array.ts

// number -> array

type ArrayOfSize<N extends number> = N extends N ? (number extends N ? boolean[] : _ArrayOfSize<N, []>) : never;
type _ArrayOfSize<N extends number, R extends unknown[]> = R['length'] extends N ? R : _ArrayOfSize<N, [true, ...R]>;

// verify
type A = ArrayOfSize<3>; // [true, true, true]
type B = ArrayOfSize<1>; // [true]
type C = ArrayOfSize<0>; // []

// array -> number

type AP = A['length']; // 3
type BP = B['length']; // 1
type CP = C['length']; // 0