I just read that Haxe 3.1 was
released (
release notes), so far it seems like everything is working. (only tested the flash target)
Except for one minor issue with the flash target and UInt. From
what I read it's related to the new UInt class in Haxe and the problem for the compiler to detect if it should use the openFL's UInt or the Haxe std one. To solve the problem you need to either move the Haxe std UInt.hx file in your source folder or rename/remove the UInt.hx file in the openFL folder.
Another wired bug appeared, on classes that extend FlxSprite the super() call now needs x and y parameters.
tl;dr; to fix the compiler error about UInt rename/remove the UInt.hx file in the openFL folder.