Automatic Type Guarding with Effect.filter* API

const RefreshTokenSuccess = S.struct({
  id_token: Token,
  refresh_token: RefreshToken,
  expires_in: S.string,
  user_id: S.string
}).pipe(S.attachPropertySignature('_tag', 'Success'));

const RefreshTokenError = S.struct({
  error: S.struct({
    code: S.number,
    message: S.string,
    status: S.string
  })
}).pipe(S.attachPropertySignature('_tag', 'Failure'));

const RefreshTokenResponse = S.union(RefreshTokenSuccess, RefreshTokenError);

const result = (u: unknown) =>
  S.parse(RefreshTokenResponse)(u).pipe(
    Effect.filterOrDie(
      (res) => res._tag === 'Success',
      () => 'Error!'
    ),
    // type error because the above isn't being type guarded I guess..
    Effect.map(res => res.id_token)
  );