{"ast_node_type":"other","tokens":[{"end":65,"kind":"keyword","start":0,"text":"FieldsShape::Arbitrary"}]}
        FieldsShape::Arbitrary { mut offsets, memory_index } => {
    let (outer_fields, promoted_offsets, promoted_memory_index) = match prefix.fields {
            let mut inverse_memory_index = memory_index.invert_bijective_mapping();