Peculiar types found in TS land

TypePeculiarities.ts

//@see https://github.com/microsoft/TypeScript/issues/23182#issuecomment-379091887
type swithcNever<T, A, B> = [T] extends [never] ? A : B;

//@see https://stackoverflow.com/a/63568058/11407695
type Flatten<T extends any[]> = T extends [infer U, ...infer R]
  ? U extends any[]
    ? [...Flatten<U>, ...Flatten<R>]
    : [U, ...Flatten<R>]
  : [];

//@see https://stackoverflow.com/a/50375286/11407695
type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends ((k: infer I) => void) ? I : never