Function f2

tests/select.test.ts:378–391

(input: Input)

      // select with an object that's a union by union
      const f2 = (input: Input) =>
        match(input)
          .with({ value: P.select({ type: P.union('a', 'b') }) }, (x) => {
            type t = Expect<
              Equal<
                typeof x,
                { type: 'a'; v: string } | { type: 'b'; v: number }
              >
            >;

            return x.v;
          })
          .with({ value: { type: 'c' } }, () => 'c')
          .exhaustive();

      expect(f({ value: { type: 'a', v: 'hello' } })).toEqual('hello');
      expect(f2({ value: { type: 'a', v: 'hello' } })).toEqual('hello');