patch 9.1.0385: Vim9: crash with null_class and null_object

Problem:  Vim9: crash with null_class and null_object
          (Aliaksei Budavei)
Solution: Handle null_class and null_object correctly
          (Yegappan Lakshmanan)

fixes: #14678
closes: #14681

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

src/eval.c

@@ -6403,9 +6403,9 @@ echo_string_core(
 	    {
 		class_T *cl = tv->vval.v_class;
 		char *s = "class";
-		if (IS_INTERFACE(cl))
+		if (cl && IS_INTERFACE(cl))
 		    s = "interface";
-		else if (IS_ENUM(cl))
+		else if (cl && IS_ENUM(cl))
 		    s = "enum";
 		size_t len = STRLEN(s) + 1 +
 		    (cl == NULL ? 9 : STRLEN(cl->class_name)) + 1;

src/evalfunc.c

@@ -11497,7 +11497,7 @@ f_type(typval_T *argvars, typval_T *rettv)
 	case VAR_CLASS:
 	    {
 		class_T *cl = argvars[0].vval.v_class;
-		if (IS_ENUM(cl))
+		if (cl && IS_ENUM(cl))
 		    n = VAR_TYPE_ENUM;
 		else
 		    n = VAR_TYPE_CLASS;
@@ -11505,11 +11505,18 @@ f_type(typval_T *argvars, typval_T *rettv)
 	    }
 	case VAR_OBJECT:
 	    {
-		class_T *cl = argvars[0].vval.v_object->obj_class;
+		object_T *obj = argvars[0].vval.v_object;
-		if (IS_ENUM(cl))
+
-		    n = VAR_TYPE_ENUMVALUE;
+		if (obj == NULL)
-		else
 		    n = VAR_TYPE_OBJECT;
+		else
+		{
+		    class_T *cl = argvars[0].vval.v_object->obj_class;
+		    if (IS_ENUM(cl))
+			n = VAR_TYPE_ENUMVALUE;
+		    else
+			n = VAR_TYPE_OBJECT;
+		}
 		break;
 	    }
 	case VAR_UNKNOWN:

src/testdir/test_vim9_class.vim

@@ -545,6 +545,52 @@ def Test_using_null_class()
     @_ = null_class.member
   END
   v9.CheckDefExecAndScriptFailure(lines, ['E715: Dictionary required', 'E1363: Incomplete type'])
+
+  # Test for using a null class as a value
+  lines =<< trim END
+    vim9script
+    echo empty(null_class)
+  END
+  v9.CheckSourceFailure(lines, 'E1405: Class "" cannot be used as a value', 2)
+
+  # Test for using a null class with string()
+  lines =<< trim END
+    vim9script
+    assert_equal('class [unknown]', string(null_class))
+  END
+  v9.CheckSourceSuccess(lines)
+
+  # Test for using a null class with string()
+  lines =<< trim END
+    vim9script
+    assert_equal(12, type(null_class))
+    assert_equal('class<Unknown>', typename(null_class))
+  END
+  v9.CheckSourceSuccess(lines)
+enddef
+
+def Test_using_null_object()
+  # Test for using a null object as a value
+  var lines =<< trim END
+    vim9script
+    assert_equal(1, empty(null_object))
+  END
+  v9.CheckSourceSuccess(lines)
+
+  # Test for using a null object with string()
+  lines =<< trim END
+    vim9script
+    assert_equal('object of [unknown]', string(null_object))
+  END
+  v9.CheckSourceSuccess(lines)
+
+  # Test for using a null object with string()
+  lines =<< trim END
+    vim9script
+    assert_equal(13, type(null_object))
+    assert_equal('object<Unknown>', typename(null_object))
+  END
+  v9.CheckSourceSuccess(lines)
 enddef
 
 def Test_class_interface_wrong_end()

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    385,
 /**/
     384,
 /**/

src/vim9type.c

@@ -2091,10 +2091,12 @@ check_typval_is_value(typval_T *tv)
 	case VAR_CLASS:
 	    {
 		class_T *cl = tv->vval.v_class;
-		if (IS_ENUM(cl))
+		char_u *class_name = (cl == NULL) ? (char_u *)""
-		    semsg(_(e_using_enum_as_value_str), cl->class_name);
+							: cl->class_name;
+		if (cl && IS_ENUM(cl))
+		    semsg(_(e_using_enum_as_value_str), class_name);
 		else
-		    semsg(_(e_using_class_as_value_str), cl->class_name);
+		    semsg(_(e_using_class_as_value_str), class_name);
 	    }
 	    return FAIL;