00300-hard-string-to-number.ts

// ============= Test Cases =============
import type { Equal, Expect } from './test-utils'

type cases = [
  Expect<Equal<ToNumber<'0'>, 0>>,
  Expect<Equal<ToNumber<'5'>, 5>>,
  Expect<Equal<ToNumber<'12'>, 12>>,
  Expect<Equal<ToNumber<'27'>, 27>>,
  Expect<Equal<ToNumber<'18@7_$%'>, never>>
]

// ============= Your Code Here =============
type ToNumber<S extends string> = S extends `${infer Num extends number}`
  ? Num
  : never