{"ast_node_type":"other","tokens":[{"end":85,"kind":"keyword","start":0,"text":"//"}]}
            // FIXME(eddyb) build a better abstraction for permutations, if possible.
            // by preserving the order but keeping only one disjoint "half" each.
            let inverse_memory_index_b: IndexVec<u32, FieldIdx> = inverse_memory_index