JS support issue of MadeHand.best(): when flutter code compiled to JS to run on Chrome or Edge browser

[wfzhou2]

In a flutter application, when the device selected to run (in VS Code) is Chrome or Edge browser (web-javascript), the MadeHand.best() method return is not always right. Probably due to integer is 32 bit in JavaScript in browser and 64 bit in Dart/Flutter?

When device is browser, MadeHand.best() hand evaluation result is not consistent at all. For example,

• cards 'QdKsQsJhTd9h8c' or 'KsQsJhTd9h' evaluated to be MadeHandType.fullHouse with a hashcode of 167
• cards '6d2s4s5h3d' evaluated to be MadeHandType.fullHouse with a hashcode of 265
• cards '6d2s4s5h3d2hQd' evaluated to be MadeHandType.trips with a hashcode of 2270
• cards 'Ad2s4s5h3d2h2d' evaluated to be right as MadeHandType.straight with a hashcode of 1609, yet the 5 cards straight 'Ad2s4s5h3d' evaluated to be MadeHandType.fullHouse with a hashcode of 265

However, if device selected is a Android emulator (Pixel 6 API 29), all the above cards are correctly evaluated to be MadeHandType.straight.

A little more digging and I think the issue is in ImmutableCardSet class, where the _indexUnion probably should be fixnum:Int64 to be JS safe. Though JS number can be as large as 2^53-1, however, any bit operations in JS are operated on 32 bit int. So any bit operation on integer larger than 2^32-1 inside JS would cause issue.