Spread syntax can't work with iterables (Set, Map) -- downlevelIteration issue

// Input
const set = new Set([1, 2, 3]);

export const spread = [...set, 4, 5];

// Output lib.esm.js
var set =
/*#__PURE__*/
new Set([1, 2, 3]);
var spread =
/*#__PURE__*/
[].concat(set, 4, 5);

export { spread };
//# sourceMappingURL=lib.esm.js.map

Current Behavior

import { spread } from 'lib';

console.log(spread);
// [Set(3), 4, 5]

Expected behavior

import { spread } from 'lib';

console.log(spread);
// [1, 2, 3, 4, 5]

Suggested solution(s)

Additional context

Your environment

Software	Version(s)
TSDX	0.11.0
TypeScript	3.7.3
Browser	Chrome
npm/Yarn	6.12.1
Node	v13.1.0
Operating System	MacOS 10.15

[ambroseus]

another solution:

1. use option "downlevelIteration": true in tsconfig
2. tsdx build --target node result - es6 as is without transpilation:

const spread = [...
/*#__PURE__*/
new Set([1, 2, 3]), 4, 5];
console.log(spread);

[ambroseus]

related: https://babeljs.io/docs/en/babel-plugin-transform-spread

"plugins": [
    ["@babel/plugin-transform-spread", {
      "loose": true
    }]
  ]

loose defaults to false. In loose mode true, all iterables are assumed to be arrays.