Test.hx

using Test;

class Test {
	var A (default, never): Int = 1;

	public function new() {
	}

	public function set(value:Int) {
		trace(value);
	}

	public static inline function add(t:Test, other:Int) {
		t.set(t.A + other); // create temp variable
	}

	public static inline function add2(t:Test, other:Int) {
		t.set(other); // doesn't
	}

	static var t : Test;

	static function main() {
		t = new Test();
		t.add(2);
		t.add2(2);
	}
}

test.js

// Generated by Haxe 4.0.0-preview.4+e926671
(function () { "use strict";
var $hxEnums = $hxEnums || {};
var Test = function() {
	this.A = 1;
};
Test.add = function(t,other) {
	t.set(t.A + other);
};
Test.add2 = function(t,other) {
	t.set(other);
};
Test.main = function() {
	Test.t = new Test();
	var t = Test.t;
	t.set(t.A + 2);
	Test.t.set(2);
};
Test.prototype = {
	set: function(value) {
		console.log("Test.hx:10:",value);
	}
};
Test.main();
})();