Require abstract classes to be explicitly declared 'abstract', in order to

avoid making developers traverse the entire class/interface hierarchy
before they can figure out whether a class is instantiable
(ok, so it makes sense :)

Zend/zend_compile.c

@@ -2214,9 +2214,7 @@ void zend_do_begin_class_declaration(znode *class_token, znode *class_name, znod
 	new_class_entry->num_interfaces = 0;
 
 	zend_initialize_class_data(new_class_entry, 1 TSRMLS_CC);
-	if (class_token->u.constant.value.lval == T_INTERFACE) {
-		new_class_entry->ce_flags |= ZEND_ACC_INTERFACE;
-	}
+	new_class_entry->ce_flags |= class_token->u.constant.value.lval;
 
 	if (parent_class_name->op_type != IS_UNUSED) {
 		doing_inheritance = 1;
@@ -2250,12 +2248,27 @@ void zend_do_begin_class_declaration(znode *class_token, znode *class_name, znod
 }
 
 
-void zend_do_end_class_declaration(znode *class_token TSRMLS_DC)
+static do_verify_abstract_class(TSRMLS_D)
+{
+	zend_op *opline = get_next_op(CG(active_op_array) TSRMLS_CC);
+
+	opline->opcode = ZEND_VERIFY_ABSTRACT_CLASS;
+	opline->op1 = CG(implementing_class);
+}
+
+
+void zend_do_end_class_declaration(znode *class_token, znode *parent_token TSRMLS_DC)
 {
 	do_inherit_parent_constructor(CG(active_class_entry));
+
 	if (CG(active_class_entry)->num_interfaces > 0) {
 		CG(active_class_entry)->interfaces = (zend_class_entry **) emalloc(sizeof(zend_class_entry *)*CG(active_class_entry)->num_interfaces);
 	}
+	if (!(CG(active_class_entry)->ce_flags & ZEND_ACC_INTERFACE)
+		&& !(CG(active_class_entry)->ce_flags & ZEND_ACC_ABSTRACT_CLASS)
+		&& ((parent_token->op_type != IS_UNUSED) || (CG(active_class_entry)->num_interfaces > 0))) {
+		do_verify_abstract_class(TSRMLS_C);
+	}
 	CG(active_class_entry) = NULL;
 }
 

Zend/zend_compile.h

@@ -89,19 +89,20 @@ typedef struct _zend_brk_cont_element {
 } zend_brk_cont_element;
 
 
-#define ZEND_ACC_STATIC		0x01
-#define ZEND_ACC_ABSTRACT	0x02
-#define ZEND_ACC_FINAL		0x04
-#define ZEND_ACC_INTERFACE	0x08
+#define ZEND_ACC_STATIC			0x01
+#define ZEND_ACC_ABSTRACT		0x02
+#define ZEND_ACC_FINAL			0x04
+#define ZEND_ACC_INTERFACE		0x08
+#define ZEND_ACC_ABSTRACT_CLASS	0x10
 
 /* The order of those must be kept - public < protected < private */
-#define ZEND_ACC_PUBLIC		0x10
-#define ZEND_ACC_PROTECTED	0x20
-#define ZEND_ACC_PRIVATE	0x40
+#define ZEND_ACC_PUBLIC		0x100
+#define ZEND_ACC_PROTECTED	0x200
+#define ZEND_ACC_PRIVATE	0x400
 #define ZEND_ACC_PPP_MASK  (ZEND_ACC_PUBLIC | ZEND_ACC_PROTECTED | ZEND_ACC_PRIVATE)
 
-#define ZEND_ACC_CHANGED	0x80
-#define ZEND_ACC_IMPLICIT_PUBLIC	0x100
+#define ZEND_ACC_CHANGED	0x800
+#define ZEND_ACC_IMPLICIT_PUBLIC	0x1000
 
 char *zend_visibility_string(zend_uint fn_flags);
 
@@ -352,7 +353,7 @@ void zend_do_case_after_statement(znode *result, znode *case_token TSRMLS_DC);
 void zend_do_default_before_statement(znode *case_list, znode *default_token TSRMLS_DC);
 
 void zend_do_begin_class_declaration(znode *class_token, znode *class_name, znode *parent_class_name TSRMLS_DC);
-void zend_do_end_class_declaration(znode *class_token TSRMLS_DC);
+void zend_do_end_class_declaration(znode *class_token, znode *parent_token TSRMLS_DC);
 void zend_do_declare_property(znode *var_name, znode *value, zend_uint access_type TSRMLS_DC);
 void zend_do_declare_class_constant(znode *var_name, znode *value TSRMLS_DC);
 
@@ -663,6 +664,7 @@ int zendlex(znode *zendlval TSRMLS_DC);
 
 #define ZEND_ADD_INTERFACE			144
 #define ZEND_VERIFY_INSTANCEOF		145
+#define ZEND_VERIFY_ABSTRACT_CLASS	146
 
 /* end of block */
 

Zend/zend_execute.c

@@ -3125,7 +3125,7 @@ int zend_switch_free_handler(ZEND_OPCODE_HANDLER_ARGS)
 
 int zend_new_handler(ZEND_OPCODE_HANDLER_ARGS)
 {
-	if (EX_T(EX(opline)->op1.u.var).EA.class_entry->ce_flags & ZEND_ACC_ABSTRACT) {
+	if (EX_T(EX(opline)->op1.u.var).EA.class_entry->ce_flags & (ZEND_ACC_INTERFACE|ZEND_ACC_ABSTRACT_CLASS)) {
 		char *class_type;
 
 		if (EX_T(EX(opline)->op1.u.var).EA.class_entry->ce_flags & ZEND_ACC_INTERFACE) {
@@ -4016,6 +4016,21 @@ int zend_verify_instanceof_handler(ZEND_OPCODE_HANDLER_ARGS)
 }
 
 
+int zend_verify_abstract_class(ZEND_OPCODE_HANDLER_ARGS)
+{
+	zend_class_entry *ce = EX_T(EX(opline)->op1.u.var).EA.class_entry;
+	zend_bool declared_abstract = ce->ce_flags & ZEND_ACC_ABSTRACT_CLASS;
+	zend_bool detected_abstract = ce->ce_flags & ZEND_ACC_ABSTRACT;
+
+	if ((ce->ce_flags & ZEND_ACC_ABSTRACT)
+		&& !(ce->ce_flags & ZEND_ACC_ABSTRACT_CLASS)) {
+		zend_error(E_ERROR, "Class %s contains abstract methods and must be declared abstract", ce->name);
+	}
+
+	NEXT_OPCODE();
+}
+
+
 void zend_init_opcodes_handlers()
 {
 	zend_opcode_handlers[ZEND_NOP] = zend_nop_handler;
@@ -4194,6 +4209,7 @@ void zend_init_opcodes_handlers()
 
 	zend_opcode_handlers[ZEND_ADD_INTERFACE] = zend_add_interface_handler;
 	zend_opcode_handlers[ZEND_VERIFY_INSTANCEOF] = zend_verify_instanceof_handler;
+	zend_opcode_handlers[ZEND_VERIFY_ABSTRACT_CLASS] = zend_verify_abstract_class;
 }
 
 /*

Zend/zend_language_parser.y

@@ -294,13 +294,14 @@ unticked_class_declaration_statement:
 			implements_list
 			'{'
 				class_statement_list
-			'}' { zend_do_end_class_declaration(&$1 TSRMLS_CC); }
+			'}' { zend_do_end_class_declaration(&$1, &$2 TSRMLS_CC); }
 ;
 
 
 class_entry_type:
-		T_CLASS			{ $$.u.constant.value.lval = T_CLASS; }
-	|	T_INTERFACE		{ $$.u.constant.value.lval = T_INTERFACE; }
+		T_CLASS			{  $$.u.constant.value.lval = 0; }
+	|	T_ABSTRACT T_CLASS { $$.u.constant.value.lval = ZEND_ACC_ABSTRACT_CLASS; }
+	|	T_INTERFACE		{ $$.u.constant.value.lval = ZEND_ACC_INTERFACE; }
 ;
 
 namespace_declaration_statement: