patch 9.0.1703: Vim9 Calling a method in an extended class fails

Problem: Vim9 Calling a method in an extended class fails
Solution: use method index directly

closes: #12778

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

src/testdir/test_vim9_class.vim

@@ -1913,4 +1913,39 @@ def Test_extends_method_crashes_vim()
   v9.CheckScriptSuccess(lines)
 enddef
 
+" Test for calling a method in a class that is extended
+def Test_call_method_in_extended_class()
+  var lines =<< trim END
+    vim9script
+
+    var prop_init_called = false
+    var prop_register_called = false
+
+    class Property
+      def Init()
+        prop_init_called = true
+      enddef
+
+      def Register()
+        prop_register_called = true
+      enddef
+    endclass
+
+    class Bool extends Property
+    endclass
+
+    def Observe(obj: Property)
+      obj.Register()
+    enddef
+
+    var p = Property.new()
+    Observe(p)
+
+    p.Init()
+    assert_true(prop_init_called)
+    assert_true(prop_register_called)
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1703,
 /**/
     1702,
 /**/

src/vim9class.c

@@ -209,6 +209,13 @@ object_index_from_itf_index(class_T *itf, int is_method, int idx, class_T *cl)
 	siemsg("index %d out of range for interface %s", idx, itf->class_name);
 	return 0;
     }
+
+    // If "cl" is the interface or the class that is extended, then the method
+    // index can be used directly and there is no need to search for the method
+    // index in one of the child classes.
+    if (cl == itf)
+	return idx;
+
     itf2class_T *i2c;
     for (i2c = itf->class_itf2class; i2c != NULL; i2c = i2c->i2c_next)
 	if (i2c->i2c_class == cl && i2c->i2c_is_method == is_method)