typomath/src/steps/four.ts

27 lines
738 B
TypeScript

import 'reflect-metadata'
import overload from '../util/overload.js'
const addImps = [
(x: number, y: number) => {
if (typeof x === 'number' && typeof y === 'number') return x + y
throw new TypeError('Can only add numbers')
},
(x: string, y: string) => {
if (typeof x === 'string' && typeof y === 'string') {
return 'Yay' + x + y
}
throw new TypeError('or strings')
},
(x: bigint, final?: string) => x.toString() + final
] as const
const adder = overload(addImps)
console.log(adder(1, 2))
console.log(adder('a', 'b'))
console.log(adder(2n))
// And make sure typescript complains on signatures not covered by an imp:
//@ts-expect-error
console.log(adder(2n, 4n))