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If<C, T, F>

EasyP3Coding

Implement If<C, T, F>: it returns T when C is true and F when C is false. C is constrained to boolean, so If<null, 'a', 'b'> is a type error.

Tests your type must pass

type cases = [
  Expect<Equal<If<true, 'a', 'b'>, 'a'>>,
  Expect<Equal<If<false, 'a', 2>, 2>>,
  Expect<Equal<If<true, { x: 1 }, never>, { x: 1 }>>,
]

// @ts-expect-error null is not boolean
type error = If<null, 'a', 'b'>

Hints

TypeScript
Run and Submit type-check your solution against the tests.