ast_node_type":"variable","tokens":[{"end":99,"kind":"keyword","start":0,"text":"let"}]}
                let variant_fields: IndexVec<VariantIdx, IndexVec<FieldIdx, CoroutineSavedLocal>> =
                // so variant_fields and variant_source_info should have 3 elements.
                    iter::repeat(IndexVec::new()).take(CoroutineArgs::RESERVED_VARIANTS).collect();