Fix GH-10377: Unable to have an anonymous readonly class

This fixes the oversight that an anonymous class should be able to be
readonly. Other identifiers such as final and abstract do not make
sense. As we still want nice errors for when users try to use these
modifiers, or use multiple modifiers, we introduce a new function
zend_add_anonymous_class_modifier that will perform verification for
anonymous class modifiers, just like zend_add_class_modifier does for
non-anonymous classes.

Closes GH-10381

UPGRADING

@@ -31,6 +31,9 @@ PHP 8.3 UPGRADE NOTES
 2. New Features
 ========================================
 
+- Core
+  . Anonymous classes may now be marked as readonly.
+
 - Posix
   . posix_getrlimit() now takes an optional $res parameter to allow fetching a
     single resource limit.

Zend/tests/gh10377.phpt

@@ -0,0 +1,42 @@
+--TEST--
+GH-10377 (Unable to have an anonymous readonly class)
+--FILE--
+<?php
+
+$readonly_anon = new readonly class {
+    public int $field;
+    function __construct() {
+        $this->field = 2;
+    }
+};
+
+$anon = new class {
+    public int $field;
+    function __construct() {
+        $this->field = 2;
+    }
+};
+
+var_dump($readonly_anon->field);
+try {
+    $readonly_anon->field = 123;
+} catch (Error $e) {
+    echo $e->getMessage() . "\n";
+}
+var_dump($readonly_anon->field);
+
+var_dump($anon->field);
+try {
+    $anon->field = 123;
+} catch (Error $e) {
+    echo $e->getMessage() . "\n";
+}
+var_dump($anon->field);
+
+?>
+--EXPECT--
+int(2)
+Cannot modify readonly property class@anonymous::$field
+int(2)
+int(2)
+int(123)

Zend/tests/gh10377_1.phpt

@@ -0,0 +1,15 @@
+--TEST--
+GH-10377 (Unable to have an anonymous readonly class) - usage variation: dynamic properties attribute
+--FILE--
+<?php
+
+$readonly_anon = new #[AllowDynamicProperties] readonly class {
+    public int $field;
+    function __construct() {
+        $this->field = 2;
+    }
+};
+
+?>
+--EXPECTF--
+Fatal error: Cannot apply #[AllowDynamicProperties] to readonly class class@anonymous in %s on line %d

Zend/tests/gh10377_2.phpt

@@ -0,0 +1,10 @@
+--TEST--
+GH-10377 (Unable to have an anonymous readonly class) - usage variation: abstract modifier
+--FILE--
+<?php
+
+$x = new abstract class {};
+
+?>
+--EXPECTF--
+Fatal error: Cannot use the abstract modifier on an anonymous class in %s on line %d

Zend/tests/gh10377_3.phpt

@@ -0,0 +1,10 @@
+--TEST--
+GH-10377 (Unable to have an anonymous readonly class) - usage variation: final modifier
+--FILE--
+<?php
+
+$x = new final class {};
+
+?>
+--EXPECTF--
+Fatal error: Cannot use the final modifier on an anonymous class in %s on line %d

Zend/tests/gh10377_4.phpt

@@ -0,0 +1,10 @@
+--TEST--
+GH-10377 (Unable to have an anonymous readonly class) - usage variation: multiple readonly modifiers
+--FILE--
+<?php
+
+$x = new readonly readonly class {};
+
+?>
+--EXPECTF--
+Fatal error: Multiple readonly modifiers are not allowed in %s on line %d

Zend/zend_compile.c

@@ -903,6 +903,25 @@ uint32_t zend_add_class_modifier(uint32_t flags, uint32_t new_flag) /* {{{ */
 }
 /* }}} */
 
+uint32_t zend_add_anonymous_class_modifier(uint32_t flags, uint32_t new_flag)
+{
+	uint32_t new_flags = flags | new_flag;
+	if (new_flag & ZEND_ACC_EXPLICIT_ABSTRACT_CLASS) {
+		zend_throw_exception(zend_ce_compile_error,
+			"Cannot use the abstract modifier on an anonymous class", 0);
+		return 0;
+	}
+	if (new_flag & ZEND_ACC_FINAL) {
+		zend_throw_exception(zend_ce_compile_error, "Cannot use the final modifier on an anonymous class", 0);
+		return 0;
+	}
+	if ((flags & ZEND_ACC_READONLY_CLASS) && (new_flag & ZEND_ACC_READONLY_CLASS)) {
+		zend_throw_exception(zend_ce_compile_error, "Multiple readonly modifiers are not allowed", 0);
+		return 0;
+	}
+	return new_flags;
+}
+
 uint32_t zend_add_member_modifier(uint32_t flags, uint32_t new_flag, zend_modifier_target target) /* {{{ */
 {
 	uint32_t new_flags = flags | new_flag;

Zend/zend_compile.h

@@ -817,6 +817,7 @@ typedef enum {
 zend_ast *zend_ast_append_str(zend_ast *left, zend_ast *right);
 zend_ast *zend_negate_num_string(zend_ast *ast);
 uint32_t zend_add_class_modifier(uint32_t flags, uint32_t new_flag);
+uint32_t zend_add_anonymous_class_modifier(uint32_t flags, uint32_t new_flag);
 uint32_t zend_add_member_modifier(uint32_t flags, uint32_t new_flag, zend_modifier_target target);
 
 uint32_t zend_modifier_token_to_flag(zend_modifier_target target, uint32_t flags);

Zend/zend_language_parser.y

@@ -282,7 +282,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 
 %type <num> returns_ref function fn is_reference is_variadic property_modifiers
 %type <num> method_modifiers class_const_modifiers member_modifier optional_cpp_modifiers
-%type <num> class_modifiers class_modifier use_type backup_fn_flags
+%type <num> class_modifiers class_modifier anonymous_class_modifiers anonymous_class_modifiers_optional use_type backup_fn_flags
 
 %type <ptr> backup_lex_pos
 %type <str> backup_doc_comment
@@ -601,6 +601,18 @@ class_modifiers:
 			{ $$ = zend_add_class_modifier($1, $2); if (!$$) { YYERROR; } }
 ;
 
+anonymous_class_modifiers:
+		class_modifier
+			{ $$ = zend_add_anonymous_class_modifier(0, $1); if (!$$) { YYERROR; } }
+	|	anonymous_class_modifiers class_modifier
+			{ $$ = zend_add_anonymous_class_modifier($1, $2); if (!$$) { YYERROR; } }
+;
+
+anonymous_class_modifiers_optional:
+		%empty				{ $$ = 0; }
+	|	anonymous_class_modifiers	{ $$ = $1; }
+;
+
 class_modifier:
 		T_ABSTRACT 		{ $$ = ZEND_ACC_EXPLICIT_ABSTRACT_CLASS; }
 	|	T_FINAL 		{ $$ = ZEND_ACC_FINAL; }
@@ -1095,12 +1107,12 @@ non_empty_for_exprs:
 ;
 
 anonymous_class:
-        T_CLASS { $<num>$ = CG(zend_lineno); } ctor_arguments
+		anonymous_class_modifiers_optional T_CLASS { $<num>$ = CG(zend_lineno); } ctor_arguments
 		extends_from implements_list backup_doc_comment '{' class_statement_list '}' {
 			zend_ast *decl = zend_ast_create_decl(
-				ZEND_AST_CLASS, ZEND_ACC_ANON_CLASS, $<num>2, $6, NULL,
-				$4, $5, $8, NULL, NULL);
-			$$ = zend_ast_create(ZEND_AST_NEW, decl, $3);
+				ZEND_AST_CLASS, ZEND_ACC_ANON_CLASS | $1, $<num>3, $7, NULL,
+				$5, $6, $9, NULL, NULL);
+			$$ = zend_ast_create(ZEND_AST_NEW, decl, $4);
 		}
 ;