FunctionThread

import haxe.macro.Expr;
import haxe.macro.Context;
using haxe.macro.ExprTools;
using haxe.macro.MacroStringTools;


class FunctionThread {

  public static macro function thread(exprs:Array<Expr>) {
    var exprs = [ for (expr in exprs) macro var _ = $expr  ];
    exprs.push(macro _);
    return macro $b{exprs};
  }
  
  
  public static macro function threadr(exprs:Array<Expr>) {
    exprs.reverse();
    var exprs = [ for (expr in exprs) macro var _ = $expr  ];
    exprs.push(macro _);
    
    return macro $b{exprs};
  }  

}

Test.hx

import FunctionThread.thread;
import FunctionThread.threadr;

class Test {

  static function sum(a,b) return a+b;

  static function getPointAsObject() 
    return {x:100,y:300};

  static function getPointAsArray() 
    return [100,300];
  
  
  static function main() {
    var x = 0;
    var res = thread(
      sum(x,1),
      sum(_,1),
      sum(_,2),
      sum(3,_)
      );
    trace(res);
    
    
    var x = 0;
    var res = threadr(
      1,
      sum(_,1),
      sum(1,2)
      );
    trace(res);
    
    var x = 0;
    var res = thread(
      getPointAsObject(),
      sum(_.x,_.y),
      sum(_,1),
      sum(_,2),
      sum(3,_)
      );
    trace(res);    
    
    
    var x = 0;
    var res = thread(
      getPointAsArray(),
      sum(_[0],_[1]),
      sum(_,1),
      sum(_,2),
      sum(3,_)
      );
    trace(res);       
    
  }
}

http://try-haxe.mrcdk.com/#f3e42

// Generated by Haxe 4.0.0-rc.2+032d959
(function ($global) { "use strict";
var HxOverrides = function() { };
HxOverrides.iter = function(a) {
	return { cur : 0, arr : a, hasNext : function() {
		return this.cur < this.arr.length;
	}, next : function() {
		return this.arr[this.cur++];
	}};
};
var Test = function() { };
Test.sum = function(a,b) {
	return a + b;
};
Test.getPointAsObject = function() {
	return { x : 100, y : 300};
};
Test.getPointAsArray = function() {
	return [100,300];
};
Test.main = function() {
	console.log("root/program/Test.hx:23:",Test.sum(3,Test.sum(Test.sum(Test.sum(0,1),1),2)));
	console.log("root/program/Test.hx:32:",1);
	var _ = Test.getPointAsObject();
	console.log("root/program/Test.hx:42:",Test.sum(3,Test.sum(Test.sum(Test.sum(_.x,_.y),1),2)));
	var _1 = Test.getPointAsArray();
	console.log("root/program/Test.hx:53:",Test.sum(3,Test.sum(Test.sum(Test.sum(_1[0],_1[1]),1),2)));
};
Test.main();
})({});

// Generated by Haxe 4.0.0-rc.2+032d959
(function ($global) { "use strict";
var HxOverrides = function() { };
HxOverrides.iter = function(a) {
	return { cur : 0, arr : a, hasNext : function() {
		return this.cur < this.arr.length;
	}, next : function() {
		return this.arr[this.cur++];
	}};
};
var Test = function() { };
Test.sum = function(a,b) {
	return a + b;
};
Test.getPointAsObject = function() {
	return { x : 100, y : 300};
};
Test.getPointAsArray = function() {
	return [100,300];
};
Test.main = function() {
	var x = 0;
	var _ = Test.sum(x,1);
	var _1 = Test.sum(_,1);
	var _2 = Test.sum(_1,2);
	var _3 = Test.sum(3,_2);
	var res = _3;
	console.log("root/program/Test.hx:23:",res);
	var x1 = 0;
	var _4 = Test.sum(1,2);
	var _5 = Test.sum(_4,1);
	var _6 = 1;
	var res1 = _6;
	console.log("root/program/Test.hx:32:",res1);
	var x2 = 0;
	var _7 = Test.getPointAsObject();
	var _8 = Test.sum(_7.x,_7.y);
	var _9 = Test.sum(_8,1);
	var _10 = Test.sum(_9,2);
	var _11 = Test.sum(3,_10);
	var res2 = _11;
	console.log("root/program/Test.hx:42:",res2);
	var x3 = 0;
	var _12 = Test.getPointAsArray();
	var _13 = Test.sum(_12[0],_12[1]);
	var _14 = Test.sum(_13,1);
	var _15 = Test.sum(_14,2);
	var _16 = Test.sum(3,_15);
	var res3 = _16;
	console.log("root/program/Test.hx:53:",res3);
};
Test.main();
})({});