type alias Tuple.Modifyimport { type Tuple } from "https://deno.land/x/ts_toolbelt_unofficial@1.1.0/mod.ts"; const { Modify } = Tuple; Modify L with LMod & the [[x]] placeholder ExamplesExample 1 Type ParametersL extends ListLMod extends Listdefinition: Cast<[K in keyof LMod]: Replace<LMod[K], x, Exclude<At<L, K>, undefined>>, List>