type alias Object.Unionizeimport { type Object } from "https://deno.land/x/ts_toolbelt_unofficial@1.1.0/mod.ts"; const { Unionize } = Object; Make the fields of O union the ones of O1 ExamplesExample 1 Type ParametersO extends objectO1 extends objectoptionalK extends Key = Keydefinition: [P in keyof O]: P extends K ? O[P] | At<O1, P> : O[P] & { }