Improve demangling of class methods when using the loader (AssemblyScript#363)

Author: kazupon

lib/loader/index.js

@@ -265,7 +265,7 @@ function demangle(exports, baseModule) {
       let classElem = curr[className];
       if (typeof classElem === "undefined" || !classElem.prototype) {
         let ctor = function(...args) {
-          return ctor.wrap(ctor.prototype.constructor(...args));
+          return ctor.wrap(ctor.prototype.constructor(0, ...args));
         };
         ctor.prototype = {};
         ctor.wrap = function(thisValue) {
@@ -289,7 +289,16 @@ function demangle(exports, baseModule) {
           });
         }
       } else {
-        curr[name] = wrapFunction(elem, setargc);
+        if (name === 'constructor') {
+          curr[name] = wrapFunction(elem, setargc);
+        } else { // for methods
+          Object.defineProperty(curr, name, {
+            value: function (...args) {
+              setargc(args.length);
+              return elem(this.this, ...args);
+            }
+          });
+        }
       }
     } else {
       if (/^(get|set):/.test(name)) {

lib/loader/tests/index.js

@@ -60,5 +60,14 @@ assert.strictEqual(fn(2), 4);
 ptr = module.newFunction(module.varadd);
 assert.strictEqual(module.calladd(ptr, 2, 3), 5);
 
+// should be able to use a class
+var car = new module.Car(5);
+assert.strictEqual(car.numDoors, 5);
+assert.strictEqual(car.isDoorsOpen, 0);
+car.openDoors();
+assert.strictEqual(car.isDoorsOpen, 1);
+car.closeDoors();
+assert.strictEqual(car.isDoorsOpen, 0);
+
 // should be able to use trace
-module.dotrace(42);
+module.dotrace(42);