It would be nice if something like this worked. It does show an error in the editor and doesn't pass the script test:types, but test passes because Jest strips all the types before preforming a test run.

// idea for packages/dinero.js/src/api/__tests__/toSnapshot.test.ts in branch feat/to-units
describe('custom transformer', () => {
  const amount = new Big(500);
  const d = dinero({ amount, currency: bigjsUSD });
  const expected = toSnapshot(d, ({ value }) => value.amount);

  it('returns the expected value', () => {
    expect(expected).toBe(amount);
  });

  it('returns the expected type', () => {
    expect(() => {
      // @ts-expect-no-error
      const typed: Big = expected;
    }).not.toThrow();
  });
});

It's a good idea to add return types to functions. Initially I disabled it because I thought inference was better, but explicit return types ensure we don't accidentally break the API or that we don't have unexpected return types as in the example you shared.

To do this, we need to:

• Re-enable this rule
• Add explicit return types to each function (once the ESLint rule is re-enabled, running yarn lint) should report all changes to make

Hi @sarahdayan am new to contributions, can I try to work on this ?