feat(compiler): 添加变量重新赋值类型检查功能

- 实现了对变量重新赋值时的类型验证逻辑
- 当变量从一种类型重新赋值为另一种类型时抛出致命错误
- 添加了测试基类用于编译器测试
- 新增变量重新赋值的单元测试用例
- 在代码差异中检测到变量类型变化时触发错误处理

phpunit/bootstrap.php

@@ -1,4 +1,25 @@
 <?php
 
+use PHPUnit\Framework\TestCase;
+use PhpAot\Php\CompilerTest;
+use PhpAot\Php\Exception\TestError;
+
 require __DIR__ . '/../bin/bootstrap.php';
 
+class BaseTest extends TestCase
+{
+    protected function exec(string $expected, string $file): void
+    {
+        try {
+            $compiler = CompilerTest::create(ROOT_PATH);
+            $testFile = __DIR__ . '/code/' . $file;
+            $compiler->addFiles([$testFile]);
+            $compiler->prepare($testFile);
+            $compiler->convert($testFile);
+        } catch (TestError $exception) {
+            $this->assertStringContainsString($expected, $exception->getMessage());
+            return;
+        }
+        $this->fail();
+    }
+}

phpunit/code/re-assign.php

@@ -0,0 +1,6 @@
+<?php
+function main()
+{
+    $obj = new stdClass();
+    $obj = "hello world";
+}

phpunit/src/AssignTest.php

@@ -0,0 +1,9 @@
+<?php
+
+class AssignTest extends \BaseTest
+{
+    public function testReAssign()
+    {
+        $this->exec('Cannot re-assign variable', 're-assign.php');
+    }
+}

src/Php/CompilerBase.php

@@ -1368,10 +1368,18 @@ class CompilerBase extends \PhpAot\Core\Translator
                         return $var . ' = ' . $this->convertExprFromType($type, $expr);
                     }
                 }
+            } elseif ($this->isVarExpr($right)) {
+                $rightVar = $this->parseIdentifier($right);
+                if ($this->hasVar($rightVar) and $this->isTypedObject($rightVar)) {
+                    $type = self::TYPE_OBJECT;
+                    $this->addObject($var, $this->getObjectType($rightVar));
+                }
             }
 
             if (!$this->hasVar($var)) {
                 $this->addLocalVar($var, $type);
+            } else if ($this->getVarType($var) != $type) {
+                $this->fatalError($left, "Cannot re-assign variable `\${$var}` from " . $this->getVarType($var) . " to  " . $type);
             }
         } elseif ($this->isPropertyFetch($left) and !$left->getAttribute('nativeProperty')) {
             return $this->parseAssignPropertyFetch($left, $right);