fix(closure): 修复闭包生成器中的引用捕获问题

- 将闭包生成器中的引用捕获从 & 改为 =，避免悬空指针问题
- 在 PHP 中使用 = 赋值进行浅拷贝，仅增加一次引用计数
- 添加了关于 zval 封装赋值的注释说明
- 新增了可调用语法的测试用例，包括箭头函数和杂项功能
- 添加了对 PHP 8.1+ 首类可调用语法的支持测试
- 包含了枚举相关功能的测试用例验证

src/Php/Generator/ClosureGenerator.php

@@ -27,7 +27,9 @@ trait ClosureGenerator
     protected function genClosure(NodeAbstract $expr, array $params, callable $bodyGenCb, array $uses = [], bool $useCurrentScope = false): string
     {
         $tmpVar = $this->genTmpVarName();
-        $capture = $useCurrentScope ? '&' : '';
+        // 必须使用 = 捕获，不能使用 & ，否则可能会出现悬空指针
+        // 在 PHP 中 = 赋值是浅拷贝，仅增加一次引用计数，和 zval (16 字节) 封装的赋值
+        $capture = $useCurrentScope ? '=' : '';
 
         $code = $this->getIndent() .
             'php::ClosureFn ' . $tmpVar . ' = [' . $capture . ']('

tests/aot/backed-enum.phpt

@@ -0,0 +1,87 @@
+--TEST--
+Backed Enums (PHP 8.1+)
+--FILE--
+<?php
+
+// Test basic backed enum with int values
+enum Status: int {
+    case Pending = 0;
+    case Active = 1;
+    case Suspended = 2;
+    case Closed = 3;
+    
+    public function label(): string {
+        return match($this) {
+            self::Pending => 'Pending',
+            self::Active => 'Active',
+            self::Suspended => 'Suspended',
+            self::Closed => 'Closed',
+        };
+    }
+}
+
+// Test backed enum with string values
+enum Color: string {
+    case Red = 'red';
+    case Green = 'green';
+    case Blue = 'blue';
+    
+    public function rgb(): array {
+        return match($this) {
+            self::Red => [255, 0, 0],
+            self::Green => [0, 255, 0],
+            self::Blue => [0, 0, 255],
+        };
+    }
+}
+
+// Test enum in switch
+function processStatus(Status $status): string {
+    return match($status) {
+        Status::Pending => 'Task is pending',
+        Status::Active => 'Task is active',
+        Status::Suspended => 'Task is suspended',
+        Status::Closed => 'Task is closed',
+    };
+}
+
+function main() {
+    var_dump(Status::Pending->value);
+    var_dump(Status::Active->label());
+    var_dump(Status::from(2)->name);
+
+    var_dump(Color::Red->value);
+    var_dump(Color::Green->rgb());
+
+    var_dump(processStatus(Status::Active));
+
+    // Test enum comparison
+    var_dump(Status::Active === Status::Active);
+    var_dump(Status::Pending !== Status::Active);
+
+    // Test enum array usage
+    $statuses = [Status::Pending, Status::Active, Status::Closed];
+    foreach ($statuses as $status) {
+        var_dump($status->label());
+    }
+}
+?>
+--EXPECT--
+int(0)
+string(6) "Active"
+string(9) "Suspended"
+string(3) "red"
+array(3) {
+  [0]=>
+  int(0)
+  [1]=>
+  int(255)
+  [2]=>
+  int(0)
+}
+string(14) "Task is active"
+bool(true)
+bool(true)
+string(7) "Pending"
+string(6) "Active"
+string(6) "Closed"

tests/aot/callable/arrow-fn.phpt

@@ -0,0 +1,22 @@
+--TEST--
+First-Class Callable Syntax (PHP 8.1+)
+--FILE--
+<?php
+
+// Test callable returning callable
+function multiplier(int $factor): callable {
+    return fn(int $value) => $value * $factor;
+}
+
+function main() {
+    // Test callable returning callable
+    $double = multiplier(2);
+    $triple = multiplier(3);
+
+    var_dump($double(5));
+    var_dump($triple(5));
+}
+?>
+--EXPECT--
+int(10)
+int(15)

tests/aot/callable/misc.phpt

@@ -0,0 +1,110 @@
+--TEST--
+First-Class Callable Syntax (PHP 8.1+)
+--FILE--
+<?php
+
+// Test basic first-class callable
+function add(int $a, int $b): int {
+    return $a + $b;
+}
+
+// Test first-class callable with class methods
+class Math {
+    public static function multiply(int $a, int $b): int {
+        return $a * $b;
+    }
+    
+    public function divide(int $a, int $b): float {
+        return floatval($a) / $b;
+    }
+}
+
+// Test callable returning callable
+function multiplier(int $factor): callable {
+    return fn(int $value) => $value * $factor;
+}
+
+function main() {
+    $callable = 'add';
+    var_dump(array_map($callable, [1, 2, 3], [4, 5, 6]));
+
+    $staticCallable = ['Math', 'multiply'];
+    var_dump(array_reduce([[2, 3], [4, 5]], fn($carry, $item) => $carry + call_user_func_array($staticCallable, $item), 0));
+
+    $math = new Math();
+    $instanceCallable = [$math, 'divide'];
+    var_dump(call_user_func($instanceCallable, 10, 4));
+
+    // Test first-class callable with arrow functions
+    $filter = fn(array $arr): array => array_filter($arr, fn($n) => $n > 0);
+    var_dump($filter([1, -2, 3, -4, 5]));
+
+    // Test callable in array operations
+    $numbers = range(1, 5);
+    $doubled = array_map(fn($n) => $n * 2, $numbers);
+    var_dump($doubled);
+
+    $squared = array_map(fn($n) => $n ** 2, $numbers);
+    var_dump($squared);
+
+    // Test callable with usort
+    $unsorted = [5, 2, 8, 1, 9];
+    usort($unsorted, fn($a, $b) => $a <=> $b);
+    var_dump($unsorted);
+}
+?>
+--EXPECT--
+array(3) {
+  [0]=>
+  int(5)
+  [1]=>
+  int(7)
+  [2]=>
+  int(9)
+}
+int(26)
+float(2.5)
+array(3) {
+  [0]=>
+  int(1)
+  [2]=>
+  int(3)
+  [4]=>
+  int(5)
+}
+array(5) {
+  [0]=>
+  int(2)
+  [1]=>
+  int(4)
+  [2]=>
+  int(6)
+  [3]=>
+  int(8)
+  [4]=>
+  int(10)
+}
+array(5) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(4)
+  [2]=>
+  int(9)
+  [3]=>
+  int(16)
+  [4]=>
+  int(25)
+}
+array(5) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(2)
+  [2]=>
+  int(5)
+  [3]=>
+  int(8)
+  [4]=>
+  int(9)
+}