[gjs] lang: Fix chaining up to interface methods w/args

[Philip Chimento <pchimento src gnome org>]

commit ea6decf10280c1db0cceb5f19827d02874b21c7c
Author: Philip Chimento <philip endlessm com>
Date:   Tue Jul 28 16:04:01 2015 -0700

    lang: Fix chaining up to interface methods w/args
    
    Calling Interface.some_method(this, arg) from inside the implementation
    of an interface did not work correctly.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=752984

 installed-tests/js/testInterface.js |   14 ++++++++++++++
 modules/lang.js                     |    2 +-
 2 files changed, 15 insertions(+), 1 deletions(-)
---
diff --git a/installed-tests/js/testInterface.js b/installed-tests/js/testInterface.js
index db370f7..d634e76 100644
--- a/installed-tests/js/testInterface.js
+++ b/installed-tests/js/testInterface.js
@@ -16,6 +16,10 @@ const AnInterface = new Lang.Interface({
         return 'AnInterface.optionalGeneric()';
     },
 
+    argumentGeneric: function (arg) {
+        return 'AnInterface.argumentGeneric(' + arg + ')';
+    },
+
     usesThis: function () {
         return this._interfacePrivateMethod();
     },
@@ -64,6 +68,10 @@ const ObjectImplementingAnInterface = new Lang.Class({
 
     optionalGeneric: function () {
         return AnInterface.optionalGeneric(this);
+    },
+
+    argumentGeneric: function (arg) {
+        return AnInterface.argumentGeneric(this, arg + ' (hello from class)');
     }
 });
 
@@ -160,6 +168,12 @@ function testObjectCanChainUpToInterface() {
     JSUnit.assertEquals('AnInterface.optional()', obj.optional());
 }
 
+function testObjectCanChainUpToInterfaceWithArguments() {
+    let obj = new ObjectImplementingAnInterface();
+    JSUnit.assertEquals('AnInterface.argumentGeneric(arg (hello from class))',
+        obj.argumentGeneric('arg'));
+}
+
 function testObjectCanDeferToInterfaceGetter() {
     let obj = new ObjectImplementingAnInterface();
     JSUnit.assertEquals('AnInterface.some_prop getter', obj.some_prop);
diff --git a/modules/lang.js b/modules/lang.js
index 5179fd9..b9d16f4 100644
--- a/modules/lang.js
+++ b/modules/lang.js
@@ -463,7 +463,7 @@ Interface.prototype._init = function (params) {
         if (typeof descriptor.value === 'function') {
             let interfaceProto = this.prototype;  // capture in closure
             this[name] = function () {
-                return interfaceProto[name].apply.apply(interfaceProto[name],
+                return interfaceProto[name].call.apply(interfaceProto[name],
                     arguments);
             };
         }