Primary AS3 itches that make me run screaming for Haxe:

1. Generics. AS3 not having proper generics in favor of that Vector.<Abomination> is just embarassing, and makes for so much code damage.

2. Reliable type inference. I don't infer members, return values or method args, but being able to infer local var types is such a godsend and makes for quicker coding. 

3. Iterable. AS3 for loops are just so verbose, and coupled with the delight of variable redefinition warnings makes writing loops and nested loops and so forth just a constant itch. Haxe lacks traditional for loops in favor of iterators and the code readability goes through the roof as a result, in addition to just making writing the code less irritating to write.

4. Inline functions. Function inlining in ASC is a pure performance thing with irritating limitations. In Haxe it can be boiled down to syntactic sugar; It lets me break down code into functions without worrying about the function call overhead. Significant code readability and reuse boost. Welcome back to AS3 with epic fucking method bodies. 

5. Better collections. AS3 could pretend to be up there with the Polygonal DS lib, but that lib is written in Haxe. With Haxe and iterators you get super clean, fast collections with proper strong typing. In AS3 you get great collections and the most irritating way of working with them ever. There's just no contest.

6. Fewer keywords(!). At first I was sad there was no abstract, or even protected or internal in Haxe. Now I'm thankful. All that god damn access control was bogging me down in management. With nothing but private and public to worry about, I spend significantly less time on nonsense "code design".

7. Variables in interface declarations. Nuff said.

I could probably think of more but the basic issue is simply that AS3 is more hassle to write, requires you to keep both hands on the steering wheel at all times, and generally performs worse. With Haxe, the set of limitations and empowerments both keep my eyes on the ball but stops me from making daft bookkeeping-mistakes. Starting out, it felt like it was trying to hold me down. Now, it just feels like AS3 is doing its damnedest to make sure I spend more time thinking about bullshit that shouldn't even figure into my thought process.
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