Fix __spreadArray for non-concat-spreadables

[rbuckton]

The __spreadArray helper uses Array.concat, which doesn't work with DOM NodeList or HTMLCollection. This changes the __spreadArray helper to fall back to Array.prototype.slice.call(from) to ensure the elements of from are concatenated properly.

Fixes TypeScript side of microsoft/tslib#153

[DanielRosenwasser]

I don't know how crazy we want to get with this one but we could also do

Suggested change

	return to.concat(ar || Array.prototype.slice.call(from));
	return to.concat(ar || (from instanceof Array ? from : Array.prototype.slice.call(from)));

[rbuckton]

I considered that, including a check for isConcatSpreadable, but it just became long-winded and the performance benefits seemed negligible.

[rbuckton]

I was originally thinking of doing this:

var __spreadArray = (this && this.__spreadArray) || (function () {
    var toString = Object.prototype.toString;
    var slice = Array.prototype.slice;
    var isArray = typeof Array.isArray === "function" ? Array.isArray : function (obj) { return toString.call(obj) === "[object Array]"; };
    var isConcatSpreadable = typeof Symbol === "function" && Symbol.isConcatSpreadable;
    function canConcat(obj) { return isArray(obj) || isConcatSpreadable && obj[isConcatSpreadable]; }
    return function (to, from, pack) {
        if (pack || arguments.length === 2) {
            for (var i = 0, l = from.length, ar; i < l; i++) {
                if (ar || !(i in from)) {
                    if (!ar) ar = slice.call(from, 0, i);
                    ar[i] = from[i];
                }
            }
            if (ar) from = ar;
        }
        return to.concat(canConcat(from) ? from : slice.call(from));
    }
})();

[DanielRosenwasser]

We'll need to cherry-pick this in for release-4.4, so ping me when you're ready to merge.

[rbuckton]

Also, take a look at microsoft/tslib#155 to fix this on the tslib side, since the concat-spreadable thing is a back-compat issue.

[DanielRosenwasser]

@typescript-bot cherry-pick this to release-4.4

[typescript-bot]

Heya @DanielRosenwasser, I've started to run the task to cherry-pick this into release-4.4 on this PR at 7c7e0eb. You can monitor the build here.

[DanielRosenwasser]

@typescript-bot cherry-pick this to release-4.4 and LKG

[typescript-bot]

Heya @DanielRosenwasser, I've started to run the task to cherry-pick this into release-4.4 on this PR at 7c7e0eb. You can monitor the build here.

[typescript-bot]

Hey @DanielRosenwasser, I've opened #45416 for you.

[typescript-bot]

Hey @DanielRosenwasser, I couldn't open a PR with the cherry-pick. (You can check the log here). You may need to squash and pick this PR into release-4.4 manually.