while () {} else {} for () {} else {}

ElseMacros.hx

package ;
import haxe.macro.Expr;

/**
 * ...
 * @author deep <system.grand@gmail.com>
 */
class ElseMacros
{

  /**
	 * ElseMacros.build( for (i in 0...10) trace(i), trace("empty loop") ); // no trace
	 *	
	 * ElseMacros.build( for (i in 0...0) trace(i), trace("empty loop 2") ); // empty loop 2
	 */
	macro static public function build(eLoop:Expr, eElse:Expr):Expr {
		
		var pre = macro var __flag__ = true;
		var body = macro __flag__ = false;
		var pos = macro if (__flag__) $eElse;
		
		return switch (eLoop.expr) {
			case EFor(it, expr): 
				macro { $pre;
					for ($it) {
						$body;
						$expr;
					}
				$pos;
				}
			case EWhile(econd, expr, true):
				macro { $pre;
					while ($econd) {
						$body;
						$expr;
					}
				$pos;
				}
			case _: throw "unsupported loop";
		}
		
		return eLoop;
	}
	
}