Disallow subclassing of some core types that are not subclasses of Instance

src/kuroko/object.h

@@ -187,7 +187,7 @@ typedef struct KrkClass {
 	size_t allocSize;         /**< @brief Size to allocate when creating instances of this class */
 	KrkCleanupCallback _ongcscan;   /**< @brief C function to call when the garbage collector visits an instance of this class in the scan phase */
 	KrkCleanupCallback _ongcsweep;  /**< @brief C function to call when the garbage collector is discarding an instance of this class */
-	KrkTable subclasses;
+	KrkTable subclasses;      /**< @brief Set of classes that subclass this class */
 
 	KrkObj * _getter;         /**< @brief @c %__getitem__  Called when an instance is subscripted */
 	KrkObj * _setter;         /**< @brief @c %__setitem__  Called when a subscripted instance is assigned to */

src/obj_base.c

@@ -79,6 +79,7 @@ static KrkValue _class_subclasses(int argc, const KrkValue argv[], int hasKw) {
 _noexport
 void _createAndBind_type(void) {
 	ADD_BASE_CLASS(vm.baseClasses->typeClass, "type", vm.baseClasses->objectClass);
+	vm.baseClasses->typeClass->allocSize = 0;
 	krk_defineNative(&vm.baseClasses->typeClass->methods, "__base__", krk_baseOfClass)->flags = KRK_NATIVE_FLAGS_IS_DYNAMIC_PROPERTY;
 	krk_defineNative(&vm.baseClasses->typeClass->methods, "__file__", krk_fileOfClass)->flags = KRK_NATIVE_FLAGS_IS_DYNAMIC_PROPERTY;
 	krk_defineNative(&vm.baseClasses->typeClass->methods, "__doc__", krk_docOfClass)  ->flags = KRK_NATIVE_FLAGS_IS_DYNAMIC_PROPERTY;

src/obj_bytes.c

@@ -379,6 +379,7 @@ KRK_METHOD(bytearray,__iter__,{
 _noexport
 void _createAndBind_bytesClass(void) {
 	KrkClass * bytes = ADD_BASE_CLASS(vm.baseClasses->bytesClass, "bytes", vm.baseClasses->objectClass);
+	bytes->allocSize = 0; /* cannot subclass */
 	KRK_DOC(BIND_METHOD(bytes,__init__),
 		"@brief An array of bytes.\n"
 		"@arguments iter=None\n\n"

src/obj_function.c

@@ -311,6 +311,7 @@ KRK_FUNC(classmethod,{
 _noexport
 void _createAndBind_functionClass(void) {
 	KrkClass * codeobject = ADD_BASE_CLASS(vm.baseClasses->codeobjectClass, "codeobject", vm.baseClasses->objectClass);
+	codeobject->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(codeobject,__str__);
 	BIND_METHOD(codeobject,_ip_to_line);
 	BIND_PROP(codeobject,__constants__);
@@ -320,6 +321,7 @@ void _createAndBind_functionClass(void) {
 	krk_finalizeClass(codeobject);
 
 	KrkClass * function = ADD_BASE_CLASS(vm.baseClasses->functionClass, "function", vm.baseClasses->objectClass);
+	function->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(function,__str__);
 	BIND_METHOD(function,_ip_to_line);
 	BIND_PROP(function,__doc__);
@@ -334,6 +336,7 @@ void _createAndBind_functionClass(void) {
 	krk_finalizeClass(function);
 
 	KrkClass * method = ADD_BASE_CLASS(vm.baseClasses->methodClass, "method", vm.baseClasses->objectClass);
+	method->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(method,__str__);
 	BIND_METHOD(method,_ip_to_line);
 	BIND_PROP(method,__doc__);

src/obj_numeric.c

@@ -136,6 +136,7 @@ KRK_METHOD(NotImplementedType,__hash__,{
 _noexport
 void _createAndBind_numericClasses(void) {
 	KrkClass * _int = ADD_BASE_CLASS(vm.baseClasses->intClass, "int", vm.baseClasses->objectClass);
+	_int->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(int,__init__);
 	BIND_METHOD(int,__str__);
 	BIND_METHOD(int,__int__);
@@ -148,6 +149,7 @@ void _createAndBind_numericClasses(void) {
 	KRK_DOC(_int, "Convert a number or string type to an integer representation.");
 
 	KrkClass * _float = ADD_BASE_CLASS(vm.baseClasses->floatClass, "float", vm.baseClasses->objectClass);
+	_float->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(float,__init__);
 	BIND_METHOD(float,__int__);
 	BIND_METHOD(float,__float__);
@@ -159,6 +161,7 @@ void _createAndBind_numericClasses(void) {
 	KRK_DOC(_float, "Convert a number or string type to a float representation.");
 
 	KrkClass * _bool = ADD_BASE_CLASS(vm.baseClasses->boolClass, "bool", vm.baseClasses->intClass);
+	_bool->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(bool,__init__);
 	BIND_METHOD(bool,__str__);
 	krk_defineNative(&_bool->methods, "__repr__", FUNC_NAME(bool,__str__));
@@ -166,12 +169,14 @@ void _createAndBind_numericClasses(void) {
 	KRK_DOC(_bool, "Returns False if the argument is 'falsey', otherwise True.");
 
 	KrkClass * _NoneType = ADD_BASE_CLASS(vm.baseClasses->noneTypeClass, "NoneType", vm.baseClasses->objectClass);
+	_NoneType->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(NoneType, __str__);
 	BIND_METHOD(NoneType, __hash__);
 	krk_defineNative(&_NoneType->methods, "__repr__", FUNC_NAME(NoneType,__str__));
 	krk_finalizeClass(_NoneType);
 
 	KrkClass * _NotImplementedType = ADD_BASE_CLASS(vm.baseClasses->notImplClass, "NotImplementedType", vm.baseClasses->objectClass);
+	_NotImplementedType->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(NotImplementedType, __str__);
 	BIND_METHOD(NotImplementedType, __hash__);
 	krk_defineNative(&_NotImplementedType->methods, "__repr__", FUNC_NAME(NotImplementedType,__str__));

src/obj_str.c

@@ -885,6 +885,7 @@ _corrupt:
 _noexport
 void _createAndBind_strClass(void) {
 	KrkClass * str = ADD_BASE_CLASS(vm.baseClasses->strClass, "str", vm.baseClasses->objectClass);
+	str->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(str,__init__);
 	BIND_METHOD(str,__iter__);
 	BIND_METHOD(str,__ord__);

src/obj_tuple.c

@@ -203,6 +203,7 @@ _unhashable:
 _noexport
 void _createAndBind_tupleClass(void) {
 	KrkClass * tuple = ADD_BASE_CLASS(vm.baseClasses->tupleClass, "tuple", vm.baseClasses->objectClass);
+	tuple->allocSize = 0; /* cannot subclass */
 	BIND_METHOD(tuple,__repr__);
 	BIND_METHOD(tuple,__getitem__);
 	BIND_METHOD(tuple,__len__);

src/object.c

@@ -327,7 +327,8 @@ KrkClass * krk_newClass(KrkString * name, KrkClass * baseClass) {
 }
 
 KrkInstance * krk_newInstance(KrkClass * _class) {
-	KrkInstance * instance = (KrkInstance*)allocateObject(_class->allocSize, KRK_OBJ_INSTANCE);
+	size_t allocSize = _class->allocSize ? _class->allocSize : sizeof(KrkInstance);
+	KrkInstance * instance = (KrkInstance*)allocateObject(allocSize, KRK_OBJ_INSTANCE);
 	instance->_class = _class;
 	krk_initTable(&instance->fields);
 	return instance;

src/vm.c

@@ -2601,6 +2601,11 @@ _finishReturn: (void)0;
 						krk_typeName(superclass));
 					goto _finishException;
 				}
+				if (AS_CLASS(superclass)->allocSize == 0) {
+					krk_runtimeError(vm.exceptions->typeError, "'%s' can not be subclassed",
+						AS_CLASS(superclass)->name->chars);
+					goto _finishException;
+				}
 				KrkClass * subclass = AS_CLASS(krk_peek(1));
 				if (subclass->base) {
 					krk_tableDelete(&subclass->base->subclasses, krk_peek(1));