new haxe metadata proposal

Limit.hx

package mylib;

//extends or implements a special class/interface
class Limit implements haxe.rtti.Meta {
	
	//the 1st param tell what kinds of field it applies, just like "using"
	//Used as @limitMinMax(0, 100) or @mylib.Limit.limitMinMax(0, 100)
	static public function limitMinMax(field:Float, min:Float, max:Float):Bool { 
		//return whether the input is valid
		return min <= max; 
	}
	
	//macro metadata! 
	//Able to take Expr as param.
	//Used as @:limitExpr(!Math.isNaN(_)) or @:mylib.Limit.limitExpr(!Math.isNaN(_))
	@:macro static public function limitExpr(field:Float, e:haxe.macro.Expr):Bool {
		//optionally process the field using some haxe.macro.Context
		return true;
	}
}

Test.hx

using mylib.Limit;

class Test 
{
	@limitMinMax(0, 100) public var field1:String; //error: limitMinMax only applies to Float
	
	@limitMinMax public var field2:Float; //error: limitMinMax takes two arguments

	@limitMinMax(10, 0) public var field3:Float; //error: the function returns false

	@limitMinMax(0, 10) public var field3:Float; //alright!

	@mylib.Limit.limitMinMax(0, 10) public var field3:Float; //alright, with fully qualified name!
	
	public static function main() 
	{
		new B();
  	}
}