Subtraction Types

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Using a clever combination of Pick to create an Omit: (Source: microsoft/TypeScript#19569)

export type Diff<T extends string, U extends string> = ({[P in T]: P} &
  {[P in U]: never} & {[x: string]: never})[T]
export type Omit<T, K extends keyof T> = Pick<T, Diff<keyof T, K>>

Better with conditional types : microsoft/TypeScript#19569 (comment)

export type Diff<T, U> = T extends U ? never : T;  // Remove types from T that are assignable to U
export type Omit<T, K extends keyof T> = Pick<T, Diff<keyof T, K>>

[basarat]

Add to never section: Using never to delete members 🌹